[Steve C.]

474ci engine running a set of 290cfm CNC ported KRE D-port heads with a 236/245 duration hyd. roller cam.

SD Performance dyno testing with a stock iron intake running a Cliff's Q-jet. After some tuning, ended up with 515hp @ 52-5300rpm and 575 lb/ft @ 4000 rpm. The next intake was another cast iron unit but with the CNC machined plenum copied from Cliff's personal intake. With some minor tuning it ended up with 527hp @ 5300rpm and 579 lb ft @ 4100rpm.

4 lb/ft lbs gain at peak torque rpm. Not stated is the improvement if any at a lower rpm, or off idle response and lower rpm drivability. Nor any track improvement. That would take a very consistent vehicle with back-to-back testing. Street only use, probably very little difference.

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[scott70]

At least its worth some power. Make me feel like I didn't completely waste my time. Lol .Only took me about 1/2 hour to drain radiator and remove intake. Probably a couple of hours massaging it.

[Steve C.]

Certainly not a waste of time, interesting project and the old adage.... every little bit counts


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[scott70]

Well Ive been to the track a couple of times since I did this mod to my intake and 1/2" spacer. Both intake and spacer started like as 4 hole quadrajet stuff. On my particular vehicle combo I really dont see any improvement at all. Mph seems about the same as well as ET,,,,60 ft actually might have gotten slightly worse. Its not a racecar,,,purely street. M21,,3.31 rear,,255/60 15 BFG. Right after I did the mods it felt like throttle response was a tiny bit worse. For the heck of it I ordered a 11/16" thick plastic 4 hole spacer from holley and will try that on my intake. I will probably still do the little notch between the secondarys before I install it. Ill try thetrack one more time before the year is out and see if I can get back that little bit of 60 ft. I think I lost and see if it feels better on the street. If the car had a auto with a little bit of converter the intake mod might of worker better,

[Formulajones]

Thanks for revisiting and reporting results.

I'd be interested in hearing what you find next.

[Half-Inch Stud]

QJET Baseplates had that 3rd screw in the center, for awhile and maybe 1969 or 1970 that screw went away, so the Manifold could loose the metal too but didn't.

@Scott77 i think if you add 30-50 more hp, you'd go even slower ETs. M21 and dry-clutch assure it.

[scott70]

Originally Posted by Half-Inch Stud

QJET Baseplates had that 3rd screw in the center, for awhile and maybe 1969 or 1970 that screw went away, so the Manifold could loose the metal too but didn't.

@Scott77 i think if you add 30-50 more hp, you'd go even slower ETs. M21 and dry-clutch assure it.

Just saying if the mods I did were to gain hp I didn't see it. If it had I would of thought I'd see an increase in mph at least.

[Formulajones]

Originally Posted by scott70

Just saying if the mods I did were to gain hp I didn't see it. If it had I would of thought I'd see an increase in mph at least.

Correct, as long as the weather conditions were similar to what you had the last time.

[mchell]

Originally Posted by scott70

Well Ive been to the track a couple of times since I did this mod to my intake and 1/2" spacer. Both intake and spacer started like as 4 hole quadrajet stuff. On my particular vehicle combo I really dont see any improvement at all. Mph seems about the same as well as ET,,,,60 ft actually might have gotten slightly worse. Its not a racecar,,,purely street. M21,,3.31 rear,,255/60 15 BFG. Right after I did the mods it felt like throttle response was a tiny bit worse. For the heck of it I ordered a 11/16" thick plastic 4 hole spacer from holley and will try that on my intake. I will probably still do the little notch between the secondarys before I install it. Ill try thetrack one more time before the year is out and see if I can get back that little bit of 60 ft. I think I lost and see if it feels better on the street. If the car had a auto with a little bit of converter the intake mod might of worker better,

No surprise really…. you run an RPM yet?

[scott70]

Never tried an rpm intake before on anything. On this car I was trying to keep the stockish look under the hood.

[mchell]

Originally Posted by scott70

Never tried an rpm intake before on anything. On this car I was trying to keep the stockish look under the hood.

10/4…. Paint the rpm blue and grind the logo off ….you’ll still be “stockish” … lol

[scott70]

I don't know if there would be a noticeable improvement going to the rpm on my particular car.

[Formulajones]

I was just talking to Cliff about that the other day.

Only time I've even jumped into the RPM intake was on a stout 455 build we ran in dad's car that had a 254/262 @ .050 hydraulic roller and some 330 cfm Eddy heads, where on the dyno the RPM did make the best power that day.

But on more mild stuff I find the stock intakes work really well and will get over the 500hp mark in stock form, I've been there and done that.

Then Cliff reminded me (I completely forgot) Rick Mahoney has his pure stock 400 RA II 68 bird running deep into the 11's, with the stock iron intake, and his modified OEM iron intake he runs in the FAST class on another 68 RAII bird is running in the 9's.

[PAUL K]

I remember an iron head engine Ken Crocie built that dyno'd around 475 HP with a modified iron intake manifold. He stated the RPM was worth 30 HP with no loss of torque.... Personally we've had good results with the RPM intake manifold.

[Steve C.]

This from 2013....



"Rick Mahoney's RAII car he runs in the F.A.S.T Series is a serious machine."

"They had 4 sets of heads custom ported by the best engine builders in America, and they were all told to go nuts on the porting. Rick said there's more money into the heads than what most guys have into their entire engine."

"And the intake has been cut and re-welded, the runners extrude-honed, and the manifold flows 300 CFM to each runner. And he goes through traps at 7000 rpm."

Source: http://forums.maxperformanceinc.com/...=736804&page=4


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[Steve C.]

Related, there is a bunch of work hiding under the hoods of these F.A.S.T. class race cars and far a far cry from using lightly modified factory intake manifolds.....

Jay DeLaigle's 1974 Trans Am.

His 1974 PONTIAC 455 "FAST Class" engine is a 501 CID Stroker !

HIS INTAKE- 1974 Pontiac EGR cast iron intake # 495106, Ported and flowed by Wilson Manifolds with support from Jon Kasse racing engines and SD performance.


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[Formulajones]

Originally Posted by PAUL K

I remember an iron head engine Ken Crocie built that dyno'd around 475 HP with a modified iron intake manifold. He stated the RPM was worth 30 HP with no loss of torque.... Personally we've had good results with the RPM intake manifold.

Yes, every time I've used one it's worked really well. Especially with a 1" open spacer.

[Formulajones]

Originally Posted by Steve C.

Related, there is a bunch of work hiding under the hoods of these F.A.S.T. class race cars and far a far cry from using lightly modified factory intake manifolds.....

Jay DeLaigle's 1974 Trans Am.

His 1974 PONTIAC 455 "FAST Class" engine is a 501 CID Stroker !

HIS INTAKE- 1974 Pontiac EGR cast iron intake # 495106, Ported and flowed by Wilson Manifolds with support from Jon Kasse racing engines and SD performance.


.

Yes, that's why I also mentioned the pure stock class where those types of modification are not permitted. Rick Mahoney's pure stock firebird has been well into the 11's with the stock iron intake.

[77 TRASHCAN]

Originally Posted by Steve C.

Related, there is a bunch of work hiding under the hoods of these F.A.S.T. class race cars and far a far cry from using lightly modified factory intake manifolds.....

Jay DeLaigle's 1974 Trans Am.

His 1974 PONTIAC 455 "FAST Class" engine is a 501 CID Stroker !

HIS INTAKE- 1974 Pontiac EGR cast iron intake # 495106, Ported and flowed by Wilson Manifolds with support from Jon Kasse racing engines and SD performance.


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Steve,
Jay sold that car, years ago. I have not heard about it since.....

[mchell]

Originally Posted by scott70

I don't know if there would be a noticeable improvement going to the rpm on my particular car.

You might be surprised….no drawback by trying one. Certainly don’t think you’ll slow down with one….