VEGA CONVERSION TIPS: A COLLECTION OF INFORMATION
from various websites
Using the 700R4 Automatic Transmission
One tip that can also help you -- try doing all the assembly (trans+shifter) while it’s out of the car... it makes it easier to sort out bugs
Dual Exhaust
Run both pipes on the passenger side, right next to each other and then up and over the rear end and put both mufflers side by side next to the gas tank, where the stock muffler was. I am using 2 1/4" pipe, with a H pipe, and Edelbrock stainless mufflers. It's a tight fit but looks and works real well. Doing it this way also gave me some ground clearance and you don't see the mufflers hanging way down under the rear seats. This works very well on a Monza- the Vega muffler mounts behind the rear axle, so it will be a bit tougher to adapt duals if you keep the muffler in the stock position.
Speedometer
Speedometers are pretty easy to adapt. The actual 'rate' of speedometers is all the same. What changes is the pickup gear in the transmission. This is how I think of it. Within the Vega lineup: If a Vega is moving at 60 MPH, the tires are covering the ground distance at that 60MPH. Staying with a standard tire size, all tires rotate at the same revolutions per minute. Different rear end gears will require the drive shaft to turn at different rates. (Faster for 4:11 gears, slower for 2:93 gears). The speedometer pickup is in the tailshaft of most transmissions. It turns in proportion to the drive shaft. No matter how fast or slow the engine is turning, or what gear the transmission is in, the speedometer picks up number of turns from the drive shaft. Since rear end gears change the number of drive shaft revolutions per measure of distance, then the pickup gear has to change based on the rear axle gear. GM color-codes these pickup gears. Find the pickup gear that goes with the rear axle you will use. Or, consult a parts man about which gear is correct.
All speedos are standardized for 1000 cable turns per mile. First get the tire diameter. This can be calculated using the following formula:
Tire Diameter =
So for a car using 205-60R14’s
2 x 205/25.4 x .60 + 14 = 23.7 inches
Next, calculate you tire revs per mile. Dividing the diameter in inches into 20,800 easily approximates this. Then multiply by the axle gear. Now you have driveshaft revs per mile.
20,800/23.7 = 878 x 3.42 = 3002 driveshaft revs per mile.
You then need a speedo gear to get this down to 1000 revs per mile. Example, 205/60R14 turns 878 revs per mile. With a 3.42 gear, the driveshaft turns 3002 revs per mile. This car needs a 0.333 speedo gear ratio.
Drive gears are available in 7,8,9 or 10 teeth; driven gears from 17 thru 25. So for my car, 7 and 21 will be very close.
Adjusting V8 Spring Height
To make up for the shallower spring pockets in the pre-1975 lower control arms you'll need to cut 2 rounds from the springs. Caution: 1) Do not use a torch to cut the springs, as the heat will ruin them. 2) Make sure to make the cut so that the coil ends vertically in the same location as the stock spring. It needs to fit back in the spring pockets on both ends of the spring. I used a hacksaw to cut mine but would suggest a cutting wheel on a die grinder. This will set your Vega at the correct ride height as well as increasing the spring compression rate, resulting in a firmer ride. I really liked the results.
Rear End From S-10
The 3-link rear suspension setup in all Monzas and post-'75 Vegas is very good. It is similar to the H-Body configuration and the Third and Fourth Generation F-Body designs. The Camaro/Firebird setup from 1982 on was designed around the H-Body configuration. With that said, you can't find a much better setup for all-around performance than the stock configuration offered by the ’75 and later H-Bodies.
Be aware not all ’75 and later H-body rear-ends are the 7.5" diameter type. From 1976-1977, the Vega used either a 6.5" or a 7.5" rear end. From 1978 on, all H-bodies were 7.5" diameter. See the http://h-body.org/ FAQ website for details on where to find rear axle codes and matching ring gear diameters.
Suspensions
3 Link (Torque Arm) and 4 Link Suspensions
The factory 3-Link Torque Arm Suspension was the best design by far. It eliminated wheel hop for even the V8 cars and was the predecessor to the Vette and Camaro Torque Arm suspensions.
If you are putting out more horsepower than stock, it is probably a good idea to update the rear end in your H-Body. The stock 6.5" rear end in a Vega is a bomb waiting to go off. While the 7.5" found in Monzas and others is better, it probably won't hold up very well over 300 hp.
You can also use the rear end out of an S-10 Truck. Try to find a 4-cyl truck since they usually have a 4.11 gear and sometimes a posi unit. The S-10 rear will hold up pretty well until you start making mega-power. You will have to weld all the brackets from the Vega rear to the S-10 rear. Because the S-10 rear is actually 1" narrower than the Vega rear, you can work with backspacing to get a 9-10" tire in the fender without tubs! You also get the five-lug pattern with the S-10 rear.
It is possible to use just the axles, ring, and pinion from an S-10 rear end with some changes to different bearings. Instead of using the whole rear end from an S-10, you can also just use the axles from an early '80's 2wd S-10 You can only use 2-wheel drive Chevy S-10 and Blazer axles for a 5-lug upgrade. The axles are the same spline (26 spline) and are only 1/16" shorter than the stock Vega axles. This makes a 5-bolt swap easy. Grab the larger drums and backing plates from the S-10 as well. Besides being larger, they are often finned (better cooling) and some of them are aluminum (lighter). This swap will only work with '76 and up 7.5" rear ends.
In some cases the shorter axles result in the rear brake drums (also 5-lug) rubbing against the rear backing plates (dust covers) around the edge where the drum meets the back cover. The backing plates may have to have about 1/16" shaved of the lip facing the drum to prevent rubbing. Mine do not rub, but if you find that yours do just remove 1/16th inch from the edge of the backplates. To do this, I would suggest scribing the backplates 1/16th inch in and using a handheld grinder, remove the excess metal. Then smooth the edge with either a file or sandpaper. NOTE: 1975 and earlier vehicles have 9" diameter by 1" wide brakes and therefore a smaller backing plate. Later model (1976 to 1980) backing plates will be required for this modification.
The 7.5" Chevy S-10 gears will fit the H-Body case, but the main problem is that, in the differential case, the hole for the pinion bearing is smaller in the H-body differential than in other GM 10-bolt differentials. You can either get a machine shop to enlarge this hole or use a special pinion bearing and race.
You`ll need; S-10 gears, S-10 posi unit (if it’s posi), and S-10 axles (2 wheel drive only!) S-10 rear end yoke, S-10 drums (if you use the S-10 axles). If you reuse the Vega axles, check if the carrier of the S-10 is a 26-spline unit. The S-10 pinion gear requires Timken bearing #16143, Timken bearing race #16283, and National seal #8610, S-10 pinion yoke, and "Combination" U-joint (Dana #5-3022X). As with most all gear sets a specific gear carrier is required for a specific range of gear sizes, so the carrier must be the correct series for the gear set that you want. In other words, you need to know what series the carrier is or what gears were installed on it from the factory. A 2-series carrier fits 3.08 and numerically lower gears (3.08, 2.93, 2.73, 2.56, and 2.29), while a 3-series carrier fits 3.23 and numerically higher gears (3.23, 3.42, 3.73, and 4.10). The exception to this is if you purchase custom gears specifically made to fit your specific carrier (i.e. you can buy 3.23, 3.42, 3.73, 4.10, and 4.56 gears to fit the 2-series carrier). If you are at all performance minded, you will probably want to have a positraction unit in your H-Body. Stock posi rear ends for these cars are actually quite abundant, but can sometimes be pricey. You can upgrade to a new or different posi carrier by getting a 26-spline carrier of the right series for your gears Auburn also makes an aftermarket posi unit for the 7.5" rear end as well. Also, the Camaro and S-10 7.5" posi unit will fit the 7.5" H-Body rear housing. I have had a posi carrier from a Camaro 7.5 rear installed in my H-Body rear since 1988 and it works fine.
So, the list is:
NOTE: Installing new gears requires setting the proper pinion depth and carrier position. Doing this wrong will destroy your gears. Even the most die-hard shade tree mechanics leave this to a professional. If you want to try it anyway, this is the basic procedure and tips from Robert (twelve_second_vega): "When you pull the carrier, mark the shims on the side of each bearing. They are cast iron and must be handled with care. Put a new crush sleeve on the pinion and install it in your 7.5" housing. Set the preload (about 10 inch pounds with used bearings) and set the carrier in place. Gently tap the shims you took out into place with a PLASTIC hammer and torque the caps. Only 1 gearset I installed needed to be reset. 99% of the time, you can just throw them in and go. If the backlash is off (.005" - .008" with used gears) you will need different shims. Subtract the amount you need (in backlash reduction) from the right shim to move the ring gear deeper into the pinion. BE SURE to add this SAME AMOUNT to the opposite shim. You MUST maintain the preload on the side bearings. When properly set-up, you will have to pry the carrier out of the housing and putting shims back in should not be easy either."
How to build a better 10-bolt
I have always had a problem with the rear axle that came with my Trans Am: Known as RPO Code GT4, my original axle assembly came equipped with ten-inch rear rotors, coupled to 26-spline axles that were splined to an Eaton Guv-lock differential with a 7.5-inch 3.73:1 gearset. Now I imagine that this was an acceptable performance piece when the car was new, but with only 39,000 miles on the car, the clutches had already worn out. This becomes a problem with the Eaton unit, as the system will free-wheel like an open differential then lock solid with a bang. I lived with this malfunctioning differential for 90,000 miles! Since I was going to Gingerman raceway this year, the LAST thing I wanted to happen was an unexpected lockup of the differential. It upsets the whole suspension and will quickly send you into a spin. It usually happens in conjunction with a hard upshift. Another problem with the GT4 is the original RPO J65 rear disk brakes: They have a faulty spring inside the piston that causes them to retract from the brake rotor. This results in excessive pedal travel, and no emergency brakes. Mine were corrected with a set of revised pistons from GM, but when I broke off a bleeder screw in the left caliper, I knew it was time to update.
My goal is to design a rear axle assembly that will hold up to about 400 horsepower. I looked at buying a 9-bolt, but parts are too expensive and hard to find. I looked at getting a Dana 44, but they were non-existent. A Ford 9-inch has alignment problems, and are easily $1500 for an entry-level assembly. What I settled on is the only solution that costs under a thousand dollars: A 10-bolt that uses the Gleason/Torsen heavy-duty Torsen differential, and aftermarket axles.
10-bolt Performance
The Torsen heavy-duty differential is a unit that is currently being sold in the 1999 Pontiac SLP Firehawk. The LS-1 based Firehawk outputs about 345 rear-wheel horsepower, and offers a warranty to boot. Therefore, a goal for a 400-horsepower capable 10-bolt seems attainable with this differential. Research indicated that the Torsen is a direct bolt-in to any 3-series 10-bolt carrier. Thus, the Torsen should be able to fit in my 1984 GT4 axle housing.
Unfortunately, the GT4, being a pre-1989 axle, uses 26 spline axles whereas the Torsen employs 28-spline axles. Therefore, a new set of axles is in order. For these axles, I called Greg Moser of Moser Engineering. Moser Engineering can cut a set of 28-spline axles for the third-generation F-car or an H-body which are much more capable of handling the high-torque demands of a performance application. Thus, the Moser axles were chosen in favor of stock 28-spline axles from a junkyard. There have been reports of broken OEM axles squirting out onto the racetrack and I want to avoid this possibility.
AAM Oil-cooling Differential Cover
This cover has a patented oil cooler cast inside it. I saw a lexan version of this cover in action at the 1997 SAE International congress--- Very snazzy. It catches gear oil as it is flung off the ring gear, and channels it through passages in the differential cover to the holes on either side of the differential case: These holes, normally used for case spreading, open up into the axle tubes on the other side of the differential bearings. The oil is dumped into the axle tubes, where it flows both to the load bearing at the wheels, and back into the differential case. Thus, your axle tubes become a method with which excess heat is drawn out of the oil. The AAM cover is also nearly half an inch thick at the mounting flanges, which should greatly increase the rigidity of the axle assembly. This should further increase reliability of the gearing.
One note: Mike Galda has just informed me that SLP is now shipping a template that shows some grinding operations that you need to perform before installing the differential. You need to grind a drain-back path for the oil.
Troy (QuikGTA@hotmail.com) has these suggestions on further increasing the strength of the 10-bolt:
Troy runs a 1992 Trans Am GTA, and is using Richmond 3.42 gears, National Drivetrain 28-spline axles, and a Summit rear girdle, along with the heavy-duty Torsen differential.
Installation of the Gears
Most people are scared of installing their own gears in a differential for fear that they will screw something up and blow the whole shebang. For good reason! After getting ripped off by a certain automatic transmission shop on a ring & pinion install, I got smart and found specialists who do gears every day: K&L Unlimited in Lansing, Michigan. K&L doesn't do automatic transmissions: They do gears. They also set up manual transmissions, and build custom driveshafts. They balance driveshafts. Pretty much any final drive piece is fair game. They don't have a lift, so you'll have to pop the parts out of your car yourself. Prices are reasonable, too! This gear installation cost me $192 in labor, which is (imho) very reasonable given their level of experience.
The Ring & Pinion chosen are 7.625" 3.73:1 Richmond gearset. I bought these gears a few years ago, and already had them in the axle assembly. It was a question as to whether they would be any good after nearly 40,000 miles of driving, but they showed no appreciable wear. Therefore, we re-used them! Richmond 3.73 gears are rather noisy from the outset, but are strong.
K&L Unlimited
2919 S. Martin Luther King Blvd.
Lansing, Michigan
Phone: (517)882-9101
Fax: (517)882-7544
The Torsen heavy-duty differential was purchased through SLP-Performance on their Internet specials page. SLP offers two different differentials: An OEM take-off version, and the heavy-duty version that they installed in the 1999 Firehawk. The OEM is a real bargain, being virtually brand new, and already sporting bearings. Bearings cost $25 or more per pair anyway, so this is a good deal. The heavy-duty version is brand new, without bearings, but comes with a cast aluminum differential cover from American Axle and Machining (AAM). The Torsen differentials are designed for use in a 3-series carrier.
10-Bolt Update
I had a conversation with Richmond engineers a few months ago on the reliability of their 7.5" ring & pinion. I wanted to know if it could hold up to 400 horsepower and they said, essentially, no. Actually, they said that 400 horsepower was "pushing it", but that a stud girdle would help greatly in preserving gear life. Richmond claims that the biggest flaw with the 10-bolt design is the flexibility of the case. When under heavy load, the pinion walks up the ring gear face, and forces the case apart. This totally throws off the gear alignment which causes premature gear failure. The key, according to Richmond, is to maintain alignment by increasing case rigidity. They claim that a stud girdle, like the one offered by Summit Racing equipment, or the TA Performance piece offered by Fast Toys, will "essentially double" the gear life of a differential used under high load conditions. A stud girdle is a very stiff cast aluminum differential cover, with studs that extend to the load bearing caps. It ties the rear of the case to the bearing cap surface, greatly increasing rigidity.
In any event, Richmond said that the useful power range of a 10-bolt stops at 400 horsepower. Further conversations with Steve Spohn along with Phillip Reddy concur with this assessment. They have both experienced failures when power increased above 350 HP, especially under launch with a modified suspension and drag racing slicks.
Related links:
Rear Disc Brakes
'98 and newer Camaro and Blazer that share the new brakes with aluminum calipers and separate drum style parking brake. The rear caliper pistons are 1.900 inch diameter (38 mm). Front Monza calipers are 2.500 inches. Together, this system will have a brake proportion of about 62/38, which is not enough front bias, so yes, I would recommend that you keep the stock proportioning valve. When you connect the brake lines to the rear calipers, make sure you use some short flex hose because the caliper moves relative to the axle. The best method is to use hard lines from the brake hose T to each end of the axle and weld a small bracket to hold the line. Then use about 6 inches of flex line to the caliper. This flex line will have a banjo fitting on the end and attach right to the caliper with a hollow bolt.
Front Disc Brakes
Get a pair of complete S-10 spindles (around $50). Rebuilt S-10 calipers and new ’76 Nova brake hoses are available from Auto Zone. Cross-drilled and slotted rotors fare available from J.C. Whitney or Summit Racing for $70-80 each. I got new bearings and seals from Autozone. The bushing adapters from Bob Gumm are Loc-Tighted (red) and installed into the spindles. I used a plastic hammer to tap them in to ensure they were seated - I didn't have to trim them. I had to install one lower ball joint because of a boot tear. I got the tools from J.C. Whitney. The spindles raise the front height by 1 inch. It's definitely a good swap.
You need to get to a mid seventies Caddy Eldorado with 4 wheel disc brakes. You need the proportioning valve and get the master cylinder for a core. I traded the core an Autozone for a rebuilt and replaced the Monza stuff. The brakes work real good. I believe I used a '76 Eldo with Hydro-Boost brakes. To verify that it is a disc brake master compare it to the Monza. It should have the cast divider in the middle of the master and not biased to one side like the Monza is. It should also be significantly taller to compensate for the additional fluid required for disc brakes. The master replaces the Monza unit perfectly - it is taller for more brake fluid volume (needed for the disc brakes) and the revised system stops the car like you can't believe. The Caddy master cylinder bolts right up to the Vega/Monza Power Booster. I spent endless hours in junkyards and Auto Zone trying to find a bolt in. The master works great. The chrome Mr.Gasket cover also fits (to add a custom toucoh). You'll be the second one with this particular combination. Finding the Caddy in a yard will be the challenge. The calipers on the Caddy are similar to the size we're using so the proportioning valve works well. As an added bonus the proportioning valve is also a BOLT IN! It has the same dimensions as the Vega/Monza unit.
I now have the easy fix listed below: Bob Gumm's spindle adapters $60.00 plus shipping. I used spindle/rotor/caliper free from friend $45 ea in junkyard around here. I replaced the rotors (rusted) from Auto Zone $23.99ea.. Repacked wheel bearings. New seals (stock s-10) $1.99 each. Auto Zone Reman Calipers for S-10 $9.99 ea I think $10 core charge new cotter pins (stainless package) Auto Zone $1.59. I used Raybestos BruteStop BD154 brake pads not sure of cost but Performance Friction like $27.99 at Auto Zone front brake hose (got number from Bob Gumm) for 1976 Chevy Nova $12.99 ea Auto Zone. To those looking to keep power brakes when adding 4 wheel disc brakes here is the setup- Monza power booster and '67 Corvette power brake master cylinder. It bolts right up. Don't forget the fender well brace. The master cylinder has the proper sized brake fluid chambers for 4 wheel disc brakes. You'll need to swap the lines to the proportioning valve front to rear. I'm using the Monza proportioning valve and I shortened one brake line. It all fits and a chrome cover is available aftermarket. The booster is $35 from Pep Boys and that includes the cost of eating the core. PROBLEM SOLVED!
LIST:
The S-10 spindles have longer tierod arms. It may rub at one point from lock to lock right when the Pitman is lined up with the steering box with the front wheels straight. You can't feel it in the steering wheel but it rubs enough to cause the tierod to deflect a slight amount. I used my die grinder to take off about a 16th of an inch off the centerlink to get it to go by without hitting but its still close.
When I changed my idler arm that there was an adjustment that you could do by turning the arm while holding the part that bolts to the frame that would effectively raises or lowers that end of the idler arm and centerlink. The objective is to have the centerlink level on both ends, you don't want one end higher than the other or it could screw up your geometry. This may be a possible reason why the centerlink is rubbing. If you just bolted the idler arm on the way it came out of the box without performing this adjustment this might cause rubbing.
H-Body/S10 5-Lug Front Suspension Upgrade
NOTE: Bob Gumm has an excellent how-to guide on his v8monza.com website. Please click here to read it.
Steering Column
How do I swap my non-tilt steering column for a tilt unit?
The columns interchange, but you'll need the right coupling for the steering box, and the ignition switch must be rotated 180 degrees.
Larry (vega_man_larry) adds:
"Any tilt column will work. Just make sure you get the column coupler shaft that connects to the steering gear box. The tilts I have found are on power steering cars. If you don't have power steering (I don't) you have to make a coupler from the upper part from a tilt column and the lower from the standard steering shaft. Heat up the shaft using a propane torch to melt the nylon that holds the shaft together where the shafts slip together for the collapsing feature. Then put the two parts you want back together. I drilled two new holes to line up with the inner shaft and cemented it back together using my wife's glue gun (basically replacing the nylon. Don't weld the column back together as you will be defeating the collapsing feature!"
Alternative Mounts
OK all, here is the scoop on how to retrofit a set of 68 327 Camaro motor mounts to your V8 Monza. However, there is one catch. First, you must be willing to hack up your original V8 motor mounts. If you don't want to do this then there are other options. Second, you must take your time doing what I will explain. Let's get started. You first need to have full access to your motor mounts (this means removing headers, etc. You then place your car on jack stands, making certain the car is level from side to side. Next, measure from the block (each side) to the floor, logging these measurements. Now, place a flat piece of wood on a jack and slightly lift on the engine at the oil pan. Unbolt the motor mounts from the mounting pads(not the block). Now, remove old mounts from engine block. Go to the auto parts store and purchase a set of 68 327 Camaro motor mounts ($10 each). Now comes the scary part. First, drill apart the 3 rivets that hold the flat plate of the block side of the motor mount and the clamshell that holds the rubber portion together. Separate the two halves, giving you better access to the loop of the mount. You are going to cut (with a steel cutoff wheel in a die grinder or drill motor) your original motor mounts at the "bend" on each leg where the leg bends going into the rubber portion of the mount (not the nut end of the leg). It is critical that you cut as close to the bend as possible. Be careful to not cut downward from the bend on the leg too far towards the welded nut end. You will need as much of these legs as you can get. Now, bolt the Camaro motor mounts to the block. Remeasure your distance from the block to the floor and match the height to your earlier measurements. NOTE: since your original mounts probably let your engine sag, you may wish to raise the measurement by 1/4" to 1/2" to get the motor where you want it. Next, bolt the cut off "legs" in their position on the motor mount pads(the pads on the unitbody portion, not the block). CAUTION!!!! this next part is the most important part of all. Manuever the legs into the proper position (install the bolts, but just finger tight) on the pads and line them up so that the holes in the sides of the Camaro motor mounts will provide the most "meat" on the legs to hold the motor once you drill the holes in the legs. So, to rephrase, you are using the "legs" of your original mounts, drilling holes in them to line up with the side holes in the Camaro motor mounts and using grade 8 or grade 5 bolts and lockwashers to bolt it all together. The best way to get the markings on the insides of the "legs" of where to drill the holes is to use a 90 degree bent pick and scribe through the holes in the Camaro mounts onto the "legs" of your original mounts. Once you have the locations scribed of where you are going to drill the holes, simply unbolt the legs, drill the holes, put the legs back in place and bolt it all together. There you have it--simple, straightforward and cheap. However, if you are afraid to cut your V8 mounts ask yourself what is better: Driving with loose, floppy motor mounts or having new rubber motor mounts. Finally, for those of you who are concerned about the strength of this set up, I am running a 350 horse 350, with 3.73 gears, Auburn posi, 15" x 8 1/2" Centerlines on z rated tires and nothing and I mean nothing moves. This set up is the best thing I have done to my Monza. Also, I recommend that you put Energy Suspension's polygraphite transmission mount in while you are under the car. You will have to cut the bottom plate off of your original tranny mount and drill a 7/16" hole in this plate to bolt into the new Poly trans mount. Once all this is done your V8 hbody will be solid and secure.
Replacing the Stock Elbow with the F-Body 1LE Elbow
This method totally removes the baffle and replaces the stock elbow with the larger Camaro 1LE (non-air-conditioned) intake elbow. The 1LE elbow doesn't have the hole in top like the Impala does, and doesn't have the hole in the bottom like the air-conditioned Camaros and Firebirds have. The '94 elbow has no provision for the vent tube from the OptiSpark distributor, while the '95 has a connector in the top for it. The '94 can be modified to accept the vent hose by puncturing it on the bottom. The Camaro elbow is wider than the Impala elbow and can thus flow more air. They are slightly expensive since they include the MAT sensor. This method is recommended for those looking for maximum flow into their engines and are willing to pay the price to keep only GM parts in the engine.
Parts Required: A '94 or '95 non-air conditioned 1LE intake elbow. The list price is $80-$90 (the '94's are cheaper), but some dealers sell them for as much as $150. P/N 25147210 is the '94 1LE w/o vent nipple ($95.63 retail) and P/N 25147187 is the '95 1LE w/ vent nipple ($155 retail!).
Procedure (from Scott Mueller):