1963 Corvair Engine detonation

[joelsplace]

I have a 110 with severely worn out valve guides that makes a tick that sounds like a lifter.

[terribleted]

1/2-3/4 turn lifter preload may indeed be too much depending on the lifters installed. I have found that Sealed Power lifters for instance do not like much more than 3/8 turn in from quiet or they may hold the valve slightly open. TRW same thing I generally set all replacement lifter (except deep dish Elgin) at 3/8 turn in. The Elgin are happy at 1/2 turn in. I never set any farther in than that. If a valve is not fully seating it will make noise (usually makes the engine idle poorly as well).

[edherba]

I have been re-adjusting the lifters several times but I don't really have a feel for it. I loosen the rocker nut until it clatters and then some. Then I tighten it slowly until the clatter stops. Then I tighten 1/4 to 1/2 turn. When I turned to 1/2 turn, it made the engine run worse. I don't know if the valve is seating or what it is doing. How long do I wait for the lifters to pump up with oil before tightening them down? Clark's told me a minute which I still have yet to try. Maybe I am not giving the lifters enough time to pump up. My plan is redo the valve lash adjustment but this time to give more time for oil to fill the lifter while it is clattering. Then slowly tighten until no clatter, then 1/4 turn.

[edherba]

The blocked idle circuit is something I never checked. I rebuilt both carbs so nothing should be blocked, but anything is possible. If I were to screw in the idle mixture screw all the way, and see if there is a change. If no change then maybe it is blocked. If there is a change, then it should be fine. Right? I could do this for each carb and see. What do you think?

The other test could be to just cover each carb and see the effect.

[terribleted]

I have been re-adjusting the lifters several times but I don't really have a feel for it. I loosen the rocker nut until it clatters and then some. Then I tighten it slowly until the clatter stops. Then I tighten 1/4 to 1/2 turn. When I turned to 1/2 turn, it made the engine run worse. I don't know if the valve is seating or what it is doing. How long do I wait for the lifters to pump up with oil before tightening them down? Clark's told me a minute which I still have yet to try. Maybe I am not giving the lifters enough time to pump up. My plan is redo the valve lash adjustment but this time to give more time for oil to fill the lifter while it is clattering. Then slowly tighten until no clatter, then 1/4 turn.

When you turn a lifter down to 1/2 turn and the engine gets rough, unless the roughness stops within about 10 seconds, that is too tight and the roughness is being caused by the lifter not closing fully. These adjustments must be done very slowly as well. engine idling loosen a rocker nut until the valve just starts to clatter, wait about 20 second to see if it stops, if it does loosen again until it just clatters, again wait and see if it stops, repeat until there is a constant light clatter. Next slowly tighten the adjustment nut to desired preload. Old original lifters are happy with 1/2 to maybe even 3/4 of a turn in before they start to hold open. Many replacement lifters will start holding the valve open (causing rough idle from compression loss) at somewhere between 3/8 and 1/2 turn in. I have been adjusting them all at 3/8 of a turn in for years with no ill effects noted.

[terribleted]

The blocked idle circuit is something I never checked. I rebuilt both carbs so nothing should be blocked, but anything is possible. If I were to screw in the idle mixture screw all the way, and see if there is a change. If no change then maybe it is blocked. If there is a change, then it should be fine. Right? I could do this for each carb and see. What do you think?

The other test could be to just cover each carb and see the effect.

To check for a blocked idle circuit (or carbs way out of balance can do similar things. Are the carbs properly balanced?), with the engine idling block the top if a carb with the palm of your hand and note what happens. Normal is the engine slows some and idle gets rougher. If the engine shuts off or nearly shuts when you cover one carb and changes very little when you cover the other, the one with the little change has issues. Likely issues are idle speed screw nearly closed or close, debris in carb internal idle passages, or carb way way out of balance with the other side (idle speed on this carb way too low or throttle plate closed.

[edherba]

Thanks Terribleted. I think I was unscrewing the rocker nut too quickly until I got lots of clatter. Then I turned it down until clatter stopped, and then added the pre-load. I understand it better now. So I will try your method. I am curious to see how this goes.