Proper valve lash?
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
Proper valve lash?
I have a '78 L-82 with stock cam and hydraulic lifters. I'm finishing up installing new intake and exhaust valve seals. Unreal how the old 'O'rings just crumbled when I removed the valve springs and checked the stems. Now, the question is, how do I make sure my valve lash is correct so I don't have to remove the damn valve covers and re-adjust once the job is done. I really hate to redo my work. 
I lashed them down to zero freeplay plus a half turn on initial reassembly one cylinder at a time when the seals were reinstalled. When I finished all the cylinders, ran my hand across the rockers to see if any were loose, and if they were tightened them to remove the freeplay. Any suggestions?
Mike
I lashed them down to zero freeplay plus a half turn on initial reassembly one cylinder at a time when the seals were reinstalled. When I finished all the cylinders, ran my hand across the rockers to see if any were loose, and if they were tightened them to remove the freeplay. Any suggestions?
Mike
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
I can't see that working. You just can't tighten them at any point you feel like.
I don't have the chart in front of me but for chevy's I have a chart. You bring the motor to TDC and adjust the following valves, rotate 180 do these, etc, etc.
Some just use the intake and exhaust closing but I don't know that method.
I don't have the chart in front of me but for chevy's I have a chart. You bring the motor to TDC and adjust the following valves, rotate 180 do these, etc, etc.
Some just use the intake and exhaust closing but I don't know that method.
Melting Slicks
Joined: Oct 2001
Posts: 3,025
Likes: 12
From: Pleasant Grove AL
Go to your service manual. It will show which valves can be adjusted at #6 TDC and which ones at #1 TDC. If you still have the manifold off, do #6 first, then #1 so you will be at #1TDC to install the distributor when you finish. I like to set the valves withthe intake off so I can really see the pushrods and lifters. Find zero lash by wiggling the pushrod. The turning method is unreliable. I like maybe a quarter turn past zero. A half turn at MOST. This method will require no readjustment if done correctly. The other method is with the engine running, but it is messy and unnecessary.
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
I didn't have th intake manifold off, nor the distributor out. I started with cylinder #1 at TDC and adjusted to remove all lash plus a half turn tighter. Turned crank 90 deg and did #8, turned crank 90 deg and did the next. Followed that procedure pretty much all around the firing order as I replaced the valve seals, intake and exhaust. Am I on the right track here?
Mike
Mike
Drifting
Joined: Sep 2004
Posts: 1,532
Likes: 4
From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark
do as you did. Then start the engine till choke dis-engages. Kill engine. Remove a valve cover. Start engine, -loosen the rocker till you hear a little "clacking" - basically till you introduce slack. Then tighten till no noise, then tighten half a turn. Gets a little messy under the hood but is worth it. Gets em just right. If you have an "extra" set of steel valve covers, you can cut out the center of them and install them instead of running without a valve cover. Sometimes you'll get a "pumper" of a hydraulic lifter and it have a good squirt and shoot out of the top anyway. Then kill engine, re-apply valve cover, and repeat for the other side. when done, check/fill engine oil and start cleaning under the hood. 
Oh yeah, make sure your parked under a good shadetree
Oh yeah, make sure your parked under a good shadetree
Drifting
Joined: Jan 2002
Posts: 1,663
Likes: 139
From: Vail AZ
Originally Posted by 78pacer
I didn't have th intake manifold off, nor the distributor out. I started with cylinder #1 at TDC and adjusted to remove all lash plus a half turn tighter. Turned crank 90 deg and did #8, turned crank 90 deg and did the next. Followed that procedure pretty much all around the firing order as I replaced the valve seals, intake and exhaust. Am I on the right track here?
Mike
Mike
Intermediate
Joined: Jun 2004
Posts: 48
Likes: 0
From: Orlando FL
Sounds good to me. BTW - this is the same procedure that the instructions tell you to use when you install a CompCams bump stick. So... I wouldn't think you would need to retighten them after you had done them once unless the valve wasn't closed the first time.
(of course the valve would have been physically closed - I was merely referring to the point in engine revolution when the valve is supposed to be closed)
(of course the valve would have been physically closed - I was merely referring to the point in engine revolution when the valve is supposed to be closed)
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Drifting
Joined: Jan 2002
Posts: 1,663
Likes: 139
From: Vail AZ
Originally Posted by ruby76
do as you did. Then start the engine till choke dis-engages. Kill engine. Remove a valve cover. Start engine, -loosen the rocker till you hear a little "clacking" - basically till you introduce slack. Then tighten till no noise, then tighten half a turn. Gets a little messy under the hood but is worth it. Gets em just right. If you have an "extra" set of steel valve covers, you can cut out the center of them and install them instead of running without a valve cover. Sometimes you'll get a "pumper" of a hydraulic lifter and it have a good squirt and shoot out of the top anyway. Then kill engine, re-apply valve cover, and repeat for the other side. when done, check/fill engine oil and start cleaning under the hood. Oh yeah, make sure your parked under a good shadetree
Oh yeah, make sure your parked under a good shadetree 
Race Director
Joined: Jun 2000
Posts: 10,040
Likes: 672
From: FL
How to Adjust Chevy Valve Lash tech tip by Lars. You can't go wrong with this info.
https://www.corvetteforum.com/techti...=116&TopicID=3
https://www.corvetteforum.com/techti...=116&TopicID=3
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
Thanks all for the help!
I'm gonna adjust as mentioned in the last thread and keep my fingers crossed. I've never attempted this job before on hydraulics, so its a new learning experience. I'm pretty tickled to be able to save mucho bucks over taking it in to a shop and never gaining the knowledge. This forum rocks!
Thanks again,
Mike
I'm gonna adjust as mentioned in the last thread and keep my fingers crossed. I've never attempted this job before on hydraulics, so its a new learning experience. I'm pretty tickled to be able to save mucho bucks over taking it in to a shop and never gaining the knowledge. This forum rocks!
Thanks again,
Mike
Drifting
Joined: Sep 2004
Posts: 1,532
Likes: 4
From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark
This is actually kind of a "fun" procedure, whether you go the engine running procedure as I described, or the engine off procedure with rotating crank 90* etc. Probably will take you longer than 30 minutes that it takes Lars, but still won't eat up your whole day. good luck and have fun!
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by 78pacer
Thanks all for the help!
I'm gonna adjust as mentioned in the last thread and keep my fingers crossed. I've never attempted this job before on hydraulics, so its a new learning experience. I'm pretty tickled to be able to save mucho bucks over taking it in to a shop and never gaining the knowledge. This forum rocks!
Thanks again,
Mike
I'm gonna adjust as mentioned in the last thread and keep my fingers crossed. I've never attempted this job before on hydraulics, so its a new learning experience. I'm pretty tickled to be able to save mucho bucks over taking it in to a shop and never gaining the knowledge. This forum rocks!
Thanks again,
Mike
Lars article is great...this is how i set up my timing marks....i layed under the car and used blue painters tape to wrap around the harmonic balancer...and i marked where the tape over lapped....i then took it off and went to my work bench and measured it into 4 equal segments and marked them 1,2,3,4 reninstalled it so the number 1 line was lined up with the timing mark....this allowed me to rotate the engine 90* by hand using a ratchet on the bolt on the harmonic balancer and because of the numbers i knew that i did not accidentally skip a timing mark....only thing you need to do is to follow the valve cycle as you are coming up to #1 to make sure you hit TDC on the compression stroke. good luck.
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by 78pacer
Thanks all for the help!
I'm gonna adjust as mentioned in the last thread and keep my fingers crossed. I've never attempted this job before on hydraulics, so its a new learning experience. I'm pretty tickled to be able to save mucho bucks over taking it in to a shop and never gaining the knowledge. This forum rocks!
Thanks again,
Mike
I'm gonna adjust as mentioned in the last thread and keep my fingers crossed. I've never attempted this job before on hydraulics, so its a new learning experience. I'm pretty tickled to be able to save mucho bucks over taking it in to a shop and never gaining the knowledge. This forum rocks!
Thanks again,
Mike
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
I installed positive seals on the intakes and umbrella type on the exhausts. Compressed air was used on all but #8 cylinder, where I had to use the old 'rope trick' to keep the valves up. (Damn header tube was interfering with the air hose) Both methods worked quite well, and I was surprised the rope was so easy and simple.
Good luck and above all, take your time.
Mike
Good luck and above all, take your time.
Mike
Drifting
Joined: Jan 2002
Posts: 1,663
Likes: 139
From: Vail AZ
Originally Posted by ruby76
What is/was the "rope-trick"? We'll be doing this on Portdawgs 79 in the coming weeks.
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,327
Likes: 5
From: 2010 C6 Grand Sport Convertible
Originally Posted by ruby76
What is/was the "rope-trick"? We'll be doing this on Portdawgs 79 in the coming weeks.
Mike