Keith Craft 331 Econo Stroker Motor

[Tom_Hughes]

Hi guy’s,

Here’s a recent dyno run I wanted to post.

Keith Craft 331 ‘Econo Stroker’. Has a Ford Motorsport Aluminum intake and a Holley Street Avenger 670 carb. Needs a bigger 850 manual secondary DiVinci or Holly HP according to the guy’s (Drew & Michael) at the Keith Craft shop in Dallas. If I did that, they believe I could pull +/- 340HP at the rear wheels.

TFS hyd roller cam Intake – 339 @ valve 542 – Duration286
Exhaust- 352 @ valve 563 – Duration 294
Rocker Ratio 1.6
Lunati street race rods
Scat cast crank
28oz balance
Mahle 4.030 flat top pistons
AFR 165 aluminum heads

Air temp was 42-49 degrees and 29.5% humidity

Run 1 – Car warm from drive over-too lean
HP-311.70 TQ-310.55

Run 2 – Car hot – Fresh fuel in secondary bowls-too lean
HP-312.60 TQ-310.13

Run 3 – Car hot – Manually opened vacuum secondaries-Too lean
HP-324.55 TQ-325.88

Run 4 – Re-jetted and air filter off – Car warm-richer
HP-316.60 TQ-322.42

Run 5 – Re-jetted and air filter on (K&N with filter top – Car hot-Fuel just right
HP-307.38 TQ-308.51

I'll take some pic's of the dyno run sheets & try to post them for you all this week end.

[Tom_Hughes]

Oh... Ignition... Autolite dual point w/Petronix. Light springs. all in at 2,800 RPM. Timing, 38 degrees at 3,000 RPM

[Ron Earp]

What sort of RPM are you getting numbers at and where does it drop off? I'd think that was enough carb for the motor and cam, particularily the heads as well. My guess is you might make a few more rear wheel ponies with a larger carb at the expense of some drivability and low-end torque.

[Tom_Hughes]

Good point Ron. With the 165 AFR's, I am sure that there is good velocity through the carb/intake/heads. Bigger would surely lose some peppy-ness.

Torque is pretty flat 3,000 to 6,100. HP peaks at 5,500 and is flat till about 6,400.

[Iron Sheik]

Tom, Great numbers, do you recall if the Dyno was a Dynojet or Dynamics? Also, what rear tires/wheels sizes do you have. And last, what gear where the pulls done at (I am assuming it is an Audi Trans).
Anything above 300 at the rear wheels is pretty damn good.

Thanks,

[Tom_Hughes]

Hi Falli...

It was a Dynojet. I have 15 inch rears with 295x50x15 Goodyears on 10 in BRM's. It is an Audi Getrag transaxle and the puls were done in 4th gear, about 2,500 rpm to 6,500 rpm. It is a hybris Audi, with a different ring & pinion mated to the best ratio box. I'll try to snap the pic's asap, and also have the run files on a diskette that I can work with once I load them down.

[jercarnut]

T, the 331 are easily cable of 420 to 425 horsepower. I have the 331 in my RF. We pulled 340 wheel horsepower on a mustang dyno a couple of years ago. We preferred the 331 as do a lot of road racers with it 1.63 rod riot. These little motors will last for ever. We run solid lifter cams with a little bit longer duration. We twist these motors to 71 or 7200 with no real modification the oiling system. Keith Craft has a excellent rep. You will be very happy with his motor. [img]/ubbthreads/images/graemlins/smile.gif[/img] Happy horsepower

[Tom_Hughes]

Ok,

Here are the individual run sheets!

[Tom_Hughes]

Run-2

[Tom_Hughes]

Run-3

[Tom_Hughes]

Run-4

[Tom_Hughes]

Run-5

--->Ron, please delete any of these pic's you believe are irrelavent to the post after a week or so... If no one has seen or read it by then, no big deal...
Thanks,
Tom

[Ricky]

Tom,
I noted with interest on the last run the significant drop off at the top end of the rev range where it looks as thought someone stepped off the gas. It is very similar to what mine did with the 8 bbl injection - Ref 347 dyno Results thread.

Cheers,