340 Full throttle hesitation

t wouldn't hurt to do a compression test while you have all of the spark plugs out. Do you know how to do a compression test? You will need a compression gauge.

It's also good to do the compression test wet and dry. First do it dry and crank it until you get the maximum reading on the gauge (4-7 strokes usually). Then see if it will hold the pressure for about half a minute. Record the reading.

I like to do each cylinder 3-4 times at least to make sure that the results are repeatable and reasonable...

After you do the cylinder dry, then get an oil can and squirt 2-3 shots of oil in the cylinder and run the compression test again. Record the readings on paper.


After doing each cylinder wet and dry, then look at the numbers to see what they are telling you.

The cylinders should be within 20 psi of each other. What pressure are they at? Is there a higher reading wet than dry?

Are the wet readings higher than the dry, or pretty close. If the cylinder improves significantly wet, then there is a ring sealing problem. If there is a low cylinder and it doesn't get any better wet, then you should for a leaking valve...


If everything looks good, then you should then start to dial in your timing. 340's like to run near 17° initial timing and 34° - 36° total advance at 2500 - 3000 RPM. You should be able to get different tension springs from Mallory to change the curve of the timing in the distributor if you need to.

That should be a good start for you.

After you get the timing dialed in, then you move on to tuning the carb....