I have been kicking around the thought of the benefits, if any, of improving the flow of a Performer intake on a small block. Mods such as cutting down the divider and porting the runners. I have done several searches here and on the internet and no info. I would be doing this to a 350 or 383 depending on which way I decide to go. I would do aftermarket heads in the 180 range for the 350 or 195 for the 383. Compression at least 10 to 1 with an undetermined Hydraulic roller cam and possibly a Holley Sniper injection set up. Why bother with doing this? I have 2 of them, hood clearance and sometimes I like to think outside of the box. The rest of the combination is a 1972 Coupe wide ratio 4-speed, 3.36 gears, p/s, p/b and ac. Almost 100% street driving. I want to enjoy driving so no getting passed by Prius's. I am also not married to the plan and yes I have other intakes which I purposely didn't mention so not to muddy the waters. David

 

Outside the box thinking is what made this country great

Have thought about it too for the experience just "to see"; if you got access to a bench it would be fun to see the results

If you can weld go for it and post up your before/after #s.
Fwiw despite what magazine dyno #s said the 350 always seemed to run, idle better and have better throttle response with the divider left alone (just weld it back in).
383 may want more plenum volume also

Messed around with TPI intakes for yrs pushing the limits of the casting; few guys have gone nutso, cut welded and made to look stock they are retired got time on their hands
Pretty cool seeing a base that looks stock but flows over 300 cfm! Its doable

 

That is more onfo (the divider) than I have been able to find. So thank you. I weld decent so I would be willing to play. Unfortunately this will be a ways in the future but if I do I will keep everyone posted. I also welcome any more comment/opinions. David

 

Experiments are great fun. Sometime they cost you money. Edelbrock does a ton on R&D on all their products.


And I'm not in any way saying I don't think it will work, I am curious if you do anything, what happens and what results you get.

 

unless you do dyno runs or track times before and after I doubt you will notice a difference but for reference purposes look at the cut down divider on the RPM Air Gap.

 

I get the curiosity part.....I have three intakes I've played with over the years. But for my advice to you. Try a carb spacer,...even if you have to keep the hood open a bit first. It will act like you cut the manifold divider. The car sounds to be set up for low end with the gears anyway, so I'm guessing you'll like the uncut manifold better.

One other side note. I once had a Chevelle with the stock 350, and decided to put a Performer on it to add some power.....Complete waste of time and money. Could not feel one extra horsepower. I later put a cam in it....OMG! it was like I added 50 horsepower to an otherwise stock 350. The cam was just an Edelbrock Performer...so not that big a cam.

 

Hot Rod mag did a comparison of intakes, and the Performer was one of the worst "performers". I went with the EPS as it was one of the best, shortest that barely fits my 71 w/flat hood AND its the cheapst. I went and port matched to a Felpro 1405 gasket. The ports needed a lot of straightening to even come close. I and just started tweeking after dumping a Victor JR...not sure of low end gain yet.

But as said the cam makes way more difference than manifolds. I was thinking of playing with the EPS divider also. Of course if hood clearance was no problem, would just do a RPM.

If you are thinking of EFI I have seen single planes being recommended.

 

I do have a RPM that I could use. I do not have any single planes in my collection. So I would have to buy one which if you saw how many manifolds I had you would understand my reluctance LOL. I saw the same test I was just wondering if the "as cast" condition could be improved.

 

This is why I am glad that I brought this subject up. I hadn't considered the carb spacer. I have run the Performer cam/manifold combo in a Pontiac 400 and it did very well.

 

I agree and there is a good chance that at a later date I will do both of those with both a modified and unmodified. I have a very unreliable butt dyno.

 

I am hoping that the only expense will be some gaskets and cutting stones. Cruising through CL the Performer's don't seem to be bringing top dollar so I feel pretty good about satisfying my curiosity. I agree that there are better manifolds and I don't expect to turn the performance world on it's head but if it's possible to improve something I would like to try.

 

A true added performance intake should be shaped like a velocity stack. Starting out big and narrow down to the cylinder head and the head to the top of the intake valve to increase the port velocity. Many of the dual plane intakes do NOT have these properties. If you have any small to bigger you end up with fuel droplets because of decreased velocity and you don't have a true ram effect of a tuned intake port.

Spacers and divider cutting adds volume, but not a true tuned port design. Back in the early 80's I used a Weiand X cellerator single plane that had an incertable divider on a hot rodded 355 ci. very debatable if it changed TQ levels I've used single planes on everything ever since to get the true ram effect. IMO the cam choice is the real heart beat in conjunction with intake and heads

 

Not to sound like a broken record but this is all great info. I am getting some great replies and have been given a lot to think about. So GKULL should the (single plane} intake be thought of as 8 venturi's?

 

check youtube, and also research forum member Bee Jay here on the forums. Check his threads. I think he did a mod on his intake. Maybe an Airgap model.

 

Cutting down or eliminating the plenum divider will hurt low end a little bit,but should help top end to a reasonable degree. A spacer raises the carburator and allows less sharp a turn into the ports.anything you can do to smooth out the way the air flows will help. Airflow hates change so the less turbulent you can make it flow the better.
I have an R.P.M air gap with a 1/2 in spacer and it works very well out of the box.

 

I have a performer intake that I have ported and opened up some. Doing some research I found that I needed around 1.9 square inches of intake cross section for each cylinder. On the performer the cross section of the runner is all over the place between 1.3 in to 2 inches. I imagine this is to help spread the power out throughout the RPM range. Not what I was after, at least not via the intake cross section size.

This last year I took that performer intake and significantyly modified it by porting out the smaller plenums, straightening where I could, opening up the plenum and rounding all the sharp corners. In addition I left the entire intake textured from the die grinder, no sanding. I also tried to shape then with the idea of ever smaller cross section as they approched the head. Not possible on all of them but at least on the ones with the smaller cross sections.

The results that I can discern is that the power is more abrubt when you go into the secondaries. But it also idles very nicely and produces good down low torque.

I am running an open 3/8" spacer to create an area in which the air can cross over the divider to enhance high RPM performance.
A guy could also drill holes through the divider vs cutting it down to see the effect of that.

On this same intake I aslo added an oil spash shield to prevent hot valley oil from directly depositing on the underside of the intake making those associated runners run hotter than the ones not exposed to the oil.

So far it seems to feed the heads just fine. About 440 HP @ 5800 RPM with a 350 original bore and AFR 180 heads.

 

This is great! I was hoping that someone would have practical experience. I purposely didn't list any horsepower goals but this is in the wheelhouse of what I was thinking. The splash shield was also something that I wanted to do and forgot to list in my original post.

 

I am willing to give up a little low end this will not be my daily driver. I like the idea of a fun road trip car not too worried about stop light to stop light. Looks like the consensus is leaning towards a carb spacer. As I stated before I have two of these and am willing to sacrifice one in this experiment. If it falls on it's face I do have a RPM that I can use.

 

I'm not sure that the RPM is anything more than a standard performer with a cut down divider. Maybe larger cross section runners, I've not had one to compare to a standard Performer though.

 

Something you might consider if you really want to stay with a particular manifold is Extrude Honing.


http://www.extrudehoneafm.com/

It has been shown to be very beneficial on the Tuned Port runners on the L98 C4's.

GUSTO