Re: Oval port or rectangular port intake???
 

More good information gentlemen.

Checkmate,
I will get those numbers to you tonight via e-mail.
I am now wondering what an intake change would do to my engine's behavior. Not trying to hijack Checkmate's thread but this all seems to be related one way or another.
Russ

Re: Oval port or rectangular port intake???
 

Why do you think this? A step up on the way to the intake can really foul up the flow. The proper way to promote fuel atomization is to have a consistent texture from plenum to valve. I know your only talking about 3/32 but I don't see how this could benefit in any way.

Roby

Re: Oval port or rectangular port intake???
 

Roby,
By putting a "bump" in the floor, the laminer flow current will "toss" the fuel up and give better mixture which results in more power. Show's it on the dyno but not on a bench.

Chris

Re: Oval port or rectangular port intake???
 

But why not maintain a swirl texture on the intake & head port to keep the fuel suspended. I have always had the best results by finishing an intake port (intake and heads) semi-smooth then going over it with a rather coarse brake hone. My method for doing this was a clockwise push and a counter-clockwise pull on the front cylinder ports. and the opposite on the back cylinder ports. When I swore off carburetors I only finished the heads intake ports. However perfect port matching was essential.

Re: Oval port or rectangular port intake???
 

The Merlin rect port manifold is perfect for a 540 low RPM motor!!

Re: Oval port or rectangular port intake???
 

I don't know how rough you leave your stuff, I like nothing less then a 40 grit finish on the intake. Better yet the texture of a golf ball. People get into the the "tumble debate" which I don't know if you are pro or anti, but I can say this by leaving the step shows gains on the dyno. I feel it picks up the "stragglers" and gets them mixed in with the others.
I know Roby some of the cup teams have experiment with a " valve seat" area on the intake face of the head. This area is cut with multiple angles then blended with a flapper wheel. These angles protrude into the path of the intake runner.

Chris

Re: Oval port or rectangular port intake???
 

Absolutely, they are cut anywhere from 5 to 6 angles then blended. but they also use the swirling method on the port just as I described. I learned this many years ago from Stock Car magazine. I used to bolt my bare heads to the intake and go at it with the flexible hone. It really works. Now on my EFI engines I have done the texture of the intake manifold is fine at 200 to 250 grit extrude hone, and the intake port of the head is swirl textured.

Roby

Re: Oval port or rectangular port intake???
 

How low? I know the increased displacement size it will work better than a 454 but at 5500 RPM the oval port intake will hold it's own I bet

Roby

Re: Oval port or rectangular port intake???
 

You have to understand that a low rpm motor to Wette Vette is around 5900 rpm :D .

Re: Oval port or rectangular port intake???
 

I am not claiming to be an expert at porting. I am just going to report what my AFR cnc'ed ports look like. They have a numerous ridges or steps going down into the port both the intake and exhaust. I called them to ask why they left them like they, they said it was so the fuel / air mixture tumbles down the port. They claim it works well. I will try to post a picture later today.