Motor knock update: need opinions please.

[turbosam6]

Today I got the car out and here is what I found; I can get it to make the knock at around 1500-2000 rpm in park when the car is fully heated up. My buddy who races Chevys put a screwdriver on the valve cover and said it was valvetrain. I listened also, it is loudest at the front of the drivers side valve cover. Put the screwdriver on the front of the block, much less noise. If I let the car cool for twenty minutes, it goes away, then returns when the car gets hot. By hot I mean heat soaked, because I don't let the car get over 180. I had to drive the car for 20 minutes or so in town to get it this warm. If you give it more gas, it goes away, like rod bearings. It is more of a loud tap than a knock. What could this be? I still haven't had the oil filter cut to look for metal, so I'm not ruling out bearings, but I do have a new 210 billet roller that was put in on the last rebuild. What could change when its warm vs. cold in the valvetrain? Lifter preload was 60 thousanths, I was told, and rocker shafts were tight last I checked. This tap is loud enough to peg my caspers knock guage. Ideas?

 

[Intercooler]

It could be anything and you will have to search for a while and may still not find it Look for metal and .060" is too much IMO.

 

[turbosam6]

I thought .060 was alot too, but this is what Comp recommended to my motor builder, and it has worked, except for this. I would think too much preload would make it not make noise. And I will find it, I have too. Can't just let it rattle.

 

[turbosam6]

I took the valve cover off the driver side, but didn't see anything. The shafts were tight, rockers didn't seem loose. Ideas?

 

[turbosam6]

anyone?

 

[Chuck Leeper]

KNOKED UP??

Sam, check the crank end play. Jack it up and remove the flywhl cover. Put the magnetic stand w/ the dial ind. onto the oil pan and check the endplay by prying the converter forward and back. Should be .004 - .007". A bunch more,[I've seen them at .250"] can cause the crank to knok back and forth in the block, causing the noise.
HTh,

PS: I FAITHFULLY check this EVERY time I change trannys, converter,engines, and just about every other oil change.

 

[turbosam6]

I don't have a dial indicator yet, so I guess I can't try that. The noise really seems to be up top. Wouldn't a crank endplay problem make noise down low, like bearings? Still waiting on oil filter analysis, should know tomorrow. Thanks for the help. Anybody have any other ideas on what could make that noise upper end wise? Bad lifter maybe?

 

[steve h]

I'd go with chuck's guess on this. You might also want to remove the fan belt too. The correct end play is barely enough to see it move. If it moves enough to measure with a ruler it's a big problem. A friend of mine had the same sound you are describing in his car. It turned out to be a bad thrust bearing. The noise in his car also sounded like it could be valve train. And if it is a rod bearing the noise won't go away. It'll get worse.

 

[TRENT THOMPSON]

I ran into this problem last week. ( although I laid it off the rev limiter ) turned out too be thrust bearing was hosed. have you monitered your oil pressure? this is what gave it away

 

[MSDGN]

If it is the thrust bearing why does the noise only occur when the engine is at operating temp...wouldn't it do it all the time?

 

[TRENT THOMPSON]

mine would do it at any operating temp under the specific load which I think was between 1750-2200 rpm. your oil press will be about the same when the motor is cold but drop like a rock when it starts too heat up this could possibly be the reason. I am a peon compared too the guys here such as chuck leeper. seems he has seen or done just about anything in these cars.

 

[steve h]

When my friend's car did it it would come and go. Check the end . It's too easy to check to wonder if?

 

[turbosam6]

The oil pressure never dropped, and this noise is so high up it really seems to be valvetrain. Talked to motor builder today, he said the oil filter is clean, no metal. Also he talked to comp cams (where my lifters and cam came from), and they said that at hot oil temps a lifter or two may not be pumping up. They recommended using heavier oil in warmer weather. If that doesn't fix it, we may have to replace the lifter(s). So going to try 20w50 penzoil, see if that helps. Thanks for the replies, I'll let you know if it works.

 

[WarpSpeed]

>>at hot oil temps a lifter or two may not be pumping up.



You got to be kidding, comp cams said that? That's a bandaid, 20-50w isn't gonna get it, especially when the oil is cold and like molasses.

 

[Turbo1dr]

Is a valve spring broke?

 

[hadav8]

What type lifters do you have, 853 comp cams or 885 comp cams? If you aren't sure, ask your engine builder. They are different. I'm not sure I've solved a similar problem yet because I haven't started the engine, but I've gone from 853's to 885's to try and eliminate valvetrain noise that seemed to be setting off my knock sensor.

The 885's are sometimes referred to as "0" lash lifters.

 

[Jimn8or]

How about something alot more simple, like the Cam Sensor? Put your screwdriver on the top of this while running...this is the source of my knock and could very easily be diagnosed as a rod bearing.
Jim

 

[Thunder]

Hey Sam, maybe it's just me, but I look at some of these problems as an oppotunity to expand my tool collection. I'd grab a dial indicator, and base... It can only help rule things out, or verify a problem. Now... or in the future.

Mike

 

[eiuskoalman]

let me know if you would like to borrow a dial indicator, i think it would be worth your time to check the end play like others have suggested. aaron