9 Engine Swaps

9A Swapping a Small Block Chevy V8

9B Swapping a Buick V6

9C Swapping a Big Block Chevy V8

9D Swapping a BOP V8

9E Swapping a Northstar V8

9F Swapping a Chevy 4.3 90-degree V6

9G Swapping a Cadillac 500ci V8

9.1 What are common engine swaps for H-bodies?

9.2 How much more weight will I add to the front of my car?

You figure it out!

Aluminum components help reduce weight. These numbers are for factory (mostly iron) engines.

9.3 Will I be able to keep my transmission?

It depends on several things:

So, basically, if you're going from a L4 or V6 to a V8, and want a reliable transmission, no.

9.4 How do I modify my tachometer?

All later tachometers are basically the same. On the circuit board is snap-in piece that goes in one of two slots. No clip = 4 cylinder, clip in upper slot = 6 cylinder, and clip in lower slot = 8 cylinder.

For Vega tachometers, the circuit board must be modified. One recommendation is to put a 1000 ohm potentiometer in-line between the meter and board, then adjust the pot until the reading on the meter is what you want (compare it to an underhood tach). Another is to add two 1u50V capacitors to the board.

A diagram of the board with modification instructions can be seen at: http://ia.yimg.com/a/77ab29b0/h/50b6570/tachv8mod.jpg

If you decide to just get a V8 tachometer from a donor car, you must also replace the capacitor on the coil trigger wire.

9.5 What can I do about cooling?

See question 2.5.

9.6 How do I install a remote starter solenoid?

See question 8.1.

9.7 Should I replace my front springs and shocks for a V8 swap?

If you have a 4 cylinder engine, yes.

For a Monza, try TRW V8 Monza springs: part #CS6476 (front) #CC617 (rear)

For a Vega, shorter springs will be needed. This is because the Monza's lower control arm has a deeper spring pocket than the Vega's. So if you put Monza springs in a Vega, the front end will sit too high. You can either swap in Monza LCAs or...

John B (vegadad) offers this suggestion:
"If you want to increase the spring rate on your car, use the V-8 Monza/Air conditioning springs. When I put new springs on my 74 panel I used these. I do recommend, if you are using the stock A-arms, cut 2 coils from the top of the new spring. This will put your car back at the proper ride height. Do not use a torch to cut springs as the heat will weaken them. Mark the cuts vertically as you want to spring to sit in the spring pocket correctly."

Tom (tjvanoverbeke) writes:
"In my experience cutting two coils off the Monza A/C springs is too much. I cut 3/4 of a coil off the left side spring and it didn't seem to drop the car much. Then I cut a full coil off the right side and it dropped to around stock height (7" from the bottom of the rocker panel to the ground, around 4.5" from the 2135 headers to the ground). It would be a good idea to cut in 1/2 coil increments."
9.8 What about AC?

Short compressor: 5.5" back of case to clutch
Long compressor: 11.75" back of case to clutch

Jeff (monzafan) has some GM AC part numbers:

    Accumulator         2724048 
    Condensor           3036617 
    Evaporator          3036664 
    A/C Vac. Tank Hose  370112 
    A/C Refrig. Lines   See Chart at end of gp. 9 (which means:
      "find" the part that looks correct and match it to numbers listed below 
      the illustrations. This chart is at the back of the parts book 
      (group 9.000).

9.9 What can I do about starter heat soak?

9.10 What can I do about fuel delivery for carbureted cars?

NOTE: Carburetors require much less fuel pressure than most fuel injected cars. Thus fuel pumps aren't usually interchangable between the two, even with regulators.

If you have a stock V8 pump, people have claimed it's good for at least a 350 with a 600cfm carb under hard driving. On the other hand, the stock 4-cyl and V6 pumps aren't going to work well with a V8 (then again, see the notes from Robert Herndon...).

Mike (monzter_327) writes:
"A while back, someone asked me about replacing a Monza's stock immersible fuel pump with an external electric fuel pump. I've just removed the pump/quantity sender unit from the Monzter's tank and have a few tidbits to share with all of you who intend to do this replacement.

Regarding tubing, Denis (denisst78) adds:
"When you use a rubber hose in the fuel tank be sure you use Very Very good quality hose. The reason is this: I used an ordinary hose in mine to replace the fuel pump and one year after I removed the tank to flush it and I discovered that the rubber hose had bulged a lot (the gas almost melted it). So now I use a steel tube welded to the oem pick up and an adaptor so the sock fits on the outside of the tube."

For his drag Monza, Phill (DRAGMONZA) did this:
"Here is what I did for my Monza, although I am set up for drag racing this will work for the street also. I removed the stock fuel pump, pick-up & sending unit for the gauge. Street guys may want to leave the sending unit, nothing more embarassing than having a cool car, out of gas. I removed the pipes from inside the pump cover & modified one of them to act as a vent line, & plugged the other. Next I drilled a hole in the front of the tank near the top (look carefully before removing tank to see your clearance). I then bent some 1/2 (3/8 for street) aluminum line in the shape of a "z" so it would rest on the bottom of the tank near the back. Using AN fittings to connect to the out side of the tank, alot of work needs to done through the gauge hole on top of the tank, so keep your kids handy (I have small hands). I then used braided line to a Holley Blue Pump then Aluminum & braid the rest of the way up front. This can be adapted to the street by relocating the "z" line so the sending unit still functions. Plus the added bonus this work can be kept hidden from prying eyes if you have a "sleeper". I have had abslutely no problems with this system, plus have the advantage of the pick up at the back of the tank for hard acceleration. To add to the other message about adding a larger hose, you are still limited by the size of the fitting exiting through the top of the tank & the poor factory bends (i.e. crimps)."

Robert (twelve_second_vega) says about stock pumps:
"I have used the Vega "In-Tank" fuel pump on V8 swaps in the past with no problems. Of course, these are fairly mild engines, mostly 350's with a Q-Jet. What I do is install a one-way check valve in the fuel line, then add an auxillary external fuel pump (one of those cheap "Click-Click" ones) in the line to the carburetor with 2 "Y" fittings. I then add a toggle switch somewhere out of sight that will activate the pump if the primary pump fails. With this primitive system, I am certain I could at the very least return home.

The reason I employed a check valve in this application was to avoid pumping fuel through a dormant pump. The "Y" fitting allows the secondary pump to remain primed but inoperative and the check valve ensures that fuel will travel in one direction only. This permanant installation is hard wired to a hidden switch that provides for immediate secondary pump operation before the car stops rolling."

9.11 What can I do about fuel delivery for fuel injection?

For cars without electronic fuel injection (i.e., all but the Cosworth!), if you plan to install fuel injection, you'll need to run a return line back to the tank. Some people just use the vapor canister line but it's not recommended--it's there for a reason! The "right" thing to do is run another line. Also, it's recommended to install a baffle in the fuel tank to hold fuel near the pump inlet tube while cornering, or else you'll get no fuel (FI doesn't have float bowls like carbs!).

Denis (denisst78) writes:
"I tried a tuned port pump on my Monza and it was easilly adaptable. It was from a 1988 Camaro with a 350). For the fuel lines here's what I'd do: Use the vapor canister line for the TPI vapor canister. Use the main Monza fuel line for the TPI return line. Install a 3/8" fuel line for the TPI fuel pressure line. If you follow the oem bends it will look just like OEM."

Dave (cuzworth) suggests:
"I have also modified my in-tank fuel pump on my Cosworth. When my external high pressure pump quit working, I discovered that a replacement was about $270 (in 1991). I did a little research and found out that the pump from a '86 Fiero V6 had similar specifications for flow volume and pressure as the stock Cosworth high pressure pump. The Fiero pump is longer than a stock Vega/Monza pump, but otherwise identical in overall diameter and power/fuel connections. I had to modify the bracket that holds the pump to the main pickup tube to make it work, but that was a very simple procedure. The best part was that the Fiero pump was only $60 and has a lifetime warranty."

Roger (monza_madness) writes:
"I plan on using an 87 TPI IROC sending unit (100 psi pump) in my Monza tank, it fits like the stock Monza unit except, the tubes in the tank have to be bent slightly for location and clearence. You should be able to get a used sending unit from a bone yard. Don't forget to make a baffle to hold fuel around the "sock" to prevent fuel starvation on corners and stops. Unlike carbs with floatbowls, injection systems need constant fuel (no reservoirs). It sucks air you lose pressure, no pressure, no squirt etc."

Tim (joyride_23_98) says:
"I have a TPI in my '72 Vega, I have a IROC pump mounted to the stock fuel pick up (don't forget to use the pulsation dampner that was used with the Camaro, or you will have a very loud knocking noise). I made a reservoir from tin that the pick up sits in and added a return line into the tank. I used the stock fuel line as a return line and added a new 3/8" line to feed the engine. All of the flex lines must be upgraded to fuel injection hose, otherwise you will have a few major leaks."

Later Tim adds:
"I made a small box out of tin (it just fits in the big opening at the top of the tank). The fuel pump pick up (sock) sits in this box, I have the fuel return line that I made dumping all the fuel back into this box. I made a few small holes in the lower sides of the box so that fuel can creap in if the fuel level is lower then the top edge of the box (heaven forbid). The box hold enough fuel so when I go around corners, the motor does not starve. I used a fuel pump from a TPI Camaro; I modified the stock bracket and tie wrapped the pump to it. Be sure to use the pulsation dampner that comes on the TPI fuel pick up, or you will have a horrible knocking noise in you fuel system.

The other option is to cut the bottom of the tank and have a small sump installed that the fuel pick up could sit in. I was going to get a rad shop to do that do mine, but they wanted a couple of hundered dollars to do it, and being the cheap Scotsman that I am, I spent $2 on roofing tin at the Home Depot and made the above system.

If you have a Cosworth fuel tank, take a look at the baffle system that GM used, it is a lot more graceful then what I did, but you will have to cut open the tank to fit it in there.

Another quick note, if you are using TBI, use the fuel pump from a TBI Fiero (or the like), the TPI pump will put out way to much pressure (you also won't need the pulsation dampner, it is only used on the TPI system).

9.12 How do I install a "generic" radiator?

This question mainly refers to the Griffin aluminum radiator (#155241, 27 1/2" X 15 5/8"). Griffin may also sell a radiator designed to fit an H-body exactly, but their exact-fit radiators are typically twice as expensive as their universal-fit radiators.

Paul (pvgatto) writes:
"It took a bit of fabrication to install the Griffin radiator. I had to remove the front radiator support and weld in a crossmember between the front frame rails. In the stock location, the radiator is actually wider than the frame rails and is also too close to the fan. By moving it forward a couple inches, I gained some fan clearance and the frame rails widen out a bit where the original radiator support sheetmetal used to be. All in all, its a pretty tight fit.

In my opinion, the Griffin radiator is really nice, but is probably not necessary unless you are running a 400 and live in a really hot climate like I do. The V8 Monza radiator is probably adequate for most applications. Even with the Griffin radiator, my car still ran hot until I installed a proper fan shroud and a good, factory style steel fan."

erdowell writes: "I just bought their 27.5" x 15.5" radiator and it is a 1/2" to wide. It is the 2 core with 1" tubes. I will notch the frame, and slip it in. It is 1/4" thicker than the 3 core monza unit I currently have in it, which will leave me approx. 1/8" of room."

9A.1 What basic parts do I need to put in a Chevy Small Block?

If your H-body came with a V8:

If your H-body didn't come with a V8:

Also Recommended but not necessary:

Robert (twelve_second_vega) provides some part numbers from the Don Hardy kit:

9A.2 What are my engine mount options for a Chevy Small Block V8?

(also see question 2.15 for more information)

If you want factory pieces, get them from an original V8 car. All factory V8s in the H-bodies were Chevy Small Blocks of various displacements, so the mounts are the same. Be sure to get the mounts (including the pieces that attach to the subframe), the transmission crossmember, and even the driveshaft and torque arm.

Part numbers:

The mounts will bolt into any Monza/Starfire/Sunbird/Skyhawk without modification. However, for the Vega and Astre, they will only bolt in after the old "outer" frame mounts have been removed and you have created a place for the mounts to bolt in. This requires drilling or grinding out spot welds and possibly a BFH (big hammer) to knock the mounts off the frame due to a hidden spot weld. Then obtain 3/8ths-16 nuts. Grind the corners so that they can be tapped in the holes, then weld them in place. You may also need to drill new holes. Once you have the nuts welded in place, the Monza mounts will bolt right up and sit flush to the frame.

Aftermarket kits are sold by a few companies.

Note that mount choice affects the headers you can use, for example, Hooker 2129s will not work with side mounts.

Finally, you can make your own. Many chassis manufacturers sell motor plates for the SBC and other engines. You then tailor them to your frame. Use 3/8" aluminum if possible.

Robert (twelve_second_vega) offers this advice:
"For those of you who may be making their own motor/transmission mounts, I would like to share my method for centering. First, the car should be supported on stands and leveled in all (4) directions.

Next, attach a piece of string to (3) 1/2" Castle Nuts and tape them to the exact center of the Crankshaft Snout, the Transmission Output Shaft and the Pinion Stem. Run a long piece of string through all (3) nuts and tape it to a Brake Drum at each end of the car. Apply tension to the string and raise/lower each individual nut until the tensioned string passes exactly through the center of each nut.

Now make any adjustments you need to keep the string in the exact center of all (3) nuts. No measurements are required, you just need a good line of sight through each nut.

Now level the engine from side to side. I do this by measuring through the centerline of the lower bolt holes in the front of the block on a Chevrolet V8. You may need a different datum point on other engines. Once you have the engine level, again check the "Plumb Bob's" to be sure you have everything on exact center.

Now place a level across the carburetor mounting pad and set the angle of the engine from front to rear. I use 0 or absolute level, but some other club members may offer different suggestions."

9A.3 What do I need to do to the oil pan for a Chevy Small Block?

The pan needs to be clearanced for the steering link. You can find insutrctions with pictures for this on many websites plus or with some engine mount kits.

You can buy a new pan for this application from Milodon, Moroso, and Hamburger. The Milodon (part number MIL-31070) will work with a 400; this part is for a left-hand dipstick (MIL-31071 is for right-hand dipstick). The Moroso is part number 710-20230 and the matching oil pickup is 710-24170. See any popular racing parts catalog.

Finally, you can try to get a real Monza V8 oil pan, either used or (possibly) new through a dealer.

9A.4 What are header and exhaust options for a small block V8?

With factory-style side engine mounts:

With front engine mounts:

Ron (vega355) writes about Doug Thorley headers:
"I bought the V8 Doug Thorley Vega kit a few years ago (and they weren't making the very useful altanator bracket anymore). I chose the Doug Thorley kit for a couple of reasons. 1) The headers stay within the frame rails, so I didnt have to compromise turning radius by cutting holes through the wheel well. 2) I wanted the Doug Thorley motor mounts, so I wouldn't have to use a motor plate. The problems I had with the headers were a) I had to cut an ear off my Turbo 350 to clear them. b) you are forced to relocate the oil filter, unless you only wanted to change it once. c) I pretty much had to use a mini starter. d) the headers point out at a angle that makes if difficult to make them street leagal. Otherwise, they fit nice and tight."

For an exhaust system, Clyde (CJBIAGI) recommends:
"Over the last 25 years I have had a number of exhaust systems on my 75 Monza and the only one I ever really liked is the one I have now. I have Hooker 2135 headers and what I had done is to run both pipes parallel to each other on the passenger side of the drive shaft, up and over the rear end and then into two Edelbrock stainless mufflers mounted side by side next to the gas tank where the original muffler was. I am running 2 1/4" aluminized pipes all the way. I have the driver side pipe coming off the header and curving behind the trans crossmember. Leave enough room to drop the trans without disturbing the exhaust system. I also had a "H" pipe added between the two sides. It's a tricky system to have bent; find a good muffler man--he's worth his price in gold. This system allows very good ground clearance and you don't see the mufflers hanging way down under the rear seats.

I forgot to add that the 75 monza uses the curved panhard bar. The panhard bar is what makes getting the pipes over the rear end so difficult. Later models that use the straight panhard bar may be easier to route the pipes. I am not really sure. If you have the curved bar it seems to work out better to run both pipes on the passenger side. There is not a lot of room to do this, but it is possible. I doubt that you could go much bigger than 2 1/4" over the panhard bar, as there is not a lot of clearance between the pipes, shock and panhard bar."

Denis (denisst78) adds that he was able to pass a 4 inch pipe over the axle in his 1978 Spyder instead of passing dual 2 1/4 pipes: "Hooker 2129 headers, about one foot of 2.5 inch pipe on both side (bend at around 20), Dynomax ultraflow mufflers (one on each side), one foot of 2.5 pipe on both side, and a 4 inch pipe that goes all the way to the rear bumper. I made this exhaust with pre-bent tube so I had to piece it up together. Nothing touches the ground (exept the damn 2129`s). Now if you want, you can omit the two front mufflers and only use a 4 inch rear muffler."

Wade (wade78spyder) writes:
"I have the mufflers under the front seat. They are Edelbrock RPM series stainless steel straight thru w/life time warranty (sound very nice). My pipes are 2.5" to end (also st. stl.) and exit behind the rear wheels. I hit once w/my 13" rims (it was a huge dip on a back road traveling about 60)--actually hit the pipe on the drives side just before it turns up to the header (Sanderson)--no damage. Now with 15" rims, I'd have to be off the road to hit! From the rear you can't see the mufflers, but you can see about 1/2 of it from side on the drivers side. You can also see about 1/2 the pipe also. Just can't run it close enough to the center of the car. I think Clyde's setup probably is the cleanest looking in terms of factory appearance. It also would give about the best clearance."

On H-pipes: Usually they are beneficial. To find the optimal place to put one, ignoring practical concerns, draw crayon lines on your current dual exhaust while it is cold. Start the engine and let it warm up. Look where the crayon stops melting on the exhaust--this is where you would add the H-pipe to balance the exhaust flow better. However, in real life, you would place it wherever it fits best and doesn't interfere with transmission maintenance. Even if the placement isn't optimal, it will still help. (Marco (Monzabudd) posted this tip.)

Mark (vsvw8) writes about Don Hardy headers:
"Received my don hardy super-twister sm. block headers today and it sure seemed like christmas to me! Nice looking, good solid weight and NEW, not looking like old stock! Most complete header package i've ever purchased, and i've bought at least 15 + sets to date! Headers, gaskets, collectors, bolts, hell they even send ya some hi heat black header paint to boot! Then there was also a couple of page long walk thru directions on how to install a small block chevy motor, complete on where to dimple the trans hump ect, a template to re-cut the heater core cover. Great kit, tubes are of equal length (supposedly tuned like they ran on their drag car) and to top it all off, they send ya a pair of really slick looking don hardy stickers with his logo!"

9A.5 How do I mount accessories?

One option is to try and gather brackets and pullies from a V8 Monza.

For the Vega, Robert (twelve_second_vega) recommends:
"With the original Vega wiring having the Alternator connections on the Drivers Side, I thought it would be of great benefit to locate the V8 Alternator in the same location. Additionally, it seemed logical to place the Alternator above the Water Pump as well. I found a combination of parts that accomplish this with the Short Water Pump (SWP) and they are a mixture of GM Pulleys, and OMC (PowerBoat) Brackets. The end result is 6" crank and water pump pulleys with double grooves and an Alternator that sits just above the Intake Manifold, just right of the Water Outlet. The Alternator Bracket bolts to the Drivers Side Cylinder Head, so you need Heads with accessory holes and the Adjuster Bar bolts to the Passengers Side upper Water Pump Mounting Bolt. Here are the part numbers. It looks and works great.

You will need to shorten the spacer on the GM Alternator slightly with the 911877 Bracket. You can also substitute a Ford Aluminum Spacer from the ScrapYard too. The very late GM Alternator (with plastic rear housing) bolts right up.

Pre-1982 Corvette and early GM Truck/Van Pulleys line up with the Boat Brackets. The Boats use the Corvette style pulleys and many aftermarket suppliers offer them. My experience has shown that Chrome Pulleys are not good for High RPM work. Repeatedly, I flip 13 Series (1/2") belts over in the Chrome Pulleys @ 8300+ RPM. This problem stopped when I switched to Painted Pulleys with Bare Steel Grooves. When selecting your belts....You want the belt to ride appoximately .060" - .080" above the groove. If the top of the belt is down in the pulley groove, it will flip the belt over and/or throw it off if you turn enough RPM. I have experienced this as low as 5500 RPM."

Bob (botizan) adds:
"I went by a boat shop and looked up the brackets & ordered them. Both #s have been superseded. The 913691 brought up the new #s but the 911877 didn't bring anything up, however, it was easy to find! It's the same mount on all 4.3 & 5.7s from at least 87 & up. I don't have the new #s handy or I would post them. I'll let everyone know If they work OK. The cost was about $40 for the set. [then later...] The OMC # 913691 adjuster bracket is a good number, however, the OMC # 911877 would not come up. After looking through the books I found the superseding OMC # is 3853883. It looks like a good set up , but I don't think it wiil work on the Vega due to the hood clearence, it mounts the alt a little high."

Robert (twelve_second_vega) replies:
"I think you will find it works nicely with the Late GM Alternator."

9A.6 How do I relocate the oil filter?

To move the filter without needing to mount it remotely or run hoses, Larry (vega_man_larry) says:
"Use the following parts to relocate your oil filter away from the headers [GM part numbers]:

I have the above parts on my Vega and the filter clears Headman Hedders and is much easier to access. Before finding these parts oil change meant dropping one hedder. Sorry no PICS available. It costs under $100 and solves the filter problem. You also get rid of the remote filter hoses and where to mount a remote filter if you choose to go that route. I had a remote setup before but I was plagued with constant leaks. This is the best solution I have found."

9A.7 What should I know about the throttle pedal and cable on an early Vega?

John B (vegadad) writes:
"One thing you may wish to look at is the floorboard area around the gas pedal. If you had to expand the tunnel on the driver's side, a common adjustment, you may have interference such that the pedal no longer goes all the way to the floor. My friend used the cable from a V-8 Monza on his 73 with a 327 and has no problems."

Bill (vegasmb383) adds:
"On mine I used a cable off of I believe, a 76 or 75 camaro. The length is near perfect in that at the point the pedal is on the floor, the carb is at WOT. And it clips right in the hole in the firewall and on the bracket on carb. I am using a team g and holley 750 dp by the way on mine."

9A.8 Can I use Monza exhaust manifolds on Vortec heads?

Denis (denisst78) says:
"Yes they can, Be sure to check if the manifold matches the gaskets. Some manifold are cast with very small openings or they may have shifted when the manifold was cast. Just a little minor porting."

9B.1 V6 General notes

First, the V6s (3.2 and 3.8) used in the H-bodies are Buick engines. If you get a V6-equipped H-body, a newer 3800 engine (200-240hp) or Buick Turbo V6 will bolt in. You'll have fuel and electronics issues, but the blocks should fit easily. Look for the book "Building the V6 Vega" by John Thawley.

Hooker sold/may still sell headers for the V6 in a Vega (should also fit Monza).
Other part numbers that may be outdated:
Hurst headers - p/n 1603
Hurst crossmember - p/n 12636 turbo 400
Hurst crossmember - p/n 12637 turbo 350
Hedman/TransDapt hedders - p/n 48050

Brew (mongoose_brew) notes:
"Unfortunately, the 3.8 will only bolt up to BOPC (Buick Olds Pontiac and Cadillac) pattern transmissions. NO CHEVYS. The up side to that is v6 or v8 makes no difference it will bolt up to all of them.

The four cylinder BOPC trans are few and far between. Most four cylinder Buick, Olds, Pontiac and Caddy CARS used Chevrolet engines.

The most feasible, hassle free 3.8 swaps are with that of the 4.1 Caddys and Buicks. Mostly, because they all use the same accessories, intake and exhaust equipment.

PS-TRANS-DAPT, as well as several other companies, makes adapter plates to mate the Chevys and BOPCs, if you're interested."

Don Hardy V-6 kit part numbers:

They claim to still have some Buick kits in stock (ask for Fernando).

John B (vegadad) writes:
"I've installed a 3.8 in my 72 Vega. Some tips you'll need to know about. 1) There isn't enough clearance between the starter motor and the frame on a 71-72 vega. You'll need to pound a dent in the rear of the front suspension web on the passenger side to mount the starter. I don't know if a mini-starter will solve the problem. If you can, test fit the block with starter in place and see where you need to bump it out and how much. 2) Removing the mounting pads is a necessary step this allows everything else to align properly. 3) When you go to bolt in the new frame stands You'll need to drill the holes in the upper part of the frame. The good news there are enough access holes in the side and bottom of the frame member to insert the nuts by hand using a socket and long extension. 4) when bolting the frame stands in place use weatherstripping glue to glue washers to the nuts. That way, when you put them in the socket they will sit near the top of the socket and will facilitate getting the nuts on the bolts without crossthreading. The more bolts you use the stronger the frame stand will be. 5) Use some kind of motor restraing system on the driver's side of the engine. The 3.8 is a has a lot of torque and will have a tendancy to break the driver's side motor mount. I wiped out a real nice flex fan, fan shroud and the radiator because I didn't know this. Also you will have to notch the K-bar on the drivers side to install the monza radiator. the lower mount will have to be lowered about 4" to do the trick. This can be done with a piece of strap steel. See if you can keep all the rubber vibration dampeners from the donar car. You may have to fabricate the lower mounts but not a big deal. See if you can get the adapter transmission mount from Hurst, It works for the 4 speed ot TH 350 installation. I don't know for sure, but I think you might also be able to mount a 200R4 as an option. Any other questions please ask. The 71-72 Vega had a smaller engine bay than the 73 and up cars. I think you'll like the results, I know I did and you won't tear up the unibody with the added stress of a V8. It's a natural."

Then he adds:
"The 231 swap is a natural for your 77. One word of advice. If you are going to install this new bullet. Reface the flywheel,and replace the clutch (pay me now or pay me later mentality). No the 140 flywheel will not fit a 231. The flywheel on my 231 weighs 50 lbs to cut down on motor induced vibration. Mine is an odd-fire engine from a 77 Cutlas S. Your requirement may be different if you are installing an even fire engine. You may also need to change the rear crossmember. If so let me know I have one from a 76 Buick Skyhawk you can have. It looks like a rounded trianglular piece. Some other members may be of help here. Be careful with the exhaust. if you stick to stock manifolds for an h-body you shouldn't have a problem. Headers are a different story. The v-6 bellhousing for my car has a starter buldge on both sides. This won't let me use hedman hedders as the driver's side header won't clear the buldge. Not to discourage as maybe Hooker makes a header for your application (Monza, Skyhawk, etc.). Would recommend a switch to a 4 barrel, Edelbrock offers a complete deal, with even fire cam and the works including a 500 cfm 4 bbl."

John (vegadad) adds about headers:
"I purchased Headman Headers for a V-6 Monza Application for my 72 Vega with a 77 231 Odd-Fire. Here are some problems I experienced.

  1. Power Brakes clear will have no problem.
  2. If you are running a 4 or 5-speed Stick, the headers will not clear the bellhousing on the driver's side. The Buick Bellhousing has a starter hump on both sides of the bellhousing for universal application(s).
  3. When mounting the power steering pump you will need to fabricate a Bushing spacer for the support arm on the pump assembly mount that goes to the first header bolt on the Driver's side of the block.

As far as the problem with the bellhousing goes, I don't think you would have a problem with using an automatic. If you do wish to use a 4 or 5 Speed I would suggest grinding off the starter hump on the driver's side then fabricate a plate to cover the hole. Short Machine screws may be tapped into the bellhousing as it is Aluminum ( easy stuff.) Don Hardy and Hooker, I believe, also make headers for this application. Make sure you check to make sure they will fit with the OE engine mounts. Good Luck.

Lenny (lenny1_70) adds about headers:
"I used the Hooker super competition set up and had no problems with them. They are a slip fit on the driver side (to fit around the steering shaft) and I have'nt had any problems with leaks. My Monza is a 231 with power brakes and steering plus A/C and has no clerance problems. I am also running a TH-350."

About frame mounts, Myles (mylesgt) writes:
"Spacers: Yes, toss em. Why? Don't need 'em.
First off, if you're using PS, the spacers interfere with the assembly. Eliminating them also enables the OEM monza Mounts to contact the 'frame rails' fully. As both the V6 & V8 plates (bottom part of motor mount assembly) grab the two holes from the 4, and carry the weight down/out, IMHO, it's better to snug em up against the rail. The RH (passenger side) plate lines up with only one of the 4's holes. The LH plate does grab both. As the six twists up from the LH side, this has not been an issue. To strengthen the anchoring (RH), you can always tap the spare, or the plate's tab resting on the top of the frame rail, with its two top holes/one on side. For 8s, I usually welded the plates on."

Then Larry (vega_man_larry) adds:
"The factory V6 mounts won't fit until the plates have been removed as the mounts and the chasiss pan "nest" together. You don't need to go high tech to remove the spacer pads. I used a very sharp chisel and five pound sledge once to break the spot welds holding the spacer pads to the unibody. If you have a die grinder grind away the spotwelds and break the pad free. Work slowly and carefully and you won't damage the unibody. Use some of the existing holes to attach the mounts and drill new holes as required."

About Turbo V6s, Larry (vega_man_larry) writes:
"I built a V6 Turbo car using an early GN carburator turbo setup. I used the MSD BTM box to retard ignition during boost. As it was carbbed I didn't have to fool around with a computer. I used a 4.1 engine which has the turbo (radiused fillet) crank. The tricky part was routing the exhaust across the botom of the car. I had a custom pipe made up that tucked between the oilpan and the bellhousing. The car had the 5 speed optional transmission. Fitting the works into the Vega was tight. I had to massage the unibody on the RH side for clearance. If you go the late model GN route get the whole donor car. You'll need to convert the tank over to the GN fuel pump and wire the car for the electronic fuel injection. You'll also have to get a cowl induction hood or hood scoop to clear all the plumbing. I didn't use an intercooler. I don't know where one would fit in a Vega so your inlet temps will be higher. Get a couple books on turbocharging. It's a little tricky. My car's setup looked like the one in Thawley's V6 Vega book, the setup in the jeep. Turbos are expensive. A rebuild on the turbo alone will run $400. A V8 is quicker and cheaper, but the turbo is rare."

9C.1 Big block General notes

Aleck (stinkybuttihave) writes:
"The headers you need are made by Hooker and they acually fit better than the small block ones because of the diferent exhaust port exit angle. The Hooker kit uses front saddle mounts similar to the small block kit. Motion's kits use Hooker headers. Also with the big block you must use manual steering because the headers wont clear the steering box or the steering shaft."

9D.1 BOP V8 General notes

Roger (ks_skyhawk) writes: "I have done a similar swap using a 350 Buick V-8, I have talked to KcKen about the Olds swap. Also, I believe the Olds (all displacements) and the small block Buick have similar external dimensions. I think both are do-able. In my case, the V-8 bolted right on the the V-6 mounts. That's where the easy stuff ended. Had to use u-joints on the steering, and modify the brace between the passenger fenderwell and floorpan to clear the exhaust. The waterpump cleared the 4-core radiator by a whole 3/4" (radiator in the factory location). I know the 455 Buick is at least 2" longer. Don't know about the Olds. I wanted to have the AC, and PS, so anything beyond these limits weren't an option. And, has been stated by my esteemed friends on this site, anything with that kind of brute torque and HP is destined to do a job on the uni-body unless serious stiffening is accomplished."

9E.1 Northstar V8 General notes

Randy (monzamiler) notes:
"Here are the specs that I got back on the Northstar:

9F.1 Chevy 4.3 90-degree V6 V8 General notes

Bob (botizan) says:
"I have a 78 Sunbird wagon with an 86 4.3/Th- 350. It wasn't too difficult a conversion. I used V-6 Monza frame plates, 200/229 Malibu (1980 or so) motor mounts then made a simple perch for each mount to set onto the frame plates. The oil pan is out of an Astro van. The Astro doesn't have the step in front of the sump like the Monte Carlo and others, which will hit your crossmember. I massaged the sides carefully for tie rod end clearence then removed 1 1/2" out of the sump.I don't think headers are available for this unless you buy the kit type and build them yourself to fit. I used a V-8 Monza cross over pipe and modified it to fit the exhaust manifolds and the original exhaust system (with the exception of a mini turbo muffler). The manifolds are 200/229 Malibu. The 4 brl however might be too tall for your hood. you might have to use an aftermarket intake. For accessories p/s, a/c, alt, I used all V-8 Monza brackets. The only thing different there was that I ran the p/s belt from just the w/p due to the steering box location interfering with the belt."

Then he adds:
"The Monza flywheel will bolt up to an 85 or earlier 4.3. but for 86 & up, you will need the later small (153 tooth) flywheel for a 4.3,305, or 350.If you go standard, the same goes just use the same clutch set for all years. My 4.3 set in the same place as the V8. This gives 4 3/8" more room in the front of the engine. Then using the V8 Monza W/P & accessories brackets makes it neat, simple & factory appearing(the long legged W/P might not allow P/S due to the location of the steering box). With this set up, the trans stays in the V6/V8 position. 1980 200/229 motor mounts are very close to the V8 Monza mounts & those are what I used. Besides, You can easily modify them to work in place of V8 Monza mounts. I don't think the S10 exhaust manifolds will work. Let me know if you find out different."

Denis (denisst78) writes:
"I just got a magazine from e-bay (Hot rod`s chevrolet high performance) (volume 2 number 3). It was sold in 1985. They have lots of info on swapping a V-6 90 in a vega. Here's what they used: Herbert automotive engine bracket, trans crossmember, custom oil pan (it looks a lot like an oil pan from a 4X4 s-10--BTW the oil pan was modified by Milodon). They used the easy to find long water pump and brackets. Headers were custom made (no shop are specified in the mag). They also use a holley # 300-34 intake with a Holley carb and it clears the hood.

Here's what i was thinking to do on my 1980: 4.3 from a s-10 truck (4x4 to have the good oil pan), fuel injection from the truck, V-8 monza motor mounts modified (need to have a 1 inch plate welded to them for the v-6), regular GM long water pump or I could use the S-10 brackets if they fit under the hood of the monza), V-6 monza radiator."

9G.1 Cadillac 500ci V8 General notes

Todd (tallen_77346) offers this advice:
"I'm the guy that WAS doing this swap. The engine physically fits. Here is what you have to do to make it happen:

1. Forget about power brakes. It won't work with the factory booster. Aftermarket may work.
2. Custom headers are required unless you use the factory manifolds. Big Block Chevy H-Body headers will NOT work. Yes, new flanges will allow them to bolt to the 500, but the ports exit to far forward causing the back tubes to go through the upper A-Arm!!
3. Forget power steering, the 500 hits the long steering gear box. For the manual gear box, the lower, right, bolt hole flange on the block must be ground off to clear (viewed from the front).
4. Forget factory A/C. The factory heater only cars have a cover that will fit with minor clearancing!
5. Motor Mounts: Custom mounts are not very hard if you have a welder. Use steel bolted to the front of the engine to attached to brackets on top of the frame rail (similar to the Hooker small-block mounts).
6. As with all big-block Chevy H-body swaps, you must install a new steering shaft that has an extra U-joint and a carrier bearing (this snakes the shaft farther out than stock to fit the big block).
7. 472/500 Caddys are about 1 1/2" wider than a big block chevy and about 2 inches longer (measured from Water pump studs to the back of the engine). You must notch the sheet metal near the bottom of the radiator to allow room for the crank pulley.
8. The stock Monza V-8 radiator still fits with about 1/4"-1/2" clearance!! A pusher style electric fan setup mounted on the outside of the radiator will be necessary. An aftermarket radiator will probably be necessary to cool this beast!!
9. The firewall near the steering column will need to be clearanced slightly to keep the driver's side head from rubbing.

As you can see, there is a bunch of work necessary to make this work. The 500 is cheaper to build than a big block chevy up until the 450-500 horsepower level, however, the custom headers alone are EXPENSIVE. Stock manifolds (ported) would be much better (as far as money goes). This is the very reason why I decided to use a Big-Block Chevy after all. The 500 (with an aluminum intake) actually weighs about the same as an iron Small Block Chevy (this allows you to use the stock V-8 springs).