MTFCA Forum

Hello Everyone
The back story:
1921 Model TT Obenchain-Boyer firetruck, City of Fowler, California, NO: 1
Was running fine in 2019 and was driving the TT back to the garage after the Cranberry Parade/Car Show.
Loud backfire, engine died, Hagerty towed it home.
Family calamity and Covid hits, so the TT sits in the garage until now.

Time to get things going again:
Find wire bare at the timer, assume there is my problem and made the repairs. Changed oil, Clean timer & plugs, Re-time the motor, drain gas tank and blowout fuel lines.
Will not start, now I'm looking that the carb and notice lot fuel leaking from the bottom of the carb and assume it's the large nut at the bottom of the bowl. Replaced the gasket under the bowl nut. Still leaking but now just a drip, from the small (weep hole??) next to the nut. I didn't notice the "weep hole" previously and don't have a clue about it's function and what a leak here is telling me?
I believe the Carb is a Model "g".
Trying to figure out how to post photos? Not finding how so far, something about "BBCode [img] tag". Most of the post about how to post a photo just confuse this old fart and no grandkids around today to explain it to me! is this a Mod "g" Holley Carb? and is it correct to my vehicle?


Red pointe shows the "weep hole" I' talking about.

Spent the last two hours roaming around the forum reading about posting photos and carb problems.
I think I figured out the posting photos but not likely to remember how next time.

Still learning about the carb, any and all help appreciated.

Old and confused in Oregon.

While disassembling Carb, notice fuel coming out of this "weep hole" (red pointer). What is the function of this?

being a gravity-fed system, nearly all "T" carbs will eventually overfill and then come out either an overflow or out the throat...ALL "T" carbs should be outfitted with an external "off" valve...OK, lecture over...

that hole is the overflow. Under the venturi, there is a small tube that sits up proud of the jet inside the carb. Your fuel level is reaching that height and then dripping out. That may be because either the float level is set too high, or the float valve is simply allowing some weeping past it and once the bowl fills up, it then slowly leaks out of the overflow. If the attached photos are of YOUR carb, you have a Grose valve for a float valve. UGH. They are known to alternately leak or quit flowing, and somehow manage to do exactly the opposite to what you want or need at the time. In the near future you will be doing yourself a service by replacing it with a more conventional valve (preferably one with a Viton rubber tip). Invest in the MTFCA Carburetor Manual and thank me for the advice later!

Your "big bang" was not associated with this and if the truck ran before and not now, it is unlikely the carb (though it DOES need attending to).

A loud backfire and failure to run has the earmark of a stripped fiber timing gear, though there could be other causes as well. I would start by checking timing of the coils to the crank location and then ensure that each coil in turn lights of exactly when required relative to crank position (firing sequence: 1, 2, 4, 3 from front to back)

good luck

Dave, from the pictures, your carb is a Holley G (rhymes with "golly gee !")
The MTFCA carburetor manual has good instructions on its care and feeding, and if you can search this forum, there have been several posts discussing this carb recently. I believe it is "correct" for your TT from the standpoint of authenticity, but barring that, most agree it is a fine carb to run on a T. Good luck, please let us know how you make out !

Scott_Conger wrote: ↑

Sun Sep 05, 2021 3:08 pm

Your "big bang" was not associated with this and if the truck ran before and not now, it is unlikely the carb (though it DOES need attending to).

A loud backfire and failure to run has the earmark of a stripped fiber timing gear, though there could be other causes as well. I would start by checking timing of the coils to the crank location and then ensure that each coil in turn lights of exactly when required relative to crank position (firing sequence: 1, 2, 4, 3 from front to back)

good luck

More family events have kept me from working on the TT until yesterday but I've cleaned and reassembled the carb, not leaking any more, also I do have a shutoff valve at the carb inlet.
Re timed it again. I suspected the cause of the breakdown in 2019 was the timer wires shorted (since repaired). But now I notice that after I re-time the TT and try to start it ........... the timing changes? I did it all again with the same results.
So now I'm wondering about the "stripped fiber gear" you mentioned. I hand cranked (no ignition) to find TDC and the valves appear to working correctly (valve closed on compression stroke and open on exhaust).
Looking at Mod T service book it's a major job to get to the gears? I want to know for sure before tearing it all down.
Any thoughts on how to diagnose this? All the photos/diagrams I'm looking at aren't telling me what I want to know.
When I changed the oil and didn't notice any debris.

Look in the oil filler. You can see the teeth of the gear. I had an Iron gear break & shift timing to no compression. It was obvious in that case.

speedytinc wrote: ↑

Mon Oct 04, 2021 4:13 pm

Look in the oil filler. You can see the teeth of the gear. I had an Iron gear break & shift timing to no compression. It was obvious in that case.

Looked in the oil filler but couldn't see much other than I have an alum gear.
Pulled the Generator for a better look and find alum shavings. Crank it around and can see the Alum gear is toast.

So I guess the next step is tear down the front end, see what's what and order parts.

So any guesses on what caused this? Very low miles on the motor less than 200. Gears not set up correctly? Wrong gear set installed?
Anything I need to keep an eye out for?

As always thanks for helping!! I guess I should start a new thread, this one is getting way off from the Mod G Carb.

Messed up, as in missing teeth, or worn badly? Not all aluminum gears are the same alloy. They expand differently. If it was set up to iron clearance(.002) Ouch. Can take out your cam bearing also. Could be generator mount too close that chewed the gear. (must be appropriately shimmed)
Best to spend a little extra up front. Dan Mcearchen bronze gear @ .004"-.006" clearence.

The correct carburetor is either a Kingston L4 or or Holley NH with off-center drain. The NH is a better choice. I have a Holley G on my '17 and have had good luck with it but it was rebuilt by a pro...I second Scott's suggestion to get the carburetor book. Alternatively, if you don't feel comfortable tearing into it you can send the carb to one of the carburetor gurus for a rebuild.

Accessing the timing gear isn't too difficult - easier done with the radiator out of the way. You'll need a gasket and seal set (get the neoprene seal for the camshaft) and either purchase or borrow a Timing Cover Alignment gauge (Lang's PN 3009T.) Again, read the manual. Good luck!