50 Plymouth (New to me) have a couple of questions

[LowMasters]

New member here. Name is Bryan, I am in no way new to cars.... but definitely new to the flathead 6. We bought a 1950 Plymouth yesterday for my wife for Christmas that needs a little work so I am in need of some advice. Previous owner had done a ton of work to her but she has some quirks we need to work out. 

 

The car has a constant hesitation feeling while driving. All 3 gears, low to high RPMs if feels as though it has a slight miss/ hesitation. Car has plenty of power to pull itself around so here is my questions. 

1. Which plugs do you guys recommend and what gap? (Currently has Champions in her)

2. Going to replace points (gap)?

3. Last. is there a good carb upgrade (if I find the hesitation is carb related)?

[P15-D24]

First, replace that battery hold down strap with a proper one. It is a dead short waiting to happen.

I prefer AC or Autolite plugs. 

Make sure the ignition is set up correctly,.including the vac and mechanical advances working. If you still have an issue rebuild the carb. Stock will work fine if it is in proper working condition. 

I'm sure someone else will chime in with the spec for points and plugs.

[Sam Buchanan]

How has that battery hold down not shorted already?? Time to toss those 12v battery cables and get some properly sized 6v cables. And....that battery cut-off is too small for a 6v system....don't need it anyway.

 

Nice looking car....it'll be a nice ride, enjoy!   

[Andydodge]

Welcome aboard from Oz.........Points gap is 20 thou, plug gap is 28 to 32 thou.........I'd recommend getting a workshop manual and also a parts manual if possible, paper versions and read both cover to cover..........that battery hold down as P15-D24 has mentioned is NOT good, at the very least I'd trim  or grind it away from the battery post and clamp.........and 6volt cables are much thicker than 12 volt cables.......as for carby parts try www.oldmoparts.com .Andy Bernbaums..............and at least install a new fuel filter......suggest you only do one thing at a time as doing multiple things can sometimes confuse the issue......lol.......we've all done this..........lol..............regards, Andy Douglas    

Edited December 26, 2019 by Andydodge

[Sniper]

Rock Auto sells the proper sized cables and the carb kit too.  Get the carb number off the air horn to verify but it should be a Carter BB and the Walker 15021B kit will work.  RA doesn't list it for a 50, but Walker does.

[Sam Buchanan]

An excellent source for proper battery cables which will improve starter performance:

 

https://www.batterycablesusa.com/1-0-gauge-battery-cables-0-awg.html

 

Here is what they look like:

 

[LowMasters]

I appreciate all the help so far. Yes I am aware of the battery hold down and cables. I have already ordered the factory style hold down, and Sam that you for the link for the cables as I just ordered those as well. 

[keithb7]

@LowMasters where abouts in the world are you located? Tell us a little about your background on working on old cars. How's your tool inventory and mechanical theory? There are many . here who will help and guide you. There are no dumb questions. 2.5 years ago I was in the exact same spot as you. I bought a new to me old Chrysler and I had only a few inklings on how everything worked. There are 10 inklings in a clue. So that gives you an idea. 

 

In terms of a miss in the engine, it could really be many things. In my opinion it is best to take some baseline measurements and develop a plan from there.  If the car is new to you, and you want reliability for your wife to drive it,  there are many things that you should do.

A few things have been mentioned, such as upping the battery cables. In the photos, the majority of cables appear to be 12V size. Which is inadequate.

Once you have a good cables, clean grounds and a good known strong battery I'd proceed to perform a compression test. Wet and dry. This may reveal valve seat issues, or maybe a cylinder with low compression. Fuel pump and carb are certainly candidates too. Old rubber parts break down and crumble over time. Especially due to additives in todays fuel. 

Again, considering you may want a reliable driver for your wife, I'd go with new spark plugs. Condenser. Cap. Rotor. Points and set. New sparkplug/coil wires. A 6V coil is not expensive, if you have no idea how old it is, I'd replace that too. In my opinion you're not throwing parts at the car here and hoping you fix it. These new parts are giving you peace of mind when your wife takes it out for a drive. These are common wearing tune up parts. With these ignition system parts replaced you'll want to set the timing. Checking mechanical and vacuum advance is a good idea. A timing light will show the spark advancing when you blip the throttle, indicating it's at least advancing.

 

After the compression test is complete review readings and make an assessment. A vacuum test would be very helpful too. See here: https://www.classiccarrestorationclub.com/article/engine-vacuum-troubleshooting/#

 

Depending on the compression test results, you may then want to proceed with a proper valve set. A valve that is set too tight will cause an engine miss. Valves normally wear and tighten up as they wear. So a valve set it part of a tune up. The carb would certainly be coming off if the previous history is unknown. You may find sediment in the bowl. There are many, many orifices in the carb that can plug up and lead to problems.  How about fuel pump pressure? Is it adequate?  Does the engine miss all the time, or mainly after it is fully warmed up? Only at certain ambient air temps? How's that choke? Is it opening fully when the car is hot?

 

Lots has been mentioned here. Just go slow, one at a time and ask lots of questions.You can do plenty to ensure the car is safe and reliable. Many of us here love diving into the mechanics of these old cars. These tasks are more like fun jobs.

 

Keith

 

 

[tom'sB2B]

Welcome

Very nice car.

Buy a shop manual on eBay

Get familiar with the search option on this forum. You will find answers to every question you have and to problems you haven't imaged yet. It's an amazing wealth of knowledge.

 

Good luck

Look forward to following your progress.

[LowMasters]

Keith, I am located in a small town in Washington called "Belfair". I am 43 years old and started working on cars as an early teen with my father. Tools aren't an issue... I am fortunate in that area. I manage a custom exhaust shop/ and full blown mechanic shop. I also build from home. I am currently replacing the full floor in a 1961 Chevy Belair (full Kustom). I have done all of the work from the 59' Imperial grill and headlight bezel conversion, frenched antennas, shaved handles, inner rockers, floor braces, full floor, and currently a 1960 Impala dash swap. I also own a 1986 Chevy C10 with a built SBC, and full air ride installed by myself. 

I am not new to mechanics or electrical in any way but from everything I have learned in life I do know is that to ask the ones who know the vehicles well as regardless of how good you may think you are, there is always something new to learn. I am also not a guy who jumps to the cheap route out of the gate. I like to do things right the first time 

 

As for the car... this is what I know due to the verification of paperwork that was with the car. The previous owner bough the car while the engine sat under a tree outside. This car has had a full rebuild on the motor (less then 500 miles on rebuild), brakes, radiator reconditioned, battery is now 4 days old, clutch, and just about everything in between. Gas tank was pulled, cleaned, sealed, along with new fuel line and fuel filter. He original "Thought" the miss was bad gas from sitting. I now know that this is not the case. All the tune up is recent, I am just one of those guys that always does a tune up when I buy something new hence the questions above.  

[keithb7]

@LowMastersWelcome to the forum. Great to have another member who's into the wrenches

 

With less than 500 miles on the engine rebuild, did it sit for a long time after the engine was rebuilt? Did you include a new condenser with the recent tune up?

Compression test and valve set would still be high on my list. Just so I know for sure. 

[LowMasters]

12 minutes ago, keithb7 said:

@LowMastersWelcome to the forum. Great to have another member who's into the wrenches

 

With less than 500 miles on the engine rebuild, did it sit for a long time after the engine was rebuilt? Did you include a new condenser with the recent tune up?

Compression test and valve set would still be high on my list. Just so I know for sure. 

I have yet to do any work until this weekend. Plan is plugs, cap, rotor, points, and condenser. I will so a compression test as well while I am in there. 

 

I wouldn't say the car sat for a long time. They drove it weekly to the store, however, that was only about 5 minutes from their house. The first "drive" this car really did was when we brought it home which was about an hour at around 50 mph.

[keithb7]

While you are in there, closely inspect the wire to the points. The area where the wire enters the distributor especially. Ensure the isolation pieces are in place. Inspect it closely and right up to the coil.

[dpollo]

sounds like you have covered nearly all the bases    check the float level in the carb and the accelerator pump.  The "almost" stumbling could be as simple as a too lean mixture.   a quick test would be to contrive to close the choke just a little .... say with a bit of wire..... and see if the engine runs better.

 

If the engine has been rebored, the increased displacement could be demanding just a little more fuel.   The accelerator pump can be enriched by moving the link to the outermost hole on the lever. also, the jet may need cleaning... a welding tip cleaner will work.... remove the tapered soft plug which is just below the lid on the engine side. A pair of diagonal wire cutters can be used to tease it out of its hole.   If your engine is not broken in yet, it will continue to improve with use, up to about 2500 miles.  Re tighten the head bolts soon.  65 to 70 ft lbs   .  start with the bolt in the middle between 3 and 4 .  a tightening sequence can be found in the shop manual or in a Motors manual.

 

I got my first 50 in 1965 and have never been without one.

Edited December 27, 2019 by dpollo
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[9 foot box]

   Hey LowMasters,   To reply to the first post, I would run Autolite 295's, at .028" with solid core plug wire. Any variance in gap and plug type causes problems. A resistor plug is set at .035". Champion's have failed me in the past. 

[Dodgeed]

Great looking car you've got there. ?

[LowMasters]

Another question for you guys. Every gauge in the car works except the temp gauge. What am I looking at here for diagnostic?

[TodFitch]

1 hour ago, LowMasters said:

Another question for you guys. Every gauge in the car works except the temp gauge. What am I looking at here for diagnostic?

Inspection first. I think they were still using the “mechanical” temp gauge on your car. See if the capillary tube has been damaged.

 

The way it works is there is a bulb filled with ether in the head. As the engine warms up the ether tries to evaporate and in doing so builds up pressure in the capillary tube. The dash unit is basically a pressure gauge.

[Young Ed]

8 hours ago, TodFitch said:

Inspection first. I think they were still using the “mechanical” temp gauge on your car. See if the capillary tube has been damaged.

 

The way it works is there is a bulb filled with ether in the head. As the engine warms up the ether tries to evaporate and in doing so builds up pressure in the capillary tube. The dash unit is basically a pressure gauge.

Yes they still had the direct connection gauge. I don't think they switched to electric until 55. 

[Dartgame]

If the ignition work does not improve the performance, look at adjusting the valve lash. I suggest finding NGK equivalent plugs for your champions. I've had extremely bad luck with champions. Also trying setting the base timing at someplace between 5 and 10 Degrees advanced. Watch out for pinging, and reduce base timing as needed. 

[greg g]

In order to get proper tune up parts, cap, rotor, points, condenser, you need to order by distributor number.  This is found on the tag one the distributor body.  Esaiest way to get it is to pull the dist from the engine. This is the easiest way to service it anyway.  Trying to replace the points and gap them in the car is a pain in the butt.

 

Pull the cap and mark the rotor position relative to the body and mark the vacuum advance relative to the block.  Then remove the hold down bolt, disconnect the wire from the coil and lift it out.

 

The number for parts will begin with three letters, igs, iat, etc are typical and they dictate the parts needed.

 

Two trouble areas in the distributor which can cause miss fires are the insulator where the coil wire enters the body, and the thin flexible wire connecting the points.  Both can loose insulation and ground to the body, not good.  The thin wire also moves with the breaker plate many times per drive.  It can look fine but may have broken strands inside the insullation.  Napa usually has replacements. Don't try to replace it with wire from a spool, it's not flexible enough to allow proper movement of the breaker plate.  Once that inspection is done Chuck the distributor in a vice and replace the points and condenser and adjust the gap.  A caution on points, most modern ones are junk, try to get them from Napa, quality care or car quest.  The ones from advance Auto zone have weak springs, soft cam blocks, no lube wicks etc.

[plymouthcranbrook]

Here is a thread I posted on AACA  site regarding carbureration for Mopar flatheads:

 

https://forums.aaca.org/topic/334923-carter-yf-carburetor/

[Ranger]

Beautiful car. Have fun.