Well I decided to go with the vac gauge.

The question is which port should I pull the vac reading from?

I have the carter afb / edelbrock 600.

I can pull vac easy from either of the 2 small ports on the front of the carb

Or

I can pull vac from the large port used for power brakes on the rear of the carb.

Is there a difference?

Which one should I use?

Thanks

-Gun

 

Hooray! Glad you liked that idea

Use manifold vacuum. Ported vacuum has no real use other than for the vacuum advance. Pull manifold vacuum from anywhere under the throttle plates. One of the front ports on the carb will be manifold vacuum (the other is ported vacuum), or you could also screw a nipple directly into an intake runner and use that.

 

I dont like the idea of drilling the manifold....Ill find out which one on the carb is manifold vac!!

Thanks for the great idea and helping with this question

-Gun

 

wahheeee :-)
on any edelbrock when you look at them the left one is ported, the right one is manifold vacuum.
you are interested in manifold vacuum. as said looking at it the right port (driver side).
when you cruise you have a certain amount of vacuum, as soon as you get serious it'll drop. record the vacuum just when you start getting serious/light accelleration. us that for your PV then.
example you cruise at 8" but on light accelleration your vacuum drops to 6", then you want 7" springs (in edelbrock) or 7.5PV in holley. at least that's my opinion on it

 

Okay Kalli thanks for that info....

If I read that correctly the port on the driver's side is manifold vac....

Or the right side when viewed from the front of the carb...Or the left side when viewed from the back of the carb....

-Gun

 

Most aftermarket manifolds have a threaded port in one of the rear intake runners for a vacuum tee. Lacking a port on the carb or spacer, that's where you would hook up your brake booster and tranny line.

 

The Edelbrock RPM manifold has a 5/8" (iirc) port on the passengers side in the rear. As SF stated most aftermarket manifolds have this port. I plugged but ours for now but have been thinking of using it for a vac gauge as well. I really need to call Classic Instruments and request additional gauges so they match.

 

thats a great idea. i think i might get one too.. or ill just hang my shop monster gauge off the dash somewhere for tuning. i never thought about using kalli's method. sounds like im in for a few more horses.

 

Works good...pulls about 15 in/hg at 2500 rpm at cruise power......about 23" when you back off the gas rolling and 0" under full power....







-Gun

 

what's with your tach? how did you manage 7" vacuum (accellerating) at 400rpm ???
and someone correct me oin this one, but i believe you should never have higher A/F ration than the 14.5:1 unless you let off the gas pedal (vacuum gauge indicates accelleration). but it's probably not valid anyway since you're not driving (no load)

but ya, maybe Tad or someone else has a experience on picking the spring.
Is it light accelleration up hill, and whatever you read match that with powervalve or springs?

cool looking gauge though. i like it

kalli