[Mtume]

I´m thinking of buying a pair of old cylinder heads #3991492 "LT1,Camel hump,accessory holes,64cc, straight plug"

Couple of questions:
Will they fit on my csb 71´ (#CGC) engine?

Are they, the heads, any good? What would be the gain, loss?

Can they be changed by a newbie without taking the engine out?

The ones I´ve got on now works fine, but if these are better i could be worth it, or? I dont know the # but it starts with 37..... maybe an 8 or a 3 after that.

Thanks
Newbie Anders

 

[motor]

those heads are 64 cc chambers .what is casting # of current head... www.mortec.com .I personnaly don't think it would be worth the trouble .You can buy aftermarket sb heads so superior to what gm used to do .And sb heads are cheap.Can you find some gm vortecs .they work decent for the buck ,But you'll need vortec intake.

 

[Mtume]

What difference does the cc do? There´s a possibility that the ones on now has 76cc chambers.

Could you name a good aftermarket top that´s good?

 

[MinionII]

The chamber cc has a huge effect on the compression ratio of the engine.
Definitely find out what's on the car now before thinking about changing.
Changing from 76 to 64 cc heads will bump the compression ratio significantly, and depending on where your compression ratio is now, the new compression ratio could make it impossible to run on pump gas.

 

[Mtume]

Does 76 cc have a lower ratio then the 64cc?

 

[Highway Star]

Yes, it is an indirect relationship. The bigger the combustion chamber, the LOWER the compression ratio.

 

[Mtume]

The bigger the combustion chamber, the LOWER the compression ratio.

Which for a newbie means?

 

[ftrplt]

Detonation is a very bad thing in an engine and you want to take every opportunity to reduce an engine's tendancy to detonate or "knock" at every turn. One of the many factors that can cause an engine to detonate is its compression ratio. Basically, the more pressure, the more the tendancy to detonate. There are many other factors which can affect an engine's tendancy to detonate or "the uncontrolled ignition of the air fuel mixture in the combustion chamber which results in a supersonic flame front, high temperatures and very large pressure spikes" in the chamber. Some of these are, squish and quench of the piston/head choice, ignition timing lead, octane of the fuel, chamber design and even the material the head is made of. The 1492's you are looking at represent technology almost 40 years old. This means that the chamber shape, especially if it is 76 cc's, material (iron instead of aluminum), and intake port design (not optimizing swirl) tend to make them inferior to today's heads. Hope this helps.
Dave

 

[Highway Star]

It means that by changing your heads to ones that have smaller chambers, you will increase your compressio ratio. Up to a certain point, this will help you make more power, but if you wind up with too much compression, you would have to run race gas with very high octane to keep from detonation/preignition.

You need to determine exactly what you have to make this decision. Has your engine ever been rebuilt?

 

[Mtume]

I have little knowledge about my engine, but I bought it from the states in 06. Here in sweden we have 95 octane as the lowest and 98 as the highest octane. At the moment I run on 95 without any problems (fingers crossed). The reason wjy I dont know the numbers on my cylinders is because I only have a fuzzy pic of it.

 

[Frankenstein]

I think before you do anything you need to find out what heads you have now.If you can post the casting numbers we can find out they are.Why do you want change them and what are you going pay for the camel backs, are they rebuilt or do they need work.I'm rebuilding my 70 El Camino's 350 and I'm not even going to mess with the old heads I'm going to go with new GM Vortecs.