Vacuuam Timing ?

39 STD

39 STD

Senior Member
Back in the 50's- 60's & 70's, on overhead engines, I used a vacuuam gauge to set timing. Is this still a good way to dial in the timing on a Flathead.
The reason I ask is, I have a MSD dis, and no way to put a timing light on it. I have a soild 17-17½ vac at idle, on a stock engine. Are these close to the vac #'s everyone else gets.
 
The reading you get on the gauge depends on a;ltitude as well as timing. Best bet is to advance timing until you get the highest possible reading, then back off from that reading exactly 1 inch mercury on the gauge. Thats optimum setting. Brian
 
Brian is right on. I was seeing the same numbers you have while experiancing high engine temps. I am running an electronic Mallory dizzy. Reset the timing using a vacuum gauge. My highest reading was 19". I set the timing to pull 18". It now runs cooler and stronger.
 
Tuning by vacuum works well, and if everything else is in proper working order, you're golden. Unfortunately tuning by vacuum only makes the engine idle well and has nothing to do with how it goes down de road.
 
Ol' Ron said:
Tuning by vacuum works well, and if everything else is in proper working order, you're golden. Unfortunately tuning by vacuum only makes the engine idle well and has nothing to do with how it goes down de road.
Click to expand...

Amen Ron ! I learned to vacuum time at the gas station in the 60s and have had the chance to check the vacuum against actual spark timing many times over the years and in the majority of times it is very incorrect for the engine application.....:eek:

Sat afternoon , getting ready for a ride with a new engine or car , sure do it . Then plan on setting it correctly later with a timing light.......:)
 
It takes some work & careful placement of marks to put timing markings on a crankshaft pulley plus fabricating a good timing pointer but its well worth the effort to get initial advance set. It's a must if you have one of the aftermarket adjustable distributor set ups. With the right timing light, a person can check the advance with added rpm. A feller would feel a lot more confident about where it's at after completing the marking process and checking things out. If it's a fixed distributor, having a machine like Bubbas is the way to go.

A fellow I used to work for would adjust the distributor til it would just quit kicking back on start up. That gave a fair initial advance but did nothing to check the advance curve during rpm changes and power changes. The distributor machine is a wonderful thing.

Kerby
 
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