100-4 Timing and Vacuum

[56HealeyDan]

I am timing my 100-4 after servicing my distributor and adding a Pertronix unit. I've got several questions that have come up while doing the final tuning.
What would cause some air/fuel mixture to come out (mist visible) of the carb when I rev the motor?
What is the initial timing and max timing at higher RPM's for this engine?
And, should a healthy-lunged person be able to move the vacuum plunger with lung power alone?

Thanks in Advance
Dan Whitney
Olathe, KS
'56 100-4

 

[glemon]

I don't think I have ever been able to create enough vacuum to advance the spark. Timing should be in the factory manual. If you don't have one I can dig it out and look it up.

 

[Michael Oritt]

Dan--

I can't answer your first and last questions but as concerns ignition advance, assuming your vacuum and centrifugal advances are working correctly I suggest you follow normal procedures in setting timing and simply concern yourself with total advance. I shoot for 34 or so degrees at 3000 rpm's and clamp down your distributor, then take your car out for a run to check WT at speed and assuming no overheating carry on.

 

[56HealeyDan]

A severely belated Thank You to both of you. I have owned my car for a long time and I have never been able to use a timing light to set the timing because I can't get the light in the tight quarters. The car is running great, no over heating, etc. and it hasn't bothered me. But simply because my inquiring mind wants to know, how do you use a timing light on the 100-4?
Thank you and my appreciation will be shown much sooner in the future!

 

[603000]

The mist exiting the carburetor sometimes referred to as "spit back" occurs when the mixture is too lean. You can test for the proper mixture setting with the engine running. Lift up on the small vertical pin at the base near the front of each carb below the suction chamber. This pin raises the needle a small amount. With the pin pushed, in the RPM of the engine should remain even. If the RPM drops, the mixture is too lean. If the RPM raises and continues to climb, the mixture is too rich. Adjust mixture by raising or lowering the jet bushing.
Danny

 

[56HealeyDan]

Thank you Danny for your reply. I should have closed the loop on that 2022 post regarding mist coming out of the carbs. After making additional adjustments and ruling out some issues, I checked the compression and it was very low on 3 and 4. Took the head off and found the gasket failure between 3 and 4. My compression ratio is higher than stock.
Fast forward, solid copper gasket, a valve job to correct some shoddy Paeco work to make the ratios the same on all cylinders and it runs better than ever!