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Author Topic:   Cam Break-in
Alltel
Dirt Maniac

Total posts: 180
posted April 24, 2005 06:27 PM  
Is it normal on a solid lift cam, after breaking in the cam, for the rockers to be a little loose? Mine aren't what I would call loose, but when I slide the feeler guage in, there is a little less resistance then what I set them at. I checked the cam lift on the push rods, and they were all dead on.

speedy46
Dirt Maniac

Total posts: 165
posted April 24, 2005 08:20 PM  
it depends what u set the valves to before u fired it, cause after u broke in the cam if the motor was still warm the vavles should have been tighter. so like if u run your vavles at .16 and when u put the motor together if u set them to .21 or so they might be alittle loose but if u set them right at .16 then broke it in and it is loose then there is something seriously wrong. did you take the inner valve springs out???(if you run them)

speedy46
Dirt Maniac

Total posts: 165
posted April 24, 2005 08:21 PM  
one thing i have noticed after a motor warms the valves tighten up about .03

sdhnc29
Dirt Forum Champ
Total posts: 934
posted April 24, 2005 09:41 PM  
If you set your valve lash cold, then warmed the engine up and checked your valve lash hot, you will have more valve lash. As the engine warms up, you gain lash, you do not lose lash if everything is correct. The only exception to this is if your valves are beating (wearing) into the valve seat's. Valve lash should always be set hot after your initial break-in, or after the first time you run your engine.

If you set your lash hot every time, you will notice variances in lash easier. On a flat tappet engine if you lose lash from one week to the next, then your valves are starting to pound into the valve seat's. If you are losing lash from one week to the next, then you are getting cam wear, roller rocker wear, or wear else ware in the valve train. On a roller cam engine, if you lose lash from week to week, your valves are pounding into the seat's (usually from valve float, or being on the edge of valve float). If you are gaining lash from one week to the next, then you have a roller lifter going away, a rocker going away, or something else is wrong in the valve train.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
www.hendrensracingengines.com
www.experienceodessa.com

smallrock98
Dirt Forum Racer

Total posts: 100
posted April 25, 2005 01:05 PM  
When I broke in my new solid tappet cam this year, the recommended lash setting was .022" hot. That is where I set the lash before I fired up the engine. After 30 minutes of breaking it in, I rechecked my lash with the engine hot and the lash ended up being tighter. They measured aroung .018" to .019". I then reset the lash to .022".

Alltel
Dirt Maniac

Total posts: 180
posted April 25, 2005 03:59 PM  
I set the lash cold for the first time(it's kinda hard to set them warm the very first time), and then checked it after it cooled back down. I was going to warm it up and reset the lash, but wanted to be sure something wasn't wrong first. It moved from 24 to about 25. It is a flat tappet cam, and everything is brand new except for the roller rockers. Could it just be the valves settling into the heads? Or how about just the cam lube wearing off? I checked the cam, and it is perfect on the lift.

sdhnc29
Dirt Forum Champ
Total posts: 934
posted April 26, 2005 04:32 PM  
No if your valves are seating into the valve seat's your lash would tighten up, not loosen. If you do not have a stud girdle or shaft mounted rocker's, then it's pretty difficult to measure .001" worth of lash. Be sure to set your lash again with the engine at operating temp. If you have a steel block steel head combo, you will gain about .002"-.003" lash when the engine is at operating temp. All aluminum engines gain around .012"-.016" lash from dead cold, to operating temp.

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
www.hendrensracingengines.com
www.experienceodessa.com

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