Modify 17080423 Quadrajet for use on 350 Buick?

[Jpn_Skylark]

Hello,

A while back I talked with Cliff about my Quadrajet I was rebuilding for my 1969 Skylark. The unit I'm using is a 17080243 which I believe is a 1980 Turbo V6 carburetor? I've spoken with Cliff and have the parts needed to put the carburetor back together but I'm struggling to find information on how to modify the carburetor to open vacuum to the power piston and cap off whichever ports are not needed. I've looked at the carb body and baseplate and if I'm not mistaken the vacuum source for the piston is the vacuum port directly under the fuel inlet (please correct me if I'm wrong). If that is capped off would drilling for vacuum be as simple as drilling straight through the passage from the body to the baseplate?

[Cliff Ruggles]

That's all there is to it.  If your carb has the vacuum routed in from the front of the baseplate block that passage and drill up thru the baseplate to supply vacuum to the PP directly from the intake......

[Kenth]

A different approach for full function of a Turbo unit on a non-Turbo engine would be to connect the power piston port to a manifold vacuum source on carb or intake.

[Cliff Ruggles]

Correct, they only need a vacuum signal from the manifold to work correctly, but keep in mind that rubber hoses rot, crack, and leak.  I've converted scores of turbo carbs to N/A applications and simply remove the vacuum fitting in the front of the baseplate, melt some lead into the hole from a wheel weight, swage it out with a flat punch, and drill up thru the baseplate to supply vacuum to the PP. 

It's not fussy but you do have to pay attention to the angle so you come in the hole leading up the PP correctly......

[Jpn_Skylark]

Okay, that makes more sense then. On the bottom face of the base plate there is a channel that partially goes across the front and links to a vacuum port to the right of the PP vacuum port (Not the PCV). Is this the channel I'd need to drill into at an angle to supply vacuum to the PP?

[Cliff Ruggles]

Look at the gasket used between the baseplate and main casting.  On the non-CCC units the hole will show you where you need to drill to supply vacuum to the Power Piston.....

[Jpn_Skylark]

With the gasket lined up as you say, simply drill straight through? I think I'm overthinking again but if I'm understanding correctly if drill straight through using the gasket as a guide the hole for the PP will be drilled on the edge of the manifold vacuum channel? Or would I have to drill at a slight angle?

[Kenth]

I would keep the carb original since it´s a Turbo specific unit and simply place a hose as in my picture. No need at all for drilling.

[Jpn_Skylark]

I hope Cliff clears up my confusion, but if I still have trepidation about drilling I'll likely go your route. Thanks

[Cliff Ruggles]

Coincidentally I'm building the exact same carburetor in the shop for a FAST Class application.  It's going to end up on a 520CID Buick engine with ported Stage 1 heads and 13.6 to 1 compression.  Those carbs are easily up to that task and make excellent high performance street/strip carburetors.

I removed the vacuum fitting coming in from the front and melted some lead from a wheel weight into the hole instead then gently swaged it with a flat punch instead of permanently blocking it.   I then drilled the baseplate to supply vacuum directly to the power piston.  That hole could be easily blocked later, the lead removed and the stock vacuum fitting put back in place if the carb needed to be returned to the stock configuration. 

The picture Kenth shows is a quick and easy way to supply vacuum to the power piston without modifying anything if you don't mind using rubber vacuum hose across the front of the carburetor.......Cliff

[Jpn_Skylark]

Gotcha, I decided to drill through the baseplate to reduce the amount of vacuum lines on the carburetor. To remove a vacuum fitting I assume it would involve heating the baseplate and pulling it out? With the lead I'm unfamiliar with the term swaging, is it melting the lead to a liquid form then simply filling the hole and removing the excess?

[Cliff Ruggles]

Swaging is nothing more than smashing out the exposed portion of the lead to seal off the passage.  I like doing it that way as it's completely reversible later on.

I don't understand "drilling thru the baseplate" to reduce the number of vacuum fittings?

Sometimes they pull out easily, other times you have to heat things up to get them loose, but they come right out most of the time w/o drilling.....

[Jpn_Skylark]

With drilling I meant getting vacuum to the PP, which made the vacuum fitting unnecessary and no need for a vacuum line going across the front of the carburetor. I used heat like you said to wiggle it out. Sorry for the misunderstanding

[Cliff Ruggles]

Removing the vacuum fitting and blocking the hole is a better option than leaving the fitting in place and putting a rubber cap over it so it can "rot"......IMHO...

[Jpn_Skylark]

When the hole has been filled can the body then be replated? I'm new to the whole process, I've already filled one hole in the baseplate and I'm moving on to remove any extraneous ports. Thanks Cliff