55.2-59 Firewall dimensions

[regan56]

Moving along on the build and I’m now to the point where I can mock up my engine and trans placement. I don’t have my cab near me so I’m going to try and mock a firewall to give me some perspective on how close the engine can/will be.

Is there anyone that can give me a few simple measurements?
- from CL of front cab mount to face of firewall and to the start of the bottom of the firewall at the floor
- location of the bend from top of frame rails
- distance from outside of frame rail to the tunnel edge
- total tunnel width
- height of tunnel from top of frame rails or the bend

[dsraven]

possibly some of that info is in here.

https://www.trifive.com/d1/55-59Assy.pdf


if trying to put a v8 in place where an inline 6 used to be the trucks did come with a sbc so it is do-able without any firewall work. if using the LS a lot of guys cut into their firewall to get fan clearance and keep the weight low and back as far as possible for handling etc. when I set mine up I had some pretty good rust problems to deal with along with a lot of extra holes in the firewall so I simply built a new one from 16ga and welded it in. if doing that I highly recommend you cross brace the cab so it stays in shape once that piece of structure is removed. same for step/rocker/door hinge pillar work. I would also look closely at the structure under the floor for the cab mounts as a sagged floor would have an effect on the firewall stress and could deform when cut unless supported first. I also have seen a few guys who have used a cut down/modified steel wheelbarrow shell for a firewall cut away since they have a rounded/formed shape that lends itself to look like it supposed to be there compared to a boxy fabricated cutaway. I would also recommend having your engine and trans in place, on blocks or whatever-mocked up but moveable, along with your front suspension, so you can have an idea of how the engine placement will relate to steering column shaft interference, engine oil pan to cross member or solid axle, engine oil pan ground clearance, room in front of engine, trans to floor clearance, exhaust to steering clearance etc etcetc. also, drop some bolts in your cab mounts and realize that the drivers front mount is sort of the closest fitting mount so when doing cab and sheet metal alignment that mount becomes the pivot that the cab moves around if the cab needs to shift slightly for hood alignment, fender to door gap alignment to match side to side etc. the other mounts have some room for shifting because they (were, back in the day) looser than the drivers front mount. they may all be the same looseness by now. just some input though. sorry, I don't have those dimensions because my firewall and frame are not stock anymore.

[dsraven]

this link may also have some frame dimensions that reference face of cab (firewall) to rad support mounts, cab dimensions, etc. both sites would be good to bookmark or download the info you need later. some of these have pages missing but the dimensions you need would be roughly the same for 55-57 and 58-59. the last couple of years the frames were longer out front and the rad support mounts were a little further forward so be aware of what year you go by if that dimension factors into what you are looking for.

http://chevy.oldcarmanualproject.com...esto/56134.htm

[regan56]

If I ever get to go to Cgy again, beers are in your future!

I guess I’ll ask the easy question, if you have installed new SBC motor mounts where did you set them? Might save me a lot of jacking around.

[mr48chev]

I guess I figured out that you had that figured out a couple of years ago but I am probably not the only one who has the slows and life getting in the way of build progress. http://www.67-72chevytrucks.com/vboa...d.php?t=770677

I'm thinking if someone with a V8 in a stock frame can give you the measurement of the front surface of the block next to the timing cover and the vertical centerline height of the crank in the frame and how high it sits in relation to the top of the frame rails life is good.

[regan56]

Originally Posted by mr48chev

I guess I figured out that you had that figured out a couple of years ago but I am probably not the only one who has the slows and life getting in the way of build progress. http://www.67-72chevytrucks.com/vboa...d.php?t=770677

I'm thinking if someone with a V8 in a stock frame can give you the measurement of the front surface of the block next to the timing cover and the vertical centerline height of the crank in the frame and how high it sits in relation to the top of the frame rails life is good.

Hahaha I knew I had asked that before and I honestly searched for everything but my name. And ya I was waaay ahead of myself there, and life slowed me up.

[dsraven]

here is a video of a guy setting up the panels and gaps on a task force. he mentions the driver's side cab mount as the pivot and how the cab can be moved around to get the hood or fender to door gaps symmetrical on both sides. he explains a lot and it makes sense if you think of it logically, like lining up a pile of shoe boxes to get even gaps. it is a little bit long but maybe worth the time if you're at that point or doing some major cab work.
it's called:

1955 chevy truck getting put back together"

in case the link fails to deliver.

https://www.youtube.com/watch?v=YmoBtq7lQW8

[mr48chev]

I found a photo on Washington Blue's build thread showing the tube crossmember before he cut the frame off to subframe it. I'm not sure if that helps or not.

[dsraven]

Haha, tegan. Sounds good.

[mr48chev]

This is suppose to be a 59 short bed frame. If someone with a stock V8 frame with the brackets for the mounts could tell you how far the center line of the holes in the brackets for the V8 are from the six cylinder holes that would be golden.

[_Ogre]

Originally Posted by regan56

I don’t have my cab near me so I’m going to try and mock a firewall to give me some perspective on how close the engine can/will be.

i wouldn't do it.

the engine needs to be close and at a certain height to work well. i think you'd be stabbing in the dark, even with precise measurements. get your cab on rubber mounts on your frame, even then you should have the front sheet metal on to get the cab location right

[dsraven]

I don’t have my cab near me so I’m going to try and mock a firewall to give me some perspective on how close the engine can/will be.
ogre: I wouldn't do it

thats kinda what I meant when I posted the link for adjusting gaps and using the driver's side mount as a cab pivot. unless you are using the original engine mounts then you don't really know exactly where the engine will sit, in comparison to the factory location, so you can't know how the new location will affect the fitment around the firewall, floor, etc. since the cab and other front sheet metal parts will possibly need to be shifted around to get the gaps and fitment right it is gonna be really hard to say if there will be interference when the parts get assembled all at the same time.
I would say if you can get the cab and front clip sheet metal then it may be worthwhile to do that and assemble the parts. then slip the engine and trans in place to get the mock up done.
thats just my opinion. it's your truck so you do what you think is best.

[_Ogre]

Originally Posted by dsraven

unless you are using the original engine mounts then you don't really know exactly where the engine will sit,

this is the best idea and the method i used even with my cab on the frame.
truk had the stock front mounts and a th350 rear trans mount when i bought it.
keeping all mounts intact, i built side mounts, then removed the front stock mounts.

12 years later when i did the current build, with the front clip off, i used the trans mount and fabricated side mounts off the just installed mustII x-member.
once the cab was removed, i blocked the motor up and swapped out the th350 for 700r4 and fabricated a very rigid trans x-member.
trans x-member also reinforced the cab mounts, replacing the support the stock trans x-member had.
the only fitment issue i ran into when the newly painted cab was reinstalled was i had to slightly modify the floor trans cover.
very minor