The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 55.2-59 Firewall dimensions

dsraven · 01-05-2021, 02:06 PM

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.

01-05-2021, 02:06 PM	#2
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 8,499	Re: Firewall dimensions 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.