[6x400gmc]

Okay, I've decided I'm going to ditch the Performer RPM due to hood/shaker reasons, and I have on my bench two intakes. One is a 1970 9799068, and the other is a plain 'ol Performer. Both intakes are stock with no "as delivered" metal removed. I have a set of 87cc Edelbrocks that have been cleaned up around the ports and measure out to almost exactly 2.200"

I have read every thread on the subject that I can find, but I'm still not sure if the cast iron intake will seal properly to my heads, or if the port mismatch will cause any problems. I'd like to use the stock intake, for a couple of reasons - 1. Because of Cliff's experience with the Performer and that 455 he was testing and 2. Have you seen the runner sizes? almost 1/8" narrower than stock!

So, what's the work required. I'm guess scribe the intake gasket outline on the intake and start blending?

Thanks.

Britt

[Steve C.]

Go out and buy a Fel-Pro 1233 intake gasket.

Gasket matching your intake to your heads offers power potential. Get your grinder ready.

Click on the picture here:

http://www.arkansaspontiacs.org/Tech_tips.html


Keep in mind the Performer intake will probably be differant on your 4-inch stroke combo verses Cliff's 455 testing. Also Cliff's set up is a TH400 trans and you have a 4-speed transmission. I'll suggest IF both intakes were properly port matched to your heads (width & height) then the runners properly blended you might find little differance in back-to-back testing. I'll presume testing with the Q-jet carb.





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[Lee]

As long as the intake port is SMALLER than the head port, I would not worry. frankly, I wouldn't even bother port-matching it. If you make the intake port the SAME, but then have a mis-alignment when you install, you will have the flow from the intake hitting a ridge where the head will protrude into the flow path - giving turbulence and a loss of power.

Also, on my old 455 T/A, I ran both a factory pre-EGR intake and a Performer. I ran both intakes for over a year, and made dozens of passes with each. Absolute best times for each - the factory intake was better by 0.06 seconds. Both were totally stock.

On my '67 Firebird, I divorced the water crossover, scribed the intake to the heads, and port matched the intake to the heads as closely as I could. It was not a HUGE amount of porting, but it took a few hours of grinding, and I smoothed/blended well up the intake port. At the track I saw zero difference.

Lee

[dataway]

One of those "See Snake" type fiber optic cameras by Milwaukee etc. are great for running down the intake ports to check port alignment.
JohnnyB

[Steve C.]

"As long as the intake port is SMALLER than the head port, I would not worry."

Much depends on the amount. A big distance has the potential for issues:


http://forums.maxperformanceinc.com/...ght=port+match

Also if it helps on the website I mentioned above in post #2 the topic of port alignment is discused.




.

[Steve C.]

This might be of interest....

Within another thread Skip Fix mentions that he dyno tested both a SD Performance modified Holley Street Dominator intake and a Torker II intake. It was my HSD intake he borrowed for that testing and I'm under the impression both intakes were properly port matched to his cylinder heads in use. On that particular HSD intake the port exit dimension is slightly under 2.300" tall. His dyno testing showed NO significant difference between the two intakes.

I dyno tested that same HSD intake on a very similar 462cid combination as Skip's engine along with a Torker II intake. But, and very important, the Torker II intake I used for my testing was borrowed for the test and was NOT properly port matched to my cylinder heads, whereas the HSD intake was. The intake ports on my heads are about the same as the HSD intake. Note the distance at the top of the ports between my cylinder heads and the Torker II was significant, the Torker II ports were much smaller.

My testing found the Torker II intake was down about 22 hp at peak power rpm compared to the Torker II intake. Both intakes made peak power at 5600 rpm. The torque was down about 12.7 ft.lbs. at peak torque rpm on the Torker II intake compared to the HSD intake. Both intakes had the same 1/2-inch open carb spacer installed and used the same carb for testing.

Unlike Skip's testing mine suggested quite a bit of difference between the two intakes. I suggest the mis-match with the ports on the Torker II intake played a significant part in the testing results. That said, you might not be able to tell any diferance on a street car with the seat of your pants. The amount of grinding you want to do is up to you



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[tom s]

im told the most important match is the roof of the head to intake.FWIW,Tom

[Steve C.]

"im told the most important match is the roof of the head to intake.FWIW,Tom"

X2

And if interested here is the source of the material from that other thread:

Any Port in a Match
Q I know that matching intake and exhaust ports are important for flow, and I've read that reversion also figures into the situation. Are there any other reasons that might be important? I would think that this applies to just about any engine regardless of how it's used.
Gordon Martins
Shawnee, KS

A Depending on the degree of the mismatch, cross-section area changes in the flow path can disrupt flow velocities associated with the "tuning" process. For example, if the intake-manifold runner is smaller than the port it's servicing, a sudden change in flow velocity (runner to cylinder head) can cause the total path to appear to be comprised of two shorter runners instead of one long runner. In turn, this may affect the amount of torque produced as a function of total runner length. Depending upon tuning objectives, this can be beneficial. But as a rule of thumb, you'd like to create uninterrupted flow paths for both intake and exhaust passages.

Source:
http://www.hotrod.com/pitstop/hrdp_9...#ixzz1q39xrl4u

Here is another article on the topic and a comment from it:

"No matter how you slice it, it is difficult to keep fuel in suspension in rapidly moving air as it makes the many turns required to finally get into the combustion chamber. Matching up the exits of the intake manifold runners to the entrances of the head's intake ports is usually the biggest improvement that can be made to improve flow in this area."

Read more: http://www.circletrack.com/techartic...#ixzz1q365szXw




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[6x400gmc]

The original point of this thread was to simply see if the Iron intake had enough meat at the top of the intake ports to seal to my unported Edelbrock heads. I appreciate all of your answers, but I learned the following:

The Performer intake's stock port height is 2.020" Which is the normal stock height for non SD engines. I took a 1233 gasket and laid down a spray pattern to see how much meat was there to work with.

I also did the same with the 9799068 ( 1970 Ram Air III ). These pictures show that there is plenty of aluminum around the Performer's ports to allow for full port matching up to the 2.200" port size of the heads, with about .145" left for sealing.

The Iron's ports are all over the place as far as casting alignment and sizes go. Number's 7, and 8 measure right at 1.900" tall, where the rest average out from 1.950" to 2.010" tall. The picture shows the odd (1-3-5-7) side of the intake, and clearly shows that you'd have a pretty good vacuum leak at #7. Same goes for #8 on the other side.

Not sure if this is just a casting defect with this particular intake, or if they were all this way. I'm also not sure how'd you'd go about making this intake work with 2.200" intake ports.

Hope this helps someone.

Britt

[Skip Fix]

FWIW my first ported E head motor I used an HO intake -'72-port matched to RAIV gaskets-it did seal. Used it to get to the Pontiac Southern Nationals and an HPP shootout until I could do a Shaker to fit a Holley.But when I swapped for T2 that was matched to the Felpro it picked up the car significantly as well as helped the idle quality over the Q jet worked by the Carb Shop as well as the Demon on an adpater(ran better than the Q jet by .2) on the HO intake. A factory intake on any ported E heads will be a cork/restrictor.

[Steve C.]

Very interesting. I had completely forgotten, or never paid much attention regarding the difficulty of using a stock factory iron intake with Edelbrock heads. The Edelbrock heads we have bought and used had a fair amount port work done to them and required proper intake manifold port matching to a much taller port size. That and we stopped using the stock iron intake many years ago and never looked back. I presume Edelbrock added additional material at the top of the Performer intake just for this reason.

Statement direct from the Edelbrock catalog......

"Although stock intake manifolds will fit, the

Edelbrock Pontiac Cylinder Heads are matched in size and operating

range with Edelbrock Performer RPM intake manifold #7156.

If the Performer RPM is too tall to fit under your hood, you may use the

Edelbrock Torker II manifold #5056. Additionally, any manifold that

matches Edelbrock #7280 or Fel-Pro #1233 gaskets may be used.

Manifolds may be used as-is, or port matched to the same size as the

cylinder heads for optimum performance."

http://www.edelbrock.com/automotive_...6000/60569.pdf




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[lust4speed]

Well I hope everyone appreciates that I spent the day pulling an Edelbrock head off one engine and the cast iron manifold off another just to take some pictures.

OK, the friend's heads and my manifold were sitting around my garage . Anyway these pics should confirm that a ported iron manifold can be taken out to the RAIV sized Felpro 1233 gaskets, and used on stock Edelbrock heads. This certainly doesn't mean that one should do that - only that it will work.

[Steve C.]

It appears it will depend on the specific factory intake that has been choosen for the project, and including how well or "straight" it was cast. Core shift issues (?).

[scott70]

I was actually in the process today of port matching a stock 70' intake to a ra4 gasket.The roof of the stock ports were quite uneven.The gaskets I'm using says tin indian on them that sd perf. sent with the heads when i got them back.Ive only got about an 1/8th" left at the top after porting but it looks like there will be enough left at the top to seal.

[Tim Corcoran]

My 67 iron intake is port matched to the 1233 gaskets to match the ports on my (ported)
6X heads. There is plenty of material left for sealing.