Any Flathead Experts in Minneapolis?

[new_castle_j]

Hello Everyone,

Anyone here in the Minneapolis area, I've got a 1936 Plymouth with a rebuilt motor, I can't get it to run well and am perplexed.  I should say that it actually runs beautifully for the first start of the day and until the engine warms up.  Once it's warm, the engine won't rev past a certain point anymore and it will cut out and surge, if I bring it up to the RPMs where this starts happening and sustain for a little ways, then it will backfire.  None of these symptoms occur when cold.  I've messed with everything trying to figure it out, would like to know if there are any experts in my area.

Thank You!

Jonathan

 

[Plymouthy Adams]

first off, are you running 6 or 12 volts.....if 6 volt and you have installed a 12 volt coil with internal resistor, when warm, the internal resistor will cut your coils ability to saturate and generate the needed secondary voltage....not saying it is your problem, but without further facts from you..is my first guess...

[new_castle_j]

  I am running 6 volts and the coil I ordered from Pertronix was also for 6 volts.  I will double check it though, thank you for the reply!

[bobostski]

I had the same kind of problem with one of my cars and noticed it ran better if I left the choke pulled out a little  even after it had warmed up. When I rebuild the carb. the problem went away. You might be having a problem if your choke is not pushed in all the way after the car has warmed up. I believe you car has a manual choke. Just one of the many thing that could be wrong.

[plyroadking]

5 hours ago, new_castle_j said:

  I am running 6 volts and the coil I ordered from Pertronix was also for 6 volts.  I will double check it though, thank you for the reply!

Is it an oil filled coil mounted sideways? I had the identical problem shortly after I mounted a pertronix oil filled coil sideways on my firewall, switched to their epoxy filled coil and it went away.

[plyroadking]

Come to think of it, i also had similar symptoms when the choke cable housing clamp worked itself loose on the carburetor. Every time I accelerated it would choke itself. 

[48ply1stcar]

Have you checked the timing and ensuring that the timing is advancing properly as you accelerate.

Fuel flow.  I would call be an expert, but I live in Blaine and I've been putzing with this car for the past twenty years.http://p15-d24.com/applications/core/interface/file/attachment.php?id=62263

 

[dpollo]

All of the above offer good advice. 

 Coil or condenser would be my first culprits to check followed by the flexible fuel hose to the pump.

[Plymouthy Adams]

This not an attack of any manner on the person asking for advice.  However in the very first response to a suggestion it is only then we have any information about changes in a vehicle from stock condition.  Without this pertinent information supplied in the beforehand, how can anyone truly make a call.  Changes as simple as 6 to 12 volt change all responses for the most part, the changing to the Pertronix is another twist in the mix that plays greatly in the making of a diagnosis.  ONLY when these facts are pointed out to the forum population can the forum respond with likely valid scenarios.  Any changes in the fuel or electrical systems of this engine needs be made known up front at this time to give the tech heads a valid starting point.  Please describe any changes made to your car that you are aware of, they are very important when trying to troubleshoot.  Thanks..it will benefit you greatly

[Dave72dt]

The other part of PA's response is describing what you have already done, in detail as far as testing and trouble shooting and the results of those tests..  Fuel pressure and volume test? Full Pertonix system or just the coil?  Is the coil matched to the system?  Vacuum leaks?  Advance working properly?  There's probably at least a half dozen flat head owners in the Twin Cities area that may be able to give you a personal look-see and offer a hand solving your problem.  Check the members map, send them a PM

[new_castle_j]

There have been some very good suggestions made so far, thank you for all the replies!  I will be looking into them.

I will do my best to describe the vehicle's changes from stock condition, I was reluctant to do so in the beginning because in the past I have incited much disapproval for attempting to ask for help on something that was not all original.  My previous experience was not on this forum so we'll see how it goes.

The car has 6volt positive ground with a generator and regulator.  The Distributor is a IAT 4102 from a 1953 Chrysler Windsor.  The original distributor shaft was transplanted into the IAT 4102 housing so that it would fit in the engine.  The distributor was calibrated on a SUN tester and set for the curve of a 1936 Plymouth.  The points were replaced with the Pertronix ignitor and also the flamethrower coil from pertronix.  The road draft tube was removed and replaced with a PCV system from military surplus. It has a rebult fuel pump with modern diaphragm material.  I am running non-oxygenated gas in the tank.  It has a Fish carburator which also means that there's no choke.  

I have attempted to check the timing with a timing gun, but never succeeded in making sense out of the readings, to me it appeared that at idle the timing would jump all over the place, even though the car was running fine and had snappy throttle response.  So we just set the timing farmer style, drove around the neighborhood with the hood off and fiddled with it until we were satisfied.  Anyways, I'm very pleased with the car's performance when it's cold, after 15 minutes though it won't rev, loses power, cuts out, and will backfire if you're not gentle.  Pictures attached for additional reference.

Thank you everyone!

[keithb7]

Sorry to hear of your car troubles. I hope we can help you solve them. It is frustrating at times trying to solve car trouble. I find internet forms good mostly, but sometimes you can be led all over the place by various suggestions. Sometimes people don't read all the posts and get off track. 

Your comment about the timing light exercise is interesting. The timing appeared to be jumping all over the place at idle. That might be a clue. Is this not the sign of a worn distrutor? Plates, shaft, bushings? Is vacuum advance working as it should? Weird how things appear fine cold though. 

Loses power, backfires, won't rev up when hot. Hmm. Sure sounds like ignition. 

Have you done a compression test just to give us a baseline on  engine health? 

[keithb7]

1 hour ago, keithb7 said:

Double Post

 

Edited June 18, 2017 by keithb7

[dpollo]

Is that nice braided fuel hose as good as it looks ?  I recently had one which was collapsing internally .

A lean mixture will cause backfiring too.  

 The IAT distributor is a good choice in my opinion, but it does not always have a grounding jumper wire to the points plate as the IGS does.   There is also the flexible lead from the points to the distributor terminal but this would cause trouble hot or cold.

[Dave72dt]

I had one of those Fish carbs once, long ago.  I found it to be difficult to fine tune and make the engine happy from one season to the next.   Has the engine ever run properly since you've owned it?  If yes, did it gradually get worse or all of a sudden?  Did you make some change to it just before it changed?

[JerseyHarold]

If your Pertronix ignition has a separate 'box', try putting a plastic bag with ice cubes on it when it acts up.  If the troubles go away with a cooled-off control box, that's where your problem lies.

[DLK]

When you do get a solution please post it here.  I was frustrated a couple years ago with similar problems.  With a rebuilt engine my Wayfarer had little power when warm - it had less pep than before the badly needed complete rebuild - slowing down on even moderate hills at full throttle.  In my case there were two issues - the vacuum advance was not working properly and the spark plug wires were old and shorting out.  Making those two changes solved my problems.

[Merle Coggins]

You mention a PCV system has been installed on the engine, but has the carburetor been rejetted accordingly? The PCV is a controlled vacuum leak which will change the air fuel mixture, and could create the lean condition, and backfires, that you refer to. 

Edited June 19, 2017 by Merle Coggins

[new_castle_j]

Hello Everyone,

I am pleased to be reporting back that my car troubles have been solved!  I am so happy with how my engine runs now, hot or cold it's a pleasure to drive.  I ran into a very knowledgeable gentleman at a car show (Jeff).  I explained my symptoms and he instantly diagnosed, didn't even have to see the car. Recall in my earlier post that I had attempted to check the timing with a timing light and never got any sensible readings.  This is because I was using the Pertronix ignitor, In addition to the Pertronix sensing the magnet wheel that gets installed on the distributor shaft, it also picks up interference from the EMF that is put out by the spark plug wires.  All that "noise" sets the Pertronix off at random times, indeed that was what I was seeing with the timing light!  I brought my distributor to Jeff at advanceddistributors.com and he re-built it and installed a set of iginiton points, he also re-curved it to be compatible with modern fuel.  My initial timing is now set to 14 degrees BTDC as he suggested.

The difference was dramatic, the car starts almost instantly now, previously I had to crank for 10 - 15 seconds to get it running,  The engine revs much quicker and the car will sustain 50 - 60 mph.  I can let the clutch out from a stop at idle and not kill the engine.  I've had this car for 7 years, and it's like I'm driving it for the first time, I never knew that this was how it's supposed to feel, I had no prior experience with cars from this era.  I hope this post helps someone else!

[MackTheFinger]

Thanks for that update! My lil bro lives in Minneapolis! I'd have you wave at him if you see him on the road but he drives a Volvo XC90. It's generic enough it would be hard to find in a parking lot. 

[Don Coatney]

2 hours ago, new_castle_j said:

Hello Everyone,

My initial timing is now set to 14 degrees BTDC as he suggested.

 

14 degrees is a lot. Do you have any pinging or pre ignition?

[new_castle_j]

 That's a good question, if I do have pre-ignition, I wouldn't know how to tell.  I'm familiar with what pinging sounds like on a Toyota Corolla, don't know if that same sound translates to this engine.  I guess 14 degrees seems like a lot since it's right up to the end of the scale on the crank pulley.  What do you normally set the initial timing to?  Maybe I'll go half way between what you have and what I have and see what happens.

[Don Coatney]

What does your shop manual say? I assume you have a shop manual if not you should get one.

[Plymouthy Adams]

4 minutes ago, Don Coatney said:

What does your shop manual say? I assume you have a shop manual if not you should get one.

ah....shop manual is just the design engineers' idea of how things should work

[new_castle_j]

The manual I have says to set the initial timing at 4 degrees BTDC.  I'll probably play around with it (since that's somewhat why I own this car) and also try setting the carburetor again.  Since I had previously set the carburetor with a bad ignition system, I'm thinking that there's potential to tweak it again.