Offline999

Looking for some opinions on best "bang for the buck."
My '68 Cutlass convertible was swapped over to a 455 before I bought it. It turns out it's a 1976 smogger-headed motor. I'm going to have some engine work done over the winter and was wondering if anyone had any advice on where to best spend the money to increase performance:

a. Replace the heads
b. Install higher compression pistons
c. Ditch the smogger and try to find an earlier motor

it seems like doing the heads is the no-brainer (assuming the low-compression bottom end is solid)

Thoughts?

69 Hurst

I would go with "C". It will also allow you to keep using the car while working on the other one.

BillK

Depending on your budget I would go with what 69 said. You don't even necessarily need to get an earlier engine. Just get something that you can build the way you want it and then swap it in. If you want to stick with cast iron heads then I guess an earlier engine would have better heads on it. Really just depends on what your goals are and what you budget is.

Offline999

Thanks!

I live in New England and convertible season is coming to an end anyway plus there's some suspension work I'm going to have done at the same time so the car is going to be out of commission either way.

Bolting some better heads on seems like a quick HP win even with the 8:1 pistons. I'm not sure how much difference something like a 10:1 stroke is going to add.
It would be interesting to know if anyone has numbers for big valve heads on a lower compression motor.

The thing I do like about option C is it's probably gonna cost me about the same since it's the good heads that are the expensive part. The long block isn't likely to drive the price up much more so might as well just get that "thrown in."

Fun71

My opinion is the heads won’t make as much of a difference as you think. Look at the power specs of a 71 or 72 442 to see what you could expect with everything else original on your engine. Keep in mind the 76 engine was likely rated with single exhaust and a restrictive catalytic converter.

Offline999

Good point.
It's hard to compare the 1976 stats since it's been converted to dual Flowmaster exhaust.

I'll definitely check those numbers for 1971.
THANKS!

69 Hurst

Exactly!

matt69olds

Unless you have a set of decent early heads, I’d go aftermarket in a heartbeat! It’s really hard to rebuild 50 year old heads cheap. It’s also a well proven fact aluminum heads are a bolt on 30-50 hp over iron.

Let’s say the iron heads need a complete rebuild. Resurfacing, guides, springs, maybe a couple valves, possible valve seats,etc. Obviously the earlier heads will Breath better than the smoggers you have now, the engine will perform closer to what it would have in the early years. Now think about the money you would need to spend on the iron stuff to gain the 30-50 hp with the aluminum? The cheaper iron head rebuild isn’t such a bargain.

If the engine is mechanically sound, mill whatever heads you decide to use, run thin head gaskets, that will help with the lousy compression.

cutlassefi

Uhhh guys, you're forgetting what's coming early next year! Smaller chamber Edelbrock heads, but with the bigger valves.
Your stock J heads are roughly 83-84cc, these will be 68. Use a thin head gasket as mentioned and you're looking at almost a full ratio increase.
Add an intake etc and it'll be a different car, guaranteed. Stay wahhhm! Lol!

OLDSter Ralph

I must have missed it. You are referring to the Big Boy Olds heads ? There has been so much chatter about the Small Boy Olds heads that I thought nothing was happening with BBO heads. What size valves and ports ?

Offline999

I've been reading about Edelbrock heads in other threads.
Might be worth holding out for.

Offline999

Thanks for the perspective.

android 211

Being that there isn't much difference between a 68 shortblock and a 76 shortblock you ought to buy the new aluminum heads if money isn't a big factor.
If you want to keep the factory look and save a few hundred dollars then get some 'C' heads, not hard to find and exchange them on your '76 shortblock.

Offline999

Thanks!
That's exactly the guidance I was looking for.

ajr2820

I have a completely rebuilt set of C heads if you are interested.

edzolz

Something I learned a long time ago, "There is no substitute for high compression or more cubic inches".

Offline999

Absolutely!
The question is...where to spend finite dollars.

Does replacing the smogger "J" heads with bigger-valve better-flowing heads (essentially a bolt-on job) increase horsepower more than tearing apart the lower end to replace the dished pistons with non-dished pistons. (A much bigger job)

DROLDS707172

Couple of years back, I slapped a stock set of "C" castings onto a 74 455 with an elgin super stock cam and an edelbrock performer intake, 850 double pumper and cheap headers the 70 cutlass it was in smoked a friend at work's new coyote mustang. If the bottom is tight, save some cash and slap those new Edelbrocks on!

Offline999

NICE!
That sounds like a good plan.

Thanks