Just started my 69 Camaro and wanted to know what the required manifold vacuum should be with the following application.

396 BBC bored 30 over
Erson Cam 585 lift 294/302 dur
Holley 650

I know with an aftermarket cam the vacuum is much lower than stock. I am getting about 9". It that too low?

Thanks!

 

1) set the ignition timing to where you want it
2) adjust air for desired idle speed
3) adjust idle mixture for max RPM or max vacuum
4) repeat 1 to 3 several times till nothing changes
Whatever idle vacuum you get now, that is what you going to live with. Increasing idle speed will increase the idlevacuum. Actual vacuum numbers are no big deal as long as the vacuum operated stuff still works. You will still have to tune the carb for proper engine performance, such as jetting, valves, pump stroke, etc..

 

Thanks Pete! That is where I am now, trying to find the correct power valve and jets. The 9" vacuum with maybe +/- .5 of fluctuation seem lowto me.So that would mean a4.5 power valve? I will change this next, just wanted to make sure I am headed in the right direction. Here is what I have so far:

Idle about 900 RPM
Inginition Timing 16 degress before TDC
Manifold vacuum at 9"
Seems to be burning rich at idle.

Fernando

 

If it running rich at idle, try adjusting the idle mix for max RPM, this will give the best AF ratio and possibly increase the vacuum. You may have tolower the idle speed if it came upwhen youadjusting the idle mixture.

 

Pete,
Just made adjustments to idle mix screws for max RPM's vice trying to set it with the vacuum. That seems to work better for me. I also adjusted the ditributor for 12 degrees before TDCwhich also increased RPMs so Ithen turned down the idle screw.
This is what I have now;

Idle at 900 RPM's
Manifold vacuum 8.5
Much leaner at idle (probably not going to get much better)
I brought the RPM's to about 3000 and then stompped on it and it kind of poped and backfired. What do you think?

Thanks for your help! I have the holley tuning DVD but noting beats experince. I just want to get the car turned before I dump any more money into it.

 

May want to change the accelerator pump stroke one way or the other. You got a lot of cam, so you cant expect too much vacuum.

 

Pete,
I think I got the carb dialed in at idle so I took it out and got on it. It hesitates at the top of each gear but when I baby it it seems to respond o.k. The 3.5 power valve in is is fine and not blown. Set the accelerator pump according to the DVD I have. What would you do next?