# pontiac 461 carburetor port issue



## sameold01 (Jun 21, 2020)

building a 461 for my 69 gto automatic car. Years ago buying stuff I had an opportunity to buy a fully restored carburetor with an engine block and intake manifold. I bought it all and got all the machine work done to the block and so on. Well, today the edelbrock 7156 intake is on and I went to put the qjet on 7040263 carb # and I have no front vacuum ports. Just one for the choke pull off I assume right front of carb. So, I have to hook up the vacuum modulator and it look like the line is above the throttle blades on front of the carb. So, my question is where am I going to hook up my vacuum advance for the distributor and where can I tee into the trans for the modulator. I have a vacuum feed off the back of the carb, can I tee into that for the modulator and the hideaway headlights? Tee into the front of the carb for the distributor?


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## sameold01 (Jun 21, 2020)

Pictures of carb


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## PontiacJim (Dec 29, 2012)

sameold01 said:


> building a 461 for my 69 gto automatic car. Years ago buying stuff I had an opportunity to buy a fully restored carburetor with an engine block and intake manifold. I bought it all and got all the machine work done to the block and so on. Well, today the edelbrock 7156 intake is on and I went to put the qjet on 7040263 carb # and I have no front vacuum ports. Just one for the choke pull off I assume right front of carb. So, I have to hook up the vacuum modulator and it look like the line is above the throttle blades on front of the carb. So, my question is where am I going to hook up my vacuum advance for the distributor and where can I tee into the trans for the modulator. I have a vacuum feed off the back of the carb, can I tee into that for the modulator and the hideaway headlights? Tee into the front of the carb for the distributor?


Looks like you may have a 1970 year carb as they did not have the front vacuum nipples.

Option 1 - back of the carb. Find a fitting that Pontiac used that has multiple nipples - one big one for the Power Booster and several smaller nipples on the sides - often called a "vacuum tree."

Option 2 - You can use a carb stud on the rear to replace the short bolts - I believe you won't have any clearance issues. The threaded holes must go through the intake into the plenum/runner where it can pick up engine vacuum. They make these repop and were used more on the early 1965-67 Pontiacs.

Option 3 - drill and tap a hole in the intake and use an aftermarket threaded nipple like those used for gas line hose on a carb. They also repop a square/block fitting used on some intakes (1968) for the PCV valve hose hook-up.

Check out InlneTube as they seem to have a nice assortment of items that will work for you.


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## sameold01 (Jun 21, 2020)

Can I use manifold vacuum for the modulator ? Above the blades in mounted in my 69 and that’s ported vacuum.


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## sameold01 (Jun 21, 2020)

Well reading a bit it looks like I can use manifold vacuum for the modulator . What the chance to T into the vacuum pod on right front of carb for the distributor?


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## Baaad65 (Aug 29, 2019)

No port on the back of the manifold? I had to get creative for mine with brakes, advance and factory vacuum gauge.


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## Baaad65 (Aug 29, 2019)

The fittings are out there just keep searching.


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## sameold01 (Jun 21, 2020)

Distributor wise what can I run? I really don’t wanna run manifold vacuum.


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## BearGFR (Aug 25, 2008)

sameold01 said:


> Distributor wise what can I run? I really don’t wanna run manifold vacuum.


Why not? The topic of the "correct" vacuum source for the advance can is one of those "Hatfields and McCoys" arguments all over the place that tends to turn into something of a religious war over which one is "correct". The reality is, try both - use the one that your engine seems to like better. That's all that matters.

For power brakes, you definitely should use non-ported vacuum. It's nice to have brakes even at idle, right?

For the modulator, I prefer non-ported but in actual practice it shouldn't matter: How often does the transmission modulator have to "do its thing" while at idle when a ported source would be "turned off"? Never. 

Bear


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## sameold01 (Jun 21, 2020)

Ok well I have the carb and dizzy calibrated so I will just situate the ports.. thanks agsin


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## Zeypher69 (Dec 25, 2020)

BearGFR said:


> Why not? The topic of the "correct" vacuum source for the advance can is one of those "Hatfields and McCoys" arguments all over the place that tends to turn into something of a religious war over which one is "correct". The reality is, try both - use the one that your engine seems to like better. That's all that matters.
> 
> For power brakes, you definitely should use non-ported vacuum. It's nice to have brakes even at idle, right?
> 
> ...


It's the internet fault. I started as a mechanic in the 70's and always learned ported was the correct vacuum for the advance. Then in the 80's manufacturers were mostly using manifold vacuum.
I switched a lot of my customers cars back then to ported and they ran a lot better.
I have experienced that argument on the internet and I was surprised. Now I just keep that and the GTO was a Le Mans in 64 to myself.


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