Conversion/Upgrade

[Chris Kennedy]

I've owned my '81 4 spd for about half of its 177K miles and pretty much have everything the way I like it, and am considering at some point in the future either replacing the stock engine with either the GM crate ZZ4, 383 or even the " mild" 454 (not the 502s). While I know this work can be done, I am a little concerned with strength and safety issues. Replacing the 4-spd with a beefier, earlier unit is no problem (I replaced the BW T-10 that came with the car with the Richmond Gear T-10 that has the better 1-3 acceleration ratios, but it's a lower-torque rated unit). Long ago I also replaced the trailing arms with the offset units. What does concern me is the aluminum crossmember and differential. While I will not be doing burnouts, one thing I don't want to have happen is have the crossmember and frame tear itself/themselves apart. Does anyone have practical experience with doing these conversions/upgrades? I sort of have this dream of also getting '69 style side exhaust, too. I have seen several 1980 models advertised on ebay with the uprated engine or big block conversions, emailed the owners but got no response. Also, if anyone knows whether any shops do this work I would appreciate the advice.

Thanks,

--Chris Kennedy

 

[69MyWay]

Chris,

I think you will be fine. The late C3 aluminum rear assembly is much like the C4. I am pounding tons of excessive power through my 90 and it is all still there.

Like anything, if you abuse it too hard, it will break. However, the mods you have mentioned have been done thousands of times, and I don't think there are too many problems.

Sounds like a fun project, you already have the trailing arms, etc, so go for the gusto!

 

[Chris Kennedy]

Thanks for your input---yeah, it should be fun!

--Chris Kennedy

 

[Stingray6974]

I hate to be the wet blanket here. The only problem you will have is with state inspection. Although you will be excempt from tailpipe testing in three years, you still have to pass the visual emissions. EGR valve, A.I.R. system, thermostatic air cleaner, frech air hoses, and vapor recovery/EFE systems.

Mike

 

[Chris Kennedy]

Thanks, Mike. I have the same concerns as you do, as I want to remain legal. Frankly, there are lots of cars running around in total violation of emissions/safety (I live in Houston and, as you know, the condition of cars down here is horrible and I can only think that a widepsread system of bribery is what results in them getting compliance stickers), and I have thought about this idea in the context of an early model C3, as well.

--Chris