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Which intake to use
I have a .030 455 to go into my 71 formula, it's 9.8 -1 comp, hydraulic roller cam, well ported 96 heads (to appear correct). whichever intake I use will be ported to match the heads. Should I use the stock intake off of my 400 or is there any power to be gained going with a factory 71 HO intake or a performer, besides the weight savings?
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I’d be using a ported iron intake if it were my engine.
No performance advantage going to either of those aluminum intakes, the Performer would likely be a downgrade. |
And hood clearance can be a little tight..
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If you're worried about power, the factory iron is a good choice.
It's said that the factory aluminum HO and RAIV intakes actually hurt power production to a degree because they don't have as much plenum floor, it's a bit more shallow thanks to the separate heat cross over that fits under it. However I've run both the factory iron and the factory aluminum at the track (a reproduction aluminum at that) and I've found no difference in ET or MPH on my particular combo. |
A few years back I back to back tested an HO intake (reproduction), factory iron, and an RPM on a 428 engine with KRE heads on it.
The HO and iron were both cleaned up nicely in the runners but no "porting", and opened up under the carb to the same size/shape as the RPM. I'll add that the HO had a pretty significant port miss-alignment which I spend some time with helping it out some. The HO intake made 487hp, the RPM 491hp and the iron intake 497hp. Same carb and gasket used on all three and no spacer.......Cliff |
You say the heads are ported, do you mean home ported or done by a professional and then flow tested, as I ask this because it would be nice to know the flow numbers and valve lift your 455 build is working with to make power.
Many Moon's ago before I got my flow bench I home ported my set of 1971 number 96 heads with the guidance of the HO racing Pontuac Assy and build book. These heads went on my 455 that was supercharged and solid roller Camed. Some years later when I had my flow bench I pulled the heads off the motor to swap over to better made Ferrea valves, and while I had the chance I flow tested them and was quite shocked at how little extra they flowed on the Intake side! Peak flow came in at .650" lift ( I was only running .510" with lash) at which I had 225 cfm. Only some 20 cfm over stock and I would have thought that with the amount of work that I put into each Intake port that I would have been seing close to 240 cfm. The work I did on the heads Exh side worked out well as I picked up the flow from a stock of 162 cfm or so up to 195, but this came about with a bad loss of low lift Exh flow, as back then I did not fully know where to rework the Exh ports and where not to! The main good thing out of the Intake port work I did back then was that I had a bit of the needed extra port volume for the 455 over the 400 motor the 96s came off of. In short knowing on your heads atleast what you have for Intake flow could guide you to the best Intake Manifold for your needs. You did not post up what rear gears the car has, or will have but I hope your running atleast 3.23s. Pretty much as posted here with your combo I would run a iron Intake or the performer rpm , especially if the car has 3.42 gearing. |
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it's the SR replacement intakes cast after 1972 that had the higher plenum floor as well as the repros made today. its about 1/4" difference. IMO, for a 455 with a bigger cam, i would not use the performer, its been proven to be a choke point compared to factory intakes. im dealing with hood clearance issues on a formula hood car too & went with the factory intake fully ported by SD performance to match round port e-heads. have gone low 11's at 120+mph with it & a q-jet & fits under the hood with a thick 1/4" gasket. the weight savings of the alum HO is nice & its looks better, but it was no faster than the ported iron intake that was on it. i say factory HO if you have it, or factory iron if not. you can also look into the other intakes that are stock height like holley street dominator, torker 2 if you run a holley or the repro like a tomahawk or other names they go by today. |
Correct, and I'm using the repo.
I should note though I think the differences found are likely on bigger more powerful engines. I'm not using mine on a 455 with ported heads or a big cam. I'm experimenting with mine on a stock RAIII 400 that's lucky to make 360-370hp based off the weight and MPH it runs. I should have clarified that and likely why I find no difference in performance. The biggest reason I wanted to try it was for the separate heat cross over setup. I drive mine in the cold 30 degree temps as well as the 100+ desert summer temps. I needed to keep the choke, and I wanted to see if separating the heat from the intake was beneficial to the summer driving heat soak or posed any issue with cold intakes in the winter. I'm extremely pleased with that portion of the intake, it's worked better than the iron piece in that regard in all types of driving. |
i agree, the bigger & higher hp engines is where a performer intake will suffer. for a 400 or smaller making less than say 400hp, a bone stock intake or even the performer would be fine.
i drive my cars in the colder weather too, almost until it snows & they put that crap on the streets, youre lucky to not have to deal with that in the winter! i will say on my HO intake e-head car, it does not like the colder temps untill the engine warms up some, i can drive for 20+ minutes & when i feel the intake & carb they are barely even warm! for that first ~20 minutes you can tell the engine runs a little rougher than when fullly warmed up, likely due to the fuel not atomizing as well as when the intake is up to temp. once the temps hits the 40's for highs that car goes into storage! |
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Also the HO intake is 15-20lbs lighter than a cast iron!
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When the Intake port goes Turbulent, then all aspects of the Port job, including Super-Stock CSA efforts go to pot, like maybe 220 CFM peak at some mid-range Valve lift. The Port is choked by moding. Noisey on the flow bench huh. My efforts show the shaved pushrod bulge and perhaps the correct Intake Manifold Runner angle can mitigate Moding. Also other intake Manifolds can induce moding on 4 ports or all 8 ports ((good grief if a fella runs a manifold that induces all 8 ports to mode then he might be running 14s or slower huh.)) |
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I don't have a performer on anything here, not even a ford or chevy, lol. |
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Hurricane intake?
Guys I was looking around and found the hurricane intake, I know its single plane. I could paint it and try to make it look factory, is this the way to go for the most power out of my build?
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the hurricane is the tomahawk. if you didnt know, the tomahawk intake is a china made intake patterned after a SD ported holley street dominator intake. it should be a good intale & allows for q-jets or holley. i have a polished one & the ports looks nice & straight, but the plenum area is pretty rough & can definitely use some cleaning up.
shop around & on ebay, they are usually pretty cheap. |
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IF the Hurricane/Tomahawk Intake is to be used much will depend on the size of the cylinder heads ports in use. The intake 'as cast' has small port exit dimensions to fit unmodified factory cylinder heads. Example IF the cylinder head port uses the common FelPro 1233 intake gasket, which is about 2.200" tall, then the intake takes quite a bit of work for a proper port match and blending up inside the runners to fit. The intake ports can go to about 2.300" tall and have about 0.125" above to seal.
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