Rat Bastid said

I explained it as simply as I could. And that teacher was an idiot. You have the discussion at the level of the student, but the goal is to get the student to learn, increase his vocabulary and to learn on his own.

Let me dumb it down some more for you. Do not make the port smaller than the head, ever. The goal is to make the port in the manifold the same size as the port in the head. If there is a mismatch, make the manifold bigger than the head, just enough to get everything else lined up.

Was that simple enough for you?

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Rat Bastid said

It’s funny, I watched that webinar live. I also asked a question or two on that one.

The first example you wanted me to look at was the 351C. I suggest you go back and look at all my posts in this thread. First I will remind you we aren’t discussing the 351C or the BBC. The OP a was asking about SBM. Secondly, I said there are a few, very few scenarios where the intake can be mallet than the head. In fact, in one post I said back in the mid 90’s a guy in Arizona published an article about doing that very thing. In that case, yes it helped. But...pay attention here...had the guy used the PROPER SHAPED AND SIZED HEAD he would have made more power.

So the hypocrite is you. I answered a very specific question with a specific answer for that question. Then I suggested you watch some videos to learn. All you did (which is what the sub moronic dolt Hysteric does) was to pull one example of a time when the manifold could be smaller than the head and ran with it. It’s not even close to what the OP is working with.

Now I’m off to watch the second part of the video to see what else you’ve taken out of context.

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Rat Bastid said

I just watched the second section of the video and you again didn’t pay attention. Darin said to make it line up. That’s exactly what I said. He also said that the air will shear off the sharp edge. I said that very thing. And doing that won’t cause vortices to form.

Darin says a .050 mismatch at the roof is too much and he said why. We’re you paying attention RF? I suggest not, or you still wouldn’t be arguing a wrong point.

Darin didn’t say a damn thing I didn’t say.


For the OP. Don’t do the port match unless you have a better understanding of air flow.

Also, if you use a head with ports that are poorly shaped and have too much cross section you CAN help it (its a CRUTCH for sure) by using a manifold that is smaller everywhere. That’s certainly not the right way to do it. But it’s what you do if it’s what you are working with.

Dan, if you watch all the videos I posted and you think you are ready to do some port work, I’m all for it. Other than that I say pass on it.

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