Square pipe over a round hole?

[Cethern]

This past week I took off my N-47 head and replaced it with a N-42 at that time I added a N-42 intake with the 60mm TB and a 3-2-1 header. I now have no compression in #6 the other 5 are at 130psi there is no oil in the coolant or leaking around the outside around the head gasket. I have not pulled it back off to see what is up but I feel the head is bad as the car ran just fine before I messed with it :surprised
Right now I'm planning on putting the N-47 head back on. My question is can I use the square port header or should I put the round port header on?

Thanks

Eric

[280~Master]

You can put square on round but you can't put round on square.

[Cethern]

I heard you could do one or the other..lol

[sblake01]

If you have both, why not use the one that matches the port shape of the head you'll be using?

[Cethern]

Sblake01

Well for a couple of reasons one I'm cheep and just had the header welded up to fit. And I don't plan on running the N-47 head for long, I had planned on sending a N-42 headed out for a valve job and port.

But if comes down to it I could use the one I have for sale.

Eric

[DaveN]

The car should run with header and ports that don't match but you'll lose some power. Any sudden change in the port cross section, either shape or area, will create resistance to gas flow. A sudden contraction causes more resistance than a sudden expansion, so a round port header on a square port manifold causes more power loss than going the other way.

[Cethern]

Thanks DaveN

It all went back together today and I have to say the over all performance of the 60mm TB a semi ported N-42 intake the 3-2-1 header Has improved the over all performance.
I should of done this a long time ago. Now I need to get my N-42 out for a porting