Aluminum heads

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03-18-2005, 09:25 PM

#61

mikes280

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Re: Aluminum heads

Quote:

Originally Posted by tomcat

Hey Mike: We talked several times in Miami, and I know your stuff works. Maybe you have tested a combination that answers my question from above.

Suppose you have good aftermarket heads with the kind of exhaust that most of us a using, e-tops or maybe sport tubes. Your flow numbers are in the 375/250 CFM range at .600 lift on intake/exhaust. You try increase exhaust flow by:

a) porting
b) duration
c) both porting and duration

What has been your experience if you have done this back to back? Of course I'm thinking blower engine. Not after specific trade secrets here, just whatever you can share.

a.lift and b. duration sometimes we try 1.8 rockers on the exhaust but we have had good luck with adding duration to the exhaust. Also if you go to the 1.8s and it picks up what does that tell you.

Last edited by mikes280; 03-22-2005 at 08:12 PM.

03-18-2005, 11:08 PM

#62

tomcat

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Re: Aluminum heads

That's a good way to test; doesn't take too long to change rockers.

03-20-2005, 10:27 AM

#63

GPM

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Re: Aluminum heads

Quote:

Originally Posted by WETTE VETTE

Give it a shot GPM!! At the RPM levels you turn you may just be on to something. I could see the added exhaust duration allowing some cylinder pressure to be lost in the lower RPM's, but at 7500 there isn't much time for too much to sneak out!!

I tried 4 cams last spring, 2 on the dyno and 2 in the boat, what's another one. Keeps life interesting.

03-20-2005, 03:24 PM

#64

KAAMA

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Re: Aluminum heads

Just an honest qestion here----what added amount of duration does a 1.8 ratio rocker give over the standard 1.7 ratio rocker arm? Thanks

03-20-2005, 06:43 PM

#65

formula31

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Re: Aluminum heads

Quote:

Originally Posted by KAAMA

Just an honest qestion here----what added amount of duration does a 1.8 ratio rocker give over the standard 1.7 ratio rocker arm? Thanks

hehe, you caught em. good one

03-20-2005, 07:14 PM

#66

KAAMA

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Re: Aluminum heads

Quote:

Originally Posted by formula31

hehe, you caught em. good one

Well, actually not trying to catch anyone really. I just really want to know. I think it's common knowledge among most of of us that a 1.8 ratio adds so many thousandths of valve lift over a 1.7 ratio rocker----but I was just wondering about the duration they add (if any) since rocker arm ratio was brought up.