Coldsnap wrote:
Gotcha. So any of them can be built out pretty easily it seems.
What are some first HP gainer changes to make to a G body?
There is good news and bad news. The good news is that any of the V8s from GM that go in there are good power waiting to happen. The bad news is that they are all wheezers and its not just a cam or intake away from more ponies. The 305 chevy and 307 Olds will be the more common V8s you'll find. Pontiac's last V8 was 1981 and it was the 301. All of them have tiny head ports, low-8s compression, and tiny cams. The good news is that most of them will have a Qjet on it which will work for nearly anything you put under it from a 3.8 V6 up to a Caddy 500. An example; the 307 Olds that you might find is an 8:1 combo with tiny head ports (as in, they fit your thumb and not much else) and a cam that specs out to something like 181/193 duration. 140 hp and it felt like 100 tops. Many of the chevy 305s will be similar and in the 125-150hp range.
But, like I said, you can plop a Vortec 350 longblock under it, bolt on the intake and Qjet and HEI, and you're a breath away from 300 hp after some tuning and a better cam.
My point is, don't try to upgrade what's in there. You'll spend more money on a comprehensive package of pistons, heads, cam, intake, etc than you would just buying a reman 350 or a used Olds 403, or a buick 455, or a...
Especially don't try to upgrade the 305. Chevy made the 305 by shrinking down the bores. You'll be very limited on how much power you can make because of the poor breathing associated with the small valves to fit in that bore. Plus, once you spend your first $300 on a cam or heads, you've already spent more than you would on a used, running 350.
The easy swaps are same for same; olds for olds, buick for buick, etc since you know the starters, alternators, distributors, fuel lines will all be a direct swap, but it is not hard to extend a fuel hose or starter cable. Just something to consider when swapping an engine. Of course you probably also know that BOP bellhousings are all the same, but different from the chevy bellhousing. If going from chevy to BOP or vice versa, you'll need a correct bellhousing.
... which brings me to the good news about transmissions. GM saw the need for multiple applications of the same chassis and made it easy on themselves. Most of the G-bodies got one of three transmissions; a TH350, a THM200, or a 200-4r. The first two are three speeds and the last is an OD 4 speed. Not only do they all interchange (length, output shaft configuration, shifter style, etc), they almost all came cast with both bellhousing patterns. The only main differences are kickdown style (vacuum or switch), and the 200 types will make you slide the tranny crossmember back to the rear hole in the frame. There is also a wee bit of difference in the shifter throw. I replaced the 200 in my Elky with a TH350 and noticed that it required a lot less shifter movement to go through the gears, but there are adjustments that can be made in the bellcrank to compensate.
Now for the really good news... if you happen to find one with a 700r4 (rare, but they're out there) that means a T56 is nearly a bolt-in as well. That was another GM stroke of genius; to make a T56 fit in where a 700r4/4L60e was. There are also some G-bodies that came with manuals (again, rare) but that means that parts are out there to put a T10 in it.
Edit: one more thing on automatics... The THM200 is fine for daily driver behind a 120-hp engine. It likes to explode at 120.337 hp. Not really, but its a very light duty transmission. The TH350 is bulletproof. The 200-4r is actually quite a nice transmission. In stock form they won't take a ton of abuse, but its what GM put behind the GNX and 442 higer-hp engines. They can be built to take a lot of abuse.
