Tuning using vacuum gauge works!

Jack 34pu

Jack 34pu

Senior Member
I had a day to work on the 34pu so I decided to use everything - timing light, portable tach and a vacuum gauge. I ended up using the vacuum gauge for final adjustments - working for highest number. WOW - I really can tell a difference on the road. The final setting on dist for highest vac was exactly at center mark which surprized me. Also, the vac brake screw ia all the way out with no ping - I really never have been able to get the engine to ping under load. Try it - you'll like it!!
 
Did you go for highest vacuum reading and stay there? I found I had to back it off about from max reading to one inch of vacuum lower.
 
:Dyea after getting it to the highest vacuum reading you back it off 1 inch and leave it there.
if you have it at the highest reading now you will really like it onec you drop it down the 1 inch.
rich
 
I see you were talking carb adj. I've got that but I was talking initial timing on dist. Mine reached highest vac when on center mark.
 
Nope, I'm talking adjusting the distributor to get max vacuum. In my logic you would do that first to set your timing to optimum. Then, one would move to the carb(s) to adjust them to highest vacuum. To me, the markings on the crank pulley, if that is what you are referring to as the "center mark", don't mean anything. By setting your timing with vacuum, you are ignoring those marks. On my 8BA I have the 409 Chevy water pump set up and that makes it almost impossible to read the crank marks so I just advanced the distributor to get the maximum vacuum then retarded it for one inch decrease in vacuum. Hope that helps.
 
36tbird said:
Nope, I'm talking adjusting the distributor to get max vacuum. In my logic you would do that first to set your timing to optimum. Then, one would move to the carb(s) to adjust them to highest vacuum. To me, the markings on the crank pulley, if that is what you are referring to as the "center mark", don't mean anything. By setting your timing with vacuum, you are ignoring those marks. On my 8BA I have the 409 Chevy water pump set up and that makes it almost impossible to read the crank marks so I just advanced the distributor to get the maximum vacuum then retarded it for one inch decrease in vacuum. Hope that helps.
Click to expand...

That's the way I've always understood to do it. I've also set them (late distributor) by watching when the points open. As soon as the points move, lock it down.
 
Yes, that's what I did. I was referring to the tick marks on the side of the old style distributor. There are 3-4 marks on either side of center - 2* each I believe. I noticed that my idle is up a bit and will have to adj it back as soon as I can get back in the garage. I really appreciate all the discussion. It really helps.
 
You must log in or register to reply here.
Back
Top