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Vega crazed

The Following is transcripts of email correspondence I've had with an engineer who is also an experienced Vega modifier    "Gary Derian" <gderian@cybergate.net>

Intro   Gary's Vegas Vega Mods Power2weight
 Engines etc.   Exhaust

Torque arm ideas  Torque Arm engineering  Suspension/Steering Chassis tuning  Tranmissions

Vega? Did you say Vega? I have 3 Vegas, all 5 speed '76's. One is a stock daily driver red with yellow flames wagon. One is my son's 229 Chevy V-6 Viper blue with white stripes, Camaro brakes, Corvette wheels, etc. The third used to have a 215 Buick aluminum V8 and was to get s 350 HO but I've abandoned that project to install a Cosworth Vega engine for my younger son. I still have the engine mounts and bellhousing to fit an old rwd style Buick V-6 if you're interested. I also have the 350 HO.

What I know is that GM used the V-6 in rwd cars to 1987. This engine used the old rwd Buick-Olds-Pont bellhousing pattern. GM began using the Buick V-6 in fwd cars in '82 or '83. There was 2 versions ofthe 3.0 Iiter, a short stroke and a longer stroke. This engine used the new fwd style bellhousing pattern, a smaller crank bolt pattern, and I think the starter is on the other side. I believe starting in 1988 or so, the new generation engine for the full size fwd cars had no distributor, port injection, and the oil pump was now directly driven by the crank like the original Vega engine. Also, the cylinder banks were shifted to align the connecting rods to the middle of the pistons. They were misaligned since the even fire engines were built in 1977. Later, I think in 1992 or so, the engine was redesigned again with a lower deck height, shorter rods, and a balance shaft among other changes. This is the current form used in the Camaro.

I don't know the engine mount location or bellhousing pattern of the Camaro engine but I think is uses the fwd bellhousing pattern and a special bellhousing to mate to a rwd tranny. There have been many changes to the current generation Camaro drivetrain. The trannys had integral bellhousings for a while but I think they now have separate ones but different than the old type. If you have no parts, the best bet would be to install a complete Camaro setup from a donor car. If you have lots of old style Chevy parts you should probably build an old style drivetrain with an older rwd style block.

Another option is the 4.3 V-6 from an S-10. This is 3/4 of a 350 and has always used the same Chevy style bellhousing pattern. The current Vortec version of this engine has a balance shaft and the good modern type fuel injectlon.

I am certainly not rich but I am an engineer.  I am a mechanic as a hobby.  The brakes on the Vega are a combination '69 Camaro, actually from a '74 Nova, on the front and '80 Cadillac Eldorado rears.  I chose these to get a 70/30 brake distribution without a pressure regulator.

The front calipers have been used on many GM cars from 1968 to 1998.  There are some minor differences over the years such as metric fittings on newer ones.  I used the entire spindle from the Nova and modified the control arms to use the larger ball joints.  These spindles were used on '64-'72 Chevelle, etc, '67-69 Camaro, etc, and '68-74 Nova, etc.  These spindles are taller then the Vega spindle and increase the camber gain.  Begining in 1969, single piston sliding calipers were used.  I also increased the caster angle from -3/4 to +5 by moving the lower ball joint location forward and making new upper control arms.  The car uses power steering from a '84 Camaro Z-28 (bolt in) and has a special spool valve.

The rear calipers, rotors and brackets were adapted to a Monza rear axle.  The axle shafts were redrilled with the 5 on 4 3/4 bolt pattern.  The parking brake levers would interfere with the inner wheel well so I spaced the calipers and rotors out 1.4 inches each side.  This worked well since the front end is wider than with the Vega spindles.  I understand that 2wd S-10 axles from '82 or 83 are direct replacements for the Monza axle (7.5 ring gear) to provide the 5 bolt pattern without redrilling.  My cars are '76s so they all use the torque arm and panhard rod rear suspension. This is as good as it gets for a live axle.

The Corvette wheels are fronts from the 1984 model and are only 8.5 inches wide.  These wheels are offset 1.3 inches and compensate for the wider front and spaced rear.  I am using 245/45ZR16 tires, smaller than the Corvette size.  They fit without flares but they are too big.  I recommend 205/50R15 front and 225/50R15 rear on 15x7 rims.  I think 4wd Blazer wheels should have the correct offset and size.

I recommend the V-6 over the Quad 4.  There have been many durability problems with the Quad 4: timing belt idler, head gasket, etc.  Also,  the intake system is all wrong for a rwd car.  The throttle body would face the rear.  This stuff could be fixed but it would be a lot of work.  If you can find a complete Camaro donor car the conversion would be easy.  By the way, I got all my parts from junk yards and have about $5,000 total invested in the V-6 Vega.  My daily driver is only a $2500 investment.  I expect to have $3000 or so in the Cosworth.  These costs are for like-new cars with everything working and good parts.  A lot of man-hours, though.  I have already driven my wagon 40,000 miles over the past 3 years.  This is not expensive.  Also insurance is cheap.  I often tease my wife that her Volvo cost more than all 3 of our other cars put together.

Nice to hear from you Dean,


    The S-10 axle sounds like a good way to go.  So does the Tec II injection.  The Camaro T-5 mounts at a 15 degree angle.  A matching Camaro bellhousing will make it all fit.  I am using a hydraulic throwout bearing from Tilton to release the clutch.  The cable clutch will not last long with a V-6, too much friction.

    Positraction will definitely make it easier to loop the car, but you can get more power down before it breaks away.  Be careful and practice.  Its actually easy to control if you are aware.  Without posi, you will spend a lot of time spinning one rear tire.  Don't forget though, with an open differential, both rear tires always get the same torque.  Its just that when the first one starts to spin, thats all the torque it can take, and thats all the torque the other rear tire gets.  With posi, no tire spins until both do.  More torque goes to the more heavily loaded tire than the less loaded one.  This creates power understeer until the tires begin to slip then there is a quick transition to oversteer.

    In my opinion, a Torsen differential is best, followed by a viscous
clutch, then a conventional clutch type posi.  The Torsen will make the transition from power understeer to power oversteer much smoother but it will still happen.  At any rate, with a little practice on wet and empty parking lot you will have no problem.  My son's 229 with carb will break the tires loose in the middle of first gear.  Your's should be faster.

    I would recommend a 3.42 axle ratio with a Camaro V-8 T-5 tranny.  The V-6 versions had a much lower first gear and wider gaps between the lower gears.  A 2.92 or 2.73 would work with the V-6 tranny.  The V-8 gear ratios are 2.95/2.05/1.40/1.00/0.62.  The V-6 ratios are 4.06/2.40/1.50/1.00/0.84.

The early V-8 trannys, '84-85, had a 0.72 5th gear.  The '90 and later trannys were "World Class" designs with better synchros.  After '89, the trannys had only the electric speedo pickup.

  The Vega chassis is pretty flexible.  I don't know of any subframe connectors.  My cars are '76's and are a little better.  Perhaps you can overlay some sheet metal on the rocker panels.  The factory ones are pretty small and tuck under the body.  Nice square ones would stiffen hings up necely.  Look at a Mustang convertible for ideas.  Ford used rocker panel stiffeners.  Another weak spot is the base of the windshield pillar.  Welding16 gauge sheet to strengthen the joint to the door hinge pillar will help a lot.  Also, a cross body tube beneath the dashboard would help.  I have not done any of these strengthening modifications to my cars but they will help.  Also, replacing the bumpers with fiberglass replicas will save 150 lb and make the car more responsive.
    The front brake pistons are 2 15/16 diameter and have an area of 6.78 square inches.  The rear pistons are 2 1/16 and have an area of 3.34 square inches.  The total area is 10.12.  That makes the front 6.78/10.12 and the rear 3.34/10.12.  The front tires are a little shorter than the rears the overall I am very close to 70/30.  Disc brakes have a linear relationship between line pressure and brake torque.  Drum brakes do not.  A drum brake's braking torque increases more than the line pressure because it is self energizing.  You must use a proportioning valve with a disc/drum setup.  The latest Blazers have 4 wheel disc brakes.  Perhaps one of those axles would work for you.

Good luck!
Gary

A V-6 Vega is nearly the same as a 3/4 scale V-8 Camaro. Thats why I recommended the V-8 tranny, its gears are well matched for the smaller engine in a lighter car. The new Camaros have different tranny mounts, built-in hydraulic clutch slave cylinder, and electric speedo. I don't know about the V-6 but the new V-8 bellhousing bolts to the block and oil pan to form a very rigid attachment. At any rate, there is nothing wrong with using a complete matched engine/tranny from a Camaro. I don't know
what gears are used in the Camaro rear axle. If the newest tranny still uses the 4.06 1st gear, I think a 2.93 or so axle ratio would be good. If the S-10 axle comes with the 3.42 leave it in. If it has a ratio in the high 2's, I would leave it alone and save even more money for now.

I don't know where to get a torsen for an S- 10 rear. Try Drivelines
Unlimited in Detroit. Check Car Craft or Circle Track ads.

I think your biggest problem using the '96 Camaro tranny would be the speedo drive. Vegas of course had a mechanical cable. The Camaro tranny has a toothed wheel on the output shaft and a pickup coil. This generates an AC signal to the PCM which in turn operates the speedo, cruise, etc. There are some aftermarket companies that make speedo gear conversions for these trannys. Or you could use an electric speedo. You may need a
conversion box to set the input to the speedo.

I think you can make an excellent car with either the 4.3 or the 3800.  The complete Camaro setup would be more modern but have less flexibility. Your choice for accessories is reduced with the 3800 and things like engine brackets would be Camaro only stuff.

        You will have difficulty attaching a torque arm to the S-10 rear.  I would not weld to the cast iron case.  You could make a bracket  that bolts to the housing using the cover bolts.  The torque arm could then be a 2x2 rectangular tube that goes foreward under the driveshaft.  This has the advantage of providing clearance to the floor and allows dual exhaust on either side of the torqu arm and drive shaft.  The Vega/Monza torque arm was a tall channel similar to the Camaro arm.  The '76 and later Vega floor pan was modified to clear it, especially in the area between the rear seats.  I think a Monza/Camaro style torque arm would hit the floor of your '74.  A torque arm that attaches to the axle bolts would also provide a center mount for a Watts linkage which is superior to a panhard rod.

        The Vega/Monza torque arm had a large round rubber bushing at the front.  It bolted to a bracket that in turn bolted to the tailshaft of the tranny.  The forward end of the Camaro torque arm has a tab that slips into a rubber/metal bracket that bolts to the side of the tailshaft.  You could use a Camaro style attachment for the Camaro tranny.  Both these methods of attaching torque arms give less than optimal geometry.  The vertical reaction of the front of the torque arm is useful in providing anti-squat. If it is so far foreward the anti-squat is lost.  If you are fabricating your own torque arm anyway, why not make it shorter and attach it to a crossmember?  I think a half length torque arm would work well.  Calculate the anti-squat to make sure.  Don't do any suspension design by the seat of your pants.  While were on the subject, nothing says that the torque arm must be in the middle.  Since axle torque lifts the passenger side rear tire during acceleration, a torque arm on the passenger side would counteract this torque and make more even loading.  It would also counteract the engine torque.  This type of arm sould be welded to the axle tube and come down and foreward below the floor pan.  If you're interested, I could provide more details.
      

Narrowing a Camaro axle would be expensive.  I think it would be much easier to get a Monza axle housing and install the S-10 axles.  The 7.5 inch gear and differential case are nearly the same as the Camaro and S-10 and should be plenty strong for a V-6.  The Chevy aftermarket Camaro rear axle uses a Dana 44 which is really strong and has torsen differentials available for it.  At some point you may want to put in a Corvette aluminum rear end.  The track is a bit wide but the gearcase and attachments will fit.  Its lightweight and strong.  Choices from the sublime to the rediculous!       
 

Take a side view of your car.  Call the point where the rear tire touches the ground "P".  Draw a line up and foreward at an angle "A" to the ground.  tanA=h/l where h is the center of gravity height and l is the wheelbase.  If the foreward mount of the lower control arm is on this line, the rear suspension has 100% anti squat.  This means the tendency of the rear axle of the car to drive under the body and jack up the rear exactly cancels the rear weight transfer under acceleration.  If it is below, there is less than 100% (the rear will squat a little).  If it is above this line, the rear of the car will rise as the car accelerates.  The h for a Vega is about 20 inches.  The l is 97 inches.  This is anti squat just for the rear control arms.  

   There is also anti squat from the torque reaction of the rear axlepushing up on the front of the torque arm.  The force to accelerate the car at the rear tire footprint times h results in a torque that causes the body to squat.  This same force times the tire radius is the axle torque.  Divide this torque by the torque arm length to get the upward force at the front of the torque arm.  This upward force times the horizontal distance between the front of the torque arm and the center of gravity results in a torque on the body that counteracts the squatting torque.

    Lets say the trailing arm location gives 50% anti squat (this varies with ride height and tire diameter) and the torque arm gives 25%, there should be a total of 75% anti-squat.  This is a lot.  Drag racers use 100% or more. Road racers use 50 to 75%.  The long torque arm used on Camaros and Monzas anchor to the body in front of the center of gravity and increase squat, but not by much.  Short torque arms were used in Chevettes which was an old Opel design from the 60's.  The Chevette arm is part of the rear axle and is a torque tube.

    Running the torque arm below the center section would limit ground clearance.  It would be better to route the arm below the driveshaft then around the center section to the bracket which bolts to the cover holes. Alternately the torque arm could split near the rear u-joint and weld to the axle tubes, or as I mentioned before, it only has to be on one side. 

Vegas did come with power steering.  They used the standard GM box.  Some Monzas used a very light duty box.  Don't use that one.  The steering column is different.  There is a lower bearing at the firewall and a second joint in the engine compartment just below the brake cylinder.  You can use a column from a Monza.  Power steering was common on Monzas but not on Vegas. Get a steering box from a Z-28 Camaro.  It has much better valving.  The steering box bolts in place.  The centerlink is different (shorter on the steering box side).  Monza/Vega is the same.  '80's Camaros had a different steering box spline than the Vega/Monza.  Racing U-joints are available or use Camaro steering column sections to make it fit.  Be sure you don't defeat the collapsing feature.

    The Vega frame rail is pretty weak and flexes a bit.  Weld it up and add a cross member in front of the crankshaft pulley to stiffen it up.  A rack and pinion would be better if you could find one that is built for high performance (good steering feel).  You could mount it stiffly and get the bump steer right.  Corvette/Camaro are great but too wide.  If you shorten the tie rods, make sure the bump steer is good.  Rack mount height and tie rod length is important.  With G-body spindles and brakes you should check bump steer anyway.  The car should toe in as you jack it up and toe out as you compress the springs.  This way, when you corner, the wheels will steer out of the turn a little (roll understeer).  Try to get the bump steer close to zero.

    Use a pump that matches the steering box.  The new pumps are small and have remote reservoirs.  Rack and pinion are high volume low pressure. Recirc ball is low volume high pressure.  You will have to fab your own brackets.  The stock location of the pump is low on the block which interferes with the steering box on a Vega.  Its really a small car.

A Tremec should be bulletproof behind a V-6.  You'll be ready for a 350 when you grow used to the V-6 (I'm kidding, please resist this temptation).  I think the Tremec mounts straight up and a standard bellhousing will work. The Tremecs I know are for Fords.  Make sure yours has a Chevy bolt pattern.If its for an '80's Camaro, it would mount at an angle and require an '80's Camaro bellhousing.  If it fits straight up, it will fit any Chevy bellhousing from '55 to '92.  I have a Monza V-8 bellhousing that has cable cluch provisions if you are interested.  It fits any standard Chevy manual transmission.  Its in the V-6 car now but I will be changing to a Camaro T-5 soon.

    If you are just putting the S-10 rear end in the Vega, you must be going to use the stock 4 link suspension.  Wheel hop city!  Any street 4-link will do a poor job of holding a live axle.  The torque arm and panhard rod take the place of the upper links and do a good job.  The Vega setup was designed to save space and as a result doesn't control the axle very well.  It is also very soft to stop 4 cyl vibration from being transmitted into the body.  

Those weights on the rear of the upper arms are vibration dampers.  Replace the lower control arm bushings with urethane ones.  The uppers need to stay rubber to let the suspension move.  They're small and stiff anyway.  Raising the rear mount of the upper link on the axle will shorten the effective torque arm length and improve anti lift.  There used to be available cast iron brackets that did this.  If you are having mounts welded to the S-10 axle, have the uppers made 1 inch taller.  Check floor and exhaust clearance.

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 Every V-6 that I know has even firing within each bank.  Its the bank tobank firing that is even or odd fire.  A 6 cyl fires on average, once every 120 degrees of crank rotation.  A 90 degree block angle requires a 30 degree crank pin split to achieve 120 degree firing interval.  A 90 degree block without a split crank pin creates an odd fire engine with 90 -150 -90 -150  cylinder timing.  A 60 degree block requires a 60 degree crankpin split to get even firing.  There is no difference in exhaust pulses between a 60 degree block even fire V-6 and a 90 degree block even fire V-6.

It is very efficient to combine all 3 cyls of a V-6 bank into one log type manifold.  The exhaust events are separated enough to be independent.  If I remember, you are using the factory exhaust manifolds.  These are fine.  I don't think you will be able to fit a 2.5 inch exhaust tube to them.  The outlets probably will fit only a 2 inch tube.  Dual 2.5 is definitely overkill but there is no harm done if you can fit the system.  I think you will lose torque if the manifold pipes are larger than 2 inch, not because of low backpressure but because the first length of exhaust is part of the tuned system.  You need high velocity just after the manifold (not too high, but 2 inch is high enough) so the exhaust has some momentum.  Remember, only one cylinder is using it at a time.  After the crossover, or an expansion chamber,  there is no tuning anymore so bigger is better if it fits.

The dual system I had years ago had 1.5 inch pipes.  The OD of the mufflers was only 2.25 or 2.5.  The OD of a 2.5 inch core muffler has to be more than 4 inches, pretty big. I don't know about Moroso Spiral Flow mufflers but I bet they are loud. Borla makes long mufflers with three tibes inside.  These absorb sound well. Adding the resonator tips will help.  I would suggest trying to use a factory type muffler behind the axle.  It will be much easier to fit 2 inch duals than 2.5.  Perhaps dual 2 inch over the axle into a transverse muffler that has dual inlet and outlet.  Early 70's Camaro and Nova used such a setup.  Maybe there is a Walker Dynomax muffler for one of those cars that will work.  The old Z-28 muffler had much better flow than the standard one and gave a nice gurgle with the V-8.  A V-6 should be slightly louder.  Go to your friendly local auto parts store and ask to browse their muffler catalogue.  There is usually lots of dimensional information in the rear of the book.  Or, ask to walk through the storage room.  You may see something that would work.