496HO Rocker Assembly Question
12-06-2011, 12:26 AM
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496HO Rocker Assembly Question
Hoping some of you engine builders/rebuilders can help me out...
I blew a head gasket about 2 months ago. I'm in the process of putting everything back together now and I have a question about the rocker assemblies.
First off, my service manual does not mention anything about the rocker studs & guide plates as far as torque specs. I did find a spec in a forum regarding a 496 big block in an automobile, which says to torque the studs to 50 ft-lbs.
So, here is the procedure I did (this is after re-installing the heads and angle-torqueing them in the proper sequence described in the service manual):
1. Torque all rocker studs with guide plates to 50 ft-lbs.
2. Starting with cylinder #1, rotate the crank by hand to position piston #1 to TDC on the compression stroke.
3. Install pushrods & rocker assemblies, and torque rocker assemblies to 19 ft-lbs. Note - this is TDC on the compression stroke, so the valves are closed.
4. Repeat 2 & 3 for each cylinder.
Now, here is my question - at TDC on the compression stroke, for any given cylinder, should there be a little bit of play in both pushrods/rocker arms for that cylinder? I'm asking because there is a little bit of play (not much at all), but I had assumed there would be no play. It seems to me that this play would cause a lot of chattering once I crank it up....
Thanks,
Ed
I blew a head gasket about 2 months ago. I'm in the process of putting everything back together now and I have a question about the rocker assemblies.
First off, my service manual does not mention anything about the rocker studs & guide plates as far as torque specs. I did find a spec in a forum regarding a 496 big block in an automobile, which says to torque the studs to 50 ft-lbs.
So, here is the procedure I did (this is after re-installing the heads and angle-torqueing them in the proper sequence described in the service manual):
1. Torque all rocker studs with guide plates to 50 ft-lbs.
2. Starting with cylinder #1, rotate the crank by hand to position piston #1 to TDC on the compression stroke.
3. Install pushrods & rocker assemblies, and torque rocker assemblies to 19 ft-lbs. Note - this is TDC on the compression stroke, so the valves are closed.
4. Repeat 2 & 3 for each cylinder.
Now, here is my question - at TDC on the compression stroke, for any given cylinder, should there be a little bit of play in both pushrods/rocker arms for that cylinder? I'm asking because there is a little bit of play (not much at all), but I had assumed there would be no play. It seems to me that this play would cause a lot of chattering once I crank it up....
Thanks,
Ed
12-06-2011, 08:34 AM
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There is always some play on hyd lifters. They will pump up when the engine is started and the oil gets moving.. My bigger concern with your post is that you are doing a teardown of the head while asking questions like this. I'm not bashing you but, you should learn stuff like this on much cheaper to fix projects than this. You can forget a step or some debirs and really cost yourself some $$ real quick. Just my .02
12-06-2011, 11:23 PM
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Well, I appreciate the response. But, the fact that you said "I'm not trying to bash you" basically means you are bashing me....
I'm fully capable of removing and re-installing the cylinder heads. Yes, this is the first time I've done it on a big block, and yes this is the most expensive motor I've worked on. But, I have done it in the past on a small block chevy 350 and an old chevy 2.8L V6.
On both of those motors I've had to manually adjust the rockers after installation to give me a specific amount of lash using a feeler gauge. They were not self adjusting.
On the 496 big block, they are self adjusting. My understanding of this motor is that the lash is automatically adjusted assuming I torqued down the rockers properly with the corresponding cylinder at TDC on the compression stroke. I did that. But, the fact that they're self adjusting was just making me nervous... As I said, I've adjusted the rockers manually on other motors. I was just hoping there would be some indication in the manual of how much lash to expect with zero oil pressure.
Thanks again for the response. But, please don't assume I don't know what I'm doing.
Ed
I'm fully capable of removing and re-installing the cylinder heads. Yes, this is the first time I've done it on a big block, and yes this is the most expensive motor I've worked on. But, I have done it in the past on a small block chevy 350 and an old chevy 2.8L V6.
On both of those motors I've had to manually adjust the rockers after installation to give me a specific amount of lash using a feeler gauge. They were not self adjusting.
On the 496 big block, they are self adjusting. My understanding of this motor is that the lash is automatically adjusted assuming I torqued down the rockers properly with the corresponding cylinder at TDC on the compression stroke. I did that. But, the fact that they're self adjusting was just making me nervous... As I said, I've adjusted the rockers manually on other motors. I was just hoping there would be some indication in the manual of how much lash to expect with zero oil pressure.
Thanks again for the response. But, please don't assume I don't know what I'm doing.
Ed
12-06-2011, 11:56 PM
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Well, I appreciate the response. But, the fact that you said "I'm not trying to bash you" basically means you are bashing me....
I'm fully capable of removing and re-installing the cylinder heads. Yes, this is the first time I've done it on a big block, and yes this is the most expensive motor I've worked on. But, I have done it in the past on a small block chevy 350 and an old chevy 2.8L V6.
On both of those motors I've had to manually adjust the rockers after installation to give me a specific amount of lash using a feeler gauge. They were not self adjusting.
On the 496 big block, they are self adjusting. My understanding of this motor is that the lash is automatically adjusted assuming I torqued down the rockers properly with the corresponding cylinder at TDC on the compression stroke. I did that. But, the fact that they're self adjusting was just making me nervous... As I said, I've adjusted the rockers manually on other motors. I was just hoping there would be some indication in the manual of how much lash to expect with zero oil pressure.
Thanks again for the response. But, please don't assume I don't know what I'm doing.
Ed
I'm fully capable of removing and re-installing the cylinder heads. Yes, this is the first time I've done it on a big block, and yes this is the most expensive motor I've worked on. But, I have done it in the past on a small block chevy 350 and an old chevy 2.8L V6.
On both of those motors I've had to manually adjust the rockers after installation to give me a specific amount of lash using a feeler gauge. They were not self adjusting.
On the 496 big block, they are self adjusting. My understanding of this motor is that the lash is automatically adjusted assuming I torqued down the rockers properly with the corresponding cylinder at TDC on the compression stroke. I did that. But, the fact that they're self adjusting was just making me nervous... As I said, I've adjusted the rockers manually on other motors. I was just hoping there would be some indication in the manual of how much lash to expect with zero oil pressure.
Thanks again for the response. But, please don't assume I don't know what I'm doing.
Ed
12-07-2011, 12:29 AM
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fixx
ed,,yes it is normal to have a slight amount of play in the when assembling the rockers..just make sure you have plenty of lube on the ball sockets and the tips of the valves..when ready run the engine over from the starter solenoid with out the ignition on or the valve covers until you see oil come out of all the rockers,,check the rockers for lash,should e minimal and your good to go..
12-07-2011, 12:56 AM
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OutlawED:
The 496 -8.1L engine uses a zero lash non adjustable valve lifter preload and if all lifters and pushrods are properly in place well oiled and the retainer nuts are tightened down with the lifters on the heal (non lift side) of the camshaft lobes you should be good to go and should not expierence any clatter or noise once the lifters prime and all rockers are lubed. Tighten the retainer nuts to about 18-20 ft/lbs.
Best Regards,
Ray @ Raylar
The 496 -8.1L engine uses a zero lash non adjustable valve lifter preload and if all lifters and pushrods are properly in place well oiled and the retainer nuts are tightened down with the lifters on the heal (non lift side) of the camshaft lobes you should be good to go and should not expierence any clatter or noise once the lifters prime and all rockers are lubed. Tighten the retainer nuts to about 18-20 ft/lbs.
Best Regards,
Ray @ Raylar
Last edited by Raylar; 12-08-2011 at 03:11 PM.
