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Valve clatter
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Author:  Reed [ Sun Mar 21, 2010 7:29 pm ]
Post subject:  Valve clatter
I recently installed a rebuilt head on the slant in my brother's van. I am running a cam reground to the Erson RV10 profile. I set the valve lash to .009 intake and .018 exhaust with the motor hot. While the engine is idling and especially when the engine is revved, there is a large amount of valve noise. It is so bad that it sounds like something is hitting the inside of the valve cover very hard. I have triple checked the lash but the nouse won't go away.The clacking goes away as soon as I slip the feeler gauge between the valve stem and the rocker arm, but then the motor starts to run rough.

At this point I am thinking the rockers have worn tips which give false clearance readings. This weekend i plan on replacing the rocker arms with a different set.

Any other ideas as to what might cause this noise? It gets kind of frightening while driving. :(
Author:  sandy in BC [ Sun Mar 21, 2010 7:38 pm ]
Post subject: 
.090 and .180 are too loose.......

My rockers hit the V/v cover on the Valaint til l I got the right pushrods......
Author:  4speed [ Sun Mar 21, 2010 8:01 pm ]
Post subject: 
First are you sure you are getting oil up top? Is this a rebuilt head from an auto parts store or did you rebuild the original head? Are you re-using the original rockers? How do the tips look? How does the end of the valve stems look? .009/.018 sound close. What year engine?
Author:  Reed [ Sun Mar 21, 2010 8:08 pm ]
Post subject: 
(1) Valve clearances are .009 intake and .018 exhaust
(2) Definitely getting oil up top. It flows quite well all over my hands while I am adjusting the valves, making the 3/8 box end wrench slippery and makes me occasionally lose my grip and get skinned knuckles on the rockers.
(3) The head was rebuilt by a very reputable machine shop I take all my machine work to. www.budsmachine.com Bud has been building motors since the early 60s (and has the vintage greaser pompador to prove it).
(4) valves were checked for uniform valve height and they all check out
(5) engine is a 76 short block running a 74 head. Definitely no hydro valve train in there somewhere.
Author:  emsvitil [ Sun Mar 21, 2010 8:19 pm ]
Post subject: 
Was a hydraulic cam profile used? (no take up ramps)
Author:  Reed [ Sun Mar 21, 2010 8:29 pm ]
Post subject: 
Nope, the Erson RV10 profile:

the machine shop said the profile was as follows:

Duration @ .050 lift = 212 intake and exhaust
valve lift = .435 intake and exhaust
valve lash is .012 intake and .012 exhaust

According to the Erson catalog, the RV10 cam has the following specs:

Duration = 254
Duration at .050 = 210
Gross lift = .435
Lobe center = 111
Advance = 4 degrees
Valve lash = .022


You probably have a much better guess than me as to what the take-up ramp profile is on the cam. The clattering is definitely coming from the rocker-to-valve contact point. I will try tightening up the exhaust lash to what the machine shop recommended and loosening the intake lash, and see if that gets me anywhere.
Author:  emsvitil [ Sun Mar 21, 2010 8:39 pm ]
Post subject: 
With .012 exhaust recommended, I'd say being at .018 is the clatter.

The .009 shouldn't matter.
Author:  jimmy the C [ Wed Mar 24, 2010 9:59 pm ]
Post subject: 
in my experence i think that the cold fuel mixture of the fuel makes the intake valve shrink a little causing the lash to grow and make sound once im off the throttle it seems to queit down sound like your problem
Author:  Aggressive Ted [ Fri Mar 26, 2010 4:02 pm ]
Post subject: 
Reed,

On my reground cam from Delta it seems quite tolerant. I can run .008 and .018 with minimal clatter, fairly quietly but it looses 2" of vacuum at idle in or out of gear. So I have been running .010 and .020 for more vacuum and low end torque. If you go up to .012 and .022 it gains even more vacuum and torque, but noisier.
Using Valvoline 10-30 it is pretty noisy. Running Mobil 1, 0-30W really makes a huge difference in noise. It is very quiet with Mobile 1 and the bigger lash.

Drive it a week and re-lash it to see if it will settle down. It is tempting to run the tighter lash but not worth it.
Author:  Reed [ Fri Mar 26, 2010 4:07 pm ]
Post subject: 
I am going to try a tighter exhaust lash and a looser intake lash tomorrow and see how it does. The motor is running 10W-30 from various manufacturers. The valves are quite noisy, but I can probably hear it more since this is in a van and I drive around with the engine cover off to listen for spark knock and lifter noise, so I am less than 3 feet from the motor as it drives (can't to that in an A-body!).

I will re-do the lash and get back to you. I also want to double check the rockers to see if the tips are worn. :?
Author:  Reed [ Sun Mar 28, 2010 2:01 pm ]
Post subject: 
Success! We swapped out the old rocker arms, even though they didn't look worn. The big difference was setting the valve lash to .012 intake and exhaust. MUCH quieter, smoother, and I picked up an inch or so of vacuum. Whew.
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