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Discussion Starter · #1 ·
I have a set of 561 heads off a 97 Z28 engine, are these worth porting compared to the 643 heads? I'm building a 355 forged motor and still debating to go with stock ported heads or aftermarket heads.
 

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Those are good heads.
They don't need as much porting as the 643 heads.
Port em your self and slap em on.
Thats what I do.

-Nab
 

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Discussion Starter · #3 ·
Thanks Nab!

I had a feeling the later alum heads were better, just wasn't sure.
 

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Nab, that's not what I've heard. I'm pretty sure the later heads are not as desirable for porting and flow less than say the 643's.
 

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Nab, that's not what I've heard. I'm pretty sure the later heads are not as desirable for porting and flow less than say the 643's.
Forget which head is better.
If you want SEWAR like performance ..go aftermarket.

In the meantime you can get really nice gains porting what you have.
More with Larger Valves and of course better Springs.
Even more can be had with the Intake and Chamber reconfiguration and Polishing.

Two areas that provide the greatest improvement are
Port and Polishing Both Bowls and the Exhaust Port.

There is a solid 15 hp improvement in basic porting.
30hp to 40hp for the whole Monte.

It is all about the time and money.

Dan
 

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One Stock Elimiator guy I trust says those are the worst of the aluminum castings as cast, tried several pair, all sucked.

Several professional porters are well documented to not like them because they are thin and don't have material where they want it.
 

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They're decent heads. I ported a set and ran them for years.
Don't let these guys fool ya.
If its what you got USE IT!

-Nab
 

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I have a set on my car that were cleaned up by Race Prep and matched with an LPE211 cam and are amazing.
 

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They're decent heads. I ported a set and ran them for years.
Don't let these guys fool ya.
If its what you got USE IT!

-Nab
NAB is exactly correct..
Fix up what you got is the best and least expensive route.
Smartly porting you get hugh performance.

AS for Stock Eliminator...

I am one of those guys. I have Rare 441 Castings on my M/SA 69 Impala with 350/255. YEAH in that rhelm where no porting is allowed you seek the better flowing head.

What they don't tell you is they are skillfully cleaned up to yield about 10% better flow and still pass the very strict tear downs.

You are never going to hog out an any LT1 Aluminum Head like an aftermarket head. BUT for a whole lot less you will get excellent street/strip performance.

FWIW most racers with the best aftermarket heads really have to take their cars off the street to see the real benefit from the Sewar like flow.

HOTRODDING is often making what you have fly with little money and lots of ingenuity.

ROCK ON

D
 

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Thanks Nab!

I had a feeling the later alum heads were better, just wasn't sure.
That is not what was posted. Don't read something that is not there. I agree with Dwayne. I'm not stating they not worth porting or using. I'm not disagreeing that they are not "good" heads, or that they are bad. I'm just stating they are not the better choice of porters that know what they are doing. It is more desireable to have some 'meat' to work with, to port and shape as a good porter would prefer. For those that prefer not to remove a lot of material or would rather just do some touch up and go, then these are the heads for you. For some reason readers like to read into statements wording that is not there.

It was not too many years ago I had a hard time convincing the 'gurus' here to port good heads before bolting them on. That was before this forum group became aware of a guy name Phil or AI in general. At least this forum has made some progress. :)
 
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