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rope rear main seal #4479817
08/05/17 10:25 AM
08/05/17 10:25 AM
Joined: Nov 2004
Posts: 1,854
SD
zrxkawboy Offline OP
zrxkawboy  Offline OP
Joined: Nov 2004
Posts: 1,854
SD
I'm rebuilding my '57 Plymouth 230 flathead. I've rebuilt newer (60s-80s) engines but never rebuilt a flathead before, and it's my first time installing a rope-type rear main seal. I've read the basic procedure (roll into the groove with a pipe, etc and trim flush with a razor blade) but would appreciate any tips/tricks for success. Thanks!


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: rope rear main seal [Re: zrxkawboy] #4479826
08/05/17 10:32 AM
08/05/17 10:32 AM
Joined: Jun 2003
Posts: 17,815
Deplorable in apple valley, ca
Chris142 Offline
Chris142  Offline
Joined: Jun 2003
Posts: 17,815
Deplorable in apple valley, ca
Do any gasket manufacturrers make a neoprene seal for it?


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Re: rope rear main seal [Re: zrxkawboy] #4479834
08/05/17 10:38 AM
08/05/17 10:38 AM
Joined: Nov 2004
Posts: 1,854
SD
zrxkawboy Offline OP
zrxkawboy  Offline OP
Joined: Nov 2004
Posts: 1,854
SD
Doing a lil research on that right now. My Felpro set came with the rope.


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: rope rear main seal [Re: zrxkawboy] #4479854
08/05/17 10:52 AM
08/05/17 10:52 AM
Joined: Dec 2013
Posts: 3,756
Massachusetts
turtlevette Offline
turtlevette  Offline
Joined: Dec 2013
Posts: 3,756
Massachusetts
With a rope seal you want to get a tight fit. I compressed the ends down to get as much rope in as possible. Didn't end up trimming anything. When together I couldn't turn the engine with a breaker bar.

I did it with the engine in the car and the crank in place. Its a Pontiac engine.

Retrofit neoprene seals have their problems too.



Last edited by turtlevette; 08/05/17 10:56 AM.

USA-1
Re: rope rear main seal [Re: zrxkawboy] #4479878
08/05/17 11:17 AM
08/05/17 11:17 AM
Joined: Jun 2002
Posts: 12,645
The Motor City
Kestas Online content
Kestas  Online Content
Joined: Jun 2002
Posts: 12,645
The Motor City
I went with a split seal for my 1971 Oldsmobile 350 rocket engine. This was per recommendation from the Oldsmobile community. Ten years later and it's still sealing just fine.

I think the seal was specified for a 1957 Ford. Maybe you can find a similar recommendation.

Re: rope rear main seal [Re: zrxkawboy] #4479908
08/05/17 11:59 AM
08/05/17 11:59 AM
Joined: Nov 2004
Posts: 1,854
SD
zrxkawboy Offline OP
zrxkawboy  Offline OP
Joined: Nov 2004
Posts: 1,854
SD
Thanks for the replies. Looks like I jumped the gun, though. Here's what happened: This was one of those deals where I tore down the engine nearly 2 years ago and am just now getting around to reassembling it. (Fortunately, I took a lot of pics during disassembly.) I opened my Felpro gasket set today and it had the rope rear main seal. After posting my question, I got to thinking about it, and couldn't remember removing a rope seal. Pulled up the pics, and sure enough, it was a rubber seal. After some searching, looks like this may work: http://www.bestgasket.com/pop_up_picture.asp?PartNumber=3675


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: rope rear main seal [Re: zrxkawboy] #4479914
08/05/17 12:07 PM
08/05/17 12:07 PM
Joined: Sep 2015
Posts: 6,075
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline
Joined: Sep 2015
Posts: 6,075
Kalifornia Kollective
Rope seals work. They did for about 75 years. There are two keys to success. 1.) minimize blow by. You do not want any vapor pressure in the crankcase. So cylinder wall prep and good ring seat is critical. 2.) As mentioned, they need a bit of compression at installation. So get it in tight. Find a PVC pipe close to the diameter of the crank journal and clamp it in place with the seal in the groove. Take a piece of decent hardwood and make a tapered square end that will fit the seal/groove. Trim seal on one end maybe 1/8" above mating surface. Use square hardwood to tap end down flush. If that went OK, do other side. Remove "fuzz" from tapping.

Vaseline is all I ever used on the seal face against the crank. Nice film of Vaseline and the crank should turn by hand, but not easily. There should be some drag with the caps snugged down. If all goes OK, you can do the rods and other mains. By the time it is all together, you will have a hard time turning it with a breaker bar.

I can't remember for sure, but I seem to recall that there is a slinger collar on the crank just ahead of the seal area ... Some old fattie I worked on years ago had a pressed-on slinger collar that was left out. It lost a fair amount of oil before we figured it out ...

Those old Chrysler flat-heads are tough. They actually run pretty good. Richard Petty won a lot of races in the early days with that little six. They can go. And I've seen one with a turbo on it that is actually quite entertaining. Won't knock a BBC down, but it runs well laugh

There is a cooling water distribution tube that needs to be in the block to get proper cooling to the rear cylinders. The exhaust exiting through the block adds to the heat load on the cooling system, so gotta pay attention to that. Many that were run on straight water will have the cooling tube rusted away and they will all overheat ...


Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: rope rear main seal [Re: zrxkawboy] #4480472
08/06/17 06:04 AM
08/06/17 06:04 AM
Joined: Nov 2004
Posts: 7,803
Texas
GMBoy Offline
GMBoy  Offline
Joined: Nov 2004
Posts: 7,803
Texas
Rope seals were a huge issue on Buick Grand Nationals right from new. They all leaked including mine.I had 2 warranty rear main seals fixed on my 1987 GN until the dealer agreed to try a replacement 1 pc neoprene style that an aftermarket Buick performance place marketed (ATR was their name). That was in 1988 at 17k miles. Today, I still have this carand it has 50k miles and still no leak. The OEM rope seal just didn't handle the pressure from a turbo well at all.

Re: rope rear main seal [Re: zrxkawboy] #4480533
08/06/17 07:20 AM
08/06/17 07:20 AM
Joined: Jun 2002
Posts: 12,645
The Motor City
Kestas Online content
Kestas  Online Content
Joined: Jun 2002
Posts: 12,645
The Motor City
How does a turbo place pressure on a rope seal?

Re: rope rear main seal [Re: Kestas] #4480562
08/06/17 07:44 AM
08/06/17 07:44 AM
Joined: Sep 2009
Posts: 325
Rockies
Scdevon Offline
Scdevon  Offline
Joined: Sep 2009
Posts: 325
Rockies
Originally Posted By: Kestas
How does a turbo place pressure on a rope seal?


It doesn't.
Not on an engine with 17k miles on it in 1988 with no blow-by and a healthy PCV system anyhow. The original rope seal was likely botched at the factory when installed and another rope seal was botched again by a flat rate dealer tech trying to beat the warranty time to replace it. Many dealer warranty rope seal "replacements" were done by packing the upper seal tighter with a hammer and a punch, cutting a small piece of new rope seal and stuffing that into the upper groove to take up the newly created void and then just replacing the lower rope piece. Just because the rope seal was "replaced" under warranty doesn't mean that it was done properly.


2003 Mustang Mach 1. 32V 4.6 Liter. Motorcraft Syn Blend 5W30
1970 Mustang Convertible 302-2V Auto (Stock) M/C 10W30
1970 VW Beetle 1600 DP

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