Another 351W Dyno Thread

[Texasdoc]

Just got back from my 1st dyno run.

Engine specs:
351W - 40 over, stock crank/rods
10:1 compression
AFR 185 heads
RPM dual plane Airgap Intake
Holley 670cfm vacuum seconday carb. Primary jets 68, secondary jets 76.
Rev limiter at 6000rpm

Comp Cams "conversion" roller cam XR276RF (tappet block with dogbone conversion kit)
Total Duration: 276/282
Duration at 50: 224/230
Lift: 0.513 with 1.6:1 roller rockers

T5z tranny, ford 9 inch rear with 3.73 gears.

For some reason I didn't get RPM on the printout. Just MPH. I asked them to run it up to 6000 which is where the rev limiter is set. So I added the blue numbers that are estimates of the RPM.

Max HP at 5700 = 324
Max torque at 4200 = 353
AFR looks pretty close to 13 throughout - maybe a little rich in the early part of the pull.

Expecting ~20% drivetrain loss, that puts it at 440ft# and 405hp at the crank. This is without head porting to match the intake or headers (next winter's project).

Overall, I'm happy with these numbers. Any thoughts/comments/recommendations?

Thanks, Tom

[vector1]

fms crate 351 was rated for 385hp with a vic jr intake and everything else similar, so i would say your's is expected. i had the fms 351 and installed afr185 heads, advanced the cam and put on the rpm air gap with 750 cfm carb and liked the results. also changed out the 40# flywheel/clutch for a 18# setup, that made a big difference. keep in mind when you use a dual plane intake, you are really using half a carb on each cylinder instead of the full rated carb cfm.

[Texasdoc]

I realize that with a dual plane intake, you are only getting half the airflow to each side, but each side has only half the total number of cylinders. So it should balance out for a street tuned car. Most of what I've read says that a dual plane setup is better for the street. Only high RPM (race) prepped machines do better with the single plane. Mine is a driver. I may hit the track at some point, but mostly just cruising.

Ok, so what is an 18# flywheel/clutch setup? I'm guessing an aluminum flywheel - but any special clutch? My engine is externally balanced - do the aluminum flywheels come with the 50oz external balance weight? Or would I have to tear down the bottom end to have it internally balanced? If so, that may be more than I'm interested in right now.

[vector1]

I think it is more like, with a single plane each cylinder has the opportunity to pull from whatever cfm the carb is rated for, with a dual plane, each cylinder is pulling from half the carb.

Your 351w should be 28 oz. imbalance but you can get whichever weight you need and it bolts on then if you prefer you can take it to a machine shop and have them check the balance between the old flywheel and the new, cost me $100. Then if you ever go zero balance take the weight off. You would probably have to change the throwout bearing to get a round face bearing.

Bought this one from levy, and have a mcleod on the other car i bought used. I don't think they cost over $1k if at all.