Check your jets on rebuilt carbs

[christian]

Ever since I got my 160b running last fall I had a terrible issue with the idle. I had to have the idle adjust screw pretty much closed down all the way to get it to run at idle, and even then it had a lope that I just wasn't comfortable with. Since the plugs ran nice and tan and I had no issues with driving speed I just accepted it as being a quirk of an 82 year old car.

The carb I'm using is a rebuilt zenith from a reputable rebuilder whom claims all jets are flow tested, yet another reason I wrote off the lousy idle. While going through my junk box I found an old marred up originally numbered idle jet, on a whim I figured I would compare the two, I was astonished....

The nice shiny new idle jet that was supposedly flow tested was literally half the size in orifice diameter than the cruddy old numbered jet, I swapped them out for kicks and to my amazement, 1 and 3/4 turns out from stop the thing idles like a dream.

Check your jets !

[H. L. Chauvin]

Hi Christian,

Tested a few original jets in my carburetor junk pile a few years ago -- all numbered ones were right on.

It has been advised very often by many kind folks not to discard anything orignal unless totally unserviceable.

Also, in trying to get a new distributor body that fits an original distributor, (with little or no loose play), not long ago I bought a dozen or so from different Model A vendors; however, even though new, they all fit very loosely about like stockings on a chicken.

Gap between new rotors & distributor body contacts varies "drastically" when one slightly moves the distributor body in any direction.

Have one (1) original distributor body with "Ford" Script -- appearance ??? -- looks like Moses used it for a tea cup while crossing the Sinai Desert in departing Egypt -- but it fits tightly with no play -- again, original.

[christian]

I have the same issue with distributor bodies, not one from any vendor fits snugly. I spent over 30 minutes, measuring and filing contacts to get just the right rotor gap, only to find it moves about and then the gaps get all out of whack.

[H. L. Chauvin]

Hi Christian,

Looks like somebody could invent something to correct this "loose" distributor body problem.

Maybe:

1. First, turn distributor body upside down & lay on a flat surface.

2. Second, drill four (4) tiny holes, (centered in the bottom of the rim of the distributor body), with each of the four (4) holes located between each distributor body metal point of contact for plugs numbers 1 - 4, & tap each hole with about a #4-40 or so bottom tap.

3. Third, directly above each of the four (4) holes, (distributor body still turned upside down), remove about a 1/8" wide x about 1/32" deep of distributor body material.

4. Insert a tiny brass, flat slotted, flat head machine screw, (like maybe a #4-40 or whatever it takes), in each hole.

5. With a (3) corner file, trim in-sides of all four (4) screw heads until distributor body is centered & tight fitting & set in place with Lock-Tite.

Never tried this idea, but there may be other better ways if one would just think about it at coffee breaks.

[Pinstripe]

How have other people dealt with this problem??

[Fred]

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Originally Posted by Pinstripe

How have other people dealt with this problem??

DONT buy reproduction ones...

[Tom Wesenberg]

I haven't purchased any distributor bodies for many years, but had purchased from Bratton's and Little Dearborn and both of them fit nice and snug.

If you have a loose fitting body, I'd run a layer or two of tape around the inside to keep it centered. Not across the notch of course.

[acenewman]

experienced the exact same problem a couple weeks ago. Car didn't idle well and was prone to stalling on a decel. removed the new idle jet I put in last year and compared to the old one I took out and the hole was half the size. Now that the old jet is back in it idles like a dream and no more stalls. Stinks when your brand new replacement parts are out of spec. I have since adopted the position that all new parts are out of spec until proven otherwise!

[Bruce Lancaster]

"Looks like somebody could invent something to correct this "loose" distributor body problem.."
Or maybe just make the thing right??!?
A few years back I purchased a repro of the type of cap that uses modernish wires and terminals...I already had a good original of that, and ancient aftermarket part, which fit perfectly.
The new one, an attempted duplicate of the one I owned, was so loose that it came with a REPAIR KIT from the supplier!
As I recall, this was basically a rubber O-ring the fit around the rim on distributor to jam the cap somewhere near center.
I was astounded that someone would make something this badly, that they would sell it, and that they thought a new part with a kit to correct its fundamental and critical defects was a good idea! Bodging around with parts that can force you to walk home is dumb. Go to Hershey and buy some old dirty ones that are made right if you have to.
Meanwhile, the repro cap is now serving in a job it can perform competently...it is the happy home for a spider. Maybe I'll find a job for the O ring someday.

[TinCup]

I have spoken to a couple of online vendors about certifying the carb jets. My suggestion was to offer guaranteed flow tested jets as a way to validate the quality of their parts versus the hit and miss we get with what is being offered today. Both vendors remarked that they only have one supplier for the jets. I check every jet before I install one today but I would be happy to pay a little more for a set of jets I didn't have to work over.

[Bruce Lancaster]

I'd be happy to get some of the original jets people seem to be tossing for repros...after 80 years of unknown history they need checking, but I think a happy result would be much likelier.

[redmodelt]

Even if they were flow tested maybe they are on the low end of the scale and for your car was too small. It's a bit of a pain, but you could get a set of twist drills and open the hole a bit more.

[Tom Endy]

My experience has been that three important things are essential for a good functioning Zenith. The internal passages must be open. The float level should be properly set, and the jets should be flow tested and re-sized.

Original jets can be incorrect as well as reproduction jets. Over the years people have been pushing welding tip cleaners through them. I flow test both originals and reproductions, solder them closed and re-size them. Either one will work fine as long as it is the proper size

Flow testing and re-sizing is a tedious and time consuming task. A Model A club should build a flow tester and have a flow testing seminar every so often. Our club has one scheduled for next month.

Tom Endy

[Mike V. Florida]

Originally Posted by TinCup

I have spoken to a couple of online vendors about certifying the carb jets. My suggestion was to offer guaranteed flow tested jets as a way to validate the quality of their parts versus the hit and miss we get with what is being offered today. Both vendors remarked that they only have one supplier for the jets. I check every jet before I install one today but I would be happy to pay a little more for a set of jets I didn't have to work over.

I thougtht I read on Fordbarn about a guy that sells flow tested jets?

[29er]

Today I installed my spare Zenith on Henrietta ('29 special coupe) which I rebuilt using flow-tested jets I bought from Renner's Corner:

http://rennerscorner.com/carburetor.html

Once I got the float valve adjusted properly, she ran better than I've ever had her running! I'll probably buy another set for my other Zenith. The jets came with data indicating their actual flow rates (cc/min).

Incidentally, if you don't have Tom Endy's dissertation on rebuilding the Zenith carb, you can find it here:

http://modelabasics.com/Carb/ZenithC...l2011-2007.pdf

Dave Gerold also has a paper on performance-testing the Zenith carb:

http://www.durableperformance.net/PE...ODEL_A_Web.pdf

Mike

[TinCup]

I picked up some parts to rebuild a B distributor but missed the jets. Thanks for the heads up. I have used Tom's procedures with great results.

[redmodelt]

Re; "1 and 3/4 turns out from stop the thing idles like a dream." Are you talking about the air idle adjusting screw or GVA? If it's the air idle screw, that sounds about right.

[Mike V. Florida]

Renners corner, I knew I read that someone is selling tested jets.

[christian]

Originally Posted by redmodelt

Re; "1 and 3/4 turns out from stop the thing idles like a dream." Are you talking about the air idle adjusting screw or GVA? If it's the air idle screw, that sounds about right.

Yes air idle screw. Before the air idle screw had to be fully seated or idle wasn't happening reliably.

[Don S]

What causes a hickup during accelleration ? Float level, jet size or ??? It also backfires a bit in second going down a hill Thanks