Author Topic: LEAKDOWN TEST VARIANCE IN FRESH ENGINE  (Read 331 times)

vabeach56wagon

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LEAKDOWN TEST VARIANCE IN FRESH ENGINE
« on: September 18, 2021, 01:18:44 PM »
A 302cu in SBC, fresh with Eagle crank, rods,JES forged 11-1 pistons, comp flat tappet cam, heads fresh, fel-pro 17030 composite head gaskets, square decked block....

Did a leakdown test out of curiosity after the right bank cylinder head had to be replaced because of a cracked seat. Newly-done head was installed but has developed slight head gasket leakage into #6.

Pulled the head, replaced the damaged gasket, retorqued head and got out the leakdown gauges. All four cylinders on that bank are at a 20psi difference. All four cylinders on the left hand bank are at 10-15 psi difference. Pressure applied was 80psi.

Should I be trembing in dismay or should I finish buttoning up the motor with the thought that the seal on the right bank will improve once the engine has fired again?

paul

jwbavalon

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Re: LEAKDOWN TEST VARIANCE IN FRESH ENGINE
« Reply #1 on: September 18, 2021, 07:25:33 PM »
I was wondering, based on the CRG Report, if there is a value to doing a leakdown test on a 302.   Both valves will be partly open at TDC resulting in a leakage.

 From the CRG Research report, "The traditional method of adjusting cylinder head valves one or more cylinders at a time, with each cylinder at TDC (top dead center), is fine with hydraulic valve lifters and with most solid-lifter camshaft designs. But this method cannot be used with the factory "30-30" solid-lifter cam (PN 3849346) used in 1967-69 Camaro 302/290hp Z/28 engines, as well as in 1964-65 Corvette L-76 327/365hp and L-84 327/375hp (F.I.) engines. This cam derives its 30-30 nickname from the factory rocker arm clearance of 30 mils (0.030 inch) for both intake and exhaust. It has VERY long clearance ramps that are 0.020-inch high, and at TDC for any cylinder, both the intake and exhaust valves for that cylinder are still on their ramps rather than on the cam's base circle, which is why the Service Manual for all cars so equipped specifically says to set them "hot and running".

dannystarr

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Re: LEAKDOWN TEST VARIANCE IN FRESH ENGINE
« Reply #2 on: September 20, 2021, 09:59:45 PM »
Many of us have been using the cold adjustment method for years. Seems to work very well. Click on link. ... Danny

                  http://www.camaros.org/302valves.shtml

 

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