I have a 1974 455 in cutlass supreme. Looking for a little more power, run a little more like early 70s versus mid 70s. Will cam and intake be noticeable without different heads?

 

You most likely have low comp pistons so your choices are limited.
I’d do dual exhaust and maybe even a gear change first.

 

Tuning and optimizing what you have may be a good place to start before you go spending too much money.

What are you starting with? Is it 100% factory or have other modifications already been made?

 

[QUOTE=BangScreech4-4-2;1578652]Tuning and optimizing what you have may be a good place to start before you go spending too much money.

What are you starting with? Is it 100% factory or have other modifications already been made?[/QUOTE It’s factory dual exhaust, planning to upgrade new rebuilt quadrajet, comprsssion is from 120-130 on all cylinders. It runs well, but would like a little more.

 

I have factory dual exhaust, I think it could be larger diameter and help. Gear is about as low as I’d want to go for highway, 2100 at 65mph. Tops out at 4000rpm 126mph gps

 

Optimize carb, advance timing, tune advance curve would be easy & cheap.

Headers & exhaust depending on taste, headers don’t need to be loud but will pretty much always be louder than cast iron manifolds.

Tune transmission governor for higher WOT upshifts. Good quality (less slippage driving) higher stall converter?

Some more gear as tolerable, then again a fair amount more gear and overdrive will make a really noticeable difference with no downside, other than financial!

After that stuff, you’re pretty much building an engine, you just can’t do a lot with the low compression via bolt ons. You could put a mild cam in it but that’s gonna bring limited bang for the buck and effort. An efficient aluminum intake wouldn’t hurt, but again, low bang for the buck on its own and to get much out of them, your headed towards that cam and now headers and all that heads you towards gears…

See where this is going?!?

​​​​​​….

 

@Dave442

This CO member might be able to help you out. He's got a Holley rebuilt 800 CFM Q-Jet which really sounds perfect for your application. I think it's $325. I was actually thinking of getting it myself but my Q-Jet is running pretty nice right now.

As far as the rest of the stuff goes, you're getting some good advice above: with a rebuilt carb, a distributor tune and curve (original points type, right?) and fresh plugs, you might wake it up pretty good. Then you can decide whether that's good enough or if you want to move forward with headers, a mild RV-type cam and whatever else.

Remember though, as has been pointed out, with that low compression you're going to run into the law of diminishing returns pretty quick.

 

I forgot to add, it does have hei distributor in it.
Thanks for the advice guys! I’ll probably just work on the exhaust and advance curve and maybe find an engine to build while I drive this one!

 

Is that a factory style GM HEI or an aftermarket one? Depending upon the mechanical advance amount, the initial timing may need to be raised significantly from the original points setting. Either way, ensure the total timing is 32-ish degrees. Too low full advance will cause low power and slower acceleration.

 

since you didn’t really get an answer to your original question..yes, you’ll see a big improvement with intake and a cam swap.

if the engine is in good shape, a short duration higher lift cam and a performer intake will really wake it up. the higher velocity small ports in the intake plus the cam will increase your cylinder pressure. The cam is more important than the intake..you can stay with the factory intake.

go with something in the low 260 adv range and 200 to 210 max int duration at .050 with as much lift as you can find. a free flowing exhaust is will help.

 

Your original factory cam is probably the 400117, which had advertised duration of 258/272° and lift of 0.435". They used that for 7 years in the base 455. I had that one in my 1970 Vista Cruiser and I agree with you that it does not have much punch (with your lower compression, it would be even more disappointing).

A longer-duration, higher-lift cam will definitely be a noticeable improvement for you--as it was for me.

 

Note above post(s). Go easy on the duration -- OP has considerably less compression to work with than you did.

I would still get it running as well as possible in its current state before doing anything else -- if only to establish a baseline for future modifications.

 

yep, stay away from long duration on low comp engines with numerically low gears