Well a Hi Ram intake for the Ford 351W !

[427dart]

I see Holley finally has it out! They say you can get the plenum top to run dual carbs so from looking at the runner length how do you think it would
run on my 427 sized Dart Windsor with the TFS Highport 225 heads thru 6200 RPM?

[NormS]

It looks to me like it would favor higher RPM's than 6200. I suspect that it was designed for peak RPM's over 7500. It's a nice looking manifold, but it looks like it would just start working at 6200.

I just found this in one of Holley's online documents:

APPLICATIONS:
"This Holley Hi-Ram intake manifold series is designed for Ford 351W engines. This intake manifold is designed for use with aftermarket
cylinder heads. OE cylinder heads can also be used, but some modifications may be required.
This Hi-Ram style intake manifold is designed for high performance engine applications up to 427-440 cubic inch displacement and
maximum engine speeds of 7500-8500 rpm, depending on the engine combination. The Hi-Ram intake manifold is intended for
maximum performance applications and will not accept stock components and hardware. A modified hood will be required for most
vehicle applications".


If your willing to cam the engine to run more RPM's( a lot more), then this intake would be among the reasonable choices.

[1972ho]

6200 you can get a dual plane to work that kind of rpm unless you just feel the need to spend some extra cash.

[427dart]

From more info I just read with EFI it is very streetable and was designed for engines up to 440 cubes and up to 7500 RPM.
They took the Hi Ram from the LS engine and designed it to fit the Ford 351W.
Right now I'm running the Price Motorsports dual Holley inline dual plane type intake which is like a scaled down Ford 427 FE manifold.
It runs well but does lack some of the top end pull I had with my Edelbrock Super Victor and 950 Holley setup due to the runners not being as large as the Super Vic.
I'm using dual 650 Holley 4160 carbs right now and low end and mid range is great!

Can't help it but I'm old school and love the dual inline Holley carbs...not racing the thing just my weekend hot rod....1985 Mustang LX with 427 Dart Windsor!

[NormS]

I think what is more realistic, is that the Hi-ram was designed for at least 427 cubic inches, and at least 7500 RPM.

Going to this Hi-ram would probably be a big trade-off...a noticeable loss of low end and mid range characteristics to pick up a little more top end. That's not a good trade off for a street driven car. The Hi-ram runners are just too short to work well in your current rpm range.

I found a picture of your Price Motorsports intake, and there is a lot that can be done in the first inch or two below the carb flanges to help top end flow of air/fuel mixture. You might also consider using 1" phenolic modified clover leaf carb spacers. These mod's will allow each cylinder to draw from more venturis.

[427dart]

I think what is more realistic, is that the Hi-ram was designed for at least 427 cubic inches, and at least 7500 RPM.

Going to this Hi-ram would probably be a big trade-off...a noticeable loss of low end and mid range characteristics to pick up a little more top end. That's not a good trade off for a street driven car. The Hi-ram runners are just too short to work well in your current rpm range.

I found a picture of your Price Motorsports intake, and there is a lot that can be done in the first inch or two below the carb flanges to help top end flow of air/fuel mixture. You might also consider using 1" phenolic modified clover leaf carb spacers. These mod's will allow each cylinder to draw from more venturis.

I did some inside port work,as much as I could get to. to the intake. I bored out the 4 hole plenums to 1.700 to compliment the bore size of the 1 11/16 Holley 650-750 size carbs. Then opened up and radiused runner area coming into the plenums.Also running 1.5 inch tall 4 hole carb spacers which worked better than an open spacer. I have seen where the PME intake can support 500-550 HP. It's been on the engine for about a year or so and seems to work well on the street letting the engine run on a leaner A/F at cruise than the Super Victor/ 950 Holley setup which was a real strong runner from 3500 RPM up.
The dual quad PME intake was aimed at the replica Cobra type setup using 351-427 cube Windsors with mid level type cylinder heads and not the larger runner TFS 225 High ports and other similar heads. It's such a well setup and fitted induction package with my custom air filter air box,I'll most likely keep it on.

[NormS]

That's good that you have those spacers on there. You might try some some cloverleaf spacers, or open up the top half of your 1.5" 4 hole spacers into an open plenum shape. That will shorten your effective runner length a little, and allow each cylinder to draw from more venturis. Both those things would help top end, and should have very little effect on low end and mid range.
Another thing that is possibly contributing to your top end issue is the fact that on many Holley vacuum secondary 4 barrel carbs, the secondaries don't open all the way. On some they don't open at all. All that can be fixed.

[F-BIRD'88]

That tunnel ram will work great on your 427w.
The vacuum secondary carbs will limit the potential.

I'd use 2 edelbrocks on it. (Street strip)
You may like the new 650 AVS2 with the improved annular booster.

I'd make my own top for it. Might experiment with plenum volume and carb height
to find the sweet spot with carbs.
Ignore the rated rpm range.

[F-BIRD'88]

I could see adding a raised RIB right down the center of the plenum floor
to help the carbs function. Could be bolt in. Allows playing with it to optimize.

Remember once you buy it, it is your intake so don;t be afraid to play with the internal shape volume and height of the plenum to get it right for your motor.

You can even extend the runner effective length with added plenum insert port entry plates. This will add port length if desired.

Once the carb top is on its your lil secret whats going on inside.

So did you order yours yet?

[NormS]

If the proper mods are done to get the vacuum secondaries to open all the way, those carbs will make the make power as double pumpers that are equal in venturi size, throttle bore size , booster type, etc. Once all the butterflies are fully open, the engine doesn't know what got them there.

You have to keep in mind that this is a street car. Torque is the name of the game with street cars, not top end HP. The goal here is to improve the top end power without giving away any low speed driveability and mid range torque. In other words, we want to broaden the power curve, not shift the whole thing to higher RPM's.