215hp street build

Leakdown test complete, well on cylinder 1, 2 & 3 would not stay up, thats adding air slowly at about 50psi the piston was going down strongly, wtf, i put a breaker bar with a pole and i thought it was gonna snap the crank. They’re definitely not leaking so i think im forced to move on as i dont like the idea of holding the crank with so much force, ? Any suggestions? Im gonna do starter cylinder pressure test next, its 60 degrees farenheit in garage so the aluminum is cold in here.
 

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As I recall when we did compression test on aircraft engines, we would set the prop till tdc then slowly add about 25 psi while holding the prop, then move the prop back and forth until no air pressure moves the prop for a true TDC, then apply 80 psi and measure psi drop in cylinder. You could do the same with the crankshaft.
 
Kevin frazier said:
Leakdown test on cylinder 1 went good, cylinders 2 & 3 the pistons would not stay up when applying air into cylinder for test.
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have you tried to use something like a philips screw driver and hold it with your fingers and work the crank till you have it perfect
 
I will put a straw in spark plug hole ( long screw driver) and set tdc closer to ( dwell point) better and see if that does it. I must have just been off ( one side or other) on tdc on 2 & 3.
 
Kevin frazier said:
I will put a straw in spark plug hole ( long screw driver) and set tdc closer to ( dwell point) better and see if that does it. I must have just been off ( one side or other) on tdc on 2 & 3.
Click to expand...
Sounds like missing tdc on each cyl. and air pressure is moving piston down. Turbo is correct, this is a great way to check for leakage regardless of the cause.
 
Gerald said:
Sounds like missing tdc on each cyl. and air pressure is moving piston down. Turbo is correct, this is a great way to check for leakage regardless of the cause.
Click to expand...
in my case theres no leakage felt it now just need to see it to be satisfied, 4% on a cold fresh rebuild i think is awesome. Yes a leakdown test tells alot. Im feeling pretty good about this engine.
 
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