Assuming that a lengthy first post doesn’t violate any rules, I’d like to access the Hive Mind for its views on a project I’m giving some thought to. I’ll try to break it down into bite-sized chunks, so feel free to comment on any or all of the content.

I’m thinking of buying an early (steel bumper) C3, but prices for nice cars just seem to go up and up. Since I’m looking for a weekend driver rather than a show car, a NOM car seems to make sense from an affordability standpoint of course, but there’s another reason to avoid numbers-matching cars — I’m planning an unusual engine transplant and don’t want to mess up an original car. I used to have a ‘73 L82 4-spd coupe that I replaced with a ‘91 auto convertible. I still love the C3 design, but the L98 motor in my C4 (TPI, HEI, aluminum heads, roller rockers, tunnel ram intake, etc.) was way cooler and more high-tech, with the same horsepower and more low-end torque than the L-82.
So, says I to myself, why not look for a NOM C3 and a low-mileage TPI C4 and swap the engines? Then sell the C4 to somebody who likes its more modern brakes and suspension but prefers the old-school pre-86, carbureted small block. Why not just find a junk-yard L98 and avoid the hassle and expense of having to buy two cars and then selling one (a Frankenstein at that)? First, a junkyard motor may or may not be in good running condition; second, the small block from the C3 — assuming that its a garden variety, 2-bolt block — is worth more in a car than out of it.
Are you guys with me so far? Good. Questions for the collective:
1. Is the above plan brilliant or dumb-a$$? Feel free to explain.
2. If even potentially brilliant, what are the issues with the following:
a. L98 bolt-pattern compatibility with a Muncie 4-spd.
b. Tunnel ram EFI in a C3 (ECM; in-tank fuel pump; air intake/air filter routing; hood clearance, etc.)
c. Assuming that (a) is OK, the old-school block should bolt up to the C4 trans, yes?
d. Clearance of low-rise manifold, carb and air cleaner under stock C4 hood.
e. Possible need for old-school fuel tank in C4 chassis. Problems?
f. Possible accusations of Bubba-modding a perfectly good C4.
f. Show-stoppers that I haven’t thought of.

If I get the wrong answer to #1 above, I’ll only nurse a grudge for a little while and then come back with another, really brilliant idea. So don’t worry about kicking a noobie in the groin. Looking forward to feedback from the many brilliant minds that post here. You other guys can chime in, too.

 

Rookie here, too...
I was with you until the C4 chassis/C4 hood showed up.
What am I missing?
Members are doing LS engine/trans swaps...
is that similar to what you want to do?

 

Thanks for the reply. If I’m not mistaken, LS is lower profile than a small block with carburetor and standard air cleaner.

I should clarify: I want to put an L98 (with its tall tunnel ram plenum) in a C3. The LT and LS motors are much lower profile (allegedly so they could fit under the hoods of the ‘90s Camaros. They gave up torque but gained hp in doing so).

 

Hmm. Didn’t there used to be a guy with a similar name that posted a few times here? Any way, welcome aboard, Doorgunner!🙃

 

 

that block is essentially the same dimension wise and is still considered the same generation SBC...there are some differences like the rear main seal, heads and intake are different and they may or may not have a fuel pump provision. I know the big blocks deleted it and those blocks may have as well. read this if you like engine history https://en.wikipedia.org/wiki/Chevro...ond-generation)

 

My memory generally sucks, but I’m almost sure there have been multiple C4 motor-to-C3 chassis swaps mentioned on here. Difficulty probably smack in between 1st Gen small block and LS swap.
As mentioned, physically compatible with your existing small block, just need to square off the ancillary equipment, ignition, fuel pump, etc.

 

Yup, there are many carry-overs in the later design. My uncertainty is in regard to the height of the L98 plenum (will it fit under a C3 small block hood), the front-loading L98 FI throttle body (where do you locate the air filter so you’re not drawing hot, thin air through the C3 radiator), and the L98 bell housing bolt pattern (will the Muncie M20/21 bolt up to it). The motor mount locations are, iirc, the same, the FI fuel pump is electrical (not mechanical) and the accessory mounts can be made to work.