Intake Manifold for 351W - 4bbl

[Mike_Windsor]

I've been toying with the idea of changing out the intake manifold on my car to upgrade to a 4 barrel carbeurator instead of the stock 2 barrel unit on there now.

Was wondering what all you gurus thought the ideal intake manifold and carbeurator to go with it would be.

I've heard that a single plane is better than a dual plane unit.

What are your thoughts?

[turbo2256b]

Depends on the engine build Most single plans run best with well ported heads and not necessarly all that wild of a cam. Gears are a must.

[Mike_Windsor]

Please elaborate on the "gears" bit.

[gadget73]

honestly I'd mess with the exhaust first before putting more carb on top. If the air can't get out of the engine, it can't get in either.

[Mike_Windsor]

Mess with it how? It has a dual exhaust system on it.

[turbo2256b]

Most performance mods move the power ban higher in the RPM range which requires lower gearing. Some builds with mismatched parts = more gearing than some higher output builds with properly matched parts.

[P72Ford]

Having had a 351 P72 that I did a "performance" build on...

Unless you're gonna change the heads and cam, just stick with the stock 2 bbl, unless its a VV. If its a VV, do some research and get the right Holley 2bbl replacement. Tossing a 600 cfm 4 bbl and a performer manifold on an otherwise stock 351 is an excercise in futility, in my opinion. With heads and a cam, its a different story.

If you're gonna swap the heads and cam, then a performer RPM (or Performer RPM Air Gap), is a tough manifold to beat. Its a dual plane; unless you intend to use a radical OTS grind and big heads, or put a "package" on the top end (custom cam, and heads matched to a single plane intake), I'd stay away from a single plane for a street car/ cruiser. A Holley Avenger (vac secondary) in 670 cfm, or a 650 cfm (750 if its a hot build) DP (if you have deeper gears and a converter) would suffice. Conventional wisdom says a VS carb is better for a heavy street car. My tribal knowledge has taught me that you can get away with a DP on a heavy car, with the right supporting mods (like a 3400 stall converter, and 3.73s). Not only can you get away with it, it is the definition of throttle response. Fuel mileage is definitely better with a VS carb, though.

[turbo2256b]

Having had a 351 P72 that I did a "performance" build on...

Unless you're gonna change the heads and cam, just stick with the stock 2 bbl, unless its a VV. If its a VV, do some research and get the right Holley 2bbl replacement. Tossing a 600 cfm 4 bbl and a performer manifold on an otherwise stock 351 is an excercise in futility, in my opinion. With heads and a cam, its a different story.

If you're gonna swap the heads and cam, then a performer RPM (or Performer RPM Air Gap), is a tough manifold to beat. Its a dual plane; unless you intend to use a radical OTS grind and big heads, or put a "package" on the top end (custom cam, and heads matched to a single plane intake), I'd stay away from a single plane for a street car/ cruiser. A Holley Avenger (vac secondary) in 670 cfm, or a 650 cfm (750 if its a hot build) DP (if you have deeper gears and a converter) would suffice. Conventional wisdom says a VS carb is better for a heavy street car. My tribal knowledge has taught me that you can get away with a DP on a heavy car, with the right supporting mods (like a 3400 stall converter, and 3.73s). Not only can you get away with it, it is the definition of throttle response. Fuel mileage is definitely better with a VS carb, though.

This is basicly true unless one realy knows how to build engines. Gussing by his info I shouldnt be using a singlr plane intake on my 5800 # dually truck used to tow my 14000# trailer.

[Mike_Windsor]

Who knew an intake manifold could be so sensitive to an engine's performance.

Right, so don't do it unless I change the transmission gears, cylinder heads, and camshaft.

[sly]

transmission gears stay the same. Rear axle gears are the gears being spoken of.

[turbo2256b]

Who knew an intake manifold could be so sensitive to an engine's performance.

Right, so don't do it unless I change the transmission gears, cylinder heads, and camshaft.

I spent years testing different intakes on the same engine build. Not just one engine not just one mfg Fords Chevy Chrys Buicks, olds 6cyl V8s 3 cyl 4cyl 1 cyl 2 strokes 4 strokes. Designed intakes made sheet metal intakes.
Spent a lot of years flow testing and porting intakes and heads. Lots of dyno time and butt dyno time.
Stock E7 heads are about the worst flowing factory heads. A Performer intake is just a tad much (it compairable to so low grade factory iron ones) but not all that bad compaired to the RPM intake, Torqer II or Vr Jr.
Ported E7s done correctly could use any of these intakes with the right combos. All ported SBF small port heads flow about the same 220 CFM coming out of my shop. The Vr Jr only flows about 190 CFM bolted to even higher flowing aftermarket aluminum heads i have tried it.

The 351W with Gt 40s are realy too small but great for a 302. 2bbl 351C heads work great on a W motor. Did my first one in 72 73 for a guy. Pricy to do back then you didnt have the aftermarket there is today.

[turbo2256b]

Also should mention testing of the air gap on several engines my finding is its a gimik to get 100.00 more out of you the RPM and AirGap pull almost identical power. One test showed the Air gap to have 5hp more peak but the RPM more total by about 40 hp.

[sly]

This gives me ideas for playing with the lopo when I have time

been contemplating just putting the 19# injectors and HO upper stuff I have on the 88 and getting the SD ECM tuned (quarterhorse or some such). I know upper RPM would still be a no go, but the butt dyno would love the hell out of the torque and launch and 0-30.

[Mike_Windsor]

Well my mechanic tells me that a 4bbl carbeurator would give me the most performance out of my engine.

I never realized I'd have to do heads, camshaft, and rear differential gears. If that's the case we'll make it a package project and upgrade the rear brakes to disc (meaning replacing the axle).

[turbo2256b]

Dont have to just depends on just what you want to do and how many bucks you want to spend.