968Forums.com

Inspired by Tama's thread I took the time to do a leak down test on my engine this afternoon. I have a fresh engine with 1,632 miles on it. It's modified with a D1R stage 3 supercharger.



I used a pressure tester used for checking piston airplane engines. The standard for this test is to have a supply pressure of 80 psi and see what the cylinder is able to hold. Normally the test is done on each cylinder with the piston at <acronym title='top dead center'>TDC</acronym> and valves closed. It's also generally done on a warmed up engine.



To do the test I pulled the plugs and rocked the car in gear until I had a piston at <acronym title='top dead center'>TDC</acronym>. I jacked the left side of the car up, replaced the starter with the flywheel lock and did the test. I then had to take out the flywheel lock, let the car down and then push the car until I had the next cylinder in place. Repeat this four times and you're done.



I was very pleased with the results. #1 held 75psi (that's the test shown in the picture) and the other 3 all held 78 psi. I can safely say that my rings are seated and the valves are sealing. When I get a chance I'll also do a compression check, but this leakdown test in my opinion is much more conclusive.

Great to hear, and nice, concise explanation as to how to perform this test.

Nice comparison!

You must have felt good about the results. What changes (to head, cylinders, etc.) did you do during your rebuild. Sounds like you put in new rings?

[quote name='MB968' timestamp='1377473825' post='147959']You must have felt good about the results. What changes (to head, cylinders, etc.) did you do during your rebuild. Sounds like you put in new rings?[/quote]

Had a competition valve job done on the head. The block has Darton sleeves. Used the stock pistons with Total Seal rings speced by Lindsey Racing.

Nice

Good to hear it finally worked out for you.



Are the total seal and the Lindsey racing rings the one and same?

[quote name='Eric_Oz_S2' timestamp='1377503132' post='147991']Good to hear it finally worked out for you.



Are the total seal and the Lindsey racing rings the one and same?[/quote]

Thanks.

Yes, after phone discussions with Mike Lindsey, he ordered the Total Seal rings that he thought would be best. Because my cylinders are ductile iron now the piston clearance is greater than that for the all aluminum stock block. Had to work out the best ring diameter, ring gap and ring material for my situation.

total seal rings have been around for a long time. chevy guys have been using them for quite a while. i used them many years ago when i would sleeve a block like this (did it quite a bit in the 215). pretty sure they would tear the heck out of an aluminum bore though.

Looks like they're aptly named, though.

Just to be clear, Total Seal is just a brand name. These are not the two piece compression rings that theoretically eliminate the gap. Mine are a very normal looking ring set. Mike L consulted with TS for the size and metallurgy to fit my somewhat non-standard situation.