I just got a 1974 F100. Original engine threw a rod shortly after my bud got it, so he had a 390 built for it. Cracked the 390 heads after he had them shaved so now it has a set of 427 heads. Edel intake, looks like an RPM, Edel carb replaced the Holley that was on it, unknown size. He says it was dynoed and produced 295hp and 595lbs of torque at the rear wheels. It has broken an axle while doing a burnout. It has a bit of a chop to it, so I have no doubts it has a bit of a cam. I replaced the points to get it driveable so I could get it home, just eyeballed it, so the timing is way out there. I have conflicting info from him as to how it was built. He was originally going with ridiculous compression (14:1) then changed it up for a roots style blower. The only thing I can confirm is the motor is solid, just needs a tune and some running, probably getting the points right and timing more than anything. I have no doubts of the axle breaking story. Engine has about 15k on the clock, freshly built C6 has around 6k on it, leaks like crazy, haven't even begun to look into that. Not worried about the truck, but the drivetrain is sounding very interesting. My car buds say a 390 in a Comet sounds original, I'm thinking something smaller and dumber myself, almost strictly a strip car. The problem I have is I can't work out any combination that will give 295hp and 595ft lbs. All I can figure is a full dyno with an auto, maybe 595 came from 1st gear? Seems it would be much higher in first tho...
Wheel hop. Dyno results are only good in person or on paper. Unless you tear it down, it is hard to say what you have there.
427 heads on a 390 will never achieve a 14 to 1 comp ratio. 10 to 1 would be max with flat tops, more'n likely less than 10 though. The 390 won't fit in a Comet without doing something about the shock towers. As for those power figures, they're way off in regards to the 595 ft/lbs torque. The stock rating for most was 427 ft/lbs. The 295 hp figure could be right.
And that was a two-three year only thing (66, 67, 68) Those were the only years that a Comet had a wide enough (and then just barely) engine bay to squeeze in a big block.
We weren't counting the 60's Comets. I didn't think about them having a 390 to be honest. If I did it, there would be very little Comet front suspension left. I probably won't go that far. It isn't stock. I agree with the HP and TQ numbers not adding up, that's why I posted. See if anyone that has more experience might know of a way. I think if it showed 595 on the dyno it wasn't in 3rd gear.
The combo he posted above, should be at least another 100hp. (390 w/427LR heads, RPM intake) Could be they never got it dialed in, or the cam's installed wrong, the carb certainly doesn't help either.
I kind of like the sound of that. I've got a Holley 750 I can bolt on there, been sitting a while tho. I didn't get the chance to play with it this weekend. A thermostat for my wife's Explorer turned into an intake water leak, 15 minutes turned into 6 hours, part of it in the dark with no power. Anyways, first thing I plan on doing is getting the points set more accurately and tinker with the timing. It runs very well aside from timing/carb issues. I'm confident the workmanship was good, not too happy with the way they matched parts. 600CFM is a wee bit small for a decent spinning 390.
