i have a 1975 cutlass supreme with a very uninspiring 350 what can i do iot is a low miles engine just gutless

 

Without tearing it down and adding pistons to raise the compression into the 9.5 to 1 range and adding good cam, intake and exhaust combo not much. But you could consider upgrading the rear gearing to the 3.23 to 3.42 range. This will give it a good kick in the pants and feel like you added some hp to the engine.

 

You have 165 hp 275 ft/lbs of torque V8 with a 2.52 first gear and probably 2.56 rear gears in a 4,000 pound car. Do a compression test and put an oil pressure gauge to see how healthy it is. Does it still have the catalytic converter? It could be plugged and the factory exhaust system is restrictive, even with converter removed. If the motor is tired, it needs rebuilt with different pistons. If it has good compression and oil pressure, early 350 heads milled to 64cc and a better cam with dual exhaust will help a lot. A 2000+ stall should also be installed. We are spoiled with new cars. My similar weight Dodge Challenger GT with nearly double the HP, 305, nearly same torque 268 ft/lbs, a 4.71 to 1 first gear and 3.09 final gear ratios is like a Rocket ship in comparison, pardon the pun. Good luck.

 

Here is your cheapest path to significantly more performance:

Olds 455 complete engine $800 - ClassicOldsmobile.com

 

As said above, there's not really much you can do engine-wise to increase power without doing some major work.
Does the car still have the factory exhaust system? If so, that is a very restrictive system, so installing a true dual exhaust system would help the engine breathe.
Other than that, as said lower rear gears are the best bang-for-the-buck. Get rid of the 2.56:1 gears and install anything in the 3.xx:1 range and it will feel like you have a huge increase in engine power. Your 8.5" 10 bolt rear has lots of aftermarket support so parts are readily available.

 

Start with a good tuneup and a nice set of true dual exhaust.

 

Agreed. I neglected to mention above that the OEM catalytic converter in that era was extremely restrictive. If you must retain the cat converter, the modern versions flow a whole lot better.

 

Michael all advice already given just about covers it. But a clearer picture of your cars current state would definitely help us understand your level of disappointment.

You say low mileage but is she bone stock ? Is she already dual exhaust and she still feels like a dog to you ?

Your cars stock rear is the biggest culprit in lack of oomph. The mid to late 70s era was overweight and underpowered, then to add insult to injury they installed numerically low rear gear ratios to maximize mileage. The results were devastating across the board. Mileage was not enough to justify the fact that the cars couldn't get out of their own way.

 

As previous posters have mentioned. Right on the money. My 75 cutlas 350 was gutless. No longer. 2.56 gears changed 3.42. Huge change. 2004r tranny. #5 heads. Cam /intake and new duals. New pistons shallow dish. Thornton jr manifolds. You will have carb work to on the lean jets. It will actual burn some good rubber now. Good luck.

 

Fantastic! You have a great recipe. The ideal gear, transmission, and heads. Along with a cam that's more aggressive than the 350 stick cam. (Lunati,10420701... intake duration duration 213, exhaust 219.) Essentially the exact way I think I should go if and when I ever decide to get my 350 to be all it can be within reason.

I am figuring you may have 100 HP over stock, when you consider all modifications made and the fine tuning it took to make the engine sing. Now you have a good-looking ride that runs like it always should have. Appreciate your photo album as well. Including the layout of parts and clean finished product.

 

would i see decent improvement by putting #7 heads on my 75 cutlass 350?

 

A rule of thumb might be a gain of 3-4% horsepower for every additional point of compression added while keeping everything else the same.

 

There is a difference in combustion chamber volume between your #8 heads and the #7 heads (~80cc vs ~68-70cc). So installing the #7 heads without any other changes would raise the compression almost 1 point.

 

Your current #8 heads are probably closer to 77 or 78cc. I measured two sets that came off motors with shim head gaskets. So it probably will be almost exactly 10cc. The problem is the difference in head gasket thickness. The usual Felpro replacement are .042" compressed vs the factory .017" compressed shim head gaskets. You only gain about a 1/2 point without cutting the #7 heads. The other gain is the exhaust side flow. A bowl cutter is needed for your current #8 to flow was well. The numbers out there are about a 40 cfm on the exhaust side, similar on the intake side. Also stock pistons are around .025" below deck. I use this compression calculator, the regular part anyways.
https://uempistons.com/p-27-compress...alculator.html