Technical > Spud Miller's Cave

leak down test

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L79_Acadian:
  Hi Spud,
 I have a SBC with stack injection. The injection has been to Hilborn, along with the pump for a going over.
I have it on the car now, exactly as it was sent to me from Hilborn. Last fall I had it running(?) for a few moments. This year it ran for a minute or two, but wont idle. Its on alcohol, and the block has water in it.
 Well today I hooked a leak down tester to the inlet of the barrel valve, made sure the throttle was closed, and set the tester to 100 psi. Well the other gauge went down to about 20 psi. To me that's about 80% leakage, and I was told it should be about 15-16% leakage to get started.
 What did I do wrong, or miss?
 Thanks in advance,
                      Roger 
 I guess I should have searched a bit more before I wrote this. I didn't plug the first or secondary by-pass off.
I will do that tomorrow, and see what happens.

Spud Miller:

 Yup, block off that secondary and recheck. If your nozzles are fairly small, you might want to unhook one of your nozzle lines too.

 For methanol, I recommend a leakdown approximately 7% of your engine size. So, for a 350" motor, that would be 25%. That's assuming your idle (main) check valve is 1-2 PSI.

 Once you get it set where you want it, open the throttle slowly and you should see the needle drop and keep dropping.

 Good luck!
 Spud

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