Chasing noise, need advice, a bit long...
06-15-2005, 04:58 PM
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Chasing noise, need advice, a bit long... I'm chasing the elusive sewing machine noise. First a little history. I had a H/C install done 4 years ago. It lasted 70K miles then a faint tapping turned into a loud knock. The first thing I did was replace the lifters (Comp 850's), ran the car about 500 miles, sound didn't go away. Upon further inspection I found the camshaft all chewed up and could actually pinpoint the sound from one of the rockers, so I did my own H/C install with the mods listed in my sig. I used the newer lifters I had bought before.
After the H/C install, the sound STILL didn't go away, so figuring I had a chewed up camshaft, pieces must have gotten in the bearings and chewed them up, so I had a tuner install an 8000 mile LS6 shortblock with all of my internals AND THE SOUND IS STILL THERE!
So here's my thinking (and please, it's not a rocker problem, bent pushrod or an exhaust leak, I've replaced the rockers and pushrods and checked the exhaust thoroughly). It's either one of the "newer" lifters is bad or, it was two separate things, first the bad camshaft, now the aggressive ramp of the XER grind + the dual valve springs + the larger valves is causing a harmonic sound. I'd be suprised that a new lifter is bad and that the lifters have been in and out of the car about 4 times and moved around, but the sound hasn't moved. However it's nagging me and I just might have to pull the heads and replace them.
Finally, my question, is there any special preparation needed for the Comp 850's? Should I soak them in oil before installing them?
Thanks...
After the H/C install, the sound STILL didn't go away, so figuring I had a chewed up camshaft, pieces must have gotten in the bearings and chewed them up, so I had a tuner install an 8000 mile LS6 shortblock with all of my internals AND THE SOUND IS STILL THERE!
So here's my thinking (and please, it's not a rocker problem, bent pushrod or an exhaust leak, I've replaced the rockers and pushrods and checked the exhaust thoroughly). It's either one of the "newer" lifters is bad or, it was two separate things, first the bad camshaft, now the aggressive ramp of the XER grind + the dual valve springs + the larger valves is causing a harmonic sound. I'd be suprised that a new lifter is bad and that the lifters have been in and out of the car about 4 times and moved around, but the sound hasn't moved. However it's nagging me and I just might have to pull the heads and replace them.
Finally, my question, is there any special preparation needed for the Comp 850's? Should I soak them in oil before installing them?
Thanks...
06-15-2005, 05:56 PM
#2
How much sewing machine noise are you getting? This is a normal sound after putting in an aggressive cam. If it's excessive, it might be you're not getting enough lifter preload and need longer pushrods.
If the sewing machine noise isn't that loud, you may want to just get used to it and appreciate it as a "race engine" sound. You also may need louder exhaust to mask it, LOL.
If the sewing machine noise isn't that loud, you may want to just get used to it and appreciate it as a "race engine" sound. You also may need louder exhaust to mask it, LOL.
06-16-2005, 05:02 AM
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Originally Posted by Cal
How much sewing machine noise are you getting? This is a normal sound after putting in an aggressive cam. If it's excessive, it might be you're not getting enough lifter preload and need longer pushrods.
If the sewing machine noise isn't that loud, you may want to just get used to it and appreciate it as a "race engine" sound. You also may need louder exhaust to mask it, LOL.
If the sewing machine noise isn't that loud, you may want to just get used to it and appreciate it as a "race engine" sound. You also may need louder exhaust to mask it, LOL.
