351C, .030, F/T cast pistons, 2V heads (unported), hyd. flat cam (206/220, .481/.490, 114lca), Weiand Xcelerator intake, Holley 750 vac. sec., Accel distributor, 6AL box, Dynomax 1 3/4" pri. headers, 2.5" exhaust (Flowmaster mandrel tailpipes and 3-chamber mufflers), C6 w/ shift kit, CJ torque converter (10").

So, how did the car do? On a Mustang brand dyno, 200.8hp @5000, 224tq @4250. Does this RWHP sound about right? The reason I ask is beacuse the 351C was rated at 250 gross HP in 1970. Take away 15hp for accessory drive loss, and 30% for drivetrain loss, net HP was about 165. So, are all my mods only good for 35 RWHP?

Here's the dyno graph:

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Kyle Laramore

'63 Fairlane: 351W, 10.2:1, top-secret hyd. roller cam, Victor Jr. heads & intake, 800 DP carb, Super Comp headers, duraspark & 6AL, C4, 4500 stall, 4.11 gears, 26" slicks

'66 Mustang Coupe: 289, Offy intake, Crane Blazer hyd. camshaft, Holley 650 DP, Headman long tube headers, 3" cut-outs, Flowmaster 2-chambers, 3.80 gears

'70 Mach 1: 351C-2V, Weiand intake, 750 holley, Flowtech long-tube headers, MSD ignition, C6 trans, CJ converter, 9" track-loc rear, 3.50 gears, Flowmaster 2.5" mandrel exhaust w/ 3-chamber mufflers

My advice for building & buying:
1. "Never Assume!"
2. "Pay me now or pay me later."
3. "If it's too good to be true, it probably is."

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• VIN 1F05M139343
  
• 71 Mach 1 Ram-Air
• 351C 4V 285 HP
• F-G/Stock Aut
  
• Stockers are way cool!

quote:

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Originally posted by Kyle:
....the 351C was rated at 250 gross HP in 1970.

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I doubt if that figure was the correct one. Everyone liked to 'inflate' their numbers for sale purposes.

You also need to remember, when Ford dyno'ed thier motor, it was on an engine dyno, and didn't have any accessories to drive. No convertor slippage, no water pump, no transmission, no gear to turn, none of that. Plus, you are losing 50 hp thru the C6 alone, not counting what you lose thru the rest of the drivetrain including convertor slippage (and they all slip a little bit unless it's a 'lock up' style which the old ones aren't.)

The cam is WAY wrong for that engine. The lobe seperation is WAY too wide. It needs to be around 108 or 110 for max power on a streetable 351C, and could use a bit more duration. Duration should be around 224 @ 0.050" on the intake (with a streetable 10" or 11" converter, and a bit more on the exhaust.

Change the cam and it will make a bunch more power. Change to a 4-speed or even a C4, and more of that power will reach the rear wheels.

Good Luck!

I know this can be a controversial topic, but based on experience 30% is a lot of drivetrain loss.

But I think the accesories are more than 15hp. They ran engine dynos with no fan remember. The fan can be worth 10hp alone, throw in the alternator, perhaps a power steering pump and A/C pump. What accesories do you have?

Im sure the original 250 gross was probably around 165 at the wheels.

Your dyno run only went to 5000RPM. Looks like the power was still rising a little at that point, if you had run to 5500 you might have seen about 205-210 horses. 45 horses for your mods might make more sense.

What timing/octane did you run? I assume this was a "best" run with some fiddling between runs?
You could probably jet a little richer - might pick up a couple more ponies

And I think Kid is right that 250 sounds like an awfully round number. they probably Squeeeezed 250 ish out of their test engine but thats probably a little bit higher than most ran.