Tach and Vacuum question
 

I got this setup for $20 on Thursday in eastern AZ. Guy didn't know what he had. The 16yr old and I refurbished it yesterday and installed it. I think the tach needs to be calibrated, its not off by much.How do I calibrate it? But the vacuum didn't work. Did you guys use steel lines for the vacuum gauge?Attachment 670316

Re: Tach and Vacuum question
 

Not sure about the vacuum guage but on mine I used a barb and vacuum hose, I don't know what it came with originally. The tach can be zero'd using the screw on the back of it. That will bring you closer to actual.

Re: Tach and Vacuum question
 

How much vacuum are you running normally? Scary thing was i got this out of a c-50. I looked at the SPID in the glove and it showed it had bucket seats. It was a 68 truck. The seats were gone wonder how cheap it could have got them. lol

Re: Tach and Vacuum question
 

awesome deal!

Re: Tach and Vacuum question
 

I also run a barb and vac hose for mine. It's not real accurate but fun to watch. I think they are like the other gauges, close but no cigar. I'm interested in the adjustment for the tach. Mine reads about 400-600 to low. I do not remember the screw on the back. Does nayone have a picture of this? Later today I'll grab a flashlight and small mirror and see if I can find it.

Re: Tach and Vacuum question
 

Yeah, there is a screw hole on the back. You use a small screw Phillips. Tach does seam very accurate. Needless to say, i'm not going to trust that tach and run the motor at redline. lol

Re: Tach and Vacuum question
 

This truck didn't have a chevy motor in it. Alot of the farm truck C-50's came with tall block 427's. interesting thought wonder if you can stroke those motors?

Re: Tach and Vacuum question
 

Tall deck 427's can be made into big inch motors, I know they can be stroked out to about 550 CI (not sure maybe bigger).

Re: Tach and Vacuum question
 

I don't have a stock vac gauge, I have an aftermarket one but it has a rubber vacuum line and it works fine.

Re: Tach and Vacuum question
 

How many pounds of vacuum does it run?

Re: Tach and Vacuum question
 

a healthy SBC should pull 17-20" of vacuum at idle. If you have a cam, your idle vacuum will be lower. the bigger the cam, the lower the idle vacuum.

The vacuum gage is a handy tuning tool. You will be able to watch when you power valve and secondaries are coming in.

Re: Tach and Vacuum question
 

$20, man Ill give ya 50 for it right now...lol JK

nice find.

Re: Tach and Vacuum question
 

At idle it runs around 18-20 and drops as you get on it. There is a nice FAQ on GMC Pauls website about troubleshooting and tuning with a vacuum guage. I just like it cause it fills that hole in the dash and its fun to watch it move as I go through the gears!