rotated engine maunally - lifters pumped down?
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 931
Likes: 35
From: Rowlett, Texas
rotated engine maunally - lifters pumped down?
We were working on the clutch, and turned the motor over several revolutions by hand, with the plugs out of course.
On start up, it seemed all 16 lifters would come through the valve covers.
After what seemed forever - maybe 5 minutes, the racket had slowly subsided. Now everything is normal, no lifter noise even after sitting all night.
I can understand that the lifters might pump down a bit when turning the motor over slow (and we even turned it backwards a little bit).
But most engines I've built pumped up the lifters in less than 15 seconds.
Has anyone else experienced this scary situation?
Does it cause a problem to turn the engine backwards a few degrees
(trying to reach all those pesky clutch bolts)?
This engine has only 20k, Mobil 1 always, and has never made any unusual noise at all.
thanks,
DG
On start up, it seemed all 16 lifters would come through the valve covers.
After what seemed forever - maybe 5 minutes, the racket had slowly subsided. Now everything is normal, no lifter noise even after sitting all night.
I can understand that the lifters might pump down a bit when turning the motor over slow (and we even turned it backwards a little bit).
But most engines I've built pumped up the lifters in less than 15 seconds.
Has anyone else experienced this scary situation?
Does it cause a problem to turn the engine backwards a few degrees
(trying to reach all those pesky clutch bolts)?
This engine has only 20k, Mobil 1 always, and has never made any unusual noise at all.
thanks,
DG
Melting Slicks
Joined: Apr 2001
Posts: 2,877
Likes: 7
5 mintues is a long time, when I had my mine apart for the cam swap they were fine after 15 - 20 seconds at the most.
If it is running fine now I wouldn't worry about it might be worth checking your pushrods to make sure everything is in order and nothing got bent or tweaked
If it is running fine now I wouldn't worry about it might be worth checking your pushrods to make sure everything is in order and nothing got bent or tweaked
Drifting
Joined: Jan 2001
Posts: 1,347
Likes: 4
From: Slidell La
Air in the lifters
It doesn't take much air for lifters to make noise. When you turned the engine over with no oil pressure the valve springs compressed the lifters. This compression pushed the oil out and allowed air to come into the valve lifter body. The lash didn't change since you didn't turn the rocker nut. After start up there was enough oil to open the valves to allow the engine to run. The air was still there and compression everytime the toe of the cam pushed a lifter. The lifter compressed the air until the valve began to move. You had to run the engine long enough for all 16 lifters to purge the air. Normally when I build an engine I put the lifter in oil and compress it to allow it to purge the air and prevent the problem you had.
I would expect it to shorten your engine life by about 1 mile or less
.
So just keep
. 99 Nassau Blue
I would expect it to shorten your engine life by about 1 mile or less
.So just keep
. 99 Nassau Blue
Le Mans Master
Joined: Dec 2003
Posts: 5,561
Likes: 448
From: Atlanta metro Ga.
I had the same issue during an oil change one time..
One lifter bled down, and I assumed it had an air pocket..
I knew that the motor had oil, and the pressure was fine.. What can you do? Nothing.
I drove it down the block and it stopped on the way back..
One lifter bled down, and I assumed it had an air pocket..
I knew that the motor had oil, and the pressure was fine.. What can you do? Nothing.
I drove it down the block and it stopped on the way back..
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 931
Likes: 35
From: Rowlett, Texas
Thanks, guys. Yeah, kinda scary to work on stuff, then have it rattle like a can of marbles.
Now I'll tell why I was working on the clutch: I had the dreaded pedal vibration, that the dealer tried to resolve 5 years ago. Never went away though, even when they replaced the entire clutch, FW, Throw- out bearing assembly.
Well, we sneaked in and loosened all the prerssure-plate bolts evenly, rotated the assembly and tapped gently on the Pressure plate to kinda center it, then sequentially tightened the bolts back down.
IT REALLY HELPED. Vibration is not totally gone, but it's at least as good as 4 other Vettes I have tested.
Of course, I didn't notice the foot massage as much until I replaced the exhaust and got this great sound at about 3500 rpm. Now I tend to rev it to 4000 or more in every gear just to hear it howl.
It's the MOD Syndrome: change one thing, gotta change something else.
DG
Now I'll tell why I was working on the clutch: I had the dreaded pedal vibration, that the dealer tried to resolve 5 years ago. Never went away though, even when they replaced the entire clutch, FW, Throw- out bearing assembly.
Well, we sneaked in and loosened all the prerssure-plate bolts evenly, rotated the assembly and tapped gently on the Pressure plate to kinda center it, then sequentially tightened the bolts back down.
IT REALLY HELPED. Vibration is not totally gone, but it's at least as good as 4 other Vettes I have tested.
Of course, I didn't notice the foot massage as much until I replaced the exhaust and got this great sound at about 3500 rpm. Now I tend to rev it to 4000 or more in every gear just to hear it howl.
It's the MOD Syndrome: change one thing, gotta change something else.
DG
