Ok... So I have a 79 351w in my truck right? The previous owner of the truck was my cousin who had bought it rebuilt with like 100 miles on it and it has a edelbrock performer cam, 4bbl 650cfm carb, bored .030 over, have no idea about the pistons and such... It is basically stock other than that. So as far as power goes I want to put some aluminum heads on the truck. I want better and more power than the gt40 heads I need some advice on what to get. I also have hedman long tubes on there aswell. If I have to change cam i will... Just want more power need help

 

Just replacing the heads with aluminum heads may not help much at all. The reason being that without knowing what heads or pistons are on/in the engine you won't know what combustion chamber size to go with. And the main beauty of aluminum heads is the ability to run higher CR on pump gas w/o pinging.

But, if we assume you have something like D8OE heads, which have 69cc chambers, pistons with a 15cc dish, and use a .039" head gasket you currently have 8.5:1 compression ratio. If you go with, say, Edelbrock Performer heads, which have 60cc chambers, you will have 9.3:1 compression ratio, and that will certainly help your power. But there are other heads available with different combustion chamber sizes, so you will have to choose.

 

Ok, afr has some heads with 185cc and say it's a 95hp gain over the gt40X heads. I don't know how much they are so like I said I'm not so sure. Will the heads I am talking about be good for more power?

 

Also it is between 72cc chambers or 58cc chambers. So i don't know what to do or go wth

 

No heads have combustion chambers of 185cc. Forget runner size for the moment, focus on combustion chamber sizes.

You need to understand what you are talking about. And, you do not. If you did you would not even mention heads with 72cc combustion chambers. That's because, assuming you are running the stock 69cc heads, 72cc combustion chambers would be a step in the wrong direction. Let's say you shell out $1000 for those heads - would you be happy with having LESS performance for $1000?

Please do some reading about heads, compression ratio, etc. Then ask some questions on here.

 

Camm - I'm sorry. Maybe I woke up on the wrong side of the bed this morning. I didn't mean to talk down to you.

So, are you interested in learning about compression ratio, pistons, heads, etc? If so, I'm happy to help. But please don't jump all over the place on subjects or go off on tangents. If you want to learn just say so. But you absolutely cannot make an informed choice on heads without some knowledge on the subject.

 

Of course i live to learn about anything I can involving cars and trucks... My cousin had told me to compare any other heads to the GT40X heads that came on the for lightning.. And the cc's of one head pair is 58 which is stock in gt40 heads from factory. So idk if upping the cc's will make more power or what... The afr heads are good and would like to go in that direction.

 

You can't compare to GT40X heads w/o considering what you have. What you have is the starting point and other heads must be compared to it, first. Then, and only then, if the other head passes that test you can compare them to each other.

The absolute, before anything else, first test is compression ratio. You MUST see if the head being considered will increase your compression ratio or decrease it. If it decreases it then you forget that head. If it increases it then you have to ask how much, as there is a narrow range that is acceptable. An iron head running 87 octane gas is only good for about 9.3:1 compression ratio, max. And that may be too much. However, an aluminum head might be able to go closer to 10.0:1. And more compression means more power, better torque, and better MPG - up to the point at which you get pinging or detonation, which will ultimately destroy the engine.

So, you need to understand compression ratio. An absolute requirement before going on. Here's a calculator that does a good job, and you need to play with it and understand how it works before taking the next step. Here are the parameters:

• Type: Set it to "1" for inches
• Cylinder Bore: For a 351W with a .030" overbore it should be 4.030"
• Piston Stroke: For a 351W with standard stroke enter 3.5"
• Head Gasket Bore: Most head gaskets will be 4.100"
• Compressed Head Gasket: The two most common are .049" and .039"
• Combustion Chamber: You enter the size of your head, which is probably 69CC for your heads, assuming stock heads.
• Piston Dome Volume: This is the size of the dish, with a negative sign, or dome of the piston. If you have the stock style piston enter "-15". Make sure to enter the negative sign.
• Deck Clearance: Most pistons on a stock block will be .020" down in the bore, so enter ".020"

I entered all of those #'s and get 8.406:1 compression ratio. I'd bet that's what you have, but the only way to tell for sure is to pull the heads and look on the bottom side for the casting #. However, the stock heads had 67-70cc combustion chambers for many years, and most of those I've measured were ~69cc so that's what I put in.

Now put in 58cc's for the GT40 heads and see what you get. (I get 9.33) That is a bunch, and maybe too much for 87 octane. But, if you go with an aluminum head with that size chamber then you are golden.

See how it works? Play with the calculator until you get a good handle on it. And watch this .