I have been looking at my Performer manifold and wondering if I should clean up the runners. After measuring the ports I found out that they aren't even close to being the same size.
Should I clean them up and match them up to the heads?
Is it better to leave them smaller the the head ports?
Should they aleast be brought up to the same size?
Should I leave well enough alone?

 

This is a topic that opens very lively debate. I almost always port match but I realize that there is no substantiative evidence that supports this as doing anything statistically significant as far as measured flow or horsepower. So let's just say I do it because it makes me feel good and leave it at that.

Now there are other issues that come into play. The Performer is designed as a high-velocity intake and by opening up the manifold, you are decreasing velocity. You also have to look at the degree of mismatch. If it is substantial (like over a quarter inch all around) then there are two things to consider. One is Bernouli's principle which says that when you move a fluid from a small hose into a large hose that your pressure decreases which could stall the airflow. Ideally, you want the mixture to be, more or less, monolithic column of air from the time it enters the plenum all the way to the valve head. The other thing you have to consider is that "some" port mismatch can be beneficial in a street engine. There is always some intake reversion and the smaller manifold lip will block some of that backflow into the plenum (or a smaller exhaust port leading to a larger header doing the same thing).

Now most of this is only proveable in very high horsepower applications where an increase in power or efficiency is measureable beyond the margin of dyno error. In a fairly mild street engine, it won't make any difference that you can feel. So get out your grinder if you just want to do it for grins. You have neither anything to gain or loose except your time.

 

If you feel confindent you won't take off too much material, go for it. Performers are nice, but I have heard they drop way off, power-wise, after 5200 or so rpm. I have read a few stories about dyno tests that showed the factory Chevy aluminum intake made almost as much power up to 5 grand and was still making power all the way to 6 grand. JMHO.

 

That would lead me to believe that they should aleast be made the same size. Some of the ports have a little lip in them about .060", almost like flash. I checked with other manifolds at the parts store and they all seem to have this condition. It just seems funny to me that Edelbrock would CNC the ports in the heads yet leave the manifolds as is.

 

I agree. If you need more power go to either an Performer EPS or Performer AIRGAP.

Getting more airflow through the Performer would increase high RPM power. The secret would be to open up the runners evenly. Try investigating ExtrudeHone (http://www.extrudehone.com/). They past an abrasive material through the manifold. Since this material is a liquid, it removes material in the direction of the flow of air. Don't know anyone who has tried it, only read about it. It sound interesting.

Here is some info from the website:

"..Extrude Hone’s Powerflow processing of intake manifolds and cylinder head intake ports already has met the challenge for viability, reliability and cost effectiveness. Its value was proven in a four-year, $8 million effort supported by Ford, GM, and the Advanced Technology Program of the National Institute for Standards and Technology."

...The process is applied to intake and exhaust manifolds, and cylinder heads, in order to remove rough cast surfaces that restrict horsepower efficiency. Powerflow enlarges and uniformly polishes air and fluid passages to maximize flow velocity through the component. All polishing is performed parallel to the air/fluid flow. The result is a surface finish "grain" achieved in the same direction.



[Modified by 69stingray, 8:15 PM 11/27/2002]

 

The Performer intake is no better than a stock Q-Jet intake,and if Edelbrock's tech support knew better,I would not have wasted time and money finding this fact out for myself. The RPM intake has larger runners and a high rise plenum,which in effect straightens the path from the carb to the intake port slightly. This is what allows the intake to pull to 6500rpms and up.
I suggest you buy a 1" taller filter element than you're currently running,and drive the car for a week to see if there's any hood contact. (Yes the engine actually moves around when you drive,so the closed hood in the driveway test is not a good test.) If you find no evidence of hood contact,feel confident and order the RPM style inake. If you do have contact,save your money and be happy with the stock intake. Run a Performer cam,or a Comp 268H cam. This will keep the package very torquey and streetable.
Good luck!

 

You would at least clean up the flash.

There are at least 2 Performers- a smaller & larger one. The non egr smaller Performer is about 10+ hp better than the stock cast iron non egr on a mild engine.
W/ the larger Performer, it is possible to make 430+ HP on a 383 w/ a spacer.

 

After looking up the Edelbrock Web site it seems that the performer RPM is .600" taller than the Performer and the airgap is 1.2" taller. My cyurrent setup only has .50" between the hood and the outside ring of the stock air cleaner: Barely enough room for the rubber seal. Since I already have the Performer, I am going to size the runners to aleast be the same size and go with it.
Thanks all