Rear Main Seals Replacement - revisted

[My49Plymouth]

Hi guys, I did a search and saw several posts discussing rear main seals but I still have some questions. I have a 49 P18 and have it apart to replace the rear main seal.

I purchased a rope seal kit as spec. for a 49 218 L6. After removing my rear cap I see I have a neoprene seal.

According to my Plymouth Service Manual 1946 to 1953, the neoprene seal is for the 1953 model. Rockauto.com still lists a rope seal for a 53 and a picture they show for a neoprene 55 Canadian does not look like my seal.

Another point of confusion - I saw posted in a previous post that a top half of a neoprene can't be replaced with the crank in place. My service manual states that the upper half "is easily removed.

My questions are - are the rope and neoprene interchangable? should I order a neoprene for a 1953 or should I try to use the rope seal I purchased (maybe the guy before put in the wrong seal?), and as the manual states can the top be replaced with the crank in place?

Also, I noticed that on the crank the edge of the rear main bearing thrust face is sharp / has burrs - so I will dress this.

Any help would be appreciated - thanks!

[busycoupe]

You may have seen my post about replacing the neoprene rear seal. I could not replace the top half of the seal with the motor in the car because there was not enough clearance to get a wrench in, and the bolts out. My car has fluid drive, so perhaps the flywheel is different than on your car. My engine is a P23 block, which I think is a '51 or '52 Plymouth block.

Just replacing the bottom half of the seal made a huge difference in how much oil my engine lost. .. Don't forget to replace the 2 little rubber pieces that press into the top of the bearing block.

Dave

[My49Plymouth]

Thanks Dave,

So as I understand it, your seal has 3 bolt holes.

My cap has 3 bolt holes (I did not chack the top half - will later) that were not used for the current seal. The seal that takes the 3 bolts is the one (or similar) that Rockauto.com shows for 1955 - 1959 L6's - they list them as Canadian built. On Rockauto.com I did not find a seal for late 40s to late 50's that looks like mine - could be that somebody used a different seal altogether.

I am trying to verify the engine year - but the pad where the stamp should be is blank.

I am still trying to figure out the best approach:

1. use a rope seal for a 49

2. order a newer neoprene (are the neoprene and rope interchangable?)

[Dodgeb4ya]

Just use the rubber 2 piece rear main seal as already is in your car. Push and roll out the upper 1/2 of the seal- carefully apply a very small amount (only in the seal groove) of permatex sealer in the groove of the seals. Wipe the rubber lip of each seal half with just a small amount of oil or gease for initial lubrication. Lip faces the oil (inside) side of the engine. Carefully roll the upper seal into place. Push the cap seal half into the cap. Replace the 2 rubber cap seals. Read the shop manual for more detailed instructions.

The rope type seal is easier done with the flywheel out or preferably the engine out of the car. The rope type seal is crimped into the 2 metal retianer plates that bolt to the block and main cap with 6 small 1/4 X 20 thread cap screws. The rope seal needs to be rolled and shaped to fit the crank- not too easy to do if you have never done one and don't want it to leak-especially with the crank and flywheel in the car! The rubber type is much easier. Cleanliness is a must too.

Your rear main thrust surface is down to copper and you say you need to do some de-burring ?

Thats not a normal thing to do. This Usually means signs of excessive thrust bearing wear. You need to check your crankshaft end play. Specs are in the shop manual.

[54Illinois]

(are the neoprene and rope interchangable?)/QUOTE]

I found this...hope your neck does not get sore.

[Dodgeb4ya]

Several people on this forum have installed the rubber 2 piece seal on 1952 and earlier engines. I have too. But there are a couple things to be done depending on the design and HyDrive ect. No need to go into that as you already have the rubber 2 piece. Your engine is probably a later engine-Is your engine the original engine and what is the number. Really it doesn't matter at this point if you stay with what you have and you should.

[My49Plymouth]

Several people on this forum have installed the rubber 2 piece seal on 1952 and earlier engines. I have too. But there are a couple things to be done depending on the design and HyDrive ect. No need to go into that as you already have the rubber 2 piece. Your engine is probably a later engine-Is your engine the original engine and what is the number. Really it doesn't matter at this point if you stay with what you have and you should.

Thanks 54 Illinois ... when I look at Fig 19 that looks like what I have now. However pics of the neoprene seal I have seen for sale do not look like this.

Dodgeb4ya ... assuming my block is a 49 - is it possible using a neoprine in place of the rope could cause an oil leak?

Next question is actual year of engine - my block does not have anything stamped on the pad at the typical location - what is the signifigance? Head does have a large P on it.

Thanks for the feedback guys.

[Frank Elder]

Thanks 54 Illinois ... when I look at Fig 19 that looks like what I have now. However pics of the neoprene seal I have seen for sale do not look like this.

Dodgeb4ya ... assuming my block is a 49 - is it possible using a neoprine in place of the rope could cause an oil leak?

Next question is actual year of engine - my block does not have anything stamped on the pad at the typical location - what is the signifigance? Head does have a large P on it.

Thanks for the feedback guys.

More than likely if your pad is blank the original motor has been replaced by a dealer or an aftermarket replacement. Example if it is painted green it is a Jasper motor and has an ID tag riveted to the block. Dealer blocks are supposed to be stamped with a serial # by the mech installing it for warranty purposes but that didn't always happen or the owner purchased the block from chrsler and installed it himself.

So sometimes the pad is blank.....your engine could be any year, it could have been made 3 years before the car was built or made in 58, or later.

I would say something about the "infamous" P head but it might stir things up!:D:eek:

[Niel Hoback]

There should be a casting date below the distributor. It will give you an idea when it was made, but it may have seasoned for a year or more before it was used.

[My49Plymouth]

There should be a casting date below the distributor. It will give you an idea when it was made, but it may have seasoned for a year or more before it was used.

Thanks Frankie.

Thanks Niel - there is "1946 2EC" forged into the block to the right of the distributor.

I have seen posted elsewhere on here on how to measure stroke - I will probably do this to verify that I have a 218.

Dodgeb4ya - on the crank - it is actually the very edge where the circumference is narrow - it is chipped up a bit - perhaps from being roughly handled while out of the car at some point in its past life.

[Frank Elder]

3 years older than your car:)

[Jerry Roberts]

My 1939 engine had the rope seal and when the machine shop rebuilt it , they put in a neoprene seal . The guy said that some machining was necessary for the swap .