Do you pull more vacuum from the intake than from the carb? Reason I'm asking is, Friday I installed the 650 Holley and because of the bowl height I had to plug the 'T' that my modulator and headlights were hooked to. The lights I hooked to the front of the carb on the lower right. The modulator is now hooked to the rear bottom center of the carb. Both are places that I thought would have plenty of vacuum. But now my driver light stays up when turned off and my RPM's have to get a little over 40K before the tranny will shift into second, then it goes into 3rd really quick.

I'm going to my shop now and was hoping someone would have an idea before I left there so if I had to buy something I could get it while I'm in town. I'll check one of my comps at the shop.

I'm going to pick up a hand held vacuum pump I've read about on the forum but I need someone to let me know what they're called. (watch it be called 'hand held vacuum pump' :-)) I figure with that I can at least trace down the light problem. Thanks.

 

You need an adequate supply of vacuum for the brakes and vacuum modulator on the tranny. That small connection on the front of the carb is not adequate...it could also be a 'ported' vacuum fitting, rather than direct manifold level. If there is a large port at the very base of the carb (usually middle front or middle rear), that would be a better alternative. Better yet, would be a gang fitting on top of the manifold itself.

 

 

The vacuum supply for the brakes should be a larger volume supply source,the kind you would be proud to take out on a date.

 

I think I'm running into more than I'd expected with the change over. On the way home the head light finally went down, but when I got to a point where I had to slow down to make a right hand turn the car died. I tried to restart and it wouldn't so I went over to the side and popped the hood thinking maybe a float had stuck. A lot of gas was coming out of the top of the carb with it not running, and I couldn't get the breather off cause it's one of those that uses an allen screw instead of a wing nut, (note to self, get rid of that crap). After about 10 minutes and 5 different people stopping to help (that felt good in today's world) I figured the float had let go, maybe, and I tried it. Fired right up. Only thing is, it wont stay running unless I kept my foot in the gas. Not revving, but just enough to keep it going.
So I get it home no more problems, too hot to work on, so I turned the AC on in the garage, gonna lay down for a while (damned high blood pressure & headaches) and I'll wrestle it later.
Thanks for the advice, I'll check all that in a little while.

One other side note that's pretty cool. When I got home I had 4 people call and said they went to where I'd broke down because someone else had seen me on their way to somewhere and called them to go check on me. I thought those days were over. Glad I'm wrong.

 

I have a Holley 650 double pumper on my '73. My modulator is connected to the front port of the carb. Tranny shifts fine. My PCV is connected to the rear port. The headlights and brake booster are connected directly to manifold vacuum.

Yep - "hand held vacuum pump". You can get one at Sears - either the Mityvac brand or the Craftsman. I would recommend the metal bodied pump. It's more expensive but I had the plastic model first and the release trigger didn't last. The metal one has a better gauge as well.

DC

 

Why do you want a vacuum pump? Don't you just want a vacuum gauge to check vacuum level?

 

^^^^^ I was thinking a pump so I could start at the source (headlight) and trace back to see if any of the lines are cracked, broken or whatever. If it is a leak, finding it is the big thing now. But like I said earlier, I'm starting to think it all stems back to having to go from the intake vacuum to the carb vacuum when I switched carbs.