Vetal

iTrader: (3)

Let's say on a street/strip combo, with fairly mild cam and turbo on the smallish side so backpressure would be let's say 2:1.
So, is port-matching good idea?
I've kinda automatically port matched my headers to heads, but then started to doubt. I have fairly mild cam with 0* overlap at .05".
Should I open up the ports in headers again so there is a step?
I couldn't find any real testing done on this subject for now...

stevieturbo

I'd say you'd be hard pushed to see any noticeable or measurable difference by spending the time doing it.
that would go for both the port matching or the step. Unless there was a huge mismatch in the first place.

But if you have time to kill and are inclined to do so...go for it.

I'd sooner put the effort into a better turbocharger

Orr89rocz

iTrader: (13)

Ideally, the header should match the head port so a smooth transition exists. Going from head port into a larger header tube (as in a step up in cross section area when the header tube covers more than the head exhaust port itself) slows down gas velocity and changes pressure wave dynamics. You want velocity through the system although a slight step has been said to be a anti reversion dam, but if the valve events are right in the first place, there really shouldnt be much reversion. Now if header tube is smaller than port, it can be a minor flow restriction but doesnt seem to hurt as most exhaust gas comes out through the center of the port. But a turbo car doesnt seem to be as sensitive to header design like n/a setups I wouldnt worry about a minor mismatch, just get it close and enjoy.
How much of a mismatch are you looking at?

Vetal

iTrader: (3)

I had upto .1" mismatch in some spots. Now I matched one head perfectly and the other head I mostly matched before I've remembered about anti-reversion features of port mismatch.
stevieturbo, how can you put effort in a turbocharger? You just save money and buy it )

RonSSNova

iTrader: (3)

The truck manifolds we all use have ports larger than the heads. I certainly would not match the heads to the manifolds or headers

stevieturbo

Exactly. Spend that time earning the money instead of doing frivolous things.

You could spend hours with port matching and achieve almost nothing. Or spend hours earning money to buy a turbo that will achieve plenty.

MillsMotorvation

Any thing you can do to help, cant hurt!

Vetal

iTrader: (3)

Thing is, I already matched them. So now I can leave them alone, or open up headers ports back again

stock48

iTrader: (17)

It prob won't make a huge difference either way but I would want the header same or a tad larger than the head just so there is no lip against flow.

Vetal

iTrader: (3)

There will be no header protruding into head port because I've put 2 .1" dowels on each header so they will always go the same way

Forcefed86

iTrader: (4)

What heads are you talking about specifically?

Vetal

iTrader: (3)

Patriot Stage 2 LS1 heads

Forcefed86

iTrader: (4)

Ah, don't know a thing about those. I know lots of folks port the "D" shape out of the OEM LS heads exh ports and that's a no-no. Was just going to suggest not doing that.

Vetal

iTrader: (3)

No no no, I'm not going to mess with port shapes or anything else, just wanted to get rid of the lip (leave not more than .05" in few spots but closer to .02" or even flush in majority of the circumreference, just for slight misalignment even with locating dowels).

stoning_volcom

iTrader: (6)

I would like to think that port matching wouldnt hurt. The back pressure if it wasnt port matched i would think would cause turbulence.

Vetal

iTrader: (3)

Decided to finish port matching. Consulted few books, and it SEEMS like this shouldn't be an issue with cam with mild overlap.