Oldsmobile Engine Guru's Needed

[Wraith]

Need some help from the collective on the 350 in the Mercury we are working on. High points are what looks to be a 1974 Oldsmobile 350 with #8 heads, HEI, stock cast exhaust manifolds, 2" exhaust piping, factory cast iron 4bbl intake, Edelbrock 1406 carb. We need some more power out of this engine and were thinking a cam and intake at least, headers if they would gain us HP, plus new exhaust pipe.

Any ideas for us? I know little to nothing about Olds engines.

 

[Texas82GP]

olds307 and 403 and Clutch and Rus and JAMCAR223 are among the Olds gurus.

 

[bracketchev1221]

All of the above will gain some power. Mufflers, intake, cam, will help as will a lower gear in the rear if you can swing it. Timing can help a little as well. I don't know where you are right now, but basics apply to all engines.

 

[Texas82GP]

The manifolds and 2" exhaust have to be restrictive. I don't know anything about those heads though.

 

[Wraith]

All of the above will gain some power. Mufflers, intake, cam, will help as will a lower gear in the rear if you can swing it. Timing can help a little as well. I don't know where you are right now, but basics apply to all engines.

Figured all the same mods would apply, the #8 heads I know drop the compression quite a bit, something around 8.5:1

 

[oldsofb]

#8 heads are usually called "Smog Heads". They had horrible 79cc chambers and low compression.

IMHO the place to start is finding some better heads first. Some 70's 6, 7, or 7A heads would be a good choice. If too expensive try to find some 80's 5A - 7A castings from the 307's

All will yield you a mid 60cc chamber (64-67cc) and the 70's heads will get you larger valves. That change first will get you a better "bang for your buck" with cam, intake, exhaust changes down the road.

Hutch

 

[L92 OLDS]

Figured all the same mods would apply, the #8 heads I know drop the compression quite a bit, something around 8.5:1

The #8 heads flow reasonably well but like you say, drop compression quite a bit with their huge 79cc smog chambers and for that reason are not first choice for building power.
You say this engine is in a Mercury? That could be a first.

If money allows, find a good set of aftermarket heads (check olds307 and 403 build) or #5, 6 or 7 heads. They all have a 64 cc chamber and will increase your compression ratio. Combine that with an Edelbrock performer RPM intake, headers and a good cam and you will be well on your way. It just depends on how much you want to spend and what your goals are.

 

[Wraith]

The #8 heads flow reasonably well but like you say, drop compression quite a bit with their huge 79cc smog chambers and for that reason are not first choice for building power.
You say this engine is in a Mercury? That could be a first.

If money allows, find a good set of aftermarket heads (check olds307 and 403 build) or #5, 6 or 7 heads. They all have a 64 cc chamber and will increase your compression ratio. Combine that with an Edelbrock performer RPM intake, headers and a good cam and you will be well on your way. It just depends on how much you want to spend and what your goals are.

Like to not spend a ton on this project, talked him out of an LS swap, but use what we have. It was sold to him as a 455 which the numbers proved wrong lol, so we are trying to make the best with what we have. I wouldn't have a problem swapping heads to a stock 5,6,or 7, don't want to spend the extra on Edelbrock or other brands BUT you never know with my buddy.

 

[olds307 and 403]

As said, 8 to 1 compression if it still has the shim head gaskets. My two sets of #8 heads measured 77 and 78CC, slightly less. There is a lip under the 1.625" exhaust valve that a bowl hog cutter or a grinder should remove if the heads are off. Unless flat top pistons or early 350 heads are used, you are stuck with 8 to 1. Something like a generic 204/214 cam and headers will make a noticeable difference and go with 2.25 or 2.5" dual exhaust. Tune that POS Edelbrock carb too.

 

[Clutch]

There's always the aluminum A-4 307 intake and a grinder if you're on a tight budget if you get early heads and you don't get headers it's still not going to breath threw those small manifolds. On one of mine I did #6 heads and 71 A-body manifolds with an A-4 intake and went nuts with a porting bit or 2 that all seams to have worked well of course if I added up my labor I'd say I had way too much time in all that but for who I was giving the car to it would have been worth it. Just a cam swap and dual exhaust would probably show improvement though.