Date:         Mon, 25 Jun 2001 13:27:59 EDT
Reply-To:     Wolfvan88@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Robert Lilley <Wolfvan88@AOL.COM>
Subject:      Re: WBX big valve heads and flow bench results
Content-Type: text/plain; charset=ISO-8859-1

While the numbers alone look impressive, what is more important is how they work in the engine, installed.

I put in larger valve heads in a T1 and lost mileage with no real increase in power.  I also put larger intake ports in a T4 engine and gained no power increase and loss of mileage.

With larger ports and /or valves the intake air speed decreases.  This causes low end power loss and also moves the power band up the rpm scale.  Which is not bad, if you do not mind shifting more at lower engine speeds due to lack of low end torque.

What will affect the effectivness of the larger ports and valves is how they will work with the long air runners.  Also important is the cam selection, exhaust, muffler, filter choice.


If you are considering big valve heads and or large scale porting,
you will give up in the low end to gain in the top end, and have a loss of mileage.


What I did to my stock AMC port was to clean up casting marks, apply a racing valve job on seats and valves, increase the size of the intake and exhaust ports and air runners, leave the castings rough and match port the intake and exhaust, I would guess my ports are flowing close to Bobs modified ports.

I choose the ratio rockers rather than the bigger valves to keep from losing low end air speed and to improve the bottom end.

I wanted to incease power but also increase mileage and I did both.

Warnings about polishing intakes:

http://www.marlinmedia.com/pvt/ZJ/tech/intake-porting.html

Basic guide to basic porting
http://www.sa-motorsports.com/diyport.htm


The first section is important:
Cylinder Head "101"

http://www.alternativeauto.com/catalog/heads.html#Head Porting

Fundamentals of 4 Stroke/Cycle Piston Engine Performance:

http://home.att.net/~jroal/perftheory.htm#Intake


The important point is to match ALL the systems to the changes you make to the engine.

Robert