I'm having problems believing 14.5 psi of vacuum is all I can get. I tuned my carb this weekend with the vacuum gauge. When I first hooked it up the reading was at about 10psi then I managed to adjust the idle mixture screws to get 14.5. I've heard of people getting a hell of a lot more than this. Whats up?? Is it the low compression I have?? Or the cam? The cam Isn't radical at all and so I was guessing the vacuum should have been around 17. Anyone??

 

Whats your timing set at?

Rockers that are a little tight can cause a lower than normal vacuum also amoungst other things.....but check the easy stuff first.

 

I have about the same setup on my car and get about 16.5 inches of vacume wiht a smaller cam. Take a look at my sig.

 

Two thing you need to do before monitoring vacuum with a carb'ed engine...set the timing properly and lower the idle stop screw to close down the throttle blades.

But you do have a healthy enough cam to keep vacuum lower than stock cam (about 18-20in/hg).

 

I always set the timing by ear now (I have a timing light but I never use it). I'll find out what the timing is. What should the idle speed be set at when tuning and reading for vacuum. The cam is healthy but not really that big so I figured that I should be hitting at least 16. the compression is 8.5:1.

 

TTT