V12 One Piece Rear Main Seal

Okay I believe I have found a replacement made by SKF it is part number: SKF 44926 it is the right dimensions an everything but it states that its maximum shaft speed is just under 6,000 rpm. Now it does not specify whether that is the maximum sustained rpm allowed or the actually max rpm no matter the time it’s at that speed. if its the former then this would be a good seal as the engine will only see over 6,000 rpm for a few seconds at a time. The other thing that boades well i think is this statement from SKF about Permissable shaft speeds “Generally, SKF WAVE seals can be operated at higher circumferential speeds than those obtained from the [diagram 3]because of the hydrodynamic form of the lip.” anyone have thoughts?

Diagram 3 :https://www.skf.com/binary/12-14886/1__en__rss_5d_tcm_12-14886.gif

Alright I have been in contact with SKF and they say that the seal should be sufficient for this application. I also see that SKF 44926 appears to be the same seal that Rob Beere racing sells. You can source it for anywhere between $70-$90 which is amuch better price than the 86 pounds plus shipping that RobBeere are selling it for or the $180 or more that US suppliers want for a special order seal.

what machining would be required for this ? Cap and block , crank or both ?

If you’re considering updating an earlier rope seal engine, forget it. Among other things, you’d definitely need a new crank. Might as well just find a 6.0 engine and swap it in.

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Unfortunately, this will only work for a 5.3 or 6.0 that came with a factory one piece rear main seal. I am sure its possible to adapt a rope seal style engine, but like Kirbert said its probably more work than its worth.

Understood , was just wondering. Will be trying a hail mary 1/2 piece lower section replace to get me thru a year or so before engine comes out.

Eric Stammer

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Good luck! hope it works!

Just to add a little bit to this thread from info found fleetingly in a FB group:

The aftermarket cheaper seal that subs in for the OEM Jag one at SNG Barrett is a Bentley Rolls Royce one PN UE73312 https://www.introcar.co.uk/oil-seal-crankshaft-rear-p262276 Around $90 as of last check.

(Borrowed Photos)

One person sourced an alternative seal under $20 Euro marked:
114.3 x 136.52 x 11.11 (4&12" x 5&3/8" x ~7/16 +/-")


NBR standing for Nitrile Rubber which I’m not sure is as suitable as Viton. I would think the SFK would be better but it shows up by google PN search at $100+ at many places.

SFK cheap here: https://simplybearings.co.uk/shop/p306359/SKF-CR44926-Double-Lip-Viton-Rotary-Shaft-Seal-4.5x5.376x0.438-inch/product_info.html

The seal needs to be able to take a certain Feet Per Minute turning speed.

Timken makes two seals that would technically fit, but I’m not sure they’re rated for enough surface speed feet/min, and they’re split seals.

25003-6015 Model 23 4.5x5.375x0.5 Nitrile (black) Split 250°F
25006-6015 Model 23 4.5x5.375x0.5 Viton (green) Split 450°F (Best Candidate)

~Paul K.

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WOW! were was this info hidding! :smile:. Thanks for the info!

Yup when i talked to SKF they said that NBR would be insufficient due to the shaft speeds that it would be seeing. SKF had one made from NBR for around 20-30 but I quickly found out that that was only rated for 1500 rpm max. I will report back with pictures and a small write up on weather or not it works properly when I have the engine running.

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Yea I found that too, but keep in mind that’s 90 Pounds not USD. out of stubbornness I refused to pay over 100 USD for a rear main seal so I went looking, it took me a few nights spread over a month or so to find the right one. I managed to find one on eBay for $70 USD 158500 New-No Box CR CR-44926 Oil Seal 4-1/2" ID for sale online | eBay at the time of this post the seller seems to have one left.

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Rob Beere Racing in the UK can supply a complete lip seal to replace the rope seal. Crankshaft machining is required to remove the scroll.
The seal is not cheap, but fairly easy to fit.
I’ve fitted 2 with good results. If you’ve got the engine in bits, well worth doing.

Just had my crank ground 10-10 and had the rear modified to carry the chevy vitron with two lips not cheep for it needs to be line bored and shoulders put in, crank surface at seal reduced but should solve the problem. If interested have some pics

Hi how did it go with NBR seal? Any experience please? Thank you