Progress update and my findings on how to make it fit:
The 7.3L is a WIDE and TALL motor that completely fills the engine compartment on the mid 50’s Chevy trucks, but it does fit in there. The original engine cross member will need a couple modifications to allow clearance for the front of the oil pan and harmonic balancer, plus a couple other things. The cross member needs to stay since it’s a structural component of the frame. See one of the pics on this post for the mods I did, they include: oil pan cut out, recess for harmonic balancer, cut out for the lower radiator hose and two cuts for radiator clearance.
There’s little room for a radiator so I went the custom built route versus fooling around with the original radiator. The radiator I designed is 24” wide by 36” tall and drops below the original engine cross member where it can meet the lower radiator hose. At 24” wide it fits the original radiator support and uses the original 6 bolts for attachment. The only modification needed on the radiator support (yet to be done) is cutting two small pieces from the top (one on each side) to allow space for the top tank. I’ll post more on this when I make this modification.
The original transmission cross member needs to be removed and discarded and a new cross member made for the ZF5
. I have some reservation with removing it since it’s clearly a structural component that connects the left/right frame rails at the spring perch mounts, but there’s no way to keep it in there. Making a replacement “bridge” isn’t practical because of the size of the new transmission. The new cross member will mount much more rearward, so it doesn’t really do the job of the original member. However, an additional cross member is being added for the engine, so it “somewhat” offsets the removal of the original transmission cross member.
Depending on your steering setup (original box versus custom power steering) the engine will need to be placed about .75” off center to the passenger side. I’m keeping the original steering box, so I set the engine off center. If you’re working on a pickup chassis (I have a medium duty chassis) then you have several commercially available options for changing the steering and the suspension. In my case, I have none. If you remove the steering box and go with an “outboard box” then you can set the engine dead center. Also note, placing the engine off center gives room for the power steering pump to clear the inner fender. Placing the engine dead center will require some “massaging” of the inner fender to make clearance.
The other challenge with engine placement is leaving clearance at the firewall for the exhaust down pipe. I found a little firewall massaging with the 4lb hammer is required to “set” the clearance needed. I went with a custom built down pipe, but I did try a commercially available pipe first and found it fits fine with the light firewall massaging. The good news is there’s plenty of room for the up pipes and turbo because of the deep recess already in the cab.
Lastly, you will likely run into issues with clearance between the bottom of the oil pan (rear sump area) and the top of the axle. This is not an issue with the medium duty chassis since it sits very high compared to a pickup truck. If you’re working on a 4x4
truck and have it lifted then it won’t be an issue either, but if you’re working on a “slammed” 2wd you’ll have to convert the suspension to an A-frame style.
More to come as I make progress and get past the next step.