How does valve clearance tighten?

rebar · Jul 1, 2010

I have had the dealer check my valve clearance but I forget how many miles ago since it was in 87. I dont have over 25K on her though.

Im thinking about doing it again because I dont trust anyone, but wondering if its worth it.

How does the clearance get smaller?:ummm:

maleko89 · Jul 1, 2010

I believe it's due to the heat/cooling cycles.

I just know that exhaust tighten over time and the intakes rarely do.

rebar · Jul 1, 2010

maleko89 said:
I believe it's due to the heat/cooling cycles.

I just know that exhaust tighten over time and the intakes rarely do.

Thanks Mark. So what kind of conditions does a tight exhaust valve create?

Shouldn't wear the cam lobe excessively..:confused2: But might keep the exhaust valve open when hot?:ummm:

I was listening for cam/valve noise but couldn't hear anything over the norm.

What have you guys found?? Intakes good to go, but exhaust needs smaller shims?:confused2:

Has anyone had issues NOT adjusting clearance?

maleko89 · Jul 1, 2010

That's what I was thinking. When I checked mine at 53,000 miles all my exhaust valves were .006 inches which is pretty tight. The cam lobes looked perfect. I don't think I was losing compression due to a valve hanging open because compression values didn't change from what I recall.

Once I set them all to .0115 inches it seemed to run much better. It's almost like a sync of the carbs but instead you are syncing the engine.

one2dmax · Jul 1, 2010

The lobes don't typically wear down. The seats and valves wear and recess slowly and that lets the valve move closer to the camshaft thus decreasing the clearance.

Sean

satariel666 · Jul 2, 2010

one2dmax said:
The lobes don't typically wear down. The seats and valves wear and recess slowly and that lets the valve move closer to the camshaft thus decreasing the clearance.

Sean

And in the result it affects on the lifting time.