Pushrod preload to avoid sewing machine noise?
Pushrod preload to avoid sewing machine noise? Heres the back story...
I had a running Ls1 w/ BTR Stg2 cam. It had oem GM ls7 lifters in it with 7.5 pushrods, and TFS220 heads. It had zero sewing machine noise to it. It was great.
I ended up with a wiped bearing after a road course day due to not realizing that I should run extra oil in the pan due to long sweepers. I ended up rebuilding the engine. The cam was in good shape so I re-used it. I went with Delphi ls7 lifters this time thinking they would be the same thing. I now have a running healthy engine, but with sewing machine noises. Everything else is the same. I thought, ok perhaps its the pushrod length.
Measuring the pushrod I get 7.38 with no preload and being able to rotate the pushrod in place. Ive read that I should aim for .06-.07 preload on the ls7 lifters. That would put me at 7.44-7.45.
So my question is, is that additional .05 enough to cause sewing machine noises? Ive saw some people suggest running .1 preload on them to "avoid excess valvetrain noise". It seems I have excess already. Where should I be trying to set these things? I want my silent valvetrain back that I had before the rebuild!
I had a running Ls1 w/ BTR Stg2 cam. It had oem GM ls7 lifters in it with 7.5 pushrods, and TFS220 heads. It had zero sewing machine noise to it. It was great.
I ended up with a wiped bearing after a road course day due to not realizing that I should run extra oil in the pan due to long sweepers. I ended up rebuilding the engine. The cam was in good shape so I re-used it. I went with Delphi ls7 lifters this time thinking they would be the same thing. I now have a running healthy engine, but with sewing machine noises. Everything else is the same. I thought, ok perhaps its the pushrod length.
Measuring the pushrod I get 7.38 with no preload and being able to rotate the pushrod in place. Ive read that I should aim for .06-.07 preload on the ls7 lifters. That would put me at 7.44-7.45.
So my question is, is that additional .05 enough to cause sewing machine noises? Ive saw some people suggest running .1 preload on them to "avoid excess valvetrain noise". It seems I have excess already. Where should I be trying to set these things? I want my silent valvetrain back that I had before the rebuild!
LS1Tech Sponsor
Joined: Feb 2008
Posts: 300
Likes: 18
The exhaust lobe acceleration rate has more of an effect than anything. If you didn't have noise before, it won't this time around.
__________________
TECH Resident
Joined: Apr 2014
Posts: 985
Likes: 12
TECH Senior Member
Joined: Jun 2016
Posts: 22,293
Likes: 3,617
From: Central Cal.
If that were true, why do the lifters all have the same part number? If somebody had to replace a lifter there would be different numbers for intake and exhaust lifters. That is not the case.
TECH Resident
Joined: Apr 2014
Posts: 985
Likes: 12
was looking for a response from someone with a little Merit.
