Timing Mech vs Vac advance Good Read

[malibu71]

under part throttle EVERY engine will slightly increase it's vacuum, doesn't matter which port you use. under full throttle EVERY engine will lose it's vacuum, no matter which port. everyone can check it and see for themselves and run it however they want, doesn't matter to me. and no i did not put Fred up to this. i fight my own battles.

 

[78 Elky]

I have a question on this. When I first put my engine together, it ran, but it ran like crap. So I took it to a guy to have it tuned up. I ran a mallory unilite with vacuum advance, a 750 speed demon carb, and a roller cam with 232/240 @.050. When I picked it up, he had taken off the advance line, and said he set the by reving the engine to 3000 or around there and set it at 34 degrees. The initial was around 18 degrees. What I know is that it ran ten fold better. Throttel response every where improved and the car no longer bogged when I stabbed the gas. Maybe vacuum advance doesn't apply here, but I know that my engine runs a lot better without it.

 

[malibu71]

with that cam it is possible that your vacuum advance wasn't working properly because it didn't have enough vacuum. personally i don't run one on anything but a mild daily driver.

 

[Supe]

Sounds like your timing was way off to begin with, or your vaccum advance weights were wrong for your combination.

 

[Anonymous]

I must agree with BJ on that not enough vaccum for the dist to work on, I won't even start on that Mallory Unilite :roll:

 

[78 Elky]

Actually I was able to pull more vacuum than you would think. I got about 12 inches at idle. And just out of curiosity, is there a problem with unilites, or is it a preference issue?

 

[Supe]

Lots of horror stories about the pickup and the module burning out due to being very sensitive to voltage.

 

[Anonymous]

All I will say on this is go to the race track and look at the dist in all the cars and see what they are running. There is a reason why they run them and not the others.

 

[liquidh8]

Set your initail timing with the vacuum advance unhooked. I answer this question about timing and vacuum advance on a different topic on like page 3 or something. He just did it in more detail.

Well said

 

[Got Torque]

Thank's to Fred, I now know enough to ditch my "Harry High-school" carburator setups that I used until now.

Thank's again Fred for explaining the vacuum advance bit the understandble way!

I think this knowledge will come in handy when it's time to beef up the caddy engine i hope to be the proud owner of this weekend.