F-427 and RPM

[hotrodfeguy]

Why is it on the "old forum" some people can't get it through those thick skulls that the RPM works better? I made a post over there trying to help out ERIC who had made a nice exhaust improvement and loves it. I told him he could prolly get more by swapping intakes from the F-427 to the new RPM per the FE comparo book and guys still said no we need to gonk this. I was like what? Jay has proven this by DYNO, anyways sorry for the rant and I think I am about done over there. It's just gotten so off topic and when it is on FE it's retarded. Ok hotrod is off the soapbox. 

[Drew Pojedinec]

I like Jay's book... but it seems many of the local drag racers preferred the F427 in their smaller, stockish 390's for some reason.  Dyno'd or not, I think there must be something to it.
Perhaps superstition or ignorance on their part?  I dunno.

[My427stang]

Its a very mild 390 over there, although I do think the RPM will make more peak power.  My hunch is it wouldn't make the big numbers on that specific motor. 

I also think with a COM, relatively tall gears, marginal heads, and the small displacement, down low it wouldn't gain much at all and could even be a little softer in some areas.

With that being said, when he built it, we tried to push him to an RPM, but now that it's together, I don't think it would gain enough to make the swap worthwhile.

The RPM is a hell of a manifold, but on a 300 hp motor in a truck, it wont be magic.

[jayb]

If its only a 300 HP motor, my book really didn't cover testing down to that level, so I wouldn't want to make a blanket statement that the RPM intake would be better for that application.  I think it would be, and of course when the bug bites and the owner decides to upgrade the engine to 400 HP the F427 will be holding him back.  But at 300 HP there probably isn't a big difference.

[My427stang]

Its a 9.5:1 390, 270S, shortie headers, 600 Holley, C8AE-H heads with a pocket port.   Good running truck motor

Might be a little more but I doubt a lot, he posted some significantly sub 300 chassis numbers a while back

[fe66comet]

A stock motor is just that. We all know if you improve one part another has to be upgraded to support it.

[hotrodfeguy]

I agree and now that he uncorked the exhaust. I thought that was a good time to improve the intake.

[jayb]

Its a 9.5:1 390, 270S, shortie headers, 600 Holley, C8AE-H heads with a pocket port.   Good running truck motor

Might be a little more but I doubt a lot, he posted some significantly sub 300 chassis numbers a while back

Hmmmm, that sounds like substantially more than 300 HP to me; I dynoed a similar motor with normal headers and CJ valves, and it made 400 HP.  I'd say he's at least at 350, and in that case the Performer RPM would show a significant advantage.  Based on that info I'd have to agree with hotrodfeguy, that he is leaving a significant amount of power on the table with the F427.

[My427stang]

I don't know what it really makes or how well he tunes, both would affect how well the RPM worked

On the FE Forum he posted "I dynoed 288HP and 343 TQ at the rear wheels"

At 15% loss that would be 338 so a little more than I thought.  However, before I blamed that intake for anything I'd see what the heads flow.

A C8AE-H has an exhaust port masquerading as an intake port with only 210-220 cfm.  I still think that whatever it gained would be lost down low, unless he did some big work to the heads, which I don't think he did

I am an absolutely an  RPM fan too, don't get me wrong, the difference on top on my 489 was incredible over an SD and an SM, but I also think it has very low speed tuning issues that would be compounded with a mild motor, stock converter, and tall tires or gears.

[jayb]

Chassis dynos are often down a lot more than the 15%-18% drivetrain loss, especially with an automatic transmission.  I'll bet he's got at least 350 HP at the flywheel, with the cam, carb, intake and headers.  I see your point though about those intake ports...

[fe66comet]

Head work, intake, cam and carburetor are my first mods I do. Mainly because you need flow to make anything else happen. Headers and exhaust soon follow.

[Drew Pojedinec]

I swapped a T intake for an Edelbrock RPM,  at first it seemed kinda down in power from a stop, and I'll admit, I was a lil put off.
After a bit of fussing and tuning, it runs just as well as the ole T iron beast from a stop, and I certainly gained a good bit on the top end.

My truck 390 is comparable to his in this regard. 
He isn't here to defend himself, but him mentioning that me getting 14-15 mpg (he claimed sub 10mpg) with this setup makes me think he has some sorta unaddressed tuning issue, be it timing or carburetor.
I know he went to someone to tune,  I never did that, I'm more of the "mess with this, go drive 5 miles, come back and tinker some more."  After a good 300 miles I might not have the most power, but I'll certainly have the most driveable vehicle.

[comet2]

i have an f- 427 to sell if they love them so much!! i have a rpm now . previously had port matched sidewinder, and holley street dominator . i strongly believe the sidewinder was the strongest runner and the lightest of the lot by a good margin.

[hotrodfeguy]

Well look at Bill's 390 on the other string. Obviusly that single plane intake is helping make some power with that same cam. It goes without saying if it works there and in a Galixie should also work in a truck. With the numbers Bill just posted I think his Galaxie would run circles around that truck 

[jayb]

i have an f- 427 to sell if they love them so much!! i have a rpm now . previously had port matched sidewinder, and holley street dominator . i strongly believe the sidewinder was the strongest runner and the lightest of the lot by a good margin.

My dyno data doesn't back that up.  The Sidewinder did reasonably well in my testing in the 400-500 HP range, but it wasn't as good as a Performer RPM or the single plane intakes.  The Performer RPM made 504 peak HP on my 390 stroker engine, the Holley Street Dominator made 499, and the Sidewinder made 496.  Also, the Sidewinder weighs 25 pounds, the Performer RPM weighs 27 pounds, and the Holley Street Dominator weighs 25 pounds.  The lightest FE wedge intake I've ever measured is the 4V tunnel port intake, which weighs 18 pounds.