The other day while I was driving my car, it suddenly developed a small knock. To me, it don't sound like a spun bearing because it is not that loud of a knock. I thought it may be a broke valve spring, so I pulled the valve covers, nothing found there. I decided to drain the oil and see if there was any metal shavings or parts there, nothing there either.

Weird thing about it is that it takes forever to crank up now...it has to turn over like 7-8 times before it will crank up. It has great oil pressure when running though, around 55-60 psi at idle. What could possibly be my knock? Lifter? Broken cam lobe?

Just for a FYI...I have just recently installed PRC stage 2.5 5.3 liter heads and a MS3 cam in my car from Texas-Speed. I replaced the lifters at the time of the heads/cam install. Thanks for the help in advance.

Zach

 

check #7 spark plug, you may have gotten bitten in the *** by the imfamous #7... I hope not but check it.

 

sound like this
http://www.youtube.com/watch?v=CfNfdj-wtt8

there are alot of us with this sound...dont know for sure what it is... i ahve replaced lifters,o ring and rod bolts ect ect and mine still sounds this way... i just drove it 4 hours and it didnt have any issues so i am going to forget about it and just drive.

 

ill check the number 7 and see what comes up.

 

This is the first I have read of the infamous #7 and search results didn't turn up much. What seems to happen to #7?

 

off topic,but what rod bolts do you have.I pm you before and you said it was still stock.Did you replace them by any chance with ARP or Katech.I have a98 myself and was wondering if i should be concerned with rod bolts

 

Number 7 is notorious for being the lean cylinder, which leads to detonation, and broken ring lands on the piston. Hopefully thats not the case, but worth checking.

 

stock rod bolts.

 

sounds just like it, beats the **** out of me what it could be.

 

slightly streatched rod bolts perhaps?

 

Hmmm.... usually leads to spun bearings and/or low oil pressure though, no?

Certain its not an exhaust leak? Maybe a loose plug? Header gasket? Band clamp? It was hard to make anything out from that video...

 

welp it wasnt a bent pushrod, and its not number 7. Any more suggestions?

 

like i said man.... SEVERAL people have gone through their whole assembly and still have this noise.. i stilll have it only when warm now.. 7.35 pushrods helped out ALOT!

pretty sure its my LS7 lifters but this is my 2nd set so i am not willing to retry it again.

a few guys have replaced their lifters and o ring with success.. some say its the AC pully. some say piston slap. long tubes seem to amplify the sound on the drivers side. sounds a hellovalot like a rod knock but its not.

you can look this subject up countless # of times. i have replaced everything twice and its still there so like i said before get a louder stereo and exhaust and drive the hell out of it.

 

well the thing of it is, i have trouble cranking my car up, it has to roll over like 8 times and then it will backfire before it cranks. Then the knocking noise comes and goes.

 

that sounds like something else then? any codes?

almost sounds like a vaccum leak.

 

no codes. a vaccum leak dosent cause knocking. to me, a backfire indicates a bent valve, but it dont explain why the knocking gets quiet and then louder again.

 

dont know man...

i guess start with the basics... (which sounds like you have covered)
do a compression test on each cyl
did you pull your pushrods and check for a bent one?

check your plugs make sure one hasnt backed out

 

Some of these noises are very difficult to pin down. They sound like they are coming from under the driver's side but I am convinced that is just the way sound travels with the fbody LS1.

First, check your preload with a pushrod length checker and get it to .060 to .100, .080 desired. Many problems and noises are caused by marginal preload that strats out OK but then after a few miles you're at .040 and have a tap.

Second, do a top end clean, with either sea foam or GM top end cleaner.

Third, exhaust leaks can sound exactly like a tap - I had a loose 02 sensor that I would have sworn was a bad lifter. Check thoroughly for exhaust leaks.

 

yeah i have checked the pushrods, straight as an arrow. I have yet to do a compression test, thats next on the list. I think it may be a bent valve but im not real sure.

 

Finally figured it out and got it fixed. One of the top timing chain bolts sheared off and the other 2 backed out. Bout got fucked big time. Got her all up and runnin now though.