P-15 Engine Bay Details

[47 Coupe Tom]

Hi all - Still sorting through my 47 Club Coupe details/ I did get a new battery, but of course the only cables available locally are relatively light duty 12v ones. I now have a correct braided ground strap and have ordered a proper 0 gauge battery negative cable. Can anyone tell me the correct OEM attachment point for the braided ground strap? And what is the proper routing for the black/negative cable to the starting solenoid? I have my current ground going to the generator adjusting bracket because it was convenient  - but I suspect it should probably be a cylinder head nut or some such? Is he negative cable suppose to tuck under the inner fender flange then head South to join up with the solenoid? I see some cable routing clips on the inner fender but would like to know what's correct. Thanks (again) Tom

[greg g]

Your car is positive ground. The braided strap usually  goes to one of the generator bracket bolts.  If it is still there one of thr bolts will have a threaded portion above the bolt head to accept the strap and a washer and nut.  The negative cable goes to the starter solenoid on the terminal facing the radiator support.

 

Also check your coil connections,  the wire to the distributor should be connected to the pos terminal, with negative connected to the wire from the ignition switch.  As a further enhancement to the cars electrical items, a second  ground strap should be connected between a bolt on the  firewallto the engine frame or bell housing.  The key to 6v systems is having the least resistance in the circuits.  Clean tight connections and clean tight connections are necessary to proper functions. 

[chrysler1941]

 Let's not keep repeating the same mistakes of others.

 

Mopar never used braided ground straps in 1947 or even later. They used cable.

Ground cable connected to generator bracket stud, Never on a head bolt that connects through  water jacket. Chrysler had some the best engineers, they would never make such a mistake.

 

Attached Plymouth part list showing ground cable. Also list showing detailed stud and bolt for ground. And a photo showing stud.

[Young Ed]

20 minutes ago, chrysler1941 said:

 Let's not keep repeating the same mistakes of others.

 

Mopar never used braided ground straps in 1947 or even later. They used cable.

Ground cable connected to generator bracket stud, Never on a head bolt that connects through  water jacket. Chrysler had some the best engineers, they would never make such a mistake.

 

 

I believe in the 50s they switched to a special headbolt that was threaded for a smaller bolt to hold the positive cable. 

[47 Coupe Tom]

WOW! I love this forum. Thank you all for this valuable info. It occurs to me I am a long way from worrying about concourse correctness, but I hate to buy parts twice and do work twice if I can avoid it. My color-coded wiring diagram should arrive today in the mail. I do see a yellow wire from the + coil connection to the distributor. I have new plugs, wires, cap, rotor, etc. just waiting for me to show them some love. I also ordered a Pertronix ignition (6V + Ground) and have that now. I have used their system for years on many vintage  cars and have been extremely happy with them.  There are no external wires or ignition boxes, it all hides under the dizzy cap.

 

chrysler1941 - I am guessing this should be "0" gauge ground cable - and should it be a vinyl-wrap cable or cloth? Are the cable color-coded red/black? And would my newly-acquired  braided cable be correct if it were used as a secondary ground as suggested by Greg G?

 

I will look for that generator bracket attachment point today. Unfortunately the coupe is in a storage unit - but only about a mile from my house. I need a bigger toy box at home. 

[chrysler1941]

10 hours ago, Young Ed said:

I believe in the 50s they switched to a special headbolt that was threaded for a smaller bolt to hold the positive cable. 

Please prove it. As mentioned, head bolt through water and sealant on threads makes a poor ground.

A couple of my head bolts are also threaded but for air cleaner bracket, vacuum tube clips and throttle bracket.

Edited July 15, 2021 by chrysler1941

[chrysler1941]

10 hours ago, 47 Coupe Tom said:

WOW! I love this forum. Thank you all for this valuable info. It occurs to me I am a long way from worrying about concourse correctness, but I hate to buy parts twice and do work twice if I can avoid it. My color-coded wiring diagram should arrive today in the mail. I do see a yellow wire from the + coil connection to the distributor. I have new plugs, wires, cap, rotor, etc. just waiting for me to show them some love. I also ordered a Pertronix ignition (6V + Ground) and have that now. I have used their system for years on many vintage  cars and have been extremely happy with them.  There are no external wires or ignition boxes, it all hides under the dizzy cap.

 

chrysler1941 - I am guessing this should be "0" gauge ground cable - and should it be a vinyl-wrap cable or cloth? Are the cable color-coded red/black? And would my newly-acquired  braided cable be correct if it were used as a secondary ground as suggested by Greg G?

 

I will look for that generator bracket attachment point today. Unfortunately the coupe is in a storage unit - but only about a mile from my house. I need a bigger toy box at home. 

So 0 gauge is 55 mm² is like the original. Battery cables on Chryslers where cloth braided, so I presume Plymouth too. 

 

Secondary ground is good idea, you can never have enough ground connection.   So from battery to stud as mentioned above. from stud to frame. Also two hidden on starter bolt and Transmission.

 

Just as a info, 1941 Chrysler was first model to use vinyl wrapping on engine bay wiring.

[Plymouthy Adams]

29 minutes ago, chrysler1941 said:

Please prove it. As mentioned, head bolt through water and sealant on threads makes a poor ground.

Well Mo......things changed over the years and not sure the cut off date on your books but in the 1946-54 Plymouth repair manual there is a a picture, Fig 41  Points to check for easy starting,  page 158 that distinctly shows the ground cable from the battery to the bolt on top the head.  Now we must consider at this time that even if the bolt is into the water jacket and maybe the builder did use sealant...the contact patch of bolt bottom of the special bolt to that of the head itself is sufficient.  My 54 has this special bolt, think it is number two (see update below) bolt back from front of engine along the generator edge of the head.  

 

 

 

UPDATE..................I just sourced the very pictures of my original low mileage 54 and the the first bolt at front is the location of the special head bolt that is drilled and tapped for the battery cable....

Edited July 15, 2021 by Plymouthy Adams

[61spit]

Here are a couple of period photos. Hopefully the battery ground connection can be seen in them. One is from the Vol. 6 No. 4 Service Reference Book put out by Chrysler and the other is from a Fall 1954 How To - magazine article on how to hop up your Plymouth. I don't know if this is proof of the head bolt ground but it sure seems to show that is where it was in 1953-54.

[chrysler1941]

9 hours ago, Plymouthy Adams said:

Well Mo......things changed over the years and not sure the cut off date on your books but in the 1946-54 Plymouth repair manual there is a a picture, Fig 41  Points to check for easy starting,  page 158 that distinctly shows the ground cable from the battery to the bolt on top the head.  Now we must consider at this time that even if the bolt is into the water jacket and maybe the builder did use sealant...the contact patch of but bottom of the special bolt to that of the head itself is sufficient.  My 54 has this special bolt, think it is number two bolt back from front of engine along the generator edge of the head.  

Don't have Plymouth manual for these dates. 

 

61spit first picture is useless but second shows there was a special bolt for ground cable. Thanks We learn very day. 

 

But OP car from 47 and a 48 Dodge I worked on did not have this special bolt- Would be interesting to see what year they moved ground to head.

[chrysler1941]

Alright think I found the answer.

 

Viewing 1947 The Case Of The Lazy Gas Thief film strip, shows a Plymouth. I have no idea what year it is but experts here will know. ground cable clearly goes downwards.

 

I will speculate when they changed thermostat housing type. Older had bulky forged ones. What year was that?

Edited July 15, 2021 by chrysler1941

[Kilgore47]

The ground on the block of my 1947 P15 is on a stud just below the generator bracket.  But my car does not have the original engine.  The PO told me that the engine was replaced in the mid 70's when they puled it out of a field and put it back on the road.

[Plymouthy Adams]

I am not sure when this started....I tend to recall my 51/52 has the cable on the head but I will not make that statement as an affirmative.  I can state that my 47 Dodge Town Sedan which is another good example of originality has the ground cable as you indicate in your pictures...no special bolt on head at front of engine.

[greg g]

The wide belt for the generator suggests pre 49.

Edited July 15, 2021 by greg g

[chrysler1941]

9 hours ago, Kilgore47 said:

The ground on the block of my 1947 P15 is on a stud just below the generator bracket.  But my car does not have the original engine.  The PO told me that the engine was replaced in the mid 70's when they puled it out of a field and put it back on the road.

That's even a better ground, directly on block. Upgrade

[chrysler1941]

9 hours ago, greg g said:

The wide belt for the generator suggests pre 49.

Cool. Will a dashboard photo help identify year more precise?

[allbizz49]

Both, my 49 and 53 are grounded to the head. So unless two different people from two different states bought the exact same head bolt with a threaded hole and installed them in the exact same location, Young Eds point is proven.

[ccudahy]

I believe my engine is original to my '47 Plymouth it has a P15 stamped in the serial number and a 9/17/47 cast into the block. My engine has the ground to the special stud that holds that holds the generator bracket to the engine, like @chrysler1941 has info for. This is the best picture I have right now.

 

[chrysler1941]

9 hours ago, allbizz49 said:

Both, my 49 and 53 are grounded to the head. So unless two different people from two different states bought the exact same head bolt with a threaded hole and installed them in the exact same location, Young Eds point is proven.

Mitchell catalog (not official) has new type thermostat housing starting in 49. Yes Young Ed's point was proven by 61spit. ? 

[desoto1939]

I just looked in my 36-42 Desoto Master parts book they show that they did use 4 cylinder head screws that had the tapped head and 18 bolt head screws on the cylinder head starting in 1939 thry 42 according to my catalog.

 

 

Rich Hartung

desoto1939@aol.com

[chrysler1941]

9 hours ago, desoto1939 said:

I just looked in my 36-42 Desoto Master parts book they show that they did use 4 cylinder head screws that had the tapped head and 18 bolt head screws on the cylinder head starting in 1939 thry 42 according to my catalog.

 

 

Rich Hartung

desoto1939@aol.com

Same with mine. 2 for throttle bracket. One for air cleaner bracket and one for vacuum tube clip

[JBNeal]

additional information - flathead starter performance minor upgrade

[greg g]

The new type Stat housing doesn't hold water either.  I have seen 36 engines set up for internal bypass and external with the cast housing and short hose.  My 56 230 as well as my 46 engine are both internal bypass with the sheet metal housing.