Low compression but good leak down
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Roller lifter failure causee loud tapping noise or wipes lobe off cam. You could try to power balance by disconnecting injectors to see if there is a weak cylinder. You numbers really don't indicate a obvious problem. Why do you feel you're down on power? ET, dyno, lap times?
Thread Starter
Race Director
Joined: Feb 2008
Posts: 19,691
Likes: 322
From: Alexandria VA
Roller lifter failure causee loud tapping noise or wipes lobe off cam. You could try to power balance by disconnecting injectors to see if there is a weak cylinder. You numbers really don't indicate a obvious problem. Why do you feel you're down on power? ET, dyno, lap times?
Also, all fuel injectors have recently been serviced and have flow reports for.
Last edited by RandomTask; Jan 10, 2021 at 06:09 PM.
Thread Starter
Race Director
Joined: Feb 2008
Posts: 19,691
Likes: 322
From: Alexandria VA
Drifting
Joined: Jul 2014
Posts: 1,426
Likes: 46
From: Lynchburg, VA
Funny, I've got the opposite problem. I was showing somewhere around 200psi cranking compression (if memory serves), but leakdown tests were really abysmal. I recall it reading 50% or higher leakdown. I'm ~75% sure the issue was just a low-quality leakdown tester, as I noticed results varying dramatically depending on the supply pressure. I suggest making sure you can trust the results from the leakdown and compression tests you did. I'm interested what you find.
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Verdad Gallardo
Pro
Joined: Sep 2019
Posts: 716
Likes: 135
From: Buchanan, Michigan
Couple thoughts.. worn timing chain/gears could be retarding cam timing. And excess lifter and or their bore wear could be decreasing lift. That COULD be losing lift, so when trying to take a "gulp" of air during compression test you're basically losing .035" or so of valve lift. Basically sounds like she's"tired" ready to be freshened up.
