Manifold/Intake port mismatch

[HakosukaJD]

So I replaced my clutch with a SPEC model (came with a throwout bearing that was quite different by the way) and since I had to remove the header while doing so, decided to replace the intake/exhaust gasket.

 

I had a stock replacement gasket. When I took it apart, I find that the new gasket has intake ports about 5mm smaller in diameter than the old one (which matches the N42 cylinder head). The new, smaller diameter gasket does match the manifold ports....so what's the deal? Is it common to be a port mismatch between the manifold (smaller) and the cylinder head (larger). Where can I get a manifold with larger ports? Would it help? I would think you would get stall where the air dumps into the larger cylinder head port...any suggestions?

[spork]

I'm not sure exactly what the problem is, so bear with me while I try to help.

 

It is very common to see the intakes have smaller runners than the head (if thats what you're describing). It can either be port matched to smooth the transition, or you can get a an aftermarket intake, or you can have your intake cut apart and ported out properly and then welded back together. Most people opt for option 1 because it's easy and a lot of people have done it themselves. Option 2 can run you anywhere fro $600 on up for a new manifold, but you may come across a used one cheaper than that. Option 3 varys depending on where you take it to have the work done.

 

Now if your saying your gasket has smaller ports than the one you took off...then maybe you should check and see if it looks like someone has ported the head and then modified the gasket .

[HakosukaJD]

That was indeed what I was describing. So port matching myself?...

Is that simply taking the manifold off, putting the gasket in position, marking the extra material and going crazy with el dremel?

 

I'm not sure exactly what the problem is' date=' so bear with me while I try to help.

 

It is very common to see the intakes have smaller runners than the head (if thats what you're describing). It can either be port matched to smooth the transition, or you can get a an aftermarket intake, or you can have your intake cut apart and ported out properly and then welded back together. Most people opt for option 1 because it's easy and a lot of people have done it themselves. Option 2 can run you anywhere fro $600 on up for a new manifold, but you may come across a used one cheaper than that. Option 3 varys depending on where you take it to have the work done.

 

Now if your saying your gasket has smaller ports than the one you took off...then maybe you should check and see if it looks like someone has ported the head and then modified the gasket .[/quote']

[JMortensen]

I had a gasket that where the intake holes were smaller than the ports. Funny part is that I didn't notice and ran it for a while. Then I took it off for some other reason and noticed. It hadn't torn up at all when I took it off, so I dremeled the holes out to match the port size, and that was that.

[HakosukaJD]

The gasket is fine....its the ports on the manifold that are too small.

 

I had a gasket that where the intake holes were smaller than the ports. Funny part is that I didn't notice and ran it for a while. Then I took it off for some other reason and noticed. It hadn't torn up at all when I took it off, so I dremeled the holes out to match the port size, and that was that.

[spork]

A dremel won't get you very even results due to the small sanding drum, but it can be done that way. I would suggest 1 inch sanding drum on a drill connected to some all-thread rod. It'll allow you to get into the port some while cutting a larger surface keeping things smoother and less chance of cutting lots of ribs in the manifold. You still can't get all the way up the ports this way, but you should do much better than you would with a dremel. Its pretty simple to do yourself. Just mark it like you described with a magic marker or something and then sand it away until you can't see the marker anymore and blend it up into the runner some. Be careful of the lumps in the runners if this is a fuel injected manifold. You can sand them completely off and smooth things out but you will need to use some epoxy to fill the holes where you end up sanding through to the injector hold down bolt holes. Epoxy it up and then sand off the extra.