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Posted by: Mueller Nov 22 2004, 09:01 PM

So I was thinking, (oh no Mr. Bill ) the exhaust side of the /4 heads is supposed to be the main weak link when it comes to getting any decent power gains from the type IV motors.....the ratio of what the intake flows compared to the exhaust is too lopsided (the exhaust should flow 75%-80% of the intake or something like that to be ideal?????)

If one was to keep the stock cam (not really keen on splitting the case) and just install a much larger exhaust valve and re-work the exhaust port only, would it make any appreciable difference?? This is for a 1.8 motor with a European racing header.....otherwise all stock...currently D-jet, but that can be changed

Posted by: SirAndy Nov 22 2004, 10:17 PM

and just install a much larger exhaust valve and re-work the exhaust port only, would it make any appreciable difference?? This is for a 1.8 motor with a European racing header.....otherwise all stock...currently D-jet, but that can be changed

Posted by: Brad Roberts Nov 23 2004, 01:03 AM

HUm... *somebody* you know has been asking this question for a few years now.


B

Posted by: Mueller Nov 23 2004, 01:07 AM

I'm going to try to get to whats-his-names shop this week to drop off my heads...we'll discuss pricing for such an "experiment"

Posted by: Mueller Nov 23 2004, 01:08 AM

QUOTE(Mueller @ Nov 22 2004, 07:01 PM)

and just install a much larger exhaust valve and re-work the exhaust port only, would it make any appreciable difference?? This is for a 1.8 motor with a European racing header.....otherwise all stock...currently D-jet, but that can be changed  :smash:

yes, that's the theory ...

put it on the dyno before and after so we'll all know for sure ...
Andy

Posted by: Brad Roberts Nov 23 2004, 01:49 AM

I'm working a guy in Mountain View for "use" of his engine dyno for "our" testing. He has one identical to Jakes so we should be able to compare some numbers (Mountain View is 10 feet above see level)


B

Posted by: chunger Nov 23 2004, 02:11 AM

What happens to a type IV if you make the exhaust valves really bigger at add NOS?

Posted by: Rgreen914 Nov 23 2004, 02:46 AM

What happens to a type IV if you make the exhaust valves really bigger at add NOS?

Posted by: chunger Nov 23 2004, 04:40 AM

oops NO2 the stuff that turns into N and O2 and happy fun hp.

didn't know holley bought them. Guess holley buys a lot of companies.

Posted by: Mark Henry Nov 23 2004, 07:32 AM

A big valve doesn't help much if the port is still small.

A 38mm is about as big as you will need. Porting on the exhaust port will help, but don't get too carried away, the exhaust port wall doesn't have a whole lot of meat on it.

My 2.7 nickies engine will have (most likely) 44mm intakes and 38mm exhaust and a lot of carefull exhaust port work.