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Noise at bout 2000-2500 RPM

bbptech

bbptech

New member
Well i finished the the build again and finally got it on the road. No noises from the get go until i got to town which is 7 miles from where i live. Now mind u i was not WOT. Just cruising at 65 mph breaking the motor in. Got to town, stopped at a stop light, went and could here a noise. So i stopped into a parking lot as fast as i could. There is no noise at idle, just when u give it throttle. It sounded like a coupler to me so i took it home to check it out. Sounded like thats what it was on the stethascope. Pulled the snout off and the coupler is fine. Restarted it and gave her some gas and noise is still there. I put the stethascope on the top of the valve cover and LIM and all sounds like regular engine noise.

Anybody got any ideas?

The lifters are brand new LS7's with stock pushrods. All preload was set properly. Preload settings were between 3/4 and 1.5 turns.
 


dont even know why i didnt think of that. im also going to check the fly wheel as well.

Also when i pulled off to check that noise, my oil pressure gauge was reading a little above 25 psi but before i left(the car was at operating temp.) at idle i had a little over 50 psi. Oil was still full. Why so low of oil pressure?
 
I checked both the flexplate and taking the supercharger belt off to see if thats whats giving me the noise. None of those were it.
 
can u actually do that? what would that rule out? Not saying your wrong or it wont work, just dont understand.
 


ya true. the water pump isnt a problem to me cause i got an electric water pump.

what would i be trying to rule out by taking the acc. belt off? pulley noises?
 
Yeah alternator/ac compress/ idlers/tension-er. Pretty much everything except engine internal. Could be the alternator going bad.
 
well i just tried that. It isnt it either. Its gotta be something valve train wise. I know for a fact its not bottom end.
 


i dont think i have a leak at the header but i think i do at the DP. i dont think it would make the sort of noise im hearing.
 
ok so heres the run down. I got my P1374 code figured out. it was the ignition control module that needed replaced.

But for the search for this noise. I went ahead and drained oil, and coolant and dropped the oil pan to see if i might have been getting a spun bearing. got in there, checked for rod play and they were fine. No coolant in the oil. So its gotta be either valve train noise or an exhaust leak right at the back header like mentioned above. I have the valve covers off right now and there is no play in the rockers. im running CNC ported heads, stock pushrods, LS7 lifters, stock head gaskets and XPZ cam. all preload on lifters were set between 3/4 - 1.5 turns from zero lash.

Im gonna go get new exhaust manifold gaskets and copper spray both sides so i could possibly rule out an exhaust leak.

we also unbolted the torque converter from the flexplate so only the motor would be spinning to tell if the noise was from the tranny. Noise was still there.

heres things ive tried:
1. unbolt TC from flexplate to rule out tranny
2. check for coolant in oil
3. check for play in rod bearings
4. check supercharger coupler
5. check downpipe and resealed with new gasket and copper rtv
6. check rockers for play.
7. took supercharger belt off to see if noise went away
8. took alt. belt off to see if it might have been pullys

what other things might cause this?

cam bearings were new
rod bearings were new
main bearings were new
piston rings were new
everything in heads(springs, valves, retainers, valve seals)
cam is new
double roller is new
has machined pump cover
has machined crank gear
 


Check the condition of the harmonic dampener. People have wrote off engines because they thought it was a rod knock. Rare, but they can go bad.
 
checked the harmonic balancer, its fine. this is what i wrote on my thread at clubgp.

"Ok so if uve read my posts about the noise i was hearing at 2000 - 2500 RPMs this noise has to do with either valve train noise or a header leak. We have the valve covers off. had stock pushrods in because i didnt have a full set of 7.05s at the time. preload was set properly between 3/4 to 1.5 turn for the LS7 lifters. noise started after i got into town which is 7 miles away from my house. on the back bank there are three rockers that just barely move back and forth. and i mean barely. Do u think that could be the problem or no? the other three dont. they just move side to side. They are stock rockers. please help ASAP!

thanks,
Colin
 
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