My cylinder head has the square exhaust ports with the steel liners. Is there any advantage to removing them, and how do you get them out? I was thinking that they might be an unnecessary restriction, and removing them would improve exhaust flow.

Also,

How would you recommend matching the exhaust manifold to the exhaust ports? the only thing I can think of is to use the gasket or clear plastic and compare and compromise.

thxZ

Those exhaust liners flow fine. Just have a machine shop mill the exhaust valve guides flush with the roof of the runner.

To add to Blue's comment, I've never seen an attempt to remove those that didn't look bad. (Read as ruined the head.) The ports that have the liners are not the same size/shape as the real square ports, and trying to make them match the manifold is a major PITA.

I tapped out a gasket and Sharpie-ed it then ground with dye grinder on my intake. I don't know about turning an N47's exhaust port into an N42 though.

Edited May 30, 201212 yr by siteunseen

mill the exhaust valve guides flush with the roof of the runner.

Is that a big improvement, or a small one? At this point, I might rather prefer to just get the engine back together and in the car, than ask the engine guy to start another 'project.'

BTW- it's an N47 head and N47 intake, and stock exhaust manifold..

thxZ

Edited May 30, 201212 yr by TomoHawk

If everything in there is stock, nothing will be a big improvement. Not cutting down the guides, nor removing the liners. For stock intake, exhaust and cam, I'd leave it stock and put it together.

The port liners seem to be in good condition, with no rust, so I think I will just leave them. Optimizing everything else, especially the distributor, will be enough of a job.

Wise decision......I don't believe there's any difference......my P79 heads with liners flow great!

I agree. Beandip is running a P79 w/liners on an L28 in his 240Z, runs strong.