April 09, 2018, 08:02 AM
Bigdrive88Compression vs leakdown
How can a motor have 60-70 psi lower compression in 2 cylinders and then all the cylinders have 3-4 % leakage.
April 09, 2018, 12:48 PM
wideopen231Has to cam lobes,pushrod or something not letting valve open to get air in.
April 09, 2018, 01:24 PM
ski_dwn_itquote:
Originally posted by Wooley:
Bad can lobes/lifters?
Bingo. I would measure lift of PRs on all cylinder vs good cylinders...
Configuration: 3350#, 582 C.I.,
60 - 1.24
1/8 - 5.53@ 126MPH
1/4 - 8.73@ 159MPH
3700#+210lb driver, FULL interior, through mufflers, 10.5 tire.
60'-1.333 (IN 4000ft DA! Joisy Math excluded; 1.25sec using JOISY MATH.) 
1/4 - 9.60@144MPH April 09, 2018, 05:33 PM
Bigdrive88Ok. So there seems to be an consensous here. So I will check.
Thanks for giving me a place to start
April 09, 2018, 06:16 PM
topfuelBefore you get too far into it, try repeating the compression test on 6 and 8 again, with the throttle held wide open.
April 10, 2018, 09:01 AM
Bigdrive88Yeah I am going to. The motor has gas ported pistons. the theory is since the motor sat over the winter that the rings may be stuck on those 2. Maybe when I put air in for the leakdown it popped the rings back out. Gonna look at it tonight
April 10, 2018, 09:10 AM
teamAre you doing these tests on a hot/warm engine?
April 10, 2018, 04:17 PM
TOP38I haven't read this whole deal,,,
One question, is the motor running up to par or is it slow? If its running good forget about both compression and leak down testing!
If its off then you have an issue!
April 10, 2018, 04:40 PM
Bigdrive88Its been so cold here in Maryland, havent run it yet. The main issue how this thread started was the vacuum pump filling up the overflow tank in a matter of minutes.
quote:
Originally posted by TOP38:
I haven't read this whole deal,,,
One question, is the motor running up to par or is it slow? If its running good forget about both compression and leak down testing!
If its off then you have an issue!