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Old 07-08-2018, 10:51 PM   #1
Hoogah
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Default Rear main seal options - which one?

My Ď29 motor is at the engine rebuilders after discovering white metal in the sump when chasing a rear main oil leak (see separate thread ďDropped sump, found metalĒ). Heís going to re-pour the main bearings, but is happy with the condition of the babbit on the con rods (the motor has been rebuilt once that I know of). The babbit on the rear main was mostly gone and what was there looked way too thin anyway - possibly a dodgy job to start with? Pistons and bores look OK with no ridge and just a light honing of the bores required. The motor has been bored out 80/1000Ē. We will replace the rings and valve guides.

Thatís the context, now for the question! There are maybe four options for the rear main oil seal:
1. Original style
2. Brass replacement that requires modifications to the way the babbit is poured
3. Nitrile seal replacement that requires the rear oil slinger to be removed from the crankshaft
4. Nitrile seal replacement, as above but in two parts (although my parts man is having trouble finding these)

I hate getting conflicting advice, but Iím preparing myself for it! I have read of instances where the nitrile seal does not solve the problem, and the crank has been left permanently modified/ruined. I also donít know what advantages the brass seal offers over the original style.

Is there any reason for me to do anything other than put it back as per the original design, and if not, what are the main considerations in ensuring that my rebuilt rear main has no leaks?
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Old 07-08-2018, 11:11 PM   #2
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Default Re: Rear main seal options - which one?

Hoogah, if you use the Burtís (spelling?) seal, make sure you follow the instructions. When properly installed, they work very well.
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Old 07-08-2018, 11:12 PM   #3
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Default Re: Rear main seal options - which one?

A properly restored rear main will not leak more than the proverbial few drops. No need for an after market seal.
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Old 07-08-2018, 11:55 PM   #4
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Default Re: Rear main seal options - which one?

Quote:
Originally Posted by Synchro909 View Post
Hoogah, if you use the Burt’s (spelling?) seal, make sure you follow the instructions. When properly installed, they work very well.
Synchro, didn't you have a bad experience with one of these nitrile seals not working on a B engine, after machining off the slinger on the crankshaft?

Last edited by Hoogah; 07-09-2018 at 12:06 AM. Reason: Trying to get my terminology right!
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Old 07-09-2018, 07:29 AM   #5
Dave in MN
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Default Re: Rear main seal options - which one?

With new Babbitt being poured, I suggest the standard seal system. Ask your machine shop to flatten the cap at the mating surface. Use a very thin coating of Permatex #2 on it when assembling.
Good Day!
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Old 07-09-2018, 08:52 AM   #6
Marshall V. Daut
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Default Re: Rear main seal options - which one?

Using Babbitt bearings, there is an additional defense against rear main leakage that divides rebuilders/restorers into two camps, pro and con. An excellent article appeared in a past MAFCA or MARC issue (I can't recall which at the moment) about carving a groove in the rear man cap towards the back and drilling a hole through the Babbitt into the drain passageway. What this last line of defense does is funnel oil on its way out of the rear main bearing area into the cap's internal oil passageway so that it can flow back into the pan via the drain pipe. I don't recall the exact place to carve the groove or the size of the hole (which is chamfered), but I'm sure someone can chime in with a link to the article.
I don't see any disadvantage of using this method. The amount of Babbitt material carved out is minimal. Most main bearings have spiral grooves carved into them anyway. What's one more shallow one? I like the idea of funneling soon-to-leak oil back through the cap into the pan. Unless I have missed some authoritative post-article criticism of this method, I like the theoretical concept. I did this to a friend's perennial leaker last summer and have heard zero complaints from him. And he ALWAYS complains if something isn't right in his opinion. So, it must have helped stem the flow of leaking rear main oil.
Another thing to do is to use a Chevy 350 drain pipe in the rear main cap. This larger diameter pipe will help flow more oil back into the pan, thus helping to reduce leakage.
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Old 07-09-2018, 11:33 AM   #7
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Default Re: Rear main seal options - which one?

Quote:
Originally Posted by Hoogah View Post
Synchro, didn't you have a bad experience with one of these nitrile seals not working on a B engine, after machining off the slinger on the crankshaft?
Yes, I did. When that engine was rebuilt, the seal didnít leak a drop after being installed properly. I canít remember now why I had to take it apart but I replaced the seal, thinking I was doing the right thing. I didnít have the instructions so I didnít do it right and it leaked. I have since spoken with Terry Burtz and acquired another new seal and instructions. When the opportunity arises, Iíll do it properly and hopefully, get the same result as the original seal. Iíll be very happy if it works as well as the previous one.
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Old 07-09-2018, 12:31 PM   #8
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Default Re: Rear main seal options - which one?

I think while the engine is being rebuilt I would add the bronze thrust that the vendors carry, A worn thrust can cause oil leakage. I Vote to keep it stock otherwise.
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Old 07-09-2018, 02:26 PM   #9
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Default Re: Rear main seal options - which one?

The drilling of an oil hole in a rear main cap, in the middle, and then cutting a groove in the Babbitt, from the hole to the front end of the cap, and down the thrust came out in the 30's, in a magazine, under ( Tips from Mechanics ). All it is, is a butcher job on the cap. While it does get rid of oil, it gets rid of much needed oil to the rear main. You cheat the bearing, and it will wear fast. It is like many Builders that don't put any oil grooves in, Model A's can't run with out them.


Instead of getting rid of so called excess oil, which there isn't such a thing. Using a butchered rear main cap, is like carrying around a 500 gallon air tank, because there is a nail in your tire, and not fixing the cause of the leak. Also, putting a bigger pipe on is like putting in an over size door, with the hall way that is leading to it being still smaller then the door, you gained nothing.


There are only just a few causes to a rear main leak.


1. Plugged Breather pipe.


2. Main on the crank wore uneven.


3.Crank mains reground, or wore off center.


4. Motor bearings, wore, or Aligned Bored, or wore off center. If you set a crank that is not in a true alignment through Wear, in crank grinding, and, or, align boring. When the Motor is running, the flywheel effect will force the crank to straighten in Alignment, as much as it can, so if you set the crank in one Position, and when the Flywheel is running it in a different Position, wear is eminent.


5. All main caps have to have there part lines flat, and a perfect fit, to each other. If they are not, and they rock on the block even a little, when they are tightened, they will twist, and in case of Tinned caps, it puts a tension on the bond, and can, and will brake out the Babbitt from its adhesion, that is if the builder knew how the bond in the first place. Same thing, only worse, on Peened, or even worse on Babbitt that isn't Peened.


6. As Marshall said, you have to have sealant on the shims, and also top and bottom of the rear main bolts. I also put Sealant on the 3 front and center nuts to the outside of the block with new lock washers on all 4 front, and center main nuts, along with New lock washers.


7. You have to check to see if there is Babbitt in the oil passage in the rear main cap. We always pull the plug, and run a 3/8's drill bit through the cap. If you have a old style cap, bore it out to 3/8's, never use them that way. ( Use every drill bit, from 5/16, to 3/8's, or you will have trouble ) If you use a new pipe, screw in the pipe snug, and mark what sticks up in the inside, and saw, or grind it off, leave about .020 thousandths sticking up. Use a saw file in the middle of the pipe, when it is in and welded. We wire weld on both sides of the pipe so it won't come off in use. Then go and run the drill bit through again, cleaning the passage up. Don't put the plug in until the Babbitt work is all done.


8. We set end play from .003 to never over .004 thousandths. .006 is wore out. Yes, they will still run, but don't complain about the oil ! When you cut the thrust, you have to have it all the same length, and a 100% fit to the crank thrust face, or the high spots wear off, and the crank has to much end play.


9. The shaft clearance should be from 1.000-60, to not over 2.000-10. That is .001 thousandths Per Inch!


10. You have to have the flange Face trued, so there is no wobble in the flywheel, or it can also tear a remain up, and really cut power.


11. On of the most important things, is getting the flywheel housing set at a perfect right angle to the crank, if not, that will tear them up also, and give you a Ream Main leaker !


12. Connecting rods, will also give you Premature wear, that are not balanced, an OUT of Alignment !


There, I have again told you more then I know !


Thanks,


Herm.
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Old 07-09-2018, 03:03 PM   #10
ursus
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Default Re: Rear main seal options - which one?

Herm, you said, "I also put Sealant on the 3 front and center nuts to the outside of the block with new lock washers on all 4 front, and center main nuts, along with New lock washers."

I am used to seeing main bearing nuts secured with cotters, not lock washers. With the torque required for clamping down the caps, what happens when a lock washer breaks?
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Old 07-09-2018, 05:33 PM   #11
Kohnke Rebabbitting
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Default Re: Rear main seal options - which one?

Quote:
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Herm, you said, "I also put Sealant on the 3 front and center nuts to the outside of the block with new lock washers on all 4 front, and center main nuts, along with New lock washers."

I am used to seeing main bearing nuts secured with cotters, not lock washers. With the torque required for clamping down the caps, what happens when a lock washer breaks?

Well, we have used new Lock Washers, ( not China, ) but good ones, for 54 years, I have never had one break. Many Model A's that have come in over the years, have had only the Nuts on the main bolts, and they are just as hard to get off as if it had been Keyed !



The torque should be 80 Ft. Pounds. If there is room, we put lock washers on it.


The only washers I have seen break are old rusted, reused ones that were small and used over many times.


Modern engines use lock washers, on the Mains, and rods, some use split lock nuts.


We have always bolted on Model T flywheels with lock washers.


Flywheel Housings for the Model A, we Lock washer, I would do the flywheel also, but there is no room.


I have always used Lock Washers on the Model T Piston Wrist pin, pinch bolt, those Cotter Keys are a joke !


Thanks,


Herm.

Last edited by Kohnke Rebabbitting; 07-09-2018 at 05:40 PM.
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Old 07-09-2018, 09:01 PM   #12
Marshall V. Daut
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Default Re: Rear main seal options - which one?

Good input based on experience and expertise, as always. Herm. Thanks.
Marshall
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Old 07-10-2018, 09:29 AM   #13
Hoogah
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Default Re: Rear main seal options - which one?

Thanks everyone for your input, and especially Herm for your detailed responses. I’ve asked lots of questions here and elsewhere, and based on what I’ve heard, will stick with the original setup. The original style seal didn’t leak before the babbit broke, so I’m trusting my (very experienced, like 60 years!) rebabbiter to give me a good job without making any modifications.
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Old 07-10-2018, 10:38 AM   #14
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Default Re: Rear main seal options - which one?

Quote:
Originally Posted by Hoogah View Post
Thanks everyone for your input, and especially Herm for your detailed responses. Iíve asked lots of questions here and elsewhere, and based on what Iíve heard, will stick with the original setup. The original style seal didnít leak before the babbit broke, so Iím trusting my (very experienced, like 60 years!) rebabbiter to give me a good job without making any modifications.
Canít criticize that decision.
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Old 07-10-2018, 03:52 PM   #15
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Default Re: Rear main seal options - which one?

I am now having my "B" engine built. I asked the builder about the Burtz seal and his response was "Absolutely not". I guess he has had some problem with them. He didn't go into detail.
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Old 07-11-2018, 01:38 AM   #16
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Default Re: Rear main seal options - which one?

Chris Haynes,
Please ask your re-builder to go into detail and explain his "Absolutely not" response and post it here on Fordbarn.
The instructions specify concentricity, surface finish, pressure testing, and much more.
The Burtz seal has been in production since 1976 and over 50,000 have been sold.
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Old 07-11-2018, 07:02 PM   #17
Kohnke Rebabbitting
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Default Re: Rear main seal options - which one?

Quote:
Originally Posted by Terry Burtz, Calif View Post
Chris Haynes,
Please ask your re-builder to go into detail and explain his "Absolutely not" response and post it here on Fordbarn.
The instructions specify concentricity, surface finish, pressure testing, and much more.
The Burtz seal has been in production since 1976 and over 50,000 have been sold.

Terry, I know a lot of Guys have had some bad luck with the seal, including me. I know you have to trim the O.D. so the seal part don't bubble up and leave a hole between the crank surface, and the seal. What I would like to see, is a Video, showing you, Start to Finish installing one of your seals, and pointing out the do's, and Don'ts. Do this on some ones engine, so as to give mileage reports.


Put it on U-TUBE !


Dam, I like the Seals, they should be the best.


Thanks,


Herm.
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Old 07-11-2018, 10:50 PM   #18
Terry Burtz, Calif
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Default Re: Rear main seal options - which one?

Herm,

Thanks for the reply.

This is the first time that I have heard the term "Bubble Up", however I know what you mean.

The seal is designed to fit the groove in Ford part #A-6335 and does not need to be trimmed.

Replacements for A-6335 have different grooves and the directions for the seals state that they are incompatible. I pasted the instructions below. See instruction 2 below where it states "Most reproduction block inserts have a groove that is not compatible with this seal".

Original Ford parts (A-6335) are not hard to find.

Any rebuilder that scraps a cylinder block should remove A-6335 before scrapping.



1) Thoroughly clean the grooves in the rear main bearing cap (A-6327) and block insert (A-6335) to remove all traces of dirt and oil, which may interfere with proper seal installation and sealant adhesion. Also, make sure rear main cap drain pipe is clear.
2) Without the crankshaft in place, assemble the seal with its lip facing towards front of engine, shims, block insert, and rear main cap to the engine. Check to be sure the seal fits properly in its grooves, and is not distorted or offset relative to the rear main bearing. The seal is designed to fit snugly into the original block insert (A-6335). Most reproduction block inserts have a groove that is not compatible with this seal.
3) Machine the rear slinger area of crankshaft as shown in the figure. Finished diameter shall be between 2.090 in. and 2.150 in., and concentric with the rear main journal within .001 in. to prevent whipping of the seal lip outward. Machine crankshaft to largest diameter between limits consistent with cleanup. Polish seal contact area of crankshaft to a bright smooth finish. Main bearing clearance must be between .0010 in. and .0015 in. to keep the crankshaft from whipping the seal lip outward.
4) Deburr the flywheel mounting flange. Apply some grease to the seal contact area. Carefully and without stretching it more than necessary, lubricate and slip the seal with lip facing towards front of engine over the flywheel mounting flange. A plastic sandwich bag placed over the flywheel mounting flange will protect the seal lip from damage due to small burrs, and a small blunt screwdriver may be required to ease seal over flange.
5) On final assembly, apply either an RTV silicone adhesive or Permatex #2 sparingly to both grooves and all mating surfaces where shims, rear main cap, block insert, and block meet. Avoid getting adhesive on seal lip. Also apply sealant to rear main bolts.
6) Before installing oil pan, and after adhesive has cured, test seal and rear main cap area for leakage by pressurizing the rear main cap drain pipe with motor oil to at least 10 psi and check for leaks. The seal will withstand 50 psi, however the sealant may fail at this pressure.
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Old 07-12-2018, 12:08 AM   #19
Kohnke Rebabbitting
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Default Re: Rear main seal options - which one?

Quote:
Originally Posted by Terry Burtz, Calif View Post
Herm,

Thanks for the reply.

This is the first time that I have heard the term "Bubble Up", however I know what you mean.

The seal is designed to fit the groove in Ford part #A-6335 and does not need to be trimmed.

Replacements for A-6335 have different grooves and the directions for the seals state that they are incompatible. I pasted the instructions below. See instruction 2 below where it states "Most reproduction block inserts have a groove that is not compatible with this seal".

Original Ford parts (A-6335) are not hard to find.

Any rebuilder that scraps a cylinder block should remove A-6335 before scrapping.



1) Thoroughly clean the grooves in the rear main bearing cap (A-6327) and block insert (A-6335) to remove all traces of dirt and oil, which may interfere with proper seal installation and sealant adhesion. Also, make sure rear main cap drain pipe is clear.
2) Without the crankshaft in place, assemble the seal with its lip facing towards front of engine, shims, block insert, and rear main cap to the engine. Check to be sure the seal fits properly in its grooves, and is not distorted or offset relative to the rear main bearing. The seal is designed to fit snugly into the original block insert (A-6335). Most reproduction block inserts have a groove that is not compatible with this seal.
3) Machine the rear slinger area of crankshaft as shown in the figure. Finished diameter shall be between 2.090 in. and 2.150 in., and concentric with the rear main journal within .001 in. to prevent whipping of the seal lip outward. Machine crankshaft to largest diameter between limits consistent with cleanup. Polish seal contact area of crankshaft to a bright smooth finish. Main bearing clearance must be between .0010 in. and .0015 in. to keep the crankshaft from whipping the seal lip outward.
4) Deburr the flywheel mounting flange. Apply some grease to the seal contact area. Carefully and without stretching it more than necessary, lubricate and slip the seal with lip facing towards front of engine over the flywheel mounting flange. A plastic sandwich bag placed over the flywheel mounting flange will protect the seal lip from damage due to small burrs, and a small blunt screwdriver may be required to ease seal over flange.
5) On final assembly, apply either an RTV silicone adhesive or Permatex #2 sparingly to both grooves and all mating surfaces where shims, rear main cap, block insert, and block meet. Avoid getting adhesive on seal lip. Also apply sealant to rear main bolts.
6) Before installing oil pan, and after adhesive has cured, test seal and rear main cap area for leakage by pressurizing the rear main cap drain pipe with motor oil to at least 10 psi and check for leaks. The seal will withstand 50 psi, however the sealant may fail at this pressure.

Terry, I have saved many of the original A 6335's, just for your seals. The very first Repro. I tried, I could see that it wouldn't work.


Thanks,


Herm.
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Old 07-12-2018, 02:26 AM   #20
Terry Burtz, Calif
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Default Re: Rear main seal options - which one?

Herm,

Thanks again for your comments.

Thanks also for your foresight by saving original Ford A-6335's.

I am happy that we are in agreement that the replacement A-6335's are junk and not compatible.

Can you post any experience where a seal was used with an original A-6335 and the instructions were followed including pressure testing?

Thanks, Terry Burtz
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