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Hey Forum- Need some help. So, an update on the 1966 F100 I purchased. The thing needed a new brake system, got some new rims and tires, and some period correct caps. But I am having problems with the engine. It is a 1972 300 6 cylinder, with an 1985 head on it. I have cleaned up the engine and fit an original oil fill air filter. Looks pretty good, but it at higher RPM it has no power and I cannot seem to dial in what I can ascribe as a misfire when accelerating (2000 -2500 RPM). The motor just starts sounding like it is misfiring and wont accelerate- and it doesn't smooth out- just flatlines- sounds terrible- like its misfiring. Anyway. I have went through the ignition system, got new plugs, wires, and cap. Did not replace the coil and points yet because I have on order a petronix set coming. I checked the coil resistance and it reads 1.5 ohms. Spark looks decent, but it is hard to tell, but even after installing new spark plugs, the carbon build up on them is insane. They are dry and carbon black. I cleaned the inside of the valves when I replaced the intake manifold gasket using a scribe, cleaning tools, they were filthy. Again. the spark plugs look dry and sooty. All intake and exhaust manifolds are solid- they seal up- I had to weld an ear that was cracked (#1) when I fist bought the truck- but after welding/grinding and mounting intake/exhaust- no leaks. I purchased a YF carb and dialed that in, it doesn't leak- not much to adjust there, but it sure does smell rich, Like I know the adjustment is just an air mixture screw, but the richness and spark plug black soot makes me wonder. I took off the valve cover and looked at rockers and valve movement for inspection, the rockers/valves were looking good, and the push rods spun as they stroked- seems legit. So, why does this flatline at accelerating RPMs, why does it feel like it misfires at higher RPMs? I took the truck for a spin a few minutes ago after checking the timing and all vacuum (No leaks)- I can't really go fast in this truck, this motor issue won't let me. As long as I shift into the next gear- only three- then I can keep going..... Also, vacuum, I can only maintain about 14 inches of vacuum- seems low. Is that low? Once I adjust to timing the vacuum is only about 12.5 inches. I had gotten a response to look at the harmonic balancer, it does have some cracking in the rubber- I will throw a image down below. Not sure that is the problem because it seems to idle fine. Thank you for any help. 1972 300 6Cyl, 1985 head, older valve cover painted, original type YF Carb and Oil Fill Air Filter. 1966 Ford F100 Base Model Balancer some cracking in the rubber.
What next- So I checked the compression next: 1) 105 2) 130 3) 130 4) 125 5) 132 6) 115
Looking at this forum, it seems if pressure is less than 120 psig then the engine/rings are worn. I did squirt some oil in #1 cylinder and pressure went up to around 140 psig.
So, what are your thoughts on why I am getting a misfire at high RPM? I know it might need new rings, but if I go that route, I suppose just rebuild it. Anyway, your feedback is much appreciated. I am frustrated with this thing.
