I'm making an insulation spacer for the carb (BBS) and figure I'd add a port in it for the vacuum gauge I'm adding.......

The vacuum advance port is ported so that won't work; I don't think the PCV hose would be accurate, and I think the #6 intake plug would be unsteady, so

Where's the best location for the port for a steady/consistent reading no matter the throttle position?

1. below the throttle blade on the side that the throttle blade goes up
2. below the throttle blade on the side that the throttle blade goes down
3. below the throttle blade shaft.
4. somewhere else.


I'm thinking 1 or 3

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Why not just put a pipe plug nipple where the power brake booster line goes on PB cars.

That's the #6 intake runner........... I think the gauge would fluctuate because it would mostly see the signal from the #6 cylinder

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

not sure why the pcv nipple wouldn't be accurate as it pulls manifold vacuum all the time. vacuum gauge readings will never be smooov. if size is the issue; is there another, smaller nipple at the carb base that pulls manifold vacuum?

-james

_________________

While I was playing with mine, I don't remember there being a measurable difference in vacuum between the #6 runner and the intake side of the EGR port (where I run my PCV valve to). It would seem that so long as you are below the throttle blades, the vacuum signal should be nearly equal no matter where you are.

A 64 BBS doesn't have another nipple. There's a nipple for the vacuum choke pull-off, but I think that's venturi vacuum, not manifold vacuum.

Another problem with the PCV is the big hose/tiny hose issue.

Also, I'm not sure, but because there's air flow thru the PCV hose, it may have an effect on the reading

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

You'd think so........., but I'm not sure. I'm just thinking that for when I get around to playing with the metering rods I'd want the vacuum gauge to be similiar to what the carb sees, and the closer to the carb the better, and without some possible weird airflow effects of the throttle blade.

I'm just not sure where that would be

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The #6 runner is fine. If you don't like that, then put a "T" fitting in the choke pulloff hose and tap in there.

in my experience: never share a small port like choke pulloff for a vacuumeter. Mine is connected on a small T right where the brake booster is connected (steady reading) but very close to the manifold. in fact I used one of these brake booster things that has extra small diameter hose connectors for other vacuum related applications on modern cars (hideaway lights, heather control, you name it)

if you ain't using that choke pulloff, that port would work just fine. (Say if you converted it to manual choke as I did)

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Ok, what NPT size is the plug on the #6 intake runner?

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

My vote: Tee into the choke pulloff line. It is not ported or venturi vacuum, it is manifold vacuum. PCV line works just as well, but it's easier to tee into lines of roughly equal diameter.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I've teed into this line and I get non consistent readings. My guess is that's too small to share. I know is mani vacuum but if you use it to feed both the choke pulloff and the vacuumeter somehow the vac readings hurt.

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

I don't know why you would get non-consistent readings unless either the passage in the carburetor was partially blocked or your choke pulloff diaphragm was ruptured. Vacuum should be fairly constant and consistent no matter where you tap into it.

Well, as the pull-off moves it will probably give bogus readings because you are changing the volume of the system. At that particular point, it that would be a significant change in volume. Once it's warmed up, however, there should be any changes.

Actually, the choke vacuum pulloff only moves once-- on startup when the plunger is sucked back by the vacuum. After that the choke rod and pulloff spring move the choke the rest of the way open. The vacuum only pulls the choke butterfly open far enough for the car to run without stalling out, but that is the limit of its travel.