Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 12-07-2018, 10:39 AM   #1
The Lucky Star
Member
 
Join Date: May 2010
Posts: 76
Default Best Rear Main Seal

Good morning,

I'd like your opinion on the best aftermarket rear main seal for a hopped up motor. What are the options? How good is each one? Who sells them?

Thanks!
The Lucky Star is offline   Reply With Quote
Old 12-07-2018, 10:46 AM   #2
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 8,991
Default Re: Best Rear Main Seal

Let's start by asking why do you need an aftermarket rear seal? What are you doing that requires one? Are you pressurizing the rear main? None of the options available are really geared towards the hobbyists, and there will be machine work involved such as machining the slinger from the crankshaft. If you use the Terry Burtz seal, then you need to be able to adjust the thrust (-again, machine work by the machinist) to set the proper thrust. I would pose the question to your engine machinist first, asking what he has been successful using.


As an engine rebuilder myself, I have had several failures of a type that Snyders sold and have now gone back to the stock slinger method.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 12-07-2018, 11:11 AM   #3
Purdy Swoft
Senior Member
 
Purdy Swoft's Avatar
 
Join Date: May 2010
Location: Alabama
Posts: 7,362
Default Re: Best Rear Main Seal

The original rear slinger setup works well for me as long as the oil isn't over filled .
Purdy Swoft is offline   Reply With Quote
Old 12-07-2018, 01:22 PM   #4
Dave in MN
Senior Member
 
Dave in MN's Avatar
 
Join Date: May 2010
Location: Jordan, MN
Posts: 1,195
Default Re: Best Rear Main Seal

I am in agreement with Brent. Proper rear cap alignment, bearing clearances and crankshaft end play will give you a leak free engine with the original oil slinger.

I, like Brent, also build engines. I have not found a good after market seal for the "A" crankshaft that is consistently trouble free.

If you insist on using something else that stock, I would suggest the Burtz seal. Caution: from my first hand experience, the rear slinger needs to be dead-on concentric with the rear main journal so that means it needs to be ground and polished while the crankshaft is at the crank grinder.
Good Day!

Last edited by Dave in MN; 12-19-2018 at 06:30 AM.
Dave in MN is offline   Reply With Quote
Old 12-07-2018, 08:57 PM   #5
The Lucky Star
Member
 
Join Date: May 2010
Posts: 76
Default Re: Best Rear Main Seal

Thank you for the replies. I"m planning on building an A motor with a turned down crankshaft for a salt car. Yes, it will be pressurized.

Thanks again.
The Lucky Star is offline   Reply With Quote
Old 12-08-2018, 12:50 PM   #6
Jim Brierley
Senior Member
 
Join Date: Jun 2010
Location: Temecula, CA
Posts: 2,905
Default Re: Best Rear Main Seal

"A" motor with a turned down crank. Does that mean a B or C crank? Either one is better because of their strength resulting from larger bearings. If that is your intention, turn the mains to as large of a size that you can, to keep strength. 'A' main studs are 2" between them, there are bearings available with a 2" O.D. that will just barely fit when the block is bored, I think 1.7" (I.D.) bearings. Find available bearings before you start the engine build! Most of us Salt Rats use the C crank, many are now going to 5-main cranks and a girdle. Contact me if you think I can help. jimb4e4@gmail.com
Jim Brierley is offline   Reply With Quote
Old 12-08-2018, 12:58 PM   #7
johnneilson
Senior Member
 
Join Date: Jun 2010
Location: 34.22 N 118.36 W
Posts: 353
Default Re: Best Rear Main Seal

All,

there is a Saturn rod bearing that will just fit between the studs/bolts.
finish size on crank is 1.850
largest I could find and not have to move the main bolts.
also, if HP is above 150, it is wise to weld up flange on crank and machine for 2 pc chevy seal.

J
__________________
As Carroll Smith wrote; All Failures are Human in Origin.
johnneilson is offline   Reply With Quote
Old 12-09-2018, 10:25 PM   #8
The Lucky Star
Member
 
Join Date: May 2010
Posts: 76
Default Re: Best Rear Main Seal

Thanks again for the info. Yes, I was planing on welding up the rear seal area. Is the Chevy two piece seal the best? Where can I find the spec's for the conversion?

I have a C crank that I'll be working with. Really, that's where I'm starting.

Thanks again.
The Lucky Star is offline   Reply With Quote
Old 12-10-2018, 10:23 AM   #9
johnneilson
Senior Member
 
Join Date: Jun 2010
Location: 34.22 N 118.36 W
Posts: 353
Default Re: Best Rear Main Seal

You can make the parts yourself or buy a kit.
look here, Dan McEachern makes very good parts.
https://www.hotforhotfours.com/advertisers.htm

J

PS, the 1.850 info above is to use a Mod "A" block with smaller journals.
the "B" block and "C" crank use other bearings.
__________________
As Carroll Smith wrote; All Failures are Human in Origin.
johnneilson is offline   Reply With Quote
Old 12-10-2018, 03:24 PM   #10
wensum
Senior Member
 
wensum's Avatar
 
Join Date: Apr 2011
Location: New Zealand
Posts: 417
Default Re: Best Rear Main Seal

Our improved Model A with pressure fed mains leaked more oil than I liked, so the crankshaft (a new Burlington) was built up and a two piece Chevy oil seal used which has been successful.
wensum is offline   Reply With Quote
Old 12-18-2018, 02:23 PM   #11
Terry Burtz, Calif
Member
 
Join Date: May 2010
Location: Campbell,CA, USA
Posts: 66
Default Re: Best Rear Main Seal

The Lucky Star,

A discussion about rear main seals is similar to discussions on this forum about what oil to use.

I suggest that you educate yourself by talking with people who run at Bonneville and the machine shops that build high performance engines. Don't be afraid to ask lots of questions.

Welding on a crankshaft is not a "do it yourself" modification.

Crankshaft welding needs to be done by a crankshaft rebuilder that has a crankshaft welding machine that utilizes a submerged arc. After welding, the crankshaft needs to be straightened to eliminate axial and radial runout of the flywheel mounting flange. Next the crankshaft needs to have the welded areas machined to within .020 in. of final dimensions, and re-straightened as stated above. Once straight, the crankshaft is now ready for final machining.

As originally designed, the dowel pins locate the flywheel and are loaded in shear. The 4 bolts provide the clamping force and are in tension. In my opinion, this is the best design.

Be wary of a machine shop that says they can machine the face and diameter of the flywheel mounting flange to make things run true. Machining the outer diameter to run true only opens an interface that was previously a tight fit. Machining the face of the flange to run true introduces bending forces along with tension in the 4 attachment bolts. Changing the dowel pins to bolts puts all 6 bolts in tension, shear, and bending.

Since I manufacture seals along with many other parts for our beloved Model A's, I am hesitant to comment because I don't want my response sound like an advertisement. I am a manufacturer and do not sell retail.

On a stock engine (gravity feed to mains and dipper to the rods), the rear main slinger system is adequate unless there is excessive blow-by, the crankcase is overfilled, or the rear main clearance is too large. In the Model A era, small amounts of leakage were acceptable since most driveways and garages had porous surfaces.

When an engine is modified to supply pressurized oil to the rear main, the volume of oil supplied will overwhelm the stock slinger design and a positive seal will be required to prevent leakage.

Positive seals rub on mating diameters to prevent leakage unlike slingers that throw excessive oil into a collection groove that collects and returns the excessive oil to the oil pan.

Surface finishes on the slinger areas of Model A, Model B, and aftermarket crankshafts are similar to the surface finish on 150 grit sandpaper.

This rough surface finish will quickly wear any rubbing seal that attempts to seal against it.

For any seal to work, it is necessary to provide a smooth rubbing surface that is concentric with the rear main journal.

One type of seal that has been used is a packing (asbestos rope, Teflon rope, rubber
impregnated cork, wool, and many other materials. The stock front seal for a Model A engine is a packing, and the first engines designed with a rear main seal used packing type seals.

Packing type seals work until they wear and the preload against the smooth rubbing surface is lost. If the seal rubbing surface is not concentric with the bearing, seal wear will be much faster.

Modern engines use a radial lip seal. This seal design utilizes a flexible lip that is preloaded against the smooth rubbing surface. Radial lip seals are able to flex and accommodate small amounts of runout. The ability to accommodate runout depends on several factors including resiliency of lip material, length of lip, initial lip deflection, RPM, and temperature.

Radial lip seals can be either 2 piece or 1 piece. 2 piece seals have one piece fits in the rear main cap, and the other piece fits in the cylinder block. This type seal needs to have a little crush where the seal halves meet to provide an oil tight interface. 1 piece seals stretch over the flywheel mounting flange and have no mating surfaces.

Radial seals can accommodate much larger runout than packing type seals, but there is a limit.

Regarding runout, one interesting failure was a pressurized engine that didn't leak when driven around town, however had a rear main leak when driven on the freeway. During a forensic analysis to determine the cause of the leak, the engine was removed from the car, placed on an engine stand and pan removed. Pressurizing the rear main cap drain tube to 60 psi did not result in a leak. Disassembly of the engine and checking for runout of seal rubbing surface showed .010 in. TIR, and the rear main journal also had runout. At slow speeds around town, the seal was able to flex quick enough to prevent a leak, but at high speed, the seal lips were whipped out causing a leak.

The engine above with the leak had a Burlington crankshaft that was machined to provide a sealing surface, and then drilled to deliver oil pressure to the connecting rods. Drilling the crankshaft relieved stresses and the crankshaft was distorted unbeknownst when the engine was assembled. Subsequently, the crankshaft was straightened and lasted a few years with no leaks before it broke.

I am confused regarding the comment by BRENT in 10-uh-C as to how thrust (fore and aft movement of crankshaft?) has any effect on a radial lip seal, would like to thank Dave in MN for the endorsement, but would like to know why dead-on concentric is needed. The seal mentioned above with .010 in. TIR that leaked at high speed was in San Jose, CA. MN is a much colder climate and temperature will have an effect on resiliency.

I'm available through PM on this forum, or ask your parts retailer for my contact information.
Terry Burtz, Calif is offline   Reply With Quote
Old 12-18-2018, 04:16 PM   #12
Dave in MN
Senior Member
 
Dave in MN's Avatar
 
Join Date: May 2010
Location: Jordan, MN
Posts: 1,195
Default Re: Best Rear Main Seal

See next post...

Last edited by Dave in MN; 12-18-2018 at 04:35 PM.
Dave in MN is offline   Reply With Quote
Old 12-18-2018, 04:33 PM   #13
Dave in MN
Senior Member
 
Dave in MN's Avatar
 
Join Date: May 2010
Location: Jordan, MN
Posts: 1,195
Default Re: Best Rear Main Seal

From previous post: "would like to thank Dave in MN for the endorsement, but would like to know why dead-on concentric is needed."

You are welcome Terry for the endorsement.

I have used about 10 of your seals over the past 8 years. I have had the best results with your seals when I have the seal surface ground and polished at the same time/set-up as the main journals. This method allows for "dead-on concentric" and the best result. I did not have very good results (leaks after 500 to 800 miles) when the slinger was turned by a machinist in his lathe. (He was not "dead-on.)
I only use your seals if the radial surface is prepared by my crankshaft grinder.
I don't like chasing leaks!

From previous post: "MN is a much colder climate and temperature will have an effect on resiliency."

Terry, We don't drive our Model A's much during the winters in Minnesota and temperature has nothing to do with our resiliency. Anyone living in Minnesota and staying put during the winter is very resilient! So there!

Just bored...I know you were referring to the seal but since we don't drive during the winter, I took the liberty of intentionally misunderstanding your comment. What else do I have to do when there is snow on the ground, salt on the roads and my cars are stored?

Good Day Terry!

Last edited by Dave in MN; 12-18-2018 at 04:39 PM.
Dave in MN is offline   Reply With Quote
Old 12-21-2018, 12:33 AM   #14
Terry Burtz, Calif
Member
 
Join Date: May 2010
Location: Campbell,CA, USA
Posts: 66
Default Re: Best Rear Main Seal

Dave in MN,

You are correct that having the seal rubbing surface ground at the same time the rear crankshaft journal is ground is the best method for concentricity. This method also provides a good surface finish for any seal to rub on.

Compared to modern engines, Model A and B crankshafts are more expensive to grind properly because the fillet radii on Model A and B engines are larger which requires dressing (removal of material) from the grinding wheel, and if the grinding wheel has to be narrowed for the seal surface, even more material has to be removed. Crankshaft grinding wheels are expensive and removal of material shortens their life.

To save money, you may need to find another machinist, or a machinist that does not have a worn out lathe. Most any lathe built in the last 70 years has preloaded back to back bearings in the headstock with almost zero runout. If the crankshaft to be machined is in a lathe and the rear main journal is dialed in for minimum TIR runout, machining of the seal rubbing surface will be concentric.

The likely problem of short seal life (worse for packing type seals, but will also happen with radial lip seals) is wear caused by the rough surface finish of the seal rubbing surface.

After lathe machining, the seal rubbing surface should be sanded to provide a surface finish similar to grinding. A wooden paint stirring stick wrapped with progressively finer wet or dry sandpaper can be pressed against the lathe machined seal rubbing surface while spinning to obtain the required surface finish.

There is a lot of conflicting information regarding rear main seals, and for the education of all, I ask BRENT in 10-uh-C in post 2 of this thread to explain how thrust (I assume fore and aft movement of crankshaft?) needs to be adjusted. The Burtz seal was designed for the crankshaft to be in its original location. The following is copied from Brent's post.
"If you use the Terry Burtz seal, then you need to be able to adjust the thrust (-again, machine work by the machinist) to set the proper thrust."
Terry Burtz, Calif is offline   Reply With Quote
Old 12-21-2018, 12:40 PM   #15
Jim Brierley
Senior Member
 
Join Date: Jun 2010
Location: Temecula, CA
Posts: 2,905
Default Re: Best Rear Main Seal

Terry is right about turning or grinding the flange, I run full-pressure race engines and had one that the flywheel kept loosening. My solution was to have the flange hard-chromed and ground .002" oversize to insure a tight fitting flywheel, end of problem. I also add 2 extra flywheel bolts for insurance, and never use stock bolts, they are old and likely stressed. Be careful when using new, aftermarket bolts, check that they aren't too long and damage the cap and slinger.
Jim Brierley is offline   Reply With Quote
Old 12-22-2018, 01:37 AM   #16
hardtimes
Senior Member
 
hardtimes's Avatar
 
Join Date: May 2010
Location: South California
Posts: 5,783
Default Re: Best Rear Main Seal

Quote:
Originally Posted by Jim Brierley View Post
Terry is right about turning or grinding the flange, I run full-pressure race engines and had one that the flywheel kept loosening. My solution was to have the flange hard-chromed and ground .002" oversize to insure a tight fitting flywheel, end of problem. I also add 2 extra flywheel bolts for insurance, and never use stock bolts, they are old and likely stressed. Be careful when using new, aftermarket bolts, check that they aren't too long and damage the cap and slinger.
Hey Jim B,
In your experience, is there any downside to using, say, 6 to 8 flange bolts ?
And, I know the type aftermarket bolts you use. What torque (ft lbs) do you use with those bolts ??

BTW...I have the Burtz rear main seal in my B engine for more than a dozen years without losing a drop of oil from that area.
hardtimes is offline   Reply With Quote
Old 12-22-2018, 08:52 AM   #17
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 8,991
Default Re: Best Rear Main Seal

Quote:
Originally Posted by Terry Burtz, Calif View Post
There is a lot of conflicting information regarding rear main seals, and for the education of all, I ask BRENT in 10-uh-C in post 2 of this thread to explain how thrust (I assume fore and aft movement of crankshaft?) needs to be adjusted. The Burtz seal was designed for the crankshaft to be in its original location. The following is copied from Brent's post.
"If you use the Terry Burtz seal, then you need to be able to adjust the thrust (-again, machine work by the machinist) to set the proper thrust."
Terry, sorry for any confusion in my comment, -and you covered my intent as it has been my experience that not all engine rebuilders place the crankshaft into Ford's specified thrust location, and not all crankgrinders grind the cranks in the thrust area equally.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 12-22-2018, 12:28 PM   #18
Jim Brierley
Senior Member
 
Join Date: Jun 2010
Location: Temecula, CA
Posts: 2,905
Default Re: Best Rear Main Seal

Hardtimes, Many guys use 8 bolts but I feel the dowels are the best to take the shear forces. I torque stock V8 bolts to 65 lbs, ARP bolts to 75.
Jim Brierley is offline   Reply With Quote
Old 12-23-2018, 03:30 PM   #19
hardtimes
Senior Member
 
hardtimes's Avatar
 
Join Date: May 2010
Location: South California
Posts: 5,783
Default Re: Best Rear Main Seal

Quote:
Originally Posted by Jim Brierley View Post
Hardtimes, Many guys use 8 bolts but I feel the dowels are the best to take the shear forces. I torque stock V8 bolts to 65 lbs, ARP bolts to 75.
Thanks Jim,
75 it is for these Tilton !
Merry Christmas to you/yours, and ALL here ! I'm hoping next year is a bit better than this one.
hardtimes is offline   Reply With Quote
Old 01-03-2019, 08:19 PM   #20
The Lucky Star
Member
 
Join Date: May 2010
Posts: 76
Default Re: Best Rear Main Seal

Thanks for your help and advice. I have a donor C crank that I'd like to turn down for an A block while still utilizing the B throws. That's the idea anyway. Now, I really do need some suggestions and who could do the work.

Terry, you drilled my last project crank.

Thanks again.
The Lucky Star is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 10:37 PM.