silent running

After a lot of hassle I finally got the exhaust manifold off to find a few weird things. First off, there were two gaskets sandwiched between the head and manifold on each side. Is this normal?

Secondly the H&S up-pipe wasn't such a hassle to get off after all. Being as it's just got a slip joint it almost fell out, although the top half is still there attached to the turbo. It's been blowing at the up-pipe-to-manifold joint though. Is this just bad luck or because it's slip jointed so there's always some movement there while it's warming up?

Next, all the guidance I can find says that as well as porting out to the soot line at the head end ports, I should separate the crossover pipe from the headers at each end, then port these intermediate joints as well. Is this REALLY necessary? The port sizes look well matched; I can't see what you'd achieve by porting to the gasket line on these intermediate joints if you can't get all the way down them.

Last thing - the exit of the exhaust manifold looks way smaller than the entrance to my 2" up-pipe. Should I gasket match this port, or leave it alone with a small-to-big step in bore?

911

2 gaskets are not right, just the one.
There should be no leaks anywhere as this is lost pressure to spin ght e turbo.
Clean/file every flange flat and use fresh Subaru gaskets.

As to porting, unless you can port smoothly deall deep the all you make is a system of open cavities and restrictions.
The smaller exhaust size to up-pipe is ok, I ported my cast headers to the head gasket soot line only in the end as i came to the same conclusion as you.

Graham

silent running

Great help again, Graham, cheers. Looks like a visit to Subaru parts desk is in order then. The thing I don't get though, is that clearly there's a big soot line on the exhaust ports on the head - as big as the ones on the headers i.e. the gaskets are oversized but the ports are actually fairly well matched in size already. Yet everyone seems to get good results just porting the manifold rather than the head itself.

911

Simple:
Just imagine you are a stream of vey fast moving exhaust gas on your way to the turbo.
If you come to a hole smaller than the one you are traveling along then that will be a restriction, so ideally you would blend it open to the same diameter/shape, and so you keep going.
Where the gasket hole is larger than the port hole/shape all that presents to the gas flow is a groove that will generate some turbulance to the outer laters of the gas stream, so can really be forgotten.

The best people are API Engines and Harvey for ported headers, and at about £170 a set that is cheap.

Graham

Jay m A

iTrader: (2)

Regarding the H&S slip joint, yes they do pull apart when cold. They also blow a bit when cold too. But once warm they seal. Its pretty easy to spot by the rasp the exhaust makes when blipping the throttle when warming the car up. The rasp should disappear once up to temp.

silent running

Great answers, many thanks. Think I have my plans sorted out now - which will involve Harvey.