Problem with lash closing up
 

Today we were running an engine on the dyno . We broke in the engine , and afterwards re-lashed the valves hot . Ran a few more pulls and decided to check the lash again , and one of the cylinders had closed up .003" . The initial valve lash was done using the Honda valve lash method which has worked well for me for many years . Has anyone else had problems like this ? These are shaft rockers , with solid flat tappets . Thanks for any help and ideas .

Re: Problem with lash closing up
 

Russ,
All new parts? I'd be curious about the valves, and where they were made.

Re: Problem with lash closing up
 

Shaft rockers do have a torque setting when checking valve lash. Had a friend this summer setting the lash at the track. He says the lash was tightening up on the intakes. As I watched him, I noticed he was really over tightening the adjustors. I borrowed him my LSM torque wrench, preset at 24 ft. lbs and problem fixed. He was shocked because he has been setting them that way for years. Just a thought.

Re: Problem with lash closing up
 

What's the Honda method? Never heard of it. I always set the intake when the exhaust just starts to move and the exhaust as the intake is almost closed.

Re: Problem with lash closing up
 

Yup , That's the Honda method , Honda wrote a SAE paper on that way of lashing valves years ago , documenting the benefits .

Re: Problem with lash closing up
 

These shaft rockers are Harlan Sharp which have been on this engine for the last 4 years without any problems . They are tightened by hand , but not crammed down and the final adjustment is checked after the lash adjuster is tightened . We have a lot of experience using these rockers , and never had this problem . So that is why we are asking if other folks have had this problem . BTW , why would over torqueing the adjuster nut cause the lash to close up ?

Re: Problem with lash closing up
 

Not new parts , same Manley valves that were used last year . I was wondering if they could possibly stretch , but will need to take apart the heads to compare the valves and seats with other cylinders that did not have any lash problems .

Re: Problem with lash closing up
 

I would assume over tightening distorts the adjusters causing lash movement when heated up. Harlen Sharp website calls
for 20 ft lbs on their rockers.

Re: Problem with lash closing up
 

From what you state, you have a one cylinder problem. Has to be assumed that all 16 valves are adjusted using the same technique, so torquing of the adjuster nuts is probably not the problem. I would ask myself some questions, at this point. Are both intake and exhaust valve lash closing up, or just one of them? Does lash return to its original cold setting when the engine cools, or has lash now decreased by .003, both cold and hot? Is there ANYTHING different about the pieces used on that one cylinder (e.g. new/different rocker stand, new bolts securing the rocker stand to the head, repair to the cylinder head threads into which the rocker stand is screwed, previous cracked head repair in that immediate area, new/different valves on that cylinder, new/different lifter pair on that cylinder, valve seats replaced on that cylinder, and on and on). Good luck.

Re: Problem with lash closing up
 

No new parts were installed this year , we lashed the valves hot at .015 and cylinder 4 closed up to .012 after we ran a few pulls . That is what concerns us . Now the engine is dead cold and cylinder 4 has .015 lash on both intake and exhaust . All other cylinders are .018 . Thanks for your comments .