It never hurts to check. A tale of anxiety, discovery and relief

[cabmandone]

As you might already know, I'm in the process of putting my engine back together after suffering a mechanical over rev. Heads were rebuilt, new rings installed etc. Valve timing checked, checked and rechecked. Tin back on, intakes installed. Almost ready to go back in! So yesterday I was in the process of buttoning things up and decided to do a leak down test just out of curiosity. #1 90 in 88 hold, #6 90 in 88 hold, #2 90 in 84 hold, #4 90 in... 15 hold HOLY SMOKES what happened? I can hear air escaping through the intake.

First thing I did was take the valve covers off and back the adjusters off so it was all valve, no joy, still leaking. Bounced the intake valve with a screwdriver, no joy, still leaking. Removed the intakes so I could see the valves, nothing visibly wrong. I turn the engine over by hand so the #4 intake is open and visually inspect the seat with a bore scope. Sure enough! Looks like there's something on the seat (not Cgarr's fault totally mine) So I make a quick run to CVS to buy some long cotton swabs, dip the swabs in rubbing alcohol and wipe down the valve seat and as much of the valve as I possibly can. Recheck BINGO! 90in 88 hold.

Lesson? Even though I had the intake and exhaust ports taped off during assembly, I didn't clean my intake risers well before reinstalling. The only thing I can figure is when I put the intake risers down onto the studs, I jarred something loose that dropped into the port. As I was doing final adjustment of the valves, it slid down into the valve seat where it was caught by some assembly lube. I pulled a tiny little flake from the valve seat and that tiny little flake was enough to keep the combustion chamber from building pressure. I went through and wiped down the six intake valves as well as the valve seats.

Would things have been okay if I had installed and started the engine? Probably. But would I have been extremely mad that I had put the engine in without checking only to find a problem and needed to drop the engine again? Absolutely. It never hurts to check.

[Classic 911]

Great job in checking all so well Better safe than sorry Now you can enjoy the engine 100%


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[flat6pilot]

Great catch!

[cabmandone]

Got the engine in the last night. Took it for a drive today. Feels goooooooooooood.

[gsxrken]

Satisfying, isn’t it? I enjoyed just about every minute of my rebuild, while simultaneously knowing I never wanted to repeat the experience. So far so good.
Congratulations