gasket matching exhaust runners

[athlete3344]

This seems a bit excessive to me, but is gasket matching the exhaust runners over kill? ill put a pic up later but theres a gap of about a quarter of an inch around and on the fp manifold its about half as much

 

[athlete3344]

Heres the pic.

This just seems really excessive for the amount of material that would be removed if I were to gasket match.

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[Roberti 2G]

I did this on my stock manifold but not my FP it flows better just on design alone. But you should benefit from it if out port it just takes sometime to do it right with good carbide bits.

 

[Talyn]

Are you sure you have the right gasket for your cylinder head?(ie. 1g/2g) Because I did have my cylinder head gasket matched and it wasn't nearly that much material from what I recall.

 

[mercaholik]

You really shouldn't gasket match the fp manifold. Also you may wanna get an oem steel gasket, it should be a better fit. If you hog out that much on the manifold, what about the head? There is gonna be a a loss of velocity I would think from going that much bigger. Plus now your changing the shape of the runner which was designed a certain way. Just clean up and smooth the transitions and you should be good.

 

[NHerron]

Put the gasket on the head. Now how much is the difference?

 

[athlete3344]

The picture above is the gasket on the head.

Ill find myself an OEM gasket if theyre that big of a difference. The gasket was ordered from advance auto - felpro.

 

[NHerron]

Sorry my mistake, anyway, I meant manifold as you mayyyy have suspected.

 

[athlete3344]

Just wanted to clear that up the pic.

Yea the gasket on the manifold is much closer, but theres still about 1/8" around for a gasket match.

Low end velocity losses dont really bother me, Id rather have the top end have a bit more power.

 

[athlete3344]

Are you sure you have the right gasket for your cylinder head?(ie. 1g/2g) Because I did have my cylinder head gasket matched and it wasn't nearly that much material from what I recall.

Im pretty sure its a 2g gasket, unless advance got it wrong. It does seem like a ton of material, which is what threw the red flag. For what its worth, it does line up perfectly with all stud holes.

 

[Talyn]

Never assume advance auto or any other parts store got it right, you'll learn the hard way if you do, Like I said, I actually DID have my head gasket matched, and I don't think it was half that much excess material, double check its not a 1g gasket, I know for a fact that the 2g and 1g heads have different sized ports, though I can't remember which had the larger and which had the smaller.

 

[NHerron]

Manifold studs:
6 Bolt Head uses 9 8MM Studs.
7 Bolt Head (both 1G/2G) uses 7 8MM Studs and 2 10mm studs.

I'd just match the manifold to the head and polish to keep turbulence down.

 

[athlete3344]

Manifold studs:
6 Bolt Head uses 9 8MM Studs.
7 Bolt Head (both 1G/2G) uses 7 8MM Studs and 2 10mm studs.

I'd just match the manifold to the head and polish to keep turbulence down.

Thats what I was leaning towards too. I know for sure I have a 7 bolt head - also obvious from the difference in number of bolt holes from where the T-stat housing bolts up. Maybe Ill order an OEM gasket to see if its closer to matching the manifold, and use that as my guide instead.

 

[Mello]

I don't use the gaskets when I do this. I'll make a template from a sheet of card that I match up to the ports & manifold and then try to, as smoothly as possible, match them to each other with the least possible material removal & maybe the manifold slightly larger (when in doubt) if size is matching.

 

[njclimber36]

A number of people believe that leaving the port in the head smaller than than the exhaust manifold port as a small wall that disrupts exhaust gas reversion and as such makes more power. The bump that it creates isn't supposed to actually stop hot gasses from flowing backward, but disrupt noise waves that at certain rpms can aid in cylinder scavenging in NA motors but can hinder flow in a high back pressure turbo system. My guess is that it probably wouldn't make a noticeable difference either way on a street car.