C4 Frame Project

[rockytopper R.I.P 5-13-2017]

Looking Good!!!!

[WagonCrazy]

Dang Brian, you're moving fast! Keep it up. Good work man! Really appreciate you posting all those pics. That's good sharing of knowledge...

[Custer55]

Thanks Rocky & Paul,
It doesn't feel like it's moving along very fast to me!! More like a snails pace. I'm happy to share what I'm doing, I learn a lot from others posts too.
This past week I finished up a few details then got everything taken back apart to finished welding in a few places that were to hard to get at before.


Here is the Wilwood bracket (modified) and master bolted to the booster without the Wilwood supplied spacers. There is just enough thread without the spacers so there is no way I could use the spacers.


From this you can tell how the proportioning valve bracket has to be positioned just right for the supplied lines to work properly.


Since it will be nearly impossible to get the nuts on the bolts for the pinion support much less get a wrench on them with the body on I welded the nuts to a plate to make things much easier if I need to assembly/disassemble with the body mounted on the frame.


All bolted up with the nut plate. I made a thin rubber cushion from a couple layers of a printing press blanket. Two layers ends up being about 3/16" thick.
(I get the used ones free from work, there about 29" x 41" from our biggest press. They work great for catching oil leaks under the old cars too.)


One of the last things to do was to add the tabs for the rear brake hoses. The hoses I am using are the stock replacements for a 90 Vette from Russell.


I positioned the tabs to allow easy brake line routing over the frame. The position will allow full up and down suspension travel also.


Here I have the frame mounted on my makeshift rotisserie. (It's a lot easier to weld on things when you can just spin it around to a better position!!) All taken apart with the Corvette front K-member removed. One of my saw horses for the rotisserie stand is kind of sketchy so I hooked it up to my engine hoist also just to be safe. I finished up all the welding I needed to finish up on today so it's ready to prep for paint. I am just going to sand and wire wheel it for now. The frame had already been sandblasted when I bought it so there was no heavy rust on it, just some light surface rust in a couple of spots. I painted the whole thing with Eastwood rust encapsulater when I first bought the frame so it should hold up for a couple of years without sandblasting the whole thing again.
I'd prefer to sandblast it again but I don't have any good place to do it right now.
Once I get a half-way decent paint job on it the re-assembly can begin.
Brian.

[DannyP]

what are you doing for rear spring stock or coilovers

[Custer55]

I plan to use the stock springs front & rear since the weight of my 55 (pre C4 setup) and our 90 Corvette are so close.

[chevynut]

I plan to use the stock springs front & rear since the weight of my 55 (pre C4 setup) and our 90 Corvette are so close.

It's not just about weight, but about weight distribution. The Corvette engine sits several inches further back than the engine in the tri5 and the wheelbase is shorter. The stock C4 rear spring isn't a bad choice and it allows fairly easy height adjustment by tightening or loosening the nut on the long spring bolt. But your choice of spring rates is limited. Early and late C4 rear springs will interchange.

The front is where it becomes a bit more difficult to use the stock C4 spring. The early and late springs don't interchange so your choice of spring rates is again fairly limited. And the bigger issue is that if the car doesn't sit at the ride height you want, you have to remove the spring and add or remove shims between the spring and k-member. There's only so much room to do that. Coilovers allow easy ride height and spring rate adjustment, to a point. You just turn the nut up or down to get to designed ride height, or change the spring which isn't that hard to do.

[Custer55]

It's not just about weight, but about weight distribution. The Corvette engine sits several inches further back than the engine in the tri5 and the wheelbase is shorter. The stock C4 rear spring isn't a bad choice and it allows fairly easy height adjustment by tightening or loosening the nut on the long spring bolt. But your choice of spring rates is limited. Early and late C4 rear springs will interchange.

The front is where it becomes a bit more difficult to use the stock C4 spring. The early and late springs don't interchange so your choice of spring rates is again fairly limited. And the bigger issue is that if the car doesn't sit at the ride height you want, you have to remove the spring and add or remove shims between the spring and k-member. There's only so much room to do that. Coilovers allow easy ride height and spring rate adjustment, to a point. You just turn the nut up or down to get to designed ride height, or change the spring which isn't that hard to do.

The weight distribution is very close also, See my post from the Suspension geometry analysis below. So I think I'll be ok with the stock front spring. No doubt it would be a lot easier to adjust ride height with coil overs!! If I can't get it where I want with the stock spring I figure I can change out the stock spring for coil overs later.
Brian

"I found the book I wrote down the weights of Our 90 Corvette and my 55 Chevy.

For the Corvette the total weight was 3,413 lbs. minus my weight of 189 lbs. (there wasn't much room to get out of the car in the scale room, they weigh the race cars with the driver) for a total weight of 3,224 lbs. I can't say for sure how full the gas tank was but it was most likely at least a half to 3/4 tank.
Weight per wheel as follows: (this with my 189 lbs. in the car, obviously more left side weight added than right side)

left front - 919 lbs. right front - 856 lbs.

left rear - 865 lbs. right rear - 773 lbs.

This works out to a 52% / 48% front to rear weight distribution

For my 55 I was able to weigh it without being in the car, as a Tri 5 Chevy is much easier to get in and out of in tight quarters than a 90 Vette.
Again probably a 1/2 to 3/4 full gas tank.
Total weight was 3,410 lbs. This includes a couple of bag chairs and misc. stuff I keep in the trunk for car shows etc. Maybe an extra 20 to 30 lbs. at most.
Weight per wheel as follows:

left front - 890 lbs. right front - 878 lbs.

left rear - 805 lbs. right rear - 837 lbs.

This works out to a 51.8% / 48.2% front to rear weight distribution.

Nearly identical to our 90 Corvette. This is one of the reasons I decided to just use the stock Corvette springs and shocks.
It will be interesting to see where my 55 ends up weight wise with the new frame. I'm thinking it will be very close. The Corvette suspension parts should save 150 to 200 lbs. but I added the frame center section at about 70 lbs. or so, an extra cross member front and rear. a power steering pump, and the tilt steering column is heavier than the original. I have an aluminum water pump on order so that will save a couple of lbs. The engine is moved 3/4 forward, the radiator will be moved to the 6 cylinder position, and the gas tank is moved 3" backward. I am using the same engine and transmission though and probably the same radiator for now. I plan to upgrade to an aluminum cross flow when the budget permits."

[55 Rescue Dog]

If you can get the weight to match one of the stock springs, that would be ideal. Otherwise, the next best thing, would be if you needed a little more, just fine tune it with a light coil over spring, and let a majority of the weight ride on the traverse spring. That's the way I'm going to do it anyway. Could do the same thing in the rear.

[DannyP]

Can you please give the info on the master cylinder and booster [ part number, piston size ,booster size ]
I will be doing this front end change soon so I would like to start buying the extra stuff now

Thanks Danny P

[Custer55]

Can you please give the info on the master cylinder and booster [ part number, piston size ,booster size ]
I will be doing this front end change soon so I would like to start buying the extra stuff now

Thanks Danny P

Danny, I don't have any part numbers handy. The booster is a 7" single diaphragm. I bought it quite a few years ago from Auto City Glass at the Iola swap meet as part of a dropped spindle kit.
The Wilwood master cylinder is a 1" bore. What you want to use depends on the brake pedal ratio you have and the feel you want in your brakes. My pedal ratio is the stock ratio, I think 6. something to 1. which will require a lighter touch on the brakes with the 1" bore master. The stock Corvette master is 7/8" or 15/16" but they have a pedal ratio closer to 4 to 1. I think a bunch of this info was covered in a thread in the suspension, brakes, etc, forum.
Hope this helps.
Brian