block interchange info


Oct 17, 2015
I have been reading until my eyes are bleeding. Have checked casting numbers and understand what block i have, but I need some info that I cannot find a definitive source for.

If someone can point me to the right thread, that would be great.

I just disassembled my 85 engine and as I suspected, the block is finished. I don't need the engine as I have built an 87 and have all associated hardware to do the swap into my 85 GN.

I would, however, like to still use the heads, intake, turbo, etc. from the blown engine as it had several upgrades and I have another regal (or 95 S10?) sitting in my yard.

I have a 79 crate 3.8l, casting number 1255862 with 10,000 miles I picked up for a $100. Have had my eye on this engine for a few years, finally convinced the seller. This is my question:

How much of the engine can I use?

I assume the block for sure; but I am hoping to just swap in a cam, and bolt everything up to the shortblock and go. Am I crazy or is it going to be just that easy? Not looking for anything special, just a cheap spare engine to play with. My concerns are about compression ratio and valve clearance using the 85 GN heads, etc.

And for your entertainment, here are pics of the blown 85.

The problem is fairly obvious by the third picture.
The burned out valve is from the #1, the pieces are from #2 cylinder.


IMG_1250.JPG The parts are interchangeable but the deck heights differ. This will get you started. Brad
have the 79 engine on the stand. The deck height is the same as the 85. I read that doesn't change until 86.

What I am looking for is the engine specs so I can compare the 78 to the 85 in terms of cr and cam specs. The 85 is easy to find the specs; I just cannot find the info for the older engine, other than some very ambiguous info. GNTType has some great info, but doesn't give any specs for a NA engine from the day. I don't expect it to be the same, but would like to see if I can live with it and just slap it together. (probably will anyways)

Looks to me like the only obvious differences on first look are the knock sensor and the distributor. I will drill and tap for the knock sensor. The balancer and timing cover all seem identical.

If someone knows the specs on the 79 engine, that would be great; or point me to the info, also great.

Maybe I should post in before black?

Thanks in advance. Much appreciated.