valve train "chirp" - Team Camaro Tech
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post #1 of 22 (permalink) Old Mar 14th, 02, 03:43 PM Thread Starter
 
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I just rebuilt a 350, 30 over, new SR Torqer cast iron heads, 2.02 intake valves, 1.250" single spring 100# seat, 67cc chamber, Comp Cams 238 hydraulic cam, 262 adv duration, .462 lift. 110 separation. I used stamped steel 1.5 rockers with slotted pivot balls.
After the engine warms up, I get a "chirp" which sounds like a belt chirp but it isn't. I can narrow it down to a couple of valves and by adjusting the nut 1/8 turn either way, the "chirp" goes away, but it soon returns. I have replaced the slotted balls with smooth balls and everything was ok for about 50 miles, then the "chirp" came back. It was
suggested that I go to roller rockers but they are expensive and my machinist is not sure if this will solve the problem. Any one ever have this "chirp" in their valve train. Any help is appreciated. Thanks
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post #2 of 22 (permalink) Old Mar 14th, 02, 10:04 PM
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how much oil is getting to the rocker pivots?

------------------
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post #3 of 22 (permalink) Old Mar 15th, 02, 04:36 PM Thread Starter
 
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The pushrods (stock length) are new and so is the oil pump (stock). At idle the oil guage reads about 40 psi when the engine is
cold. When the engine is hot it is about 10 psi. With the engine running (hot) at about 600 RPM the oil is coming
out of the pushrods but not with much force (it sort of oozes out of the pushrod), but the valley of the rocker where
the ball is, is filling with oil. Revving th engine does make the oil squirt all over the place. All pushrods are rotating when the engine is running.
The chirp is not there when the engine is cold, its only after it warms up. Another mechanic looked at the oil and said it looked normal.
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post #4 of 22 (permalink) Old Mar 15th, 02, 05:19 PM
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Ron,

I remember this question before on another board or other section of this board. I don't remember what the responses were though. I had this exact thing happen on a big block in a flatbottom that I bought used. It had stock long slot rockers and when warm would start chirping. It only did it on a couple of rockers. I changed the rockers but it didn't fix it. Turned out that the lifter bores were too big (worn)on those two lifters and they didn't pump the amount of oil required. I swapped to roller rockers as I didn't feel like pulling the engine apart to bush the lifter bores.

Oil pressure on my boat engine was fine. 10 psi hot is too low in my opinion and could very well be contributing to your problem. I know you only need 10 psi per 1000 rpm but there's almost definitely something wrong with the bearing clearances, worn bearings, etc. if it's that low.

Jody
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post #5 of 22 (permalink) Old Mar 16th, 02, 09:34 AM Thread Starter
 
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Jody,
Engine has all new bearings and new oil pump.
The crank was reground and I measured all the clearances (main bearings, rod bearings, crankshaftend play, rod side clearances) and they were all withn spec. The oil pump is supposed to be a "high pressure pump". The oil gauge is a Summit (inexpensive) which may possible be reading too low. Can you desribe the amount of oil that should be coming out of the pushrods at idle. Should the oil be quirting high enough to hit the nut on the rocker? You said that when you switched to roller rockers the chirp went away. Were you concerned about the amount of oil getting to those rollers which had the large lifter bore? I can put rollers on but is the amount of oil I'm pusing sufficient? Thanks for the help.
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post #6 of 22 (permalink) Old Mar 16th, 02, 11:23 AM
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Ron,

In my case, I had a set of roller rockers already so I basically put a "bandaid" on the problem. The correct fix in my case would have been to tear down the motor and have the lifter bores bored out for bushings to get the i.d. correct again.

I would double check the oil pressure with another mechanical gauge just to verify. With a stock rocker arm you need a decent supply of oil on the ball/pivot to prevent it from getting dry. The chirping is the first symptom, quickly followed by burning up the rocker ball and arm.

I would also look for any interference areas like the rocker stud to slot on the rocker, and the retainer to rocker arm (more common with roller rockers and large springs). Is the rocker or ball turning blue like it's getting hot?

Jody
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post #7 of 22 (permalink) Old Mar 16th, 02, 02:13 PM Thread Starter
 
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Jody,
I'm going to check the oil pressure next week with a gauge that gets connected in place of the oil filter. My problem is that I am not sure what a "decent supply of oil" is because I don't have anything to cmpare to. I replace the grooved balls with smooth balls. I pulled the rockers and balls and none of them are burnt. Are the balls supposed to rotate and show a wear mark 360 degrees because the ones I pulled only show a wear mark on both "sides". I also grabbed an oil can and squirted oil on the ball, pushrod, and rocker which was chirping. No help. I looked for interference and didn't find any. These are long slot rockers. Any other thoughts? Could lifters make this chirp? Plus, I recently noticed that there is a wear ring showing up on the stud. I looked at my old stock heads with 110,000 miles on them and there is no wear ring on the stud. The wear ring is at the same spot as the bottom of the rocker. Could this cause a chirp. Could the bottom of the rocker be hitting the stud. I thought the pivot ball would keep this from happening. If it is what is possibly causing this wear ring.
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post #8 of 22 (permalink) Old Mar 16th, 02, 03:09 PM
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Ron,

It's been a long time since I've run stock rockers. I always thought the grooved balls were preferred over the smooth as they distribute more oil to the rocker. I know you changed them to see if they made a change.

I'm not sure if the rockers themselves are supposed to rub on the studs at all. I would imagine they might rub slightly as they aren't totally locked in place with the floating ball pivots they use. When I've run an engine with the valve covers off there seems to be a fair amount of oil coming out onto the rockers. I know when you loosen them up, they really spray. How far down are you adjusting them?

Jody
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post #9 of 22 (permalink) Old Mar 16th, 02, 03:20 PM Thread Starter
 
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I statically adjusted the rockers as follows: turned the engine by hand till the exhaust valve was all the way down and then started to come up. I then tightened the intake rocker while spinning the pushrod until I felt resistance. Then I tightened another 1/2 turn. I then turned the engine by hand until the intake was at full lift and then almost all the way down. I then adjusted the exhaust valve the same as above.
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post #10 of 22 (permalink) Old Mar 16th, 02, 05:04 PM
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The EO/IC method is THE way to do it. I don't spin the pushrod though; I lift up and down on the rocker arm at the valve stem until it just reaches "0" clearance. I've seen guys who spin the pushrod still have them spinning as the plunger is being depressed.

I don't think this is your problem though. It sounds like the adjustment is fine. I wish you had another set of rocker arms to try.

Jody
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post #11 of 22 (permalink) Old Mar 16th, 02, 05:21 PM Thread Starter
 
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I'll have to try your way of adjusting the rockers tomorrow... and I also wish I had another set of rockers...though no one has any to lend me... I have my old ones but they are not long slot. Thanks for the help.
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post #12 of 22 (permalink) Old Mar 16th, 02, 06:59 PM
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If I may butt in here...

The rockers definately shouldn't be hitting the stud, and most likely this is where your noise is coming from. Are they hitting on the intake side of the stud (facing the intake manifold) or the exhaust side? If they are hitting the intake side, then it sounds like either the pushrods are adjust too tightly or the pushrods are too short. If they are hitting the exhaust side, then the pushrods would be too long. If this is allowed to go on long enough, the stud will break.
Also, since the engine is running, you might try adjusting the valves with the engine running. Just back off each rocker one at a time with the engine at idle, and when it starts clicking noticeably, slowly tighten the rocker down until the clicking just quits, and then go an additional 1/4 to 1/2 turn down from there.
Hope this helps.
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post #13 of 22 (permalink) Old Mar 17th, 02, 01:50 AM Thread Starter
 
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The wear mark on the stud is 360 degrees all around the circumference of the stud. Could this be the pivot ball doing this? I did try adjusting the rockers like you suggested with the motor hot and running. Didn't help.
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post #14 of 22 (permalink) Old Mar 17th, 02, 05:07 AM
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Do these heads have pushrod guideplates???
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post #15 of 22 (permalink) Old Mar 17th, 02, 12:03 PM Thread Starter
 
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No guideplates or stud girdles.
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