Intake manifold differences
 

I was wondering about different intake manifolds. My new 455 is nearing completion and my buddy wants me to use an Edelbrock Performer RPM. I have Edelbrock round port heads and am using a hydraulic roller cam. He says it should make in the mid 500's horsepower. I would like to make my plain jane Firebird into a Formula or Trans Am. Both of them, I am pretty sure will have clearance problems with the RPM manifold. I would love to have the Formula hood functional, if I go that route. Is the aluminum H.O. manifold equivalent flowing to the RPM? I have seen the testing that Jim Hand has done and others. How well did a SD manifold flow versus the H.O.? I know that the repo H.O. manifolds are known for core shift and need to be ported to optimize port flow. Is the benefit of that manifold worth it for a low 12 second street driver? I tried searching for answers but I could not find any comparisons. I thought I would ask someone here who may have already gone down that road.

t2?

Isn't the Performer (non-rpm) designed for the hood clearance issues of some firebirds? They're cheap when used

Sent from my SM-G988U1 using Tapatalk

Having a Formula I can tell you the hood clearance sucks.

If you plan to make the Formula hood functional with the factory air cleaner you have virtually no wiggle room to play with, give or take about a 1/4" with the stock intake in place.

Been a long time since I've played with or seen a T2 but what I82much suggested might be a possible solution if you don't like the stock intakes. I do know the RPM does not fit. The problem with the single planes like the T2 is they don't really shine until you start running spacers on them, and then there goes that hood clearance again.

I've played with stock intakes on mine for years and I know many here have as well. In fact I'm pretty sure people like Cliff, Jim Hand, and others have ported different versions of the stock intakes, including the HO and iron pieces and found very little difference between them, while at the same time matching the performance of some of the aftermarket intakes.

I've had them on and off my engine and have been drag racing the car for more than 20 years. I currently run one of the aftermarket RAIV intakes on the car, (same as the HO piece) and can say without a doubt it makes no difference in ET or MPH on my car over the stock iron piece. While the ports don't look super pretty as cast, they have had no affect on performance at all. There are a lot of pretty fast Pontiacs out there with the stock intakes.

Street Doms are stock height.Tom

Are you running a carb or a throttle body injection system? If you’re going the entry level EFI route, consider the torker ii.

Dave at SD Performance can port a stock intake, iron or aluminum, to fit your needs( yes, he is still porting iron intakes, just not heads).
If you read on his website, aftermarket versions of the factory aluminum intakes can be of terrible quality and may require welding, which isn’t free.

Sounds like you have an awesome engine! You’ll have to contact Dave via email. He’s a one an band and doesn’t have time to blab on the phone. Be patient!

Dave will port your intake, he uses a CNC scan of my intake.

On the dyno on a 440CID engine my intake made 497hp. Switching to an Edelbrock Performer RPM dropped to 491hp. Swapped on one of those HO reproduction intakes next and made 487hp.

Average power was best with the modified iron intake as well. I suppose the larger RPM may have a "crossover" point someplace where it starts to make more power than my modified iron intake.

I ran an RPM intake for a while on my current 455 and HATED it. Took some "cobbling" to get it under the hood, which included raising the throttle cable bracket, going to a 1" shorter Shaker and not being able to use a stock type air filter in it. Moving the lid 1" closer to the carb KILLED engine power and I couldn't even make a full drag strip pass with a lid on the air filter!

I ended up making a custom filter for the Shaker opening. Ran that set-up for a while then bought a real HO intake that Dave at SD CNC ported for me and modified with my CNC scan.

It allowed me to go back to all the factory air cleaner parts and guess what, it runs QUICKER in 60' times than the RPM intake! It gives up about 1mph on top end, but that's nothing compared to all the cobbling and drama required to fit an RPM intake under the hood on one of these cars.....FWIW.......

X3 on the SD ported factory intake, i ran a iron one done to SD's "stage 3" porting & on a 72 firebird with 72cc Eheads & formula hood & the car runs low 11's but is mostly a street driver. i since changed to a factory HO intake with the same SD porting & runs just as good & looks much better.

to answer your question, no a stock HO or repro HO does not flow as goood as an RPM, but stock intakes are much better than non rpm performers & will probably support 12's in stock form, or you can do the notch trick on the plenum divider & do a hand gasket match to the E-head intake ports to improve it a bit. also keep in mind the factory SR (after 1972) & repro intakes have a shorter plenum depth than the original intakes according to rocky rotella's testing, not sure how much that hurts performance but something to consider if you want to get the most out of the intake.

this would be my vote too. I just did a 400 swap on my TA and went with the HSD . I wanted the ability to run different carbs easily. i'm also using an edelbrock carb which i know is not normal, but it was what i had rebuilt on hand and it actually works really well. I had to make some modifications to make it work though. ( modify air cleaner, modify throttle bracket as it is WIDE)

I did start with a Q-jet, but it was way off on calibration and will move back to it on a later date.

street dominator intake is nice... but there is also a tomahawk or current brand name that is a copy of a street dominator ported by SD. they usually need some cleaning up of casting flash etc but might be a decent option for a single plane. i have a polished version i was going to try someday.

Drop base units open up a lot of options for "other than stock" air cleaners. The WFO 1, and Gen 2 units that Butler Performance sells will give you plenty of space to run a shaker with a taller than stock intake. I've run the Performer RPM/WFO-1 with no problems.

The problem with the Performer RPM is that there isn't enough "meat" in the runners to port match KRE ported heads (which I have). I'm running a ported Holley Street Dominator that I got from our own Steve Coombs, plus a 1 inch spacer which he well documented that makes more power than without the spacer. With the G2 drop base, I needed a half inch aluminum spacer between the carb and air cleaner to get the shaker height that I want.

I'm not suggesting that anyone try to copy my formula: HSD+ carb spacer - drop base + air cleaner spacer - shaker gasket = final height

I'm just saying there are a lot of options out there to run intakes other than stock. I've found that the limiting factor has been spread vs square bore. I'd run a Kauffman Northwind, but they don't make it in spreadbore so it won't work with a Q-Jet.

Here is a link to the puzzle pieces.

https://butlerperformance.com/c-1234...s-filters.html

A first gen with factory RA pans can only use a stock height intake.No room for a spacer so a Performer or the HSD or clones are pretty much the only options to run a square base carb.For a spread bore a factory intake is really hard to beat.Tom

There is a lot to this and I have a basement full of failed attempts to get mine to work. I started with PTFB's first "attempt" at a drop base which is a miserable POS. Didn't fit, didn't drop enough and sure as hell didn't flow anything. I ended up modifying the hell out of it, then adding an Air Raid 3" conical filter. If you want some entertainment on the hassle, go here: http://transamcountry.com/community/...?topic=53872.0

After a lot of attempts, it seems like PTFB finally has a product that meets expectations and although I am not a big fan of the way Dave handles his business or attacks customers critical of his products, it appears this last version which is suspiciously similar to what I did before his was released, is probably the best available at this time. I would definitely pick it up through Butler though

Also, here is a link to an article that provides some additional measurements and comparisons: https://www.hotrod.com/articles/hppp...d-replacement/

Very few folks actually test many of these parts and combinations of parts.

What I can tell you from street and track testing is that more times than not any gains from a bigger/taller intake, or moving to a single plane intake with a spacer, then having to use a "drop base" style air cleaner is moving the air cleaner lid too close to the carburetor hurts power in the upper mid-range and top end..

Don't be fooled by dyno testing with single plane intakes with spacers on them, or the 1" taller RPM intake that show improved top end power. IF you don't back up that testing after the engine makes it to the vehicle and you've had to use a drop base air cleaner it doesn't really qualify as a complete test.

I found all this out actually testing every single intake that will fit under the hood of the Ventura. To get the taller intakes or single plane intakes with spacers to work at all I had to REMOVE the stock type air filter and make a custom one for the opening in the Shaker.

On private track rentals and even at the HPP "Shootout" at Norwalk in the early 2000's I did some back to back intake and carb testing. Kind of interesting but after all the testing the best runs were with the "modified" iron intake with no spacer on it. The highest MPH was obtained with a Tomahawk intake with a custom made well blended 1" spacer on it and my 4781-2 Holley DP carb. That combo actually ran nearly 2mph FASTER than all other combinations, but gave up enough in 60' and short times that the "modified" factory intake w/o a spacer netter a slightly quicker ET.

I also dyno and track tested 4 different 1" spacers, 4 hole, fully open, fully divided and semi-open. The best of those was the semi-open very close to what Jim Hand uses and describes in his book. It was worth nearly 2 more MPH than all other combinations.

Anyhow, the Performer intake FAILED every attempt I tried to test it. My engines just flat hate that intake and I was never able to make a complete full throttle pass with one. For some reason it induces a HUGE hesitation/stumble/bog when I go quickly to full throttle that will NOT tune out.

I suppose the engine just sees it as a restriction of some sort, doesn't matter, I gave up on it and went with the RPM until I obtained a real HO intake CNC ported to my KRE heads by Dave at SD. That intake fits, no spacer required, and outruns everything else I've tried to date........Cliff

PS: note that I call my factory iron and HO intake "modified". That just helps to keep the Trolls and other naysayers from busting my balls because I'm a "hot-rodder" and LOVE messaging factory parts to run as well as and often better than shiny aftermarket stuff!......

If your planning to go with a squarebore Holley carb my first pick would be a Torker 2. If your going with a Q-jet or another Spreadbore carb then I would say the stock intake is pretty good. I wouldn't try to run a spreadbore carb on a Torker 2 or a square bore Holley on a stock intake.

Both the Holley Street Dominator intake and the Tomahawk intake are able to be ported to a height of 2.300" with about 0.250" above for a gasket seal.


.

:Ithink:

LOL, I remember some folks having BIG issues with your "Hot Rodded" intakes...:pound:

Ya, but they never once point out that they OUTRAN intakes made by folks who had a "clean slate" to work with, so no rules and few limitations. They just cry "foul" instead.

I'd also add here that these companies are marketing genius's. They tell us that all these parts are just waiting to be installed to make MORE power at every RPM, walk on more water and leap taller buildings. I been watching folks yank the EXCELLENT cast iron intakes off of SBC engines for half a century now and replace them with aluminum intakes that do nothing more that unload some money out of your wallet and take a few pounds off the front of the vehicle. In at least 95 percent of the applications they are used in you just end up with no more if as much power and loose some thermal efficiency until the engine is really well heat soaked.....FWIW......

"If your planning to go with a squarebore Holley carb my first pick would be a Torker 2."

+2, the T-II is an EXCELLENT intake. I have seen it used more times than I can count to get the best power numbers out of these engines, and it absolutely LOVES a 1" spacer that's been well blended into the plenum areas.......