New Rebuild first start questions

Joe KCMO

Joe KCMO

Senior Member
39 all stock, new rings, main bearings, rod bearings, valves, valve springs and adjustable lifters set to 0.011". The starts first turn. Oil pressure rock steady at 20 psi on idle. Pulls 20" of vacumm with an occasional drop to 19". I hear the random back fire matching the drop in vacuum. According to the vacuum charts....Burnt or Sticking valves. The motor has only been run a total of 10 minutes. What could be the problems and solution to the random backfires? Thank You.

Note: I used loctite green as a precaution on the adjustable lifters. I had a problem with a couple of lifters staying up(before startup during assembly). I worked them free and cranked a few times to make sure they were all free.
 
i believe i would get it broke in before i worry too much, let everything stretch out and break in, then go back and adjust what is needed. check your carb if its the same carb the new engine may need more fuel or less.
 
Charlie ny said:
Joe,
I'd increase the valve lash proto...I think .011 is too tight. Eyeball the plugs
too you might be lean.
Charlie ny
Click to expand...

Not arguing, learning...Old Ron had 0.011" to 0.013" in his book. I was thinking they would wear into 0.012". Will too lean cause backfire?
 
First, do not allow a new engine to idle at low speeds during the first 15-20 minutes of operation.

Second, get the engine under a load as soon as reasonably possible.

Third, it is more common for the valve lash to become tighter rather than looser after initial run-in.
 
I'd open up the lash to at least .014 and run the engine at fast idle to break the cam in. on OHV engines the cam manufacturers recommend 2000 rpm for 20 min. maybe FH at a little less rpm, but Rons book says 2000 for 10 min then cool down retorque heads and do it again. JMHO
 
After reading the comments, I am worried about intake and exhaust both set to 0.011'. So I opened the engine up AGAIN to adjust the valves.

Here is what I have got from two books.

Old Ron's Book intake and exhaust 0.011" to 0.013".

Ford Shop Manual Intake 0.010" to 0.012" Exhaust 0.014" to 0.016"

You guys with experience, what should I set my valves to?

Thanks, I need the help. Although I am getting good at taking the top of engine apart and back together in about an hour each way.
 
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