Jeepster Ported Vacuum

Guys,
This weekend I had a few projects planned for my '67 Jeepster (see pictures previous thread). The projects included installing a remanufactured Rochester Carburetor (manual choke) and switching over to an HEI ignition.

The carburetor swap went as planned, I also installed a new Choke cable. The HEI ignition swap was a real head ache though. Most of it was self imposed though (make sure you are on top dead center of compression stroke not exhaust stroke)!!!!!!!!

Anyway, last night after getting the ignition sorted out the Jeepster was running real fine. I went to check the total advance on the distributor and noticed I was only getting approximately 25 degrees total advance at 3000 rpm. I disconnected the vacuum advance and noticed it didn't change. I hooked a vacuum gauge to the ported vacuum nozzle on the carburetor and found I could only get about 2"" of vacuum at 3000 rpm. If you popped the carburetor (rapid acceleration) it might go up to 10" but then drop right back down to 2".

Does anyone know what the characteristics of this vacuum should be? I've never really checked it before. Also, any ideas on what to check or how to fix this problem. The engine runs fine, no real hesitation off idle. The initial advance is set at 8 degrees. I have really checked for vacuum leaks, I'll do that tonight. I noticed when I was installing the carburetor that there are waht appears to be two plugs in the open chamber of the intake manifold where the carburetor bolts up, what are these for?

The engine was orginally set up with an automatic choke, but this had been eliminated before I bought the vehicle.

Any ideas on what to check would be definately appreciated.

Thanks,
Terry

 

What does the correct base gasket look like? The one I used has two holes in it for the bolts to go through and the other side has an open area that corresponds with the open chamber of the intake manifold. Where does the ported nozzle receive it's vacuum from?

 

The plugs you speak of under the carb are for carb heat. Most of them are pluged up with carbon deposits. If they are still open the air circulates under the carb to heat it. The bad thing about that is the particale in the air tend to eat away at the front bolts resulting in the bolts breaking off when you go to remove them. Unless you live in very very extreme cold you do not need to have these holes open. I filled mine and used a solid cab gasket from advance auto for a 67 Chevy C-10 truck part number 9394. The original Jeep carb part number with the open part allowing the air to circulate is 9288. A lot of times the base of rebuilt carbs do not seal on the thin strip on gasket in the 9288 gasket causing air to be pulled into the main intake giving you a vaccum leak that is almost impossible to find. Try using the 9288 gasket and plug off the holes. My 225 V6 runs much better with it.

I am attaching pics of the 2 gaskets to show the difference. The first one is the 9288 that the book calls for and you can see the narrow bit of material that can leak. The second pic is the 9394 gasket that seals off the chamber keeping your bolts from being eaten up and eliminating the vaccum leak problem.

Not sure if it will help you but it helped me find my problem.

 

You can use a piece of mechanics wire and poke gently in the port to loosen any carbon and a can of carb cleaner with the long nozzle should clean it up real good.

 

Ahhhh, Remanufactured Carburetor ????!!!!! I thought that maybe the port might be plugged also so I blew a little air through the port and got bubbles out between the carburetor base and body so I think this is probably where my vacuum problem is.

In addtion to a previous reply the full faced gasket that was mentioned before is Victor # G7327

New carb. should be here Saturday so I'll give it a try.

 

You did say reman carb, didn't you. I must have been sleeping when I read that so I guess you wouldn't have any carbon in there . But it sounds like you may have found the problem. Can't always trust remans these days.