Sewing machine - normal?
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Joined: Aug 2014
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Sewing machine - normal? I've got my engine up and running. I installed TSP heads (shorter than stock), a 224R cam and trunnion upgraded rockers, along with LS7 lifters. I used both an adjustable pushrod and dial gauge to measure for length and ended up buying 7.375" pushrods. Given the thinner gaskets, shorter heads, and taller LS7 lifters I think that makes sense... right?
However, I've got the dreaded sewing machine noise. Seems worse when hot, which I guess makes some sense given that the block and heads are both aluminum. I took a valve cover off today to get a rough check using the "turn the bolt" method - looks like a tiny bit more than one turn is what it takes to completely loosen the pushrod. Some people think it's .049" per turn, some say .075" or so, so I still don't know what to make of that other than that I should have enough preload for the thing to run.
Should I try more preload to cure the noise, or just keep driving and deal with it?
However, I've got the dreaded sewing machine noise. Seems worse when hot, which I guess makes some sense given that the block and heads are both aluminum. I took a valve cover off today to get a rough check using the "turn the bolt" method - looks like a tiny bit more than one turn is what it takes to completely loosen the pushrod. Some people think it's .049" per turn, some say .075" or so, so I still don't know what to make of that other than that I should have enough preload for the thing to run.
Should I try more preload to cure the noise, or just keep driving and deal with it?
That is common with XER lobes. Does it make the sound at idle or cruising or both? If it is quiet at idle but you get some noise low speed cruising, I would say the pre load is fine. If it is noisy idiling then you might need more pre load.
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Teching In
Joined: Aug 2014
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Thanks, these posts are reassuring. It's at both idle and cruise, and not terribly loud - far quieter than actual valve tappet. The noise seems to come from under the car almost, the area around the intake/heads up top makes a super smooth whirring noise - I think that's normal. I'm still on break-in, technically, so I'm running the Driven BR 15W-50 TSP gave me with the shortblock.
I was almost thinking this noise was an exhaust leak, but I just checked and can't find any. I think for now my plan is to ignore it, I need to get this thing tuned so I'll see what the people at the shop say about it.
I was almost thinking this noise was an exhaust leak, but I just checked and can't find any. I think for now my plan is to ignore it, I need to get this thing tuned so I'll see what the people at the shop say about it.
Oh yeah... sewing machine noise is normal. I had aggressive lobes on my PatG cam and you can almost hear the valves slamming shut.
If you're running hydraulic lifters and stock type rockers, there's not much you can do about lifer pre-load other than adding .050" into the push rods. but mostly we do that anyway.. round up just a hair from the measurement (add that .050" for preload.) I've tried adding more by adding the .5 turn to the rocker bolts and it doesn't do anything. -IMO.
Also just make sure you're running the correct Oil pump O-Ring for your oil pump. My buddy and I spent months chasing a valve knock. Come to find out it was the damn oil pump O Ring causing oil system aeration.
If you're running hydraulic lifters and stock type rockers, there's not much you can do about lifer pre-load other than adding .050" into the push rods. but mostly we do that anyway.. round up just a hair from the measurement (add that .050" for preload.) I've tried adding more by adding the .5 turn to the rocker bolts and it doesn't do anything. -IMO.
Also just make sure you're running the correct Oil pump O-Ring for your oil pump. My buddy and I spent months chasing a valve knock. Come to find out it was the damn oil pump O Ring causing oil system aeration.
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