[ted200008]

i have a 66 bonneville with a 389 n it has a carter afb carb. i have an open vaccuum hole on the front and i dont know where it goes. can anyone help me out? it is a threaded hole

[cobalt327]

Originally Posted by ted200008

i have a 66 bonneville with a 389 n it has a carter afb carb. i have an open vaccuum hole on the front and i dont know where it goes. can anyone help me out? it is a threaded hole

Originally, there'd have been a fitting screwed into that hole w/a line running to what looks to be the distributor vacuum advance as well as some other vacuum accessory(ies).

[ted200008]

i cant see it very well. but it looks like yours doesnt have anything in it either?

[cobalt327]

If you're talking about a vacuum hole way down low at the throttle plate, that's where the vacuum fitting will be. Here's another photo showing it, still not too clear. BTW, these aren't my cars.



Here's a Carter carb w/arrow pointing to the port (capped off in this photo):


This port can be used for the PCV.

[sqzbox]

If I remember correctly, the vacuum hole is for a fitting that runs the hose to the PCV valve in the valley pan. There should be another large fitting towards the rear of the carb for the brake booster if you have one.
Also, I think the PCV hose was pre bent/formed because trying to bend a straight piece of hose would pinch it rendering the PCV valve useless.

It's been 34 yrs. since my last 389 so don't quote me on it, been a long time.

[ted200008]

heres a couple pics of the port. i have a bolt in it on one of the pics.

[cobalt327]

That's a ported vacuum port. There should have been a short nipple inserted as a press fit in there, originally. It should be plugged w/something better than sticking a bolt into the hole, IMO.

The center port between the idle mixture screws that has a screw in it should be plugged off better than a threaded fastener will do (unless there are threads cut for it for some unknown reason, or this isn't a vacuum port in the first place)- and there should be a nipple there, too.

[ted200008]

its a brand new carb. the large center screw changes the idle. and the port hole is threaded. the old carb is exactly the same way.

[Bonneville462]

A brass nipple goes there.. That is for ported spark advance that the Roto hydramatic Pontiacs and Oldesmobiles used..

I use to run that center idle screw all the way in and thread the boss at the linkage and install the idle screw there... I got a much better transistion with this method and it seemed to tune some of the turning a corner stumble that AFBs have....

[Bonneville462]

Another item you'll want to look into is the choke.. Those stock choke heat tubes rust out and the carb pulls exhaust through the choke stove..

I always removed the automatic choke and either ran a cable or even better no choke at all.. You'll get a few more CFMs without that flapper..

Turn the carb to the back and open that little cover plate with one screw.. That is a hot idle compensator.. It senses heat and opens to let vacuum in.. Remove it and plug the hole.. The little gaskets go bad and leak vacuum...


I always liked the Carter AFB...

[ted200008]

it will only run half what decent with the timing advanced about 12 degrees??

[sqzbox]

Originally Posted by ted200008

it will only run half what decent with the timing advanced about 12 degrees??

Given the year of your engine, compression ratio, and todays gas octane, probably not.

[ChevelleSS_LS6]

Originally Posted by sqzbox

It's been 34 yrs. since my last 389 so don't quote me on it, been a long time.

I think it's about time that you get yourself another!

[ted200008]

Originally Posted by ChevelleSS_LS6

I think it's about time that you get yourself another!

lol... they are great arent the . everybody i know says the 389 is junk and then they blow up thiere 400 n i still have my 389. lol

[sqzbox]

Originally Posted by ChevelleSS_LS6

I think it's about time that you get yourself another!

Already been there, done that, and moved on.

PONT. 326-455

AMC. 343-401

MOPAR 273-440

CHEVY. 283-350

Built those and everything in between those to beat fords! 1970-1989.

First marriage 9yrs. (lost all toy's)

Second marriage 30 yrs. and counting. (got more toy's, then sold them) and wife said I needed truck.

Now I do it in the mud, off road. Retiring next Jan. then looking for last toy.
Don't need no 's yet but when I do, their everywhere around here.