LT 1 350 valve to piston clearance

[Dwight Southerland]

Originally Posted by Dan Fahey

Curious. Why more Clearance on the Intake vs Exhaust. ?

Should be more clearance on the exhaust than on the intake. Observe the relationship of the valve action in comparison to the rotation of the engine during the cycle. The piston is closest to the intake valve as the piston is approaching TDC and the valve is closing, so any contact will "push" the valve closed and/or the clearance will increase rapidly. For the exhaust valve action, the opposite is true. The piston is closest to the exhaust valve as the piston is approaching TDC and the valve is opening. The camshaft will push the valve into the piston and potential damage is greater.


There are other factors like what causes valve float, etc., but the above is generally true.

[Ed Wright]

Originally Posted by rawhide

Dan,

The exhaust valve runs much hotter than the intake and expands more.

Roland

The exhaust valve and the piston are moving toward each other at the closest point.
Intake Side, the piston and valve are moving the same direction. You can run them closer.

[Paul Precht]

The piston is chasing the exhaust as it's closing, if it's a little tardy it gets smacked. The intake is chasing the piston as it's heading down, if the valvetrain is tight you can run .010" on the intake and it'll never hit.

[Bob Mulry]

Come on guys you all know the answer.............

Exhaust valve is closing and being chased by the piston and depends on valve spring pressure to stay ahead or be bent.......

Intake valve is opening and chases the piston down the hole and is controlled by the cam profile.....

[randy wilson]

Originally Posted by Paul Precht

The piston is chasing the exhaust as it's closing, if it's a little tardy it gets smacked. The intake is chasing the piston as it's heading down, if the valvetrain is tight you can run .010" on the intake and it'll never hit.

I agree with this. I've ran em so tight that at zero lash on the intake, the motor would not turn over by hand. Set the valves, and turn 10,000 with no problems. The exhaust, high 70's is as close as I've ever dared. And you'd better have good springs.