2367 Thompson Way

P O Box 7409

Santa Maria, CA 93456

phone (805) 349-8243

fax (805) 922-0155

e-mail

Valve & Guide Set Up Tips

Valve Guide Set Up Tips:

1: Clean carbon from old guide O.D. before removal.

2: Guide to head press fit .0015"/.002" (head smaller than guide)

3: Heat head to approximately 200*-250* F.

4: Install the guide at room temperature (Head hot & Guide at room temperature)

5: Let head cool to room temperature before the final sizing of the bore.

6: Determine the desired clerance valve to guide. Recomended clearance Shovel Head with cast iron guides Intake .001"-.0015" Exaust .0015"-.002" (Ampco-45 add .001")

7: Select the correct plug gage by adding the valve stem diameter and clearence desired for the finish diameter.

8: Select a plug gage .0005" under the finish size for the the other end of the handle.

9: Finish hone the bore to size, check the size as you hone with the .0005" under size pin gage, finish hone to size with the finish plug gage pin.

10: Cut or grind the seats, lap the valves to seats and check valve seat concentricity befor assembling valve springs.

11: Use a good assembly lube, S'N'S works great.

12: Use valve stem seals. Factory OE seals will stay tight with guide top size +.005" to -.015" from published size.

13: After the head is assembled and still on the bench, check for any leakage valve to seat.

Valve Set Up Tips:

When Installing valves, there are some Critical measurements that Must be Checked.

1: Valve stem to guide clearance.

2: Valve seat height.

3: Valve seat angles and width.

4: Lap the valves after grinding or cutting the seats.

5: Check the concentricity, valve seat to guide bore.

6: Valve spring pack.

7: Guide to top retainer clearance.

8: Valve overlap.

9: Valve to piston clearance.

10: Valve to rocker arm. Loose rocker arm (tappet) adjustment wil resut in damaged rocker arms or pitted, chipped or broken Valves on the valve tip end (Rocker Arm End).

11: Rocker arm geometry. Incorrect rocker arm geometry will break the valve at the keeper grove.

Some Common Causes of Valve Failure:

A: Improper valve to piston clearance, (Collision Valve to Piston)

B: Weak valve springs, (Valve float resulting in collision valve to piston, Insufficient spring pressure allows the valve to bounce off the seat and reduces valve cooling.)

C: Improper rocker arm adjustment or bad lifters

D: Valve and guide not concentric to each other causing valv stem flex.(Generates side load on the stem, will break the valve).

E: Rocker arm geometry. Incorrect rocker arm geometry will break the valve at the keeper grove.

F: Excessive valve spring pressure, valve will break, usually at the keeper grove.

G: Heat, usually an air leak, wrong spark plugs, timing or carburetor jetting.