Bought My First Plymouth

[NoSaint]

I purchased a 1948 Special Deluxe convertible from an estate in Kentucky.  I wasn’t able to speak to anyone in the family but I did have a phone conversation with the neighbor.  The gentleman that owned the car for 30 years was a retired Air Force officer and had several old cars.  I had the car trailered to me in Texas.
It’s in great shape and has 71,000 original miles.  I’ve given it a tune up, replaced the plugs and wires, change the oil and gave her a good cleaning.  I have to say the forum was a great reference. I installed NGK plugs and put in straight 30 oil. A hot rod shop that’s close to my house told me I need to put an additive (zinc) in the oil.  Have any of you done this?  He also said I need to add a lead additive to the gas.  Thoughts?  

Edited May 26, 2021 by NoSaint
Add where I live

[knuckleharley]

I wish I had been smart enough to "start out at the top". It just doesn't get any prettier than a convertible.

 

"Yes", for the lead additive to the gasoline. Lead helps cool your valves.

[Marcel Backs]

Pure class act! That car looks really well sorted with a lot of hours spent getting it there. Welcome to the site which has some pretty well heeled flathead enthusiasts. M

[Sam Buchanan]

Castrol GTX 20W-50 has additional zinc and 87 octane ethanol-contaminated gas with no additives will work fine in your beautiful new ride. But the oil you are using will probably be fine, these are very low-tech engines.

 

Enjoy!

Edited May 26, 2021 by Sam Buchanan

[knuckleharley]

35 minutes ago, Sam Buchanan said:

Castrol GTX 20W-50 has additional zinc and 87 octane ethanol-contaminated gas with no additives will work fine in your beautiful new ride. But the oil you are using will probably be fine, these are very low-tech engines.

 

Enjoy!

Castrol 20w-50 is fine oil,but it is a high-detergent oil,and you can't just dump it in an old engine that has been using non-detergent oil and expect good things to happen.

 

What WILL happen is it will break free the sludge the non-detergent oil has allowed to build up in the base ban,the lifter area,and anywhere else it can build layers,and your oil pressure will drop to zero,and your oil galleries will be clogged with sludge. If you run an oil filter,it will feel like it weighs 100 lbs when you go to pull it out.

 

Yes,you CAN keep changine the oil and filter every day until you manage to flush away most of the sludge,but do you REALLY want all that trashy oil running through your bearings and oil pump?

 

If you want to run modern oils,which are certainly much better than the old non-detergent oils,the way to do it is to drop your base pan and clean it out to the point it is squeaky clean,and spray something like carb cleaner up into the the block to flush away as much of the old crap as you can get to.

 

It is a good idea to replace the front and rear oil seals while you have the oil pan off. Oftentimes,changing over to detergent oil will create front and rear main seal leaks.

 

Once you have done this,buy a case of the cheapest 30 wt high detergent oil that you can find and at least a half-dozen GOOD,high-quality oil filters. You are then prepared to run your engine while parked with your eye on the oil pressure guage,and the instant your oil pressure starts to drop,change the oil and filter. Repeat as necessary until your oil remains clean on your dipstick and your oil pressure remains steady.

 

This,of course,only applies to engines that haven't been rebuilt and switched to modern oils after the rebuild.

 

The word "Detergent" really means something when refeering to detergent oils. You will wonder how the damn thing managed to stay together with all that crap that was in it by the time you are through.

 

This all seems to apply x100 if your old engine used non-detergent Quaker State oil. I will physically hurt anyone I catch putting Quaker State oil in anything I own. I would rather have you spit in my face. I know this is irrational because the modern Quaker State detergent oils are PROBABLY ok even with all the wax in it,but don't care. 

 

 

Edited May 26, 2021 by knuckleharley

[Marcel Backs]

What would you guys suggest for oil in a rebuilt 218 for initial fire up and break in? I have always used SAE 30 non detergent oil but this thread has me wondering. Can synthetics be used after break in? I run Royal Purple synthetic in my small engines and my Tacoma as well as everything else for the past 30 years and never had any major issues with any engine. M

[BobT-47P15]

Nice looking car.   Welcome.  Here is a photo of an ad from the 1940s showing the different models of the Plymouth P15, including a yellow convertible.  

First---the entire pic, then closer in on the convert so you can read the comment.

 

 

 

Of course, I'm kinda prejudiced towards yellow.....

 

Edited May 26, 2021 by BobT-47P15

[BobT-47P15]

re: gas:  the original engines in these Plymouths have hardened valve seats from the factory.      I would suggest staying with the style of oil that was used

by the previous owner, if it is possible to tell.  Everyone has their oil of choice, therefore you get lots of opinions.....    The original  radiator uses a non-pressurized

cap.  Also the gas cap is vented to let in air.  Lots of grease zerks underneath the car.....twenty something as I recall.   Is your top still vacuum operated?   

The front grille guard and the fog/driving lights look good.  The electric system, if original, is 6 volt, positive ground.  

The windshield wiper bases are unique to the convertible and station wagon in 46--early 1949....and they use a slightly smaller size wiper motor than

the sedan models.    All kinds of fun things.

 

If your door sill rubber gets bad, there is a fellow who makes a nice looking reproduction item .... but it has to be glued in place.  

 

[knuckleharley]

8 hours ago, Marcel Backs said:

What would you guys suggest for oil in a rebuilt 218 for initial fire up and break in? I have always used SAE 30 non detergent oil but this thread has me wondering. Can synthetics be used after break in? I run Royal Purple synthetic in my small engines and my Tacoma as well as everything else for the past 30 years and never had any major issues with any engine. M

Use 30 wt non detergent oil for break-in. Switch to your favorite 30 wt /5w-30wt/10w-30 wt detergent oil after break-in. 

 

Non-detergent oil doesn't keep any "break-in trash"in suspension,but allows it to fall to the bottom of the oil pan so it can be drained away. A VERY minor worry,but why take the chance?

 

This isn't a problem with modern cars because they have much more effecient oil and filter systems.

[Sniper]

Lead additive is unneeded, the engine has hardened exhaust seats from the factory.  Lead was used as a cheap way to boost octane and was also a lubricant to an extent. 

 

As for a zinc additive, my research has lead me to understand that the issue is valve spring pressure, the higher the pressure the more an anti-scuff and anti-wear additive is needed.  We have virtually no spring pressure so I don't run it.

 

That all said, can you run those additives, well they won't hurt but it's real old school thinking that shows a lack of knowledge (need for lead additive) and misconceptions (need for more zinc).

[Marcel Backs]

Thanks for the advice. I can’t wait to fire the old codger up after the rebuild. Chrysler motors were pretty advanced for the time having hardened valve seats. M

[John Reddie]

Hello and welcome. Super looking car and a great color. You'll have great fun with it.

John R

[Booger]

9 hours ago, Sniper said:

Lead additive is unneeded, the engine has hardened exhaust seats from the factory.  Lead was used as a cheap way to boost octane and was also a lubricant to an extent. 

 

As for a zinc additive, my research has lead me to understand that the issue is valve spring pressure, the higher the pressure the more an anti-scuff and anti-wear additive is needed.  We have virtually no spring pressure so I don't run it.

 

That all said, can you run those additives, well they won't hurt but it's real old school thinking that shows a lack of knowledge (need for lead additive) and misconceptions (need for more zinc).

Cant help but agree with Sniper. No lead needed but no corn gas either. You should do fine with a dino 10w-30 oil. I also like the pan drop and remove any goo

[chrysler1941]

I still don't understand why would anyone use oil that has 10 or 20 weight as the lower viscosity during cold start. These engines are designed for 30W. 

[knuckleharley]

18 minutes ago, chrysler1941 said:

I still don't understand why would anyone use oil that has 10 or 20 weight as the lower viscosity during cold start. These engines are designed for 30W. 

It's simple. The thinner oil starts flowing and lubing the bearings quicker. Why would you think this is a bad thing,or even not desirable?

 

The cars were designed to use 30 wt non-detergent oil when they were new because it was the best oil they could get at that time. The modern oil starts out thinner and gets heavier/thicker as the engine warms. I can think of no set of circumstances where this would be less desirable.

[chrysler1941]

10 hours ago, knuckleharley said:

It's simple. The thinner oil starts flowing and lubing the bearings quicker. Why would you think this is a bad thing,or even not desirable?

 

The cars were designed to use 30 wt non-detergent oil when they were new because it was the best oil they could get at that time. The modern oil starts out thinner and gets heavier/thicker as the engine warms. I can think of no set of circumstances where this would be less desirable.

Agree modern oils start thinner and are superior, but ....cold start is what wears engines down. It's the first 10-15 min or so it's essential it receives correct lubrication for bearing etc. These need a friction film. Bearing tolerances are set after oil weight. Now we are only talking about cold start. Our engines need 30w when cold, anything thinner is metal rubbing against metal. 

They had other oil weight. Harley Davidsons from same era run only on 50W. That's how they are designed.

ours are for 30W

Edited May 27, 2021 by chrysler1941

[Sam Buchanan]

Why the assumption that modern oils have no friction film at 10W? If this was the case then modern engines would be starting with metal-to-metal contact since their clearances are much tighter than our old flatties. I realize tighter clearances create higher oil pressure, but still.......

 

Choice of oil, fuel, spark plugs and condensers are the never-ending debates based on personal bias, we'll never see a consensus. Fortunately our old (low-$$$$) engines are so under-stressed that we probably won't be able to abuse them enough under normal conditions to hurt them in our (remaining) lifetimes.  ?

Edited May 27, 2021 by Sam Buchanan

[61spit]

In the 1953 Plymouth Service Manual regarding Engine Oil Recommendations it says

Not lower than +32F use SAE 30

As low as +10F use SAE 20-W

As low as -10F use SAE 10-W

Below -10F Use SAE 5-W

 

So there would be recommended lubrication with a straight 10-W oil. Seems to me that a 10W-30 would be the best of both worlds.

[chrysler1941]

56 minutes ago, Sam Buchanan said:

Why the assumption that modern oils have no friction film at 10W? If this was the case then modern engines would be starting with metal-to-metal contact since their clearances are much tighter than our old flatties. I realize tighter clearances create higher oil pressure, but still.......

 

Choice of oil, fuel, spark plugs and condensers are the never-ending debates based on personal bias, we'll never see a consensus. Fortunately our old (low-$$$$) engines are so under-stressed that we probably won't be able to abuse them enough under normal conditions to hurt them in our (remaining) lifetimes.  ?

As I wrote earlier. engine's tolerances are made for specific oil weight. Some modern engine use 0-16W. These are made with very tight tolerances and require extremely thin oil to even pas through system. 

Lubricating an engine made for 30W when cold with 10 or 20W will wear due to low viscosity. It's all about passage and forcing a lubricating film on metal parts.

I don't how else to explain it otherwise. I know everybody has an opinion on these subjects you mentioned, and sorry if it collides with people beliefs. I'm just trying to explain the reason some engine require 0W, some 30 and others 50W as cold start weight. Stating it's because they didn't have other choices or didn't know better back then is simply wrong.

 

[chrysler1941]

4 minutes ago, 61spit said:

In the 1953 Plymouth Service Manual regarding Engine Oil Recommendations it says

Not lower than +32F use SAE 30

As low as +10F use SAE 20-W

As low as -10F use SAE 10-W

Below -10F Use SAE 5-W

 

So there would be recommended lubrication with a straight 10-W oil. Seems to me that a 10W-30 would be the best of both worlds.

If you use your car at -10 F, (-23C) yes most certainly i would use 10-30W but do we? ?

[Young Ed]

Also a lot of us have rebuilt engines. So were they rebuilt to 1940s tolerances or more modern specs. Personally I run 10w40 in all my stuff and have over 20k miles on my 48 coupe with no sign of a drop in oil pressure

[NoSaint]

On 5/26/2021 at 1:23 AM, BobT-47P15 said:

re: gas:  the original engines in these Plymouths have hardened valve seats from the factory.      I would suggest staying with the style of oil that was used

by the previous owner, if it is possible to tell.  Everyone has their oil of choice, therefore you get lots of opinions.....    The original  radiator uses a non-pressurized

cap.  Also the gas cap is vented to let in air.  Lots of grease zerks underneath the car.....twenty something as I recall.   Is your top still vacuum operated?   

The front grille guard and the fog/driving lights look good.  The electric system, if original, is 6 volt, positive ground.  

The windshield wiper bases are unique to the convertible and station wagon in 46--early 1949....and they use a slightly smaller size wiper motor than

the sedan models.    All kinds of fun things.

 

If your door sill rubber gets bad, there is a fellow who makes a nice looking reproduction item .... but it has to be glued in place.  

 

I do need some rubber door sills.  Can you send me his info

[NoSaint]

On 5/25/2021 at 9:16 PM, NoSaint said:

I purchased a 1948 Special Deluxe convertible from an estate in Kentucky.  I wasn’t able to speak to anyone in the family but I did have a phone conversation with the neighbor.  The gentleman that owned the car for 30 years was a retired Air Force officer and had several old cars.  I had the car trailered to me in Texas.
It’s in great shape and has 71,000 original miles.  I’ve given it a tune up, replaced the plugs and wires, change the oil and gave her a good cleaning.  I have to say the forum was a great reference. I installed NGK plugs and put in straight 30 oil. A hot rod shop that’s close to my house told me I need to put an additive (zinc) in the oil.  Have any of you done this?  He also said I need to add a lead additive to the gas.  Thoughts?  

The horn wire which runs through the steering column was broken.  I ran a jumper from the connection attached to the relay and horns work perfectly.  The question I have is regarding the broken wire coming out of the steering box.  Do I have to remove the four bolts and plate (on the box) to get that wire loose (out)?  

[Young Ed]

55 minutes ago, NoSaint said:

The horn wire which runs through the steering column was broken.  I ran a jumper from the connection attached to the relay and horns work perfectly.  The question I have is regarding the broken wire coming out of the steering box.  Do I have to remove the four bolts and plate (on the box) to get that wire loose (out)?  

No don't mess with the column itself. Pull the steering wheel and you can get it out that way. Then run a piece of stuff wire up from the bottom out the top to feed the new one back through

[Billy]

That is a beautiful Plymouth!