VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Carby Upgrade on a 28, Zenith of Tillotson?

Hi Guys,

I regulary see mention of carby upgrades from the standard carter to either Zenith 14991 or Tillotson JR5A. I see that the Zenith is still available as a new unit, not sure about the Tillotson.

Would appreciate comments if any one has tried either of these units and what the results were.

Also are overhaul kits still available for the Tillotson.

Regards

Ray

Most of the people I know that change from the original Carter are Aussies. I have never wanted to change from a good running RAKX-0 as they seem to do just fine. Maybe if I put an engine on a dyno and could check performance accurately I might change my mind.

Don't know of any source of rebuild kits for the Tillotson JR5A.

My 24 Olds has a more modern type zenith, not sure of the number but suspect it is the same one mentioned. I do have problems with it running rich at times and running lean at times. Seems to be no happy medium. If I adjust the high speed jet lean to get it to quit washing the cyl walls and smoking, it spits out at the carb if given the throttle. If I adjust it so it takes the throttle, it then starts washing the cyl walls and burning oil at idle and the black smoke bit. Sure wish I could find a good T4XF zenith (uncracked at the venturi) and be done with it.

Bob,
What does the Zenith T4XF look like? Anybody got an image?

Mike

For 1924 you have an option. Zenith T-4XF, Carter RB-0 or Holley SC. I have several T-4XF carbs and all are cracked. It is a common problem. Some can be fixed. I have one in the shop that I am waiting for some new venturis so I can attempt to braze the cracks and get a '24 back on the road.

Hope to have the display of pre-WWII factory installed carburetors ready for Flint. It involves some 50 carburetors. Still looking for a few of the early carbs. May need helper springs on the '70 Caprice to get them there.

The T4XF lokks looks like a T4X in a way, but is cast iron and has a brass plate bowl cover with a tab sticking out to cover the needle valve area. I have two badly cracked ones. I was working on a T4X,to just make it work on the Olds for temporary. The ventruri is stuck in that one but have a new brass one waiting for me to get buzy on it.

Hi Bob,

I think your problem with the Olds engine isn't at all the replacement Zenith Carb, but in fact, sounds like the intake manifold is operating at too cool a temperature. I am not familiar with the Olds engine, but is there a hot air pipe connection from the exhaust header that could be hooked up?

From the conditions you describe, its does sound like a classic case of fuel not vaporizing correctly. Enrichening the mixture would cause some of it to go away, but then, its way too rich, just like you say.

If no hot air pipe, you might have to bring a water pipe to the manifold to heat it up that way.

Either way, I bet the Zenith carb starts performing very well indeed once the intake manifold reaches *temperature*. On my 1926 Chevy, with its Zenith 14491 carb, I still have the hot air pipe attached, and the carb and engine perform beautifully. Starts rapidly in the past 20 degree F days we had and has excellent driveability. Its a real eye opener for people who have only known the Carter carb.

Ciao,

Jay

It does have a hot air pipe but it also has a hot spot manifold with summer and winter settings on a lever. I had cleaned out the manifold pot a few years back and it does the same running on hot setting or cold and when on hot the intake is warm on the runners. The hot air pipe is currently off the car since the new zenith doesn't have the air temp adjuster sleeve, but sounds like I may put it on and give it a try that way. It hasa small stove area that only goes half way around the exhaust pipe. Bad news is I better fix the crank thrust bearing before I do any more running it. It caused the clutch to rattle like the dickens going up the hill at Newport last fall with a car load of VCCA members in the seats. Don't want anything to break on that car since there is only 13 1924 Model 30B Oldsmobiles known to exist world wide. Parts are almost impossible to get.

Bob,

I would not worry about the hot air pipe right now vs. the crank thrust bearing. That engine might be developing the dreaded crank walk, and yes, you spotted it by noticing the clutch acting up. I hope the other VCCA guys riding with you were at least sympathetic, as they increased the *load* on that thrust bearing....

Are there thrust washers that could be made up and placed at the last main bearing before the flywheel, see, i don't even know how many main bearings the Olds four cyl has.

Best of luck with your Olds engine.

Jay

Hey Jay,

Tell me more about crank walk.

Regards

Ray

This Olds has a 6 cylinder with force fed rod and mains. Bad design though from an oiling point. They end up starving #2 and 5 rods at high speed.Oil pump was too small and the oil had to go through too many things by the time it got to the rods. That is the big reason there are so few left. They made tons of them, but most were dead by WW2 and went to scrap drives. Outside of that, great little engine, easy to work on and makes decent power. Crank walk is where the thrust on the crank changes and the crank shifts back and forth. Since the clutch is hooked up to the flywheel it made the throwout bearing and linkage rattle. I found it buy pushing in on the end of the crank and watching it move back toward the clutch and hearing a click,and also the crank on the front showed shiny area where the crank had been moving back and forth through the felt dust seal. The VCCA folks were great and loved to get to ride up the hill even if I was crossing my fingers and kept my foot slightly on the clutch pedal to keep the rattling at bay. Earlier that day when it rained, we all piled in it to stay dry during a downpour. They loved it! There was two different body designs that year for the same model. It is the second type body style which was used till 27 and was only made for a couple months before the 30C came out which makes mine one of 4-5 known to exist style wise. It is funny though how many parts are also used on Chevys of that year! Windshield is one of them, carb is another. I think I posted a video of the 24 Olds as well as the 23 Olds 1 ton truck with another VCCA member haging on for dear life in the bed at Newport Hill Climb on the National Antique Oldsmobile club facebook page. http://www.facebook.com/?ref=home#!/pages/National-Antique-Oldsmobile-Club/259961720334