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Port diameter differences....

I just bought a new Gnari manifold from Gnari for my 87 TC and it came with a mild port on the inlets already done to it. I have already ported my cylinder head exhaust ports to 1 3/8", mostly out of the tops only, the new Gnari already has port openings with a diameter of 1 1/2". I would like to know if I should open the cylinder head ports to match or is it fine to leave the head ports 1/8" smaller than the manifold inlets? If I should open up the head ports some more, is there enough room on these heads to get me another 1/8" of porting? This is a good crack free turbo head and I do not want to ruin it. Thanks

My personal opinion is to install it "as-is", since I'm pretty sure that a slight mismatch from smaller-to-larger will not adversely-hinder flow. In fact, if "reversion" occurs in turbo exh manifolding, such a mismatch might be beneficial in minimizing it. OTOH, the opposite (larger-to-smaller) would probably result in unwanted turbulence.  <shrug>

Disclaimer: I don't own a flow bench, nor do I have any experience operating one, lol.   Wink
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI

Ray, thanks for your response, I had a feeling that you would post a reply! I thought as well that going from small to a bigger opening would be fine. Thanks again

You'd probably hit water if you tried to match your port to 1.500 unless it was done really sharp right at the side of the head which wouldn't gain you anything. Just bolt it on and go.
11.42@120 no wideband.

Perfect, thanks for the answers, I thought that it would be good to go.

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