Pre - ignition Problem.

My engine had bad knock with the slightest acceleration, and I discovered the rear cylinders had rust built up and caused a hot spot. Once I got rid of the rust and back flushed the radiator the knock was gone.
 
A 5.2 head would not produce 100 psi unless it has been milled. It sounds like you have a hot spot in the combustion chamber which could be caused by a sharp edge (among other things) from the milling or running too hot a plug causing it to glow. Make sure there are no sharp edges or carbon deposits because heat can concentrate there. Ron W
 
In my newly acquired model ford instruction book :-) for a carbon knock, ford says to remove head and clean carbon off Pistons. For ignition knock when ascending at hill, retard the timeing some. When traveling on flat ground, the spark lever should not be advanced more than half way down. Hoping you don't have more serious problems like bearings, timing gear, etc. You could remove the spark plugs and look for carbon on pistons!
 
Big hammer said:
In my newly acquired model ford instruction book :-) for a carbon knock, ford says to remove head and clean carbon off Pistons. For ignition knock when ascending at hill, retard the timeing some. When traveling on flat ground, the spark lever should not be advanced more than half way down. Hoping you don't have more serious problems like bearings, timing gear, etc. You could remove the spark plugs and look for carbon on pistons!
Click to expand...


perhaps you should read it again--
"for average driving the spark lever should be carried about half way down the quadrant. Only for high speeds should the lever be advanced all the way down the quadrant. When the engine is under heavy load as in climbing steep hills,driving through heavy sand, etc, the spark lever should be retarded sufficiently to prevent a spark knock."

What I found with my car ---originally when the engine was "rebuilt" the cam was reused and the valve seats cut deep into the block ---I could get spark knock at times, now with new seats the valves sit high on narrow seats (narrow seats create high seating pressure, conduct heat better) and a good unworn cam there is no setting that causes spark knock---at any speed, any load ----the cam and valve change took the top speed from 53mph to 67 mph, fuel mileage from 15 to the low 20s
 
Sorry my bad :-( I didn't type out the manual, just trying to convey that information in the Ford instruction manuals are out there and have good info!!! Happy motoring :-)
 
On the engine that's having issues, if you turn off the igintion when she's good and hot, have you noticed the engine (I can't remember the darn term) trying to fire/cough sputter/keep tryin to run even tho the ignition is off. If you have, thats indicative of carbon buildup (piston top,spark plug,somewhere in the head) Also, what "heat " of plug are you running and what's the output of the coil, are you running stock plug wires or modern? Just some questions that will help to shed light on if it's preignition or just an ignition issue.
 
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