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Author Topic:   Differing Stances on Setting Valve Lash
Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted August 17, 2005 11:39 AM  
I'm confused (no surprise here).

Cam card says set the lash, HOT, at .026. Furthermore, the cam manufacturer's site says, if setting lash COLD, add 0.002 (for my configuration).

Yet, on this site and others, some well respected builders said to SUBTRACT 0.002.

Which way should I go?


Dirt Maniac

Total posts: 128
posted August 17, 2005 01:43 PM  
I have been told that the valve and rocker will take up that .002 when hot. But again, does the rocker stud get .002 taller. Maybe you could set one rocker on the - side and one on the + side and see which one is correct when engine is hot. I will be going through this in a couple of weeks with a new set of heads.

sc1 racing
Dirt Freak

Total posts: 419
posted August 17, 2005 02:19 PM  
i always break in loose with soft spings then, replace valve springs and set valves..002 either way will not hurt. but i would definatly set them loose untill you get it up to temp..

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted August 17, 2005 02:53 PM  
SC1, these are "old" springs that have already been run. I had to remove the valve train for some maintenance and now have to put things back together.


Dirt Forum Champ
Total posts: 2007
posted August 18, 2005 05:18 AM  
I have heard both ways as well. I would set them up to the lash on the card. then run the engine up to temp and see exactly what they change to, then readjust you cold numbers accordingly. They wont change more than a couple thousandsths either way so you should be safe, but if you set them loose and they loosen more you could have trouble. Its better to be a few thousandths tighter than looser.

But in my experience with steel block and heads the valves seem to tighten up so I set them .002 looser when cold.

Dirt Maniac

Total posts: 137
posted August 18, 2005 07:28 PM  
Too loose will hurt the cam by letting the lifter bounce.

you can tighten to .004 on tight lash cams and about .010 without hurting anything.

I set mine cold .002 looser than the hot recomendation, Ive checked mine with roller tip steel and full roller alum rockers and been good on both accounts

Dirt Full Roller

Total posts: 30
posted August 23, 2005 11:29 AM  
I add .002" to the intake and add .003" to exhaust and have never had a problem.

Dirt Roller

Total posts: 9
posted August 23, 2005 08:18 PM  
The most accurate method is to check/adjust lash while engine is at operating temp. That's how it will run on the race track, thats how you should lash it. Different componants in the engine will dictate how lash changes from cold to hot. Different pushrods, lifters, heads , rockers etc. can all change differently, so just because one guy lashes his engine cold one way does not mean it will do the same thing in your engine. Check and lash it hot to what the cam manufacturer says and you be right for your engine combo. FYI, tighter lash will increase low lift (.050") duration (make lobe duration longer) looser lash will make duration shorter.

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