With cast iron heads and cast iron arms do you guys subtract .005 from the lash for initial setup for run breakin?
On aluminum heads do you guys subtract .010?
When do you guys go to tool steel adjusters for strength/relaibility?
Is it based on the lift or spring pressure or both?
When do you guys go to roller rockers over fixed tip rockerarms?
69hemibeep
09-02-2008, 07:28 PM
I set mine up to recommended specs and readjust after break in!
When doing it that way, (above post) the valve springs do not get full movement and don't stress the other related components fully.
I have seen many of solid cams wiped AFTER break in, that way.
69hemibeep
09-04-2008, 07:32 AM
When doing it that way, (above post) the valve springs do not get full movement and don't stress the other related components fully.
I have seen many of solid cams wiped AFTER break in, that way.
I am putting a Lunati in an AMC and just double checked with them. Thats about the best I can come up with!
Meep-Meep
09-26-2008, 11:09 PM
I don't quite understand why one would need to subtract .005" - .010" for break in other than possibly having the lash end up at spec after the initial break in wear and valve and seat pounding. I don't think I would worry about it and just set it to spec., then check/adjust right after break in to see what moved and how much.
I can see altering the lash slightly for aluminum heads because aluminum has a higher coefficient of thermal expansion than iron, which means your valve train is in a different place hot than when it's cold and the steel push rods can't catch up. I'm sure the correct answer can be had by comparing cold and hot lash on an iron vs. aluminum setup.
Regarding valve spring movement and stressing components. Does this imply that the extra .005" will make a difference? Spring rate is linear, so 500 lbs at .600" lift should be 250 lbs at .300" lift, and so on, and at .590" lift the force at the valve is 9 lbs less than it is at .600" lift - or 13 lbs at the lifter after figuring the 1.5:1 rocker ratio. It just doesn't seem that 9-13 lbs would make the difference in flattening a cam. Anyway, just my thoughts.
RT/10
09-28-2008, 07:54 PM
I don't think closing the lash up would be a good idea cause you want that lifter plenty loose enough to rotate properly when breaking in. If it don't rotate it'll go flat.
Also you want to maintain a boundary layer of oil. If you tighten the lash too tight you break throught that boundary layer causing accellerated wear.
Meep-Meep
10-01-2008, 04:41 PM
Yes, the key to keep your cam from going flat is to make sure the lifter spins. I've heard people say they flattened cams right in the driveway and they blamed it on the new oil. I'll bet in most cases there was contamination in the lifter bores or a poor fit preventing lifters from rotating.
my lifters do not rotate in their bores, the tie bars prevent it...
69hemibeep
10-01-2008, 07:36 PM
my lifters do not rotate in their bores, the tie bars prevent it...---Rollers you dog:grin:
RT/10
10-05-2008, 11:09 PM
my lifters do not rotate in their bores, the tie bars prevent it...
Didn't know it was a roller cam setup. You didn't say. I still wouldn't decrease the lash just to save an hours work adjusting them after break-in. For an hours work your chancing trashing a very expensive cam and lifter setup or doing other major damage if the valves hit the pistons.
Also with a roller cam the wear isn't as much. I doubt even a flat tappet cam wears .005 off while breaking in but I've never measure one.
