I recently rebuilt the set of EX-32 carbs on my 1936 V12 as they were packed with debris from the fuel tank. So with the tank being redone, I went after the carbs and found lots of nastiness. After a deep cleaning and verifying all passages were clear, I reinstalled them with new gaskets, it fired immediately and idled the best I’ve heard it in the year that I’ve owned the car. Fantastic! So I take it for a drive, and now my top speed is 30mph, foot to the floor in 3rd gear….
So, obviously something is wrong. I’ve rebuilt many a carb, mostly Rochester, Holley and SU types. This Stromberg was about as simple as it gets, so I am assuming I have either installed an incorrect kit, or missed a very important step/adjustment. The kit I used was from Mike’s Carburetor parts, and was number K6149 for anyone curious. I have checked my fuel pressure and volume, and both appear correct for about what this car would require, as I don’t have any actual specs to verify against. I installed a Gunson Colortune, which is basically a clear spark plug that allows you to see the color of the flame in the cylinder for tuning, and the engine is incredibly lean off idle. I assume I have a problem in the accelerator pump, but am unsure as how to tell what I should have, as the leather seal on the originals were non-existent.
Any information or assistance is greatly appreciated!
It sounds like you need to adjust the Power System setting. My book says..”Pump piston to rest on seat of by-pass jet (less overtravel) with throttle valve opened 27/64″” +/- 1/64″” drill (maximum pump setting)(measure with shank end of 27/64″” drill); adjust pump stem nut to obtain correct setting.”””
As a first step, by all means follow Bob’s recommendations. But you may have a vacuum leak separate from carb adjustments. In addition to intake manifold connections, the 1936-38 cars have vacuum-assisted power brakes fed by a 1/2-inch tube back to the vacuum cylinder. That tube run also contains rubber hose which MUST be specifically vacuum hose, not heater hose. I think I paid $4/foot for the last such heavy hose I bought almost 10 years ago. I’ve seen several 1936-38 cars with lean conditions caused by damaged or collapsed vacuum hose.
If a lean condition persists after the carb adjustments, first measure and record the current vacuum at idle from the port on the vertical against-the firewall connection for the vacuum wiper hose (bob will give us the correct nomenclature!). Second, disconnect the wiper hose and measure and record idle vacuum. Third, disconnect any rubber tubing at the end of the hard-pipe tube and measure and record vacuum there. Comparing those readings will help you find any downstream vacuum leaks.
Please keep us posted on what you find!
This one will be interesting to hear about the remedy. Chris, we would appreciate any updates you can offer!
A fellow with a V12 could not increase speed above 30 mph and after looking closely at the accelerator linkage, one carb was not operating above an idle. The car was running on six of twelve cylinders with the other bank of cylinders at idle. Look at the simple stuff first..KISS.
Very good point, Dave. Best to use a Uni-Syn to ensure that each carb/bank of cylinders is drawing equally at idle, then assure that the throttle plates are opening completely and in unison (pun intended).
Most car kits available today have incorrect parts. two years ago when I was running your car it was dumping fuel at idle. You need to install the fuel line upgrade Cislak sells if he still has any available, sort the mechanical pump, and add a good electric pump. If you changed out the needle and seat, put your old ones back in, the new ones being sold are very undersized. I have seen this several times. Lots of parts being sold as correct for Pierce Arrows are for much smaller cars and just repackaged, common issue.
Start with the basics:
1. have someone step on the gas pedal inside the car, you check under the hood to see that the carbs are BOTH opening fully
2. make sure you didn’t bump the distributor timing linkage, severely retarded timing will result in poor performance but a very smooth idle.
3. You can remove the high speed jet access plug from these carbs on the engine, [if I remember correctly] if so, spray carb cleaner through the jet from below, using the small red ‘straw’ on the can of cleaner. make sure you are getting a good flow of gas through the main jet.
4. Look at each needle and seat, make sure you don’t have a stray piece of crud blocking the fuel flow.
I’m betting on only partial throttle opening, The linkage can be put together wrong.
Aftermarket needle and seats included in the kit have been up to 60 percent restricted due to wrong flow hole size and over sized needle body, causing massive fuel restriction.
I wanted to follow up on the fix(es) to this issue.
Firstly, David basically nailed it, the car was only running on the right side bank of cylinders. What I was shocked to find were so many problems, right after having both carbs apart.
On the left carb, I had intermittent fuel flow at idle, and no shot of fuel from the accelerator pump. The right carb worked on the idle, off idle and accelerator pump circuits perfectly. I found that on the left carb, the bowl was completely dry after idling for a few minutes. The ball bearing “needle” was sticking at idle, but would open when revving the engine. Soaking for another day in carb cleaner corrected this. I also found the accelerator pump sticking in its bore, I removed, cleaned and lubricated the pump seal, and this corrected that problem.
After reassembling, I still had too little fuel at idle, but now off idle and accelerator pump shot were working. So further digging found the small idle transfer jet installed from the top of the float bowl had a tiny piece of debris that compressed air made quick work of.
Now I just need to find a good set of replacement spark plugs for my fouled current set.
Thank you to everyone who offered advice and experience to help solve this problem!
The ball bearing needle is called a Gross Jet. They are no longer made. They seem to work well with very low fuel pressure systems, but also cause problems on certain set ups. They are suppose to be self cleaning but depending on the install I have seen them cause problems. While I like them on early Cadillac’s I would not run them on your Pierce. V-12 fuel system problems can be a real pain to fix, and its easiest to just do the entire system from the tank to carbs to properly sort it. Installing a bigger pick up tube in the tank, and installing an over size fuel line all the way to the pump and carbs solves all vapor lock and fuel starvation issues. You need to make all new fittings and machine them with larger holes also. It’s a fair amount of work, but well worth the time. When I looked at you car two years ago it was dumping fuel at idle and starving for fuel on the high end, possibly caused by the Grosse Jets. Also, the timing seemed retarted. I have driven more than two dozen V-12 Pierce cars, more than half had severe running issues, another forty percent we just marginal, only ten percent actually run well. If you have never driven a well sorted Pierce 12 it’s hard to understand what very good performing car they are and thus many people never get their cars set up to their full potential. A clean tank with no rust and a good fuel filter are also very important. With modern fuel rejetting the carbs both main and idle circuit should also be done, as well as a electric fuel pump to,deal with hot soak from the carbs dumping gas in the summer months. The car should start EASILY hot or cold, and rev and pull like a 60’s V-8 motor. If it doesn’t you still have issues. As a side note, have you changed out your tires and tubes yet? They were like new but quite old, and I wouldn’t run the risk of running them, especially in warm weather or at high speeds. It’s a nice car, ENJOY! Ed.
Great information Ed! I had no idea what this type of needle was, but it seemed to work, so I left them in place. On this project, I started with the tank as it was pretty rusty and the accordion bellows was leaking between the fill pipe and the tank. The previous owner has had an electric fuel pump installed near the tank, feeding the mechanical pump. This seemed counter-intuitive to me, but researching found several people do this. I installed an inline filter before the electric pump, as well as replaced the filter on the mechanical pump in the glass jar.
Is there a specific size the fuel line should be changed to, and are the original type of needles available through someone? I also imagine routing the fuel line away from the engine to the outside of the frame rail would be a good idea as well to help with reducing the chance of vapor lock.
Any ideas on a good replacement spark plug? Currently Autolite 458 are installed, but they are badly fouled with fuel from what you observed with fuel dumping at idle. I will also look into checking the timing, but honestly am unsure of how it is checked on this vehicle. I am used to using a dial style timing light to check initial and advance timing, but am unsure if that is the correct procedure for this car.
I haven’t had a chance to drive the car more than around the block yet to determine how it feels at the upper end. In using my Gunson colortune, I found I am slightly rich at the center cylinders, and slightly lean at the outer cylinders, which seems to me might be due to the design of the log style intake manifold.
The tires are still on the car! It blew me away with the way they look almost new and the actual age. It is on the “to do” list for a new set, as I don’t trust them for more than low speed duty at the moment. They are date coded 1984. Since I have been working on getting the car running correctly first, the tires took a back burner position.
Since you had fuel dumping into the cylinders enough to severely foul the plugs, be sure to change the oil before you do any real driving.
The oil could very well be suffering from fuel dilution after all that fuel being dumped into the motor at idle.