Question about exhaust porting

[Brian schanafelt]

I've read and read about doing porting on my 1.6 td head and some people suggest not porting exhaust because ithe smaller port increases velocity  to the turbine .... But cleaning up the casting  is beneficial  along with  taking  the  hard angle  under valve out .and  cleaning up around  valve  guide....... Also I have read that porting  the exhaust all the way thru increases flow..... Now this is where I  would think that velocity would be better than flow before the turbine.... I'm  wondering if there is some of you out there could help point me in the  right direction.... I'm wanting to learn what I can  on doing  it  the right way  from people that  have actually had  proven results..... I've read some of David vizards articles on porting  and really has some good info  just trying to clarify on the route I should take

[theman53]

The David Visard article at the top of the page is very key. What you have said is somewhat accurate. If you open the exhaust a bunch you will have more flow than if you don't, without the tools to measure you will not know if the velocity was improved over stock or not. General rule is to open it up to the size of the gasket and smooth out the bends. This will increase flow and velocity, for all out flow just keep opening. All out flow is best for high rpm engines/race engines/etc...pretty much not what our diesels do. Yes we can rev to 6,000 rpm but that is not where it makes power nor is it close to what gassers do, so we don't need the flow as much. Velocity is king and try to keep all the ports equal. If you need to see pictures look in my thread to get an idea.