I have a 71 F100, 360, C6, 3.25 rear.

Background: the engine was built by someone else some 8 years ago. They told me at the time that they built it stock, bored .030 over. My problem is that it has always been a gas hog and I have been suspecting that maybe the cam is not a stock grind. I had a 72 F100 360 that got 17MPG so I know this one can do better. The builder has no records or recollection of what was put in this engine but maintains that if he said he built it stock, it is stock.

<ORecent tests: I don't have a dial indicator or timing wheel nor the resources right now to go out and buy them. What I have done is I removed the valve cover and pin-pointed the time when the intake valve begins to open. I have an Edelbrock gear and chain set that I installed some time ago. I had everything set at full advance as far as the valve timing is concerned and I managed to see that the intake valve was beginning to open at 8*B. At this setting, the engine managed 115PSI worth of compression (the setup is old so I'm not too sure that there isn't any leakage from the hose or the fittings). At full retard, the intake valve began openning at 0* and I saw 105PSI of compression. At straight up, I saw the intake valve opening at 4*B and compression went up to 110PSI.

<O</OHere's some more: I have a Chilton that says that for a 71 model 360, the intake valve should be opening at 13*B.

<OHere's where I need help: The cam gear has 42 teeth; that equals 8.57* per tooth. If I time the cam to the straight-up slot on the crank gear (that's 4*B on the cam) PLUS advance the cam one tooth, that would give me 12.57*. You guys follow me? Since I don't know lift and duration, what do I need to look for as far as the exhaust valve? How far can I go before I start burning valves?

Hope you guys can help.

Thanks,
Joe<O<O</O

 

Without a degree wheel what are you using for accurate degree indications? Other than that, I'm kinda lost as to what you're doing here. Are you playing musical cam timing and then attempting to get a compression number? And with a questionable comp gauge? A three way lower gear has a mark or letter next to a keyway, then the same mark or letter on the gear to line up with the cam. OK, you've got that. Now, how are you establihing TDC? Real TDC? I would not reccomend jumping a tooth with the chain. I would bet the +4/-4/0* marks are fairly acurate when lined up with the cam gear....But would question the crank degrees if you are using the timing tab...Buy or borrow a degree wheel, find absolute TDC and THEN start degreeing the cam. No other way that I know to do it.......aMP

 

No money huh? :/

Well now's the time to call in a favor or two you are owed. :)
Oooo... no favors owed you huh? :/
Well then, now's the time to go -make- a favor or two owed you. :)
You're not above doing lawn work are you?

Alvin in AZ with many favors in the bank :)

 

A 360...17mpg??? Are you absolutely sure that was a 360 and not a 390? 17mpg is even one tick above what a well tuned 390 should get. I think you may be looking for a 390 crank and rods and just not know it yet .

 

Thanks guys- for trying to help, but I think I got it.

I consulted another Ford forum and was able to get some good information. Seems by my calculations, the stock cam was indexed incorrectly so I advanced the cam one tooth on the sprocket to correct the opeing and closing of the valves.

So far the truck runs like a champ- I'll know for sure when I hook the ski boat to it again. I was able to lean out the idle mixture quite a bit and install smaller jets in the holley. This thing runs smooth and quiet now and requires very little throttle. The exhaust won't burn your eyes out now. It starts up with just a touch of the key.

Thanks anyways- I'll keep you posted.

 

You might want to calibrate your odomiter.....MPG seems a little off, unless you have some real tall gears........aMP

 

Just for the record, way back when, (1978 or so) my cousin had a '71 F-100 with a 360/three speed and hauling cement blocks we got 18 MPG, so, 17 is not unheard of, with a manual tranny. I have never seen a Ford 3-speed auto get much more than 15, at least in a truck. His truck did have a "high-speed" rear end (His words, not mine. I don't actually know what the ratio was, but the truck would do about 135 or so.) Anyway, I'm new and I'm actually building an FE for a 68 Cougar

 

Sounds like your cousin should come on board w/ us and enlighten us to his fuel mileage magic. I've heard of guys putting small block carbs on to get better mileage but the motor wouldn't perform worth jack. Especially if he was getting that kinda mileage in '78. I think he may have had his FE crank strokes mixed up.

 

Wow those numbers, why am I pissing around with 3.54 gears with a 414 and can't get that mileage and especially that top end vs a smaller 360 motor.
Please print that engine build for us.
All this time I must of been wrong running a 3.98" crank when a 3.50" crank must have more torque to overcome the aerodynamic drag of a bumpside at 135 or so mph. I would of never known, thanks for posting.
Now if Pro Stock went to 300ci I6 motors they would be in the 5 second 1/4 mile instead of dicking around with those 500ci motors.

 

1965 F100 3.00-1 352 built into a 390 4V using the 390 GT cam. 3 Speed Borg Warner T-85 stick & overdrive. City mileage 10-12. Hwy mileage 20+ best ever = 28. Yes, set up right, good mileage is possible on the highway, but in town, forget it.

 

Numbers; you talking the C6AZ-6250A cam or the C6OZ-6250B cam?
Both were installed in the 390GT, C6AZ in 428's while the C6OZ in 428cj's.
C6AZ 256/256, .438, 37* same as 68 427 automatic.
C6OZ 270/290, .481/.490, 46* A big difference between cams.
With a good tune I have been over 15 mpg with a 414 C-6 3.54 geared CS running a C6OZ cam.

 

A "well tuned 390" with 10.5:1 compression and a 292/292 adv cam, in a '74 highboy with 33" tires and 4.10 gears, I got 15MPG on a 500 mile trip ... ONCE. Never got the chance to try it again