leakdown test
Thread Starter
Rest in Peace
Rennlist Member
Rennlist Member
Joined: Apr 2003
Posts: 2,240
Likes: 0
From: Penn State
leakdown test
I want to do a leakdown test on an engine.
If I put #1 cylinder at TDC (comp stroke) what other piston is also at TDC? I don't think the firing order is equivilant to a SBC which has 1 & 6 at TDC together, rotate 90 deg to get 5 & 8, then another 90 deg for 4 & 7, then another 90 deg to get 2 & 3.
I'd rather be able to do two pistons at a time instead of all eight individually.
Scott
If I put #1 cylinder at TDC (comp stroke) what other piston is also at TDC? I don't think the firing order is equivilant to a SBC which has 1 & 6 at TDC together, rotate 90 deg to get 5 & 8, then another 90 deg for 4 & 7, then another 90 deg to get 2 & 3.
I'd rather be able to do two pistons at a time instead of all eight individually.
Scott
Thread Starter
Rest in Peace
Rennlist Member
Rennlist Member
Joined: Apr 2003
Posts: 2,240
Likes: 0
From: Penn State
Glen;
Just trying my damndest to be lazy. I'd walk a mile to get out of walking 1/2 mile.
Probably end up doing it the old fashioned way... straw stuck in spark plug hole.
Scott
Just trying my damndest to be lazy. I'd walk a mile to get out of walking 1/2 mile.
Probably end up doing it the old fashioned way... straw stuck in spark plug hole.
Scott
Nordschleife Master
Joined: Aug 2002
Posts: 9,010
Likes: 2
From: South Texas
No two cylinders fire at the same time. There would be another cylinder on the up stroke, but both the intake and exauste valves should be cracked open.
To figure out which one it is, simply look at the distributer, the cylinder that is 180 degrees out from the one your testing is also on the up stroke. Only problem is it's the end of the exauste stroke, and the start of the intake stroke, so you shouldn't be suprised if both of the valves are cracked open. On the twin dizzy units, it'll be the 5th on in the fireing order like Glen says.
On the early 80s 928s, with our crappy cams, and the hydralic lifters, I wouldn't be suprised if both valves were closed then though. Your GTS's cams don't seem to leave as much hope though. Could try it just to see what happens and report back.
To figure out which one it is, simply look at the distributer, the cylinder that is 180 degrees out from the one your testing is also on the up stroke. Only problem is it's the end of the exauste stroke, and the start of the intake stroke, so you shouldn't be suprised if both of the valves are cracked open. On the twin dizzy units, it'll be the 5th on in the fireing order like Glen says.
On the early 80s 928s, with our crappy cams, and the hydralic lifters, I wouldn't be suprised if both valves were closed then though. Your GTS's cams don't seem to leave as much hope though. Could try it just to see what happens and report back.
