rear main seal

[DJK]

Has anyone installed a rubber rear main seal instead of the rope seal? The slinger section of the crank would need to be machined off as I understand. 

[busycoupe]

The rubber seal bolts to the back of the block.  An engine made to use a rope seal may not have the tapped holes necessary to attach the rubber seal. ... something to check.

[DJK]

My engine has the tapped holes to mount the rope seal retainers that look identical to the rubber seal retainers. Check Best Gaskets website, it shows both type of seals.

[DJK]

This is what I found from Best Gaskets: The Best 4164 seal set can be used to replace the original rope seal and retainers on most of the earlier engines if the crankshaft seal journal (2.650 in) is the correct size to match the 4164 seal. This was a common practice to do this. Some engines that were made for the Best 4164 seal set can use the Best 3675 seal set if the crankshaft does not have the cast in oil slinger and if the square ledge in the engine block and cap is correctly machined to accept the Best 3675 seal. Most engines that were made to use the Best 3675 seal may still have the bolt holes in the engine block and main bearing cap for the seal retainer. These may or may not be threaded. I had one customer who ground the oil slinger off the crankshaft in an earlier block that used a rope seal and installed the Best 3675 seal set and it didn’t leak. It all depends upon the engine design and the machining quality in the rear main seal area on what can be used. 

Just hoping someone has done this before with success.

Bob Marx was a big help @ marxparts.com

[Dartgame]

I installed a best seal neoprene lip style used in the later cars in my 52. Works great. Does away with the rope seal and the external rubber seal. You will need to plug the rough casting holes in the main cap. I used JB weld after a careful cleaning job. The threaded holes for the external rubber seal were blind (close ended) in my case, probably yours too, I left them out. Back off the other main caps to get some clearance for the upper half of the rear main seal to slide in, I used a little permatex #2 in the groove for lubricity when sliding in the seal. No leaks. There was no need to machine anything in my case.

Edited January 28, 2021 by Dartgame

[DJK]

4 hours ago, Dartgame said:

I installed a best seal neoprene lip style used in the later cars in my 52. Works great. Does away with the rope seal and the external rubber seal. You will need to plug the rough casting holes in the main cap. I used JB weld after a careful cleaning job. The threaded holes for the external rubber seal were blind (close ended) in my case, probably yours too, I left them out. Back off the other main caps to get some clearance for the upper half of the rear main seal to slide in, I used a little permatex #2 in the groove for lubricity when sliding in the seal. No leaks. There was no need to machine anything in my case.

My engine is at the machine shop and I can't visualize what it looks like. To be clear, you used the Best 3675 seal with no modifications. Thank you for the reply.

[Dartgame]

Correct, #3675 no modifications made to anything except the rear main cap. In my case, the rear main cap had some rather large ~ 1/2" diameter holes in it. These were some part of the normal casting process for my engine (218 US production) and if left unplugged would cause a huge oil leak. They might be for an oil drain back from the external rubber seal area, not sure. Your engine may not have these, but if so they are easily identified. 

 

What I meant when I said I left them out were the small bolts used for the original external seal. The best gasket people advised to install the seal halves dry where they butt up and meet, and no additional sealant anywhere else. I used permatex #2 because I did this while the engine was in the car and my crank was in the block. I needed something sort of slick to help slide in the upper half of the seal. The new seal fits in where the rope seal was originally as I recall. In addition the groove for the seal was not perfectly smooth, it was sort of rough, but the seal still fit and works great.

Edited January 29, 2021 by Dartgame

[James_Douglas]

23 hours ago, DJK said:

This is what I found from Best Gaskets: The Best 4164 seal set can be used to replace the original rope seal and retainers on most of the earlier engines if the crankshaft seal journal (2.650 in) is the correct size to match the 4164 seal. This was a common practice to do this. Some engines that were made for the Best 4164 seal set can use the Best 3675 seal set if the crankshaft does not have the cast in oil slinger and if the square ledge in the engine block and cap is correctly machined to accept the Best 3675 seal. Most engines that were made to use the Best 3675 seal may still have the bolt holes in the engine block and main bearing cap for the seal retainer. These may or may not be threaded. I had one customer who ground the oil slinger off the crankshaft in an earlier block that used a rope seal and installed the Best 3675 seal set and it didn’t leak. It all depends upon the engine design and the machining quality in the rear main seal area on what can be used. 

Just hoping someone has done this before with success.

Bob Marx was a big help @ marxparts.com

I have had nothing but trouble with the Best 3675 seal. We have tried changing it three times. I did it twice and I had a 80 year old master mechanic that works on antique cars try it. It still leaks way too much. The crankshaft in question was NOS and check (straightened and polished and balanced) so the diameter of the seal surface was spot on.

 

I have asked Best on several occasions what is the minimum shaft size and the maximum shaft size for that seal. The refuse to answer.

 

On my other engine, that was a 1963 Automotive Engineering swap rebuild the rear does not leak at all, which for a flathead is something.  That engine sat from 1967 to about 2013.  It has a rope seal in it.

 

My next engine, I will use a rope seal due to its larger surface area on the crankshaft and in my opinion a better ability to deal with distortions. The modern fine lip seals do not like it if the shaft moves at all in the block. Note that Chrysler changed the real main bearings due to stress issues when they went to torque converter. They were having issues. As the load goes up on these engines with them making more power...it is possible that the rear is moving just enough to cause issues with the micro fine lip on the 3675. In my case with a 5000 pound car...that is a real possibility.  Sometimes new technology is too sensitive to be used on old technology.

 

I have an NOS  factory (Victor) seal for a flathead. The design is totally different at the lip. Much more surface area and the rubber has an vulcanized material embedded in it.

 

James.

 

[DJK]

7 hours ago, James_Douglas said:

I have had nothing but trouble with the Best 3675 seal. We have tried changing it three times. I did it twice and I had a 80 year old master mechanic that works on antique cars try it. It still leaks way too much. The crankshaft in question was NOS and check (straightened and polished and balanced) so the diameter of the seal surface was spot on.

 

I have asked Best on several occasions what is the minimum shaft size and the maximum shaft size for that seal. The refuse to answer.

 

On my other engine, that was a 1963 Automotive Engineering swap rebuild the rear does not leak at all, which for a flathead is something.  That engine sat from 1967 to about 2013.  It has a rope seal in it.

 

My next engine, I will use a rope seal due to its larger surface area on the crankshaft and in my opinion a better ability to deal with distortions. The modern fine lip seals do not like it if the shaft moves at all in the block. Note that Chrysler changed the real main bearings due to stress issues when they went to torque converter. They were having issues. As the load goes up on these engines with them making more power...it is possible that the rear is moving just enough to cause issues with the micro fine lip on the 3675. In my case with a 5000 pound car...that is a real possibility.  Sometimes new technology is too sensitive to be used on old technology.

 

I have an NOS  factory (Victor) seal for a flathead. The design is totally different at the lip. Much more surface area and the rubber has an vulcanized material embedded in it.

 

James.

 

I also have an 80 something master mechanic available to assist me on installation. My engine is in the machine shop now and I can't picture the area the seal rides on, somewhere it was mentioned that the slinger section will need to be removed in order to use the rubber 4164 seal.

[kencombs]

I think there is some misleading info in the Best listings.  The 3675 is what I installed in my 230  But, it is a '56 model and the machining in the seal area is specfic to that seal.  The block and cap have a nicely machined area for the seal to sit and there are no holes drilled on the back for any other seal.  I haven't looked at a lot of 40s to early 50s, but the few I've seen are differently machined  in that area where that seal should fit.

 

I think the year fitment is wrong as it appears to have changed in the mid 50s.

[DJK]

10 hours ago, kencombs said:

I think there is some misleading info in the Best listings.  The 3675 is what I installed in my 230  But, it is a '56 model and the machining in the seal area is specfic to that seal.  The block and cap have a nicely machined area for the seal to sit and there are no holes drilled on the back for any other seal.  I haven't looked at a lot of 40s to early 50s, but the few I've seen are differently machined  in that area where that seal should fit.

 

I think the year fitment is wrong as it appears to have changed in the mid 50s.

When I contacted the technical dept., they weren't too sure of anything.

[James_Douglas]

44 minutes ago, DJK said:

When I contacted the technical dept., they weren't too sure of anything.

That is why I encountered. You can clearly see the massive differences between a NOS MOPAR (Vitctor) seal and the best seal. I would not use it again.

 

James

[Plymouthy Adams]

the manual is pretty direct on the statement that 46-52 and the 53 up are NOT interchangeable.  

[Dartgame]

George Asche was the person that recommended I use the best gasket seal.

[DJK]

7 hours ago, Dartgame said:

George Asche was the person that recommended I use the best gasket seal.

Which one?

[DJK]

9 hours ago, Plymouthy Adams said:

the manual is pretty direct on the statement that 46-52 and the 53 up are NOT interchangeable.  

Correct, but there is a rubber seal with bracket(4164) that Best says will replace the rope seal(4162). I would just like to hear from those that have used it with success.

[Plymouthy Adams]

I use a more modern rear seal also....it sits between the transmission and is part of the retrofit V8..?

[Bryan]

On 1/29/2021 at 12:20 PM, James_Douglas said:

I have had nothing but trouble with the Best 3675 seal. We have tried changing it three times. I did it twice and I had a 80 year old master mechanic that works on antique cars try it. It still leaks way too much. The crankshaft in question was NOS and check (straightened and polished and balanced) so the diameter of the seal surface was spot on.

 

I have asked Best on several occasions what is the minimum shaft size and the maximum shaft size for that seal. The refuse to answer.

 

On my other engine, that was a 1963 Automotive Engineering swap rebuild the rear does not leak at all, which for a flathead is something.  That engine sat from 1967 to about 2013.  It has a rope seal in it.

 

My next engine, I will use a rope seal due to its larger surface area on the crankshaft and in my opinion a better ability to deal with distortions. The modern fine lip seals do not like it if the shaft moves at all in the block. Note that Chrysler changed the real main bearings due to stress issues when they went to torque converter. They were having issues. As the load goes up on these engines with them making more power...it is possible that the rear is moving just enough to cause issues with the micro fine lip on the 3675. In my case with a 5000 pound car...that is a real possibility.  Sometimes new technology is too sensitive to be used on old technology.

 

I have an NOS  factory (Victor) seal for a flathead. The design is totally different at the lip. Much more surface area and the rubber has an vulcanized material embedded in it.

 

James.

 

James, did you ever find the diameter of the 3675 seal lip vs the diameter of the journal it rides on?  Or whatever seal you bought, the lip to lip diameter on the halves? 

[chris 48 P15]

i have used the 4164 best gasket on my 218 instead of the rope seal 

there was crud on the crankshaft where the seal made contact 

no machining needed for this seal you will need to oil pan and rear main cap

no leaks yet

[Bryan]

10 minutes ago, chris 48 P15 said:

i have used the 4164 best gasket on my 218 instead of the rope seal 

there was crud on the crankshaft where the seal made contact 

no machining needed for this seal you will need to oil pan and rear main cap

no leaks yet

Mine doesn't have the bolt holes in the rear of the block to take the plate. It uses the 2 piece rubber insert Mopar 2084325 or BestGasket 3675.   Trying to find on the rear main seals how much the seal lip is touching the journal. Slightly deflected or pushed back almost parallel?

[chris 48 P15]

never mind