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Discussion Starter · #1 ·
Hello everyone. I have gotten ahold of a 96 corvette front end with the factory 13 inch brakes. I have a few questions about it though. Its going into my 1938 Pontiac, so this will be street rod stuff. I am building my own frame for this, I don't want to use any of the bought front clips because I can make my own.

1) Is there anything I should be aware of before I make bolt on frame rails?

1) Should I keep the front leaf spring or is it worth it to go to a coilover setup? The Pontiac is 3-400 pounds heavier than what the vette was from the factory.

Thank you, I am looking forward to better handling and braking as compared to the MII I was originally planning
 

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corvette dimensions

You might be able to trim the frame to remove the coil spring mounts and flat plate the outside of the Pontiac frame, keeping the fender and radiator nd bumper mounts.
I think your 38 should be the same as our 37 sedan , our original 36 straight 8 has the original different Knee-Action front suspension


this site has a lot of dimensions that might be helpful
Model A Ford Hot Rod Chassis / Frame Plans Using C4 ...

 

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Discussion Starter · #4 ·
You might be able to trim the frame to remove the coil spring mounts and flat plate the outside of the Pontiac frame, keeping the fender and radiator nd bumper mounts.
I think your 38 should be the same as our 37 sedan , our original 36 straight 8 has the original different Knee-Action front suspension


this site has a lot of dimensions that might be helpful
Model A Ford Hot Rod Chassis / Frame Plans Using C4 ...

https://www.youtube.com/watch?v=hX7XwnBsqQw
Thank you! This is definitely pointing me in the right direction. My Pontiac is a bit of a strange one. Its a Canadian Pontiac, but seems to have the american coil spring front end, not knee action. I was planning on fabricating my own fron end, however I am open to modifying this frame and boxing it if needed
 

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Like IMSPORT said, go coil overs. You will want the ability to tailor your spring rate to match the corner weights in your car.
Also pay attention to the way the suspension arms are attached to the stock Vette frame. You will want to emulate the control arm angles to maintain anti-dive and ball joint travels.
How does the wheel base and front track width on your '38 compare to the Vette? If they are close you should be good with stock angles.
Mark
 

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A arm front suspension

our 37 was part of a package deal, has a SBC and chevy pickp rear end with 57 Caddy eldo aluminum wheels. There is a Wiki article here on hotrodders about upgrading the front suspension with later years parts but most of the cars that could donate the needed parts have long ago been crushed and sent to the steel mill.
I measured my son's 36 olds and the 37 Pontiac ac a Jag XJ6 front could easily be swapped in by trimming and flat plate, the C 4 is a lot better suspension, We started getting Jag parts when they showed up for $ 100 to 150 .
 

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the original chassis is pretty limber, consider building a front to rear modern tube chassis using the Vette front stub as is.
Art Morrison makes frame rails for various chassis builders, rear section kits, etc.
 

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Capt Mike
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Hotflint,

I've completed several C4 IFS & IRS suspension swaps including my '37 Chevy Coupe current build, I'm just now to a rolling chassis with running gear installed. I grew around Street Rods and DIY Dad, Uncles and their friends. I'm an Engineer (retired now), as was my Father and Uncles. Which makes me a bit of a perfectest and I complete my research prior to jumping into any project, especially Suspension !

There are two variations of the C4 suspension, early ('84-'87) and late. The latter is touted to be better, but both are excellent for Street Rods. One major consideration is that the early series is ~ One inch narrower. The Hub to Hub width for the late C4 IFS is 6.5 inches, and the Upper & Lower Control Arms are usually longer than older cars.

All suspension components, rack, shocks, plus the engine, are bolted onto the C4 Engine Cradle that in turn is bolted to the uni-body frame mounts on all C4's. The engine cradle can be used in a few Street Rods. However usually a custom cross member manufactured by a few manufacturers is a far superior choice. The engine cradle is heavier than a custom Cross member replacement and the motor mounts for a SBC place the Harmonic Balancer close to directly over the front axle centerline often to far to the rear for some builds, firewall issues. Typically a custom cross member is the best means for a 30's vehicle.

I'm setting mine up with Strange Coil Overs, their a US Company, high quality, equivalent price but the deal sealer for be is their option rubber Bump Stops option at a very low cost. I have all the suspension components weights, so with these and the wheels and tires weights you can calculate the coil over spring rates. see Ride Tech, https://www.ridetech.com/tech/spring-rate-calculator/


I purchased my C4 IFS cross member from Don the owner of Flat Out Engineering in Orange CA. Top quality and excellent alignment and 100% TIG welds. He's the Guy that can answer your questions on the widths plus installation, he's been at this for many many years. Your best start is to email Don to start. His C4 IFS cross members come with all the suspension mounts including the coli over shock & rack mounting.

Let me know if you need and jnfo or details if you decide to install the C4 IFS. It's well worth the effort. It isn't Rocket Science.

Michael
 

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Capt Mike
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We installed the late C4 IFS & IRS in a 1957 Desoto Statesman Fire Sweep.

This Desoto has a wider front tire track than your '38, but it's gives you some ideas. Note the Rack center has been rotated 90 degrees so the hydraulic lines are in front of the rack, Often necessary of oil pan clearance. Turn One Steering did the rack rebuild and installed their custom hydraulic lines.

We used the original C4 Engine Cradle, FRP mono filament front spring, modified shock mounts and motor mounts for the blown 392 Hemi. This has the typical MoPar Torsion Bar suspension, so the shock towers were a much smaller diameter. We were able to only modify the front frame rails and use the original Core Support.

If you would like photos using Flat Out's cross member kit just let me know.

Michael...
 

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Discussion Starter · #10 ·
Hotflint,

I've completed several C4 IFS & IRS suspension swaps including my '37 Chevy Coupe current build, I'm just now to a rolling chassis with running gear installed. I grew around Street Rods and DIY Dad, Uncles and their friends. I'm an Engineer (retired now), as was my Father and Uncles. Which makes me a bit of a perfectest and I complete my research prior to jumping into any project, especially Suspension !

There are two variations of the C4 suspension, early ('84-'87) and late. The latter is touted to be better, but both are excellent for Street Rods. One major consideration is that the early series is ~ One inch narrower. The Hub to Hub width for the late C4 IFS is 6.5 inches, and the Upper & Lower Control Arms are usually longer than older cars.

All suspension components, rack, shocks, plus the engine, are bolted onto the C4 Engine Cradle that in turn is bolted to the uni-body frame mounts on all C4's. The engine cradle can be used in a few Street Rods. However usually a custom cross member manufactured by a few manufacturers is a far superior choice. The engine cradle is heavier than a custom Cross member replacement and the motor mounts for a SBC place the Harmonic Balancer close to directly over the front axle centerline often to far to the rear for some builds, firewall issues. Typically a custom cross member is the best means for a 30's vehicle.

I'm setting mine up with Strange Coil Overs, their a US Company, high quality, equivalent price but the deal sealer for be is their option rubber Bump Stops option at a very low cost. I have all the suspension components weights, so with these and the wheels and tires weights you can calculate the coil over spring rates. see Ride Tech, https://www.ridetech.com/tech/spring-rate-calculator/


I purchased my C4 IFS cross member from Don the owner of Flat Out Engineering in Orange CA. Top quality and excellent alignment and 100% TIG welds. He's the Guy that can answer your questions on the widths plus installation, he's been at this for many many years. Your best start is to email Don to start. His C4 IFS cross members come with all the suspension mounts including the coli over shock & rack mounting.

Let me know if you need and jnfo or details if you decide to install the C4 IFS. It's well worth the effort. It isn't Rocket Science.

Michael
This is invaluable information, thank you
 

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Hotflint,

I've completed several C4 IFS & IRS suspension swaps including my '37 Chevy Coupe current build, I'm just now to a rolling chassis with running gear installed. I grew around Street Rods and DIY Dad, Uncles and their friends. I'm an Engineer (retired now), as was my Father and Uncles. Which makes me a bit of a perfectest and I complete my research prior to jumping into any project, especially Suspension !


I am considering the flat-out engineering suspension kit for my 37 Chevy Business Coupe. Do you have any recommendations or suggestions? Were you able to use the front core support? What engine did you use, and did you buy a mount or fabricate it? Any pictures would be appreciated thanks in advance

Ed
 

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Capt Mike
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ED,

The frame on my '37 Coupe is a custom design as the body is a Superior Glass Works (now out of biz due to a large fire) 37 Chevy carbon fiber body. Art Morrison Ent. in Fife WA. bent the frame rails to our CAD drawing, great perfection.

I've helped other with the 37-39 Chevy frames, but not with a C4 IFS. C4 is the most desirable for many reasons. Depending on your HP & Torque you may need to add some bracing.

Best to give Dob, owner, a cal at Flat Out Engineering in Orange CA., check out his Website He's the expert on his kits. Tell him I sent you.

If he doesn't answer, it's a busy shop, just leave a message "call evenings are okay".

Glad to help you.If you need help send me a PM and I'll forward my email address and phone number

C4 IFS & IRS are a great and economical way to go...

Michael..
 

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I'm an Engineer (retired now), as was my Father and Uncles. Which makes me a bit of a perfectest (...)
(...) The Hub to Hub width for the late C4 IFS is 6.5 inches
Trying to figure that all out...

For me the two main things w/ C4 front suspension conversions apart from fab details is, the steering rack is in an awkward place for a chassis that does not have much of an engine setback, the damper needs to go either behind it (an unusual place but normal for Corvette) or above (also unusual, e-z for trucks but other applications beware)...and then the leaf spring is not available in a range of rates although it can be lowered by shaving off the sides, so if you need a rate and height much apart from stock you're kinda stuck w/ the coilover conversion and supporting it at the top with more structure than the C4 had for it's shock-absorber-only purpose. What makes hot rodding interesting.
 

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Capt Mike
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kso,

The Rack aka R&P.

Yes C4's and C5's etc. have the Engine harmonic damper is close to being centered over an imaginary line that's centered on IFS,

Some useful info,,

The C4 was a vastly different Corvette and like most models, C1,C2,,,,, C8. Most Everything was different except all were V8's w an auto or manual trans. There's no trans cross member, a relatively simple ABS and only one real microprocessor based ECM, that had 8 fuel injectors but ran in a Batch Mode. All aluminum suspension components keeping the Un-Sprung Weight to a minimum ! The wiring is a Nightmare.

The Engine Cradle bolts to the Uni body, provides the motor mounts and the Front Steer R&P mounts. And the the wheel offsets changed dramatically. Hence the F & R track width remained in the typical Sports Car realm, and perfect for many Street Rod conversions. GM was so far behind in this design hat there was no production 1983 Corvette for pubic sale. The Engine cradle is HEAVY, and not typically suitable for most Street Rods !!

The Transverse Mono FRP Springs, there are many oem options ! However, your car will most likely be lighter than a typ C4, so Coil Over Shocks would be desirable. But, you must have the un-sprung and Sprung Weight of Your Car to be able to select the proper spring ratio. You can find a simple "Fill in the Numbers" on Ride Tech's Website. I have most of the C4 front sus weights, in addition you need to include Tire & Wheel weights.

DO KNOW,

that changing the length of coil overs by adding or lessening the Spring Pressure to set the Ride Height is Highly NOT recommended.

Setting the Ride Height must be completed carefully and accurately when installing the front C4 cross member !! IE, the outer Steering Arms on the R&P Must be level and in a straight line when the coils overs have been adjusted.

Not difficult but you must know your tire heights in advance. We always use the wheels and tires that will be run on a given car when setting the cross members into the frame and welding !! I can provide some numbers and tire sizes if and when you get to that point.

WHEELS,

My C4 has the wide ZR1 wheels front and rear, 9.5x17 & 11x17. The are several choices of oem C4 wheels or Re-Pops available. It's usually easier to find some for Fab Rollers.
My '37 has C5 Thin Spokes w Nitto's. These are a nice and low cost wheel. I have two sets, one pained semi gloss black and the other polished. Lots to choose from but they will need to be at least 17 inch

The C4 R&P being a front steer eliminated the Oil Pan problem (etc.) for Street Rod conversions, significantly made exhaust etc. easier.

I still have my old C4 Convertible, far from a stock now. But I can tell you that even with the R&P being a front mount, it's still crowded in the oil pan area. I have a LSX in my '56 Chevy and it's a rear steer R&P. Modifying the aluminum oil pan was necessary was a pita. The engine sits over the cross member as I didn't want, for many reasons, to set the engine back that require major Mod's. My '56 does have modern s/s tubular front suspension w corrected geometry and it drives quite well and I don't have issues with tire scrub etc. and she corners quite well. But back in 2007 I the didn't want to complete the massive work installing and Fab'g a complete front frame clip, hence no C4 suspension. I'll prob never even install another rear steer R&P

Placing your engine over the cross member is Typical for autos, I wouldn't concerned. Moving the engine / transmission rearwards will improve the front to rear axle weight and that improves many things. Moving the Engine / Trans rearwards is more beneficial.

My '37 firewall is slightly back from the exterior body, or very close to the windshield, so its several inches rearwards from a genuine '37 Chevy Body. My '37 Body didn't have a firewall, floors, A & B Pillar supports etc,, just and empty Shell. So we Fabricated a 1/2 square tubing framework and when completed covered it with 10 gauge steel. Bending the tubing to Snug up against the Body was very tedious. But in the end I got the engine / trans setback that I needed. And routing the R&P shaft to the steering column somewhat easier. Mod'g yours should be significantly easier...

My '37 Chevy Engine Harmonic Damper is behind the front cross member, cross member being a Flat out Engineering part. I highly recommend that whatever front suspension he you install, set the engine / trans back as far as it is practical for your car. Full firewall sheet metal sections can be purchased or you could Fad a center section. Would also significantly improve the firewall appearance.

Engine / Trans fitment.

Setting the LSX into my '56 we only "Massaged" the firewall being the passenger side cylinder head. Not having a Distributor the center area where the oem wiper motor once lived . Overall we only gained a few inches, but it was enough.

Having not been under the hood in a '37 -'39 Chevy in quite a while I don't recall the room. So this is something that you'll need to work out.

We, myself & Friends, often set a bare block with empty heads, intake, trans etc into the engine bay (front clip initially removed) and move this assembly around prior to making a Set in Concrete Decisions. On my '56 Chevy (which was a SoCal race car for quite a time) had three holes in the floorboards for previous Shift Mech's, So We cut out a rather large hole that was wide enough for the Tremic T-56. I purchased a new center floorboard section and my Friend Steve shaped it to fit over the Trans and made it removable. Having worked helping many others and at a friend Ron's shop, this was a common and major time and frustration saving method. I mention because this is often easier and having a removable Tunnel is fantastic !! Something to consider

PS, don't be concerned with a C4 IFS kit, Don @ Flat Out Eng., His are more than strong enough

Long, but I hope this clarifies much..
Michael...
 

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Just a couple things to fill-in; engine setback is a matter of foot room, add one and take away the other. Whatever you can fit to your satisfaction is good, Corvettes have a lot of set back but if it's an issue, in many cars with tall engine compartments you can position the motor above the R&P if there's not room for setback. If you're good w/ stock setback then mounts for pre-LS V8's are right there for you, otherwise you have to fab something. The Vette crossmember, made of 12 and 13 ga steel with efficient stamped shapes, is actually pretty light at 41 lbs but includes front wings to mount diagonal bracing and room inside for the leaf spring, both may or may not be needed in a street rod. Because of the front-steer and spindle design a wheel with a lot of negative offset is required, i.e. new-type wheels only. There's no fitting deep positive-offset wheels such as used in hot rods and street machines through the '70s unless you want some difficult steering. Obviously diameter has to accommodate brakes. The crossmember does not have upper shock mount provision, that is mounted on the frame stub attached to the unibody on the 'Vette. Coil-overs will require modified mounting at the lower a-arms where the leaf spring ends normally nest. Finally, GM galvanized the whole weldment, unusual and something to deal with if you expect to weld on it.

Wood Engineering Art Tool Aviation
 

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Capt Mike
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kso,

"engine setback is a matter of foot room, add one and take away the other. Whatever you can fit to your satisfaction is good, "

True,, but the C4 Corvette has an adequate foot well. I modeled the foot-well in my '37 Chevy Coupe to my C4 Convert. as it's a seating that I'm comfortable with and I can measure and model. My C5 Convertible is completely different,, & more roomy. My '37 being a Carbon Fiber body its equivalent to a 3 inch chop and a 3.5 inch sectioning and I dropped the body over the new frame we fabricated 4 inches making the interior very Tight. The Brake Booster and master cylinder are in the interior. The Vintage Air Mock-up box fits, tight but it fits between the Dash Roll cage with adequate clearance. This not being my first build and I understand engine set-back implications and gains as well.

I looked at and measure as many '37 through '39 Chevy Coupes prior to jumping into this frame and roll cage design. Here's a few measurement I took tonight that may assist you.

My engine sits Behind the Axle Center line over 6 inches and I have plenty of foot well space and the same floor to pedal, to steering column location and the C6 ZO6 sets I've got installed, Entry and exiting the car is easy.

My Cowl is shorter than oem at 4 inches at the top of the reveal, and my wheelbase is 112 inches

The mating surface of the steel bell housing to the engine is approx 8.5 inches to an imaginary line at the edge of the Body at the A Pillars, where the door skin gap at fender midway up

The IRS Axles Center Line is 38 inches to the door seam mentioned above

My door horizontal lengths are 36 inches and the seats are slightly behind the B Pillar door opening

I have a Klugle pedal assemble with brake booster and master inside the interior. You can obtain the pedal dimensions on their website.


"Because of the front-steer and spindle design a wheel with a lot of negative offset is required, i.e. new-type wheels only. There's no fitting deep positive-offset wheels"

Not necessary the front steer. The wheel offsets are part of the IFS geometry design, mathematically Change the front wheel offsets and you change nearly everything.

"Coil-overs will require modified mounting at the lower a-arms where the leaf spring ends normally nest."

No, that is incorrect, no mods are required on the lower control arms.

The C4 engine cradle is much heaver than needed, compare this to a aftermarket front IFS kits cross member, IE Flat Out Engineering.

"Finally, GM galvanized the whole weldment, unusual and something to deal with if you expect to weld on it."

Huh, I've owned several C's and junked out several and never seen one that was galvanized.

We used one on a '57 Desoto Statesman Fire Sweep, a wider and heavier car and we bolted and Stitch welded the '89 C4 Engine Cradle in place, later install the 392 Blown Hemi

BTW, not all of the wheels are Ugly..

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