Sam Buchanan

We can sense your excitement.....couldn't stifle the yawn long enough to snap a photo, eh..... ?

Put the old needle and seat back in the carb and see if that makes it happier.

I can assure you there are no deaf ears in my corner of the P15 community. The only thing I was kinda speaking to is suggestions that definitely do not address the problem I described because of lack of reading the description of symptoms I have described numerous times in this thread. But that is an insignificant issue compared to most problems we face each day (in my case the recent loss of my housemate of 45 years....who loved riding shotgun in the '48). But I've seen it said that many "carb" problems are in fact ignition problems. I'm going to give the vacuum advance a hard look and also make sure the breaker plate is moving freely with no binding. Another thought I've had is carb ice. The hesitation occurs with the throttle barely open, prime conditions for ice. I have the heat riser blocked off, don't know if this might be a factor. I do appreciate the comments, most of them are providing ideas to explore. I want to emphasize again how minor this issue is, just just enough to notice under the right conditions (and prompt "Why is it doing that?") but not significant enough to cause drivability problems.

I appreciate all the comments and suggestions. However, it is obvious that some commenters have not read all the thread and are not familiar with the history of my car even though it has been well documented on this forum the past two years. In regard to this suggestion: How about fuel delivery? At these speeds your engine is thirsty. Could be carb float height, clogged passages, jets. Fuel line, Tank. Pump, filter, swollen rubber hose. If carb is ok, try adding an electric fuel pump as a test. Not any but one with max pressure 4.5 PSI like Airtex E8902 Response: Float has been carefully checked and set slightly below book spec. Within the past two years I have installed new fuel tank, lines, filters, and electric pump (mechanical pump removed). Carb was disassembled and cleaned. Here is where the restricted fuel flow diagnosis is flawed. The engine runs great under full throttle and heavy load. I have stated this several times in this thread but fuel starvation continues to be offered as a diagnosis. And yes, the intake gasket was replaced last year and I have carefully torqued the fasteners. What kind of "vacuum test" is being suggested? I've had a vacuum gauge hooked up to verify general engine health and all looked good. The hesitation isn't a significant drivability issue, I'm just curious about it since the engine is flawless in all other regards.

Interesting. I'm leaning toward the same conclusion. Anything 73 years old has earned the right to demonstrate some character. ?

Using some choke to smooth out the hesitation leads me to think it is going lean. The condition is so slight and happens so infrequently I doubt reading the plugs would show much, especially if lean. Carter.

Yep, the hesitation is only under light, steady throttle (as I have stated several times ). The engine accelerates just fine, accelerator pump is working fine.

Don’t know, haven’t been in the carb since I returned the car to service two years ago. I’ll need to do some homework.

The float is set just a bit below book in an effort to reduce percolation, but the engine runs strong at full throttle with no signs of fuel starvation. No PVC system, just the standard chassis anti-corrosion system. Yep, the hesitation only occurs on the highway in a very narrow range of light throttle and low engine load. It can't be heard, just felt. Add some throttle and the engine pulls strongly. Drive into a headwind that requires more throttle and the hesitation doesn't occur. Maybe I just need to consider it a "feature", not a problem. ? Thanks to all for the suggestions.

I agree, guess the Mopar guys considered a little drooling as a possibility as miles accumulate, better than having oil find its way into the clutch housing. Pretty clever.

Nick, after you start driving the car the stuff that has accumulated in the muffler will clear out and you won't be seeing this. I don't see any reason to worry about the health of your engine.....carry on.

Earlier I posted: The flattie in my '48 P15 runs strong and smooth. Except.....sometimes at ~50mph on level road under light throttle I can feel (not hear) a slight miss or hesitation. This only happens when the engine is under light load. When I push down the go pedal the engine runs smooth and strong or the hesitation is so slight I can't detect it. Before I start poking around I'm wondering if anyone has seen something similar and has ideas. I've wondered if the carb throttle shaft may be worn enough to allow air to be sucked in under high vacuum. The manifold bolts are tight and I haven't seen evidence of any vacuum leaks. Just trying to ponder this before I mess up by trying to fix something that ain't broke. Update: The slight hesitation is still present at 50-55mph under light throttle. It feels like the engine is running a little lean when a nearly closed throttle is creating a lot of vacuum and now I really suspect that is the case. If I pull out some choke the engine smooths out. Now...where is the vacuum leak occurring? It seems to me it could be any of the following: Wear in the carb at the throttle shaft. But it feels tight. A leak somewhere in the wiper system. I can easily plug that line as a check. A leak in the vacuum advance unit. That one is a little harder to diagnose, guess I could plug that line and run it just on centrifugal advance. However that might introduce other issues that complicates diagnosing. A manifold leak. Could be, but everything is tight and it got a new gasket a year ago. Any thoughts?

The countershaft is below the bottom edge of the bellhousing so the gasket isn't a factor. Look at this photo carefully: You can see the change in color where the bottom of the bellhousing meets the tranny. The countershaft is below that line, so the gasket is irrelevant.

I used thread sealer, the sealer on the heads was just a belt and suspenders approach since I didn’t want to have to address this again. The sealer is Flamemaster fuel tank sealant, a superb sealer I’ve used on aircraft for 25 years. The bell housing gasket doesn’t cover the end of the countershaft.

That's what I did.

Just grab a handful of various length pre-flared brake lines and unions at your local auto parts emporium, figure out which ones you need, and return the unused ones. No need to complicate this by over analyzing it.

Yep, just give the old tranny a little extra time between shifts. Also, after you put some more miles on the new oil you may find the shifting improves.

Wow.....1/8" steel? We're hunting doves with a bazooka.... ?

Rich, I’m on the road this week, if someone doesn’t jump in to help you I’ll try to make a photo for you next week.

The cap is vented. The vents are tiny holes in the inner part of the cap that vent to little slots on the outer edge of the cap. If you are having fuel flow problems, make sure these vents are open, they are easy to overlook. Or, if you want to use a non-vented cap you can add a small hole in the filler neck for venting.

Huh? A breather tube will vent faster than that big ol' tank filler tube on our old Mopars? Well...maybe for NASCAR. ?

Or use a vented cap.

I used pre-flared brake lines when replacing all the fuel lines on my P15. Unions can be used to join various lengths of brake line to make everything come out right.

No mods required for the Vans tank in my '48 P15. The tank doesn't have the built-in filter like the original tank so be sure you install a filter in the fuel line near the tank. A great feature is that it doesn't require the funky little ferrule at the fuel line fitting, the tank fitting is just a conventional 1/8" NPT (pipe) thread.

Mine is black....but I don't know if that is the original paint.