Flathead timing key question

[Lkerley]

Im running my .030 f.h with a 94ss cam with a 3 degree advance key.will this get me buy?Or sould I run a 6 degree advance key to get the timing near 30degrees btdc..thank y ou.

 

[CarlsonMotorsports]

6* key would surely be closer to correct timing. There is no way to know for sure since the keys are not made exact and no two flywheels and crankshafts have the keyways cut exactly the same.
6* would sure be closer though.

FWIW, I generally don't use a key at all. Simply lap the flywheel to the taper on the crank with a fine valve lapping compound, clean, set the piston in the hole BTDC where you want it (30* in your instance), align the trailing edge of the magnet with the right hand edge of the pick up module, and torque to 50-60 foot pounds. Done deal and you know exactly where it is.


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Brian Carlson
Carlson Racing Engines
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[One Fast Kat]

And there you have your precision guided answer. It works very well also. You just need a degree wheel. Most engine builders use this method. If you want to get precise, timing light will help.

 

[CarlsonMotorsports]

Don't even need the degree wheel if you do it this way -- although you probably have it installed to roll the cam at the same time during the assembly.
Here's a chart that will help:

Flathead Ign. Timing:
2.437 stroke, 3.875 rod length

.148 25.0
.160 26.0
.172 27.0
.185 28.0
.198 29.0
.212 30.0
.225 31.0
.239 32.0
.254 33.0
.268 34.0
.284 35.0

If you want the timing set at 30*, then align your reference marks for timing when the piston is @ .212" BTDC.