Intake porting advice needed......

[Rommel Racing]

I was hoping some of you with porting experience could give me some insight on porting my #2907 454R intake.

I have read just about every thread on here, and have saved lots of manifold pics that have been posted, but I still have some questions.

Here are a few pics of my intake.







What I am wanting to know is, in the picture with the red arrow, the roof of those runners has a very sharp edge, but the runner next to it has a nice turn to it. Would it be a mistake to radius the roof of those runners with the sharp edge?

Somewhere, I once read that you shouldn't mess with the entry at the roof, but after seeing lots of ported manifold pics, it seems that almost all of them try to open up the top of the runner

The last 454R intake I cleaned up, I didn't reshape that area, but now I am second guessing myself. Here's a pic of that one.



Anyhow, I know what I would like to do to this manifold, but I don't want to ruin a good manifold either.

Any help would be appreciated.

Steve

[Abbottracingheads]

Radius the heck out of it.

[Fatman]

No help but more questions.

Quite often you see a larger radius into the outer runners than the inners.

Why are the 2907s almost square into just the outer runners? Poor design or was it done on purpose?

[TOP38]

I have had good results working the plenum into the roof on all ports w/this intake. I am pretty sure the papaer work from eddy states not to mess with this area and say carb signal is the reason. Radius this area for all ports and use a 1" open spacer under the carb.

[T]

Yes, like what was said. Lay the roof back as much as posible. Also, do you run a spacer? if so, bolt it on and blend it in from there. Good luck

[comet]

Is it possible that the runners of the 2907 are smaller csa in the plenum than exit csa? And why? They have a thick divider, after that a thinner
wall.If you need some more rpm can you make it thinner in the plenum or are you just destroying it?

[desoto30]

Radius the heck out of it.

What radius should we be shooting for please?

[Ron E]

Radius the heck out of it.

What radius should we be shooting for please?

Like Abbott said...Specifically, make the radius into the end runner as fat as possible. From the point you can start the cuts below the carb mounting surface, make that point to the runner-roof as big/gentle of a radius as you can. This type of manifold will appreciate it, as the long runners are typically a little down from the shorter ones. I've Incorporated aluminum (doweled, or welded) aluminum spacers on these style manifolds and started the turn above the actual carb mounting surface of the manifold with good results. Of course they were on engines that could use the extra plenum volume.

[Fatman]

What about the inner runners?

Increase the radius or just clean up the casting flash?

[Rommel Racing]

Well I started on my manifold today, do you think I should still go a little higher on the roof?

Thanks,
Steve

[T]

Nice, is that the spacer you are going to use? Plastic? If you had a wood or a alum. spacer you could blend from there. But yes, that is what you are looking for, roll the roof back. You did well.....

[Abbottracingheads]

Looks a lot better.

[Rommel Racing]

Nice, is that the spacer you are going to use? Plastic? If you had a wood or a alum. spacer you could blend from there. But yes, that is what you are looking for, roll the roof back. You did well.....

Thanks for the help guys, I will be testing a bunch of different spacers this year, but yes, I will be starting with the one in the picture,because it was the one I was using last year. I got it from Jegs http://www.jegs.com/i/JEGS/555/15436/10002/-1

So you are saying I should start my turn right from the carb flange? The one in the picture starts turning around 3/16" down from the flange.

What about the divider? Should I thin it out a bit? or just leave it the way I have it now?

Thanks again for all your help,
Steve

[Ron E]

So you are saying I should start my turn right from the carb flange? The one in the picture starts turning around 3/16" down from the flange.

What about the divider? Should I thin it out a bit? or just leave it the way I have it now?

Thanks again for all your help,
Steve

The amount of rolling into the roof can be over done. You're messing with the taper at this point. So, it's not an easy call. I've had some work well with about the amount you've done there. I've had some that started well into the spacer and required welding in extra material to achieve. It's sort of a matter of feel from this point. Thats pitiful advice, but past what you've done, it is more a sum of one's experience. (fancy way of saying you may need to screw a few up to get that experience) On the dividers, don't narrow them. Round them up like you're doing. I even leave them as fat and round as I can at the top where they blend into the plenum wall. But, I've seen them run great shaped like yours. You can take it further....at your own risk. But at this point, you've definitely helped your manifold.

[Rommel Racing]

Thanks for the help Ron, I think I'll just finish it as is.

Since it worked pretty well right out of the box, what kind of of improvement should I expect from these mods, based on your experience?

All aluminum 10.5-1 540bbc, Dart 355 Pro 1's, 1150cfm dominator, solid roller 274/282 @ .050 .750 lift @ the valve 114 lobe sep.

Thanks for everyone's help, I will let you know my results when I dyno test it again.

Steve