Offshoreonly.com
Page 7 of 7
« First
5
6
7
Show 40 post(s) from this thread on one page

Offshoreonly.com (https://www.offshoreonly.com/forums/)
-   General Q & A (https://www.offshoreonly.com/forums/general-q-20/)
-   -   Aluminum heads (https://www.offshoreonly.com/forums/general-q/97966-aluminum-heads.html)

mikes280 03-18-2005 09:25 PM
Re: Aluminum heads
 
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.

tomcat 03-18-2005 11:08 PM
Re: Aluminum heads
 
That's a good way to test; doesn't take too long to change rockers.

GPM 03-20-2005 10:27 AM
Re: Aluminum heads
 
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.

KAAMA 03-20-2005 03:24 PM
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

formula31 03-20-2005 06:43 PM
Re: Aluminum heads
 
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

KAAMA 03-20-2005 07:14 PM
Re: Aluminum heads
 
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.

rmbuilder 03-20-2005 07:17 PM
Re: Aluminum heads
 
Kaama,
No duration increase @ seat and approx effective duration increase +2*- 4* @ .200"
Bob

tomcat 03-22-2005 07:16 AM
Re: Aluminum heads
 
I have also heard that advancing or retarding the cam can tell you something about what the engine needs. Is that true?

mikes280 03-22-2005 08:07 PM
Re: Aluminum heads
 
i never said the 1.8 changed the duration it does but not anought to mater it isthe lift that changes


All times are GMT -5. The time now is 09:24 AM.
Page 7 of 7
« First
5
6
7
Show 40 post(s) from this thread on one page


Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.