Good Day All
I have a '64 Dart auto with an Offenhauser 2X1 intake manifold.
I have a pair of Holley Model 1920 (I believe the List# is 4712).
Is there a site that shows what the factory jet size was for these carbs?
Offenahuser suggests that you drop two sizes. I'm looking for the base line.
Also I would assume that the distributor line would be 'Y'd to both carbs for an adequate vacuum signal.

All responses welcomed.

You shouldn't need to tee the vacuum line.

Guzzi Mark, Madmax/6 runs that setup. Check with him on jets for the application.

CJ

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Part of Tyrde-Browne Racing

I did a search on the Offenhauser 2X1 and found several posts on the subject. The most informative one was from 2004.

It addressed some of the same issues that I'm experiencing such as:
1) rough idle
2) hesitation when you accelerate
The poster never did mention if he was able to sort these problems out or not.

I also learned that the PVC is suppose to be plumbed to the threaded hole between the carbs. Currently mine is "T"d by both carbs.

Would this cause some of my problems?

Thanks to All

The PCV is a calibrated vacuum leak. Use the port they provide.
What jets are in the carburetors you are currently running?

Hopefully Mark will see this thread and respond. His car runs great. He's very sensitive about it's color though. Don't mention the word "Pink."

I punched up your title to catch his attention!

CJ

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Part of Tyrde-Browne Racing

I thought it was Salmon or Fuschia Ceej.

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Official Cookie and Mater Tormentor.

Called Mark this evening. He had to get some sleep. Seems he's been working his tail off with his business, and hopes to get the last window in his chop top tomorrow before loading up for Vegas.
Hopefully he'll get a chance to look at this tomorrow.
Hang in there!

CJ

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Part of Tyrde-Browne Racing

From my holley book . list no 4712 had a 56 jet

Good Day All

Re-plumbed the PCV and blocked off one of the distributor vacuum ports (1 carb now runs the distributor). Went for a test drive. The throttle hesitation is less (still there when you start from a dead stop).

I disassembled the front carb the jet is a #53. As I was disassembling, I was checking parts. The cover for the economizer diaphram was not flat. If you laid it on a flat file and, using your fingers, moved it back and forth, only the outer edges (the screw holes would touch). I filed it until the entire mating surface was clean. Don't know if this had any effect on the stumbling, however, I reasoned that a flat surface would be less prone to vacuum leaks. If it makes any difference, the diaphram will go to the full 'up' position at about 6" of vacuum.

I saw no other issues with the front carb, just some very fine rust/debris. I cleaned and blew dry the passages and installed a new metal fuel filter.

Normally with any duel carb setup it takes bigger jets than just one carb would use. There is a lot of different things that come into play when it comes to jets though so its hard to call one rule as gospel.

Anyway normally there are two things right off when changing to a duel carb intake.

One, if the plenum is bigger the carb will need bigger jets. Even if only just changing intake with a one carb setup if the new intake has a bigger plenum it normally needs more jet.

Two, when going duel carb there is only half the cylinders giving a signal to the carb. This will normally cause the need for bigger jets.


Now pump squirter size normally can go down when going to a duel carb, but that doesnt allways hold true.



I ended up with #58's in my Holley 1920 ( single setup) if I am remembering right. We have very good air here though. Depending on your altitued on what jets would be needed. With it bogging, I am sure I would atleast startout with 58's in both carbs and go from there. If you are higher up in air, maybe 56's. If I was running a duel setup here on my car I would expect to have to run 60 - 62 in the carbs with mine starting out at 58 as best in a single. The 58's in mine was the best balance of economy and power, it made best power with 61's.


Now a slant six intake is a odd setup and it may act different than what I am use to on V8 engines when going to duel carbs. But with it bogging I wll bet it is lean and needs more jet.


Jess

It's SANDSTONE...

Anyway, Holley 1920 will lean-down into the "low 50's" and up into the low 60's with jet size.
I wouls start at #57 for the Dual Offy set-up and tune it from there.
DD