The Stovebolt Site Forums The Shop Area The HiPo Shop when do i have to modify the firewall?

I'm still in limbo trying to decide what motor/trans combo to use in my 53 GMC 1/2 ton. I've noticed in some restorations they had to modify the firewall and some even had to add a "hump" inside the cab to fit everything. I'd like to use a v8 or v6 motor and automatic trans and if possible and keep the orginal type radiator and not modify the firewall, is this a pipe dream?

Thank guys!
Robin

No it's not a pipe dream. Don't cut the firewall unless you have exhausted every other possibility. Check out the gallery for other trucks and you will find lots that accomplish what you want to do.

If I can stuff a 425/400 Cadillac combo in my truck w/out modifying it I'm sure any SBC or ever BBC will fit w/out cutting the firewall. You may have to move the radiator forward but other then that you shouldn't need to modify anything else other then possibly the steering if you keep the stock steering set up...joe

I have a 327 & M21 in my '49. It fits with out modifying the firewall or moving the radiator.

Thanks guys that's such a relief! I need a new radiator and wanted to use one i found that is a replica of the original and has the automatic tranmission conntections built in as well, that way it will bolt right in and it will look orginal. I also plan on adding power stering so moving the steering around was going to have to happen anyway. I'm wanting to add the mustang 2 front end for the IFS so i had enough work to do. When it's done it will be sweet, i wish i could wiggle my nose like Samantha on "Bewitched"(showing my age) and have it all done

Trucks with 4 speed have a high hump cover over the trans. This might help if nessesary.

I put a small block in a 48 4400 without moving the trans forward. All I had to do is "clearance" an area around the large cap HEI dist. If I would have gone points or Mallory, wouldn't have had to,
Scott

Thanks Wrenchblender, hopefully going with an auto trans will keep me out of trouble

I put a small block in my panel using the motor mount kit that does not utilize a crossmember. Using the measurements that came with the mounts it bolts in beautifull and I was able to have room for the automatic column shift linkage to get between the valve cover and firewall.
I am also using the big distributor and I can still get my finger in behind it so I know I can get the dizzy out if I ever have to. Another point it that rather than cut the firewall I would have gone to the small distributor and and external coil to avoid cutting the firewall.
Oh, and yes, I used a power steering box outside the frame. When doing this just be sure to measure your double "D" shaft or what ever steering shaft you use.... measure twice, cut once.
Hope this adds to what the others have said and helps you out.

I used an sbc and the HEI and moved the radiator forward about 1.25". Moving the rad forward, if needed, is much easier than cutting the firewall.

Thanks again guys...i love this forum. I know enough to get me in trouble but with a little help I just may get though this and have "James" back on the road again

Usually anything that had an inline 6 will take a small block without modifying the firewall. The 6 is 6 cylinders long, the V8 is 4 cylinders long, and the V6 is 3 cylinders long. Where you mount the engine will dictate if bottom of the firewall or floorpan work is necessary.

I also installed an SBC with an HEI.There's even room for the fan as well.
I didn't move the rad either
The only trimming I've done was to the flange on the firewall directly above the trans bell housing.
This was to allow me to get my pinion angles correct.
The only other problem I encountered was the trans dipstick, an easy fix with a flexible dipstick.

I thing to remember is, it is best to position the engine as far back as possible.

jock, your right on the money. Why didn't you tell me about the dip stick earlier??
I bought one but found out recently I would need a flex OR bend the one I have. I think I'll return it and and use the money toward a flex. No use getting frustrated over something if we don't have to.

Sorry Alvin!

I actually got my trans dipstick in but it's just touching the firewall.
There's just not enough room to allow for the engine 'torquing'

I had always planned for a flexi one for some eye candy anyway!

The only problem I had was the shift linkage. The shop that installed my engine mounted it without moving the rad. When the steering column was installed the linkage wouldn't clear the valve cover so I had to go with the floor shifter.

All rods should have floor shifters.