does valve clearance increase or decrease after initial heat cycles?

[amamet]

ill be doing my heat cycles and a few trips up the hill from my house this week (as long as the weather cooperates) on my rebuilt lemans. just curious what to expect, will valves loosen up or tighten up?   im just curious on the mechanics of the break in period

[pete mcgee]

More than likely tighten up.
Depending on what you have changed, renewed, ie cam, cam followers etc.
Not to forget head and base gaskets compressing from new size to in service size.
Take it for a good run,  dont lug it, dont over rev it, see how things are going.
Let it cool down, retorque the head bolts/nuts, reset the tappets, look for leaks, check carb balance.
Change oil at 500 to 600 miles to whatever you are planning to run after the breakin period.
Hope that helps

[Rough Edge racing]

Generally speaking, on an OHV engine, if valve clearances are speced for a fully warmed engine, you increase the clearances when done cold like on a fresh rebuild.. As said above,clearances may tighten or not depending on what was done and the quality of the work..

[moto-uno]

 One way or the other you're going to find out soon enough . Were the valve seats ground or cut ? More curious than anything ?  Peter

[Testarossa]

Normally the head and base gaskets compress, so after cooldown the rocker arm pivots settle toward the engine case. This tightens valve clearance.

[amamet]

Hey Peter, good question. Mike rich did the heads but I’m not sure of what he did except “he rebuilt the heads”. At the time we were chatting a bunch and I don’t think I ever got any paperwork on what he did. I paid him, hung out for a while and left with my parts. I should have him write me up something so I could put it with the rest of the paperwork on the bike.

[Testarossa]

Normally the head and base gaskets compress, so after cooldown the rocker arm pivots settle toward the engine case. This tightens valve clearance.