The rear seal installation is in 5 steps spanning 5 web pages.
Click green arrow at bottom to follow pages in sequence.
    A - Modify rear plate
    B - Machine slip ring
    C - Modify Viton seal
    D - Modify bearing cap
    E - Assembly
    F - Can I buy it? - (this page)
    G - Video Installation
    H - Follow-up notes

At 12:48 PM 9/1/04 -0700, Rick Pearlman wrote:
>"Is the custom rear seal a part that you carry,"

Nope. But I knew someone would ask that when I posted the design information.

>"and what is the cost."

Make me an offer I can't refuse for my car?

>"Let's say I can find a qualified local mechanic to tackle the job, what would be a fair price to pay for this?"

It's called "custom" because it is not commercially available, and you have to make it yourself, so there is no fixed price for purchase. (Maybe not even a reasonable price). But lets think about how it might work

To be commercially available, one may have to produce a batch of at least 20 sets for inventory and retail, and resolve to remain in business long enough to keep them available for many years to come, and be prepared to make more in the future if demand calls.

Figure procurement and machining of 20 engine back plates to start (and not everyone uses the same one). A back plate may cost $25 from a bone yard, so lay out $500.

Batch processing is more economical than one at a time, but what ratio of which parts would you process? If you're really cooking you might do the machining in 1 hour per part, about $50 for the machining cost on each part, so figure another $1000.

Making 20 slip rings all at once is not such a big deal. Chuck a 2 foot piece of steel tubing ($30? or $1.50 per part) in a lathe, and they might come out at 5 pieces per hour, or $10 labor per part. 20 pieces here might be $230 cost.

The Viton seal is an expensive part, maybe $40 even discounted in packs of 10 or 20 pieces. To remove the shell, maybe chuck the part in a lathe and slice it off with a cut off tool, about 10 per hour or $5 per part. Make a drill jig to locate the four holes for small production drilling, an hour invested ($50), and then the parts come out at about 20 per hour or $2.50 per part for the labor. Of course you need some spares for the customers, so figure on making up at least 30 seals. $1475 to be amortized over the first 20 customers, so $73.75 COST per seal.

For a ready to install kit you need to include a few button head screws ($10/100) and a small tube of silicone sealant, ($18 per 12 pack), so $46 amortized over 20 customers, or $2.30 each.

$ 500
$1000
$ 230
$1475
$ 46
--------
$3251 cost of batch of 20 sets.
= $162.55 cost per set. (Not even accounting for packaging).

If you're lucky you may only have to store this stuff for about 4 years before it's all sold, so add about 50% for the time cost of the invested capital. That brings the cost up to about $243.82 per set. Add at least 50% markup between the production shop and the retail customer, and it's up to $365.73 per set, (and you still don't have it installed).

Now you may begin to see the reason why this is a do-it-yourself thing. On a one-off basis you can use your existing engine plate. You might lean on a friend to do the machine work for a pack of beer, but if you have to pay going commercial rates it might cost $100 to modify the plate and make a slip ring (if you don't get gouged). You might pay $60 for the seal retail, but you can modify it yourself in about an hour with a vice, a hacksaw, a hand drill and a file, or maybe pay your mechanic $25 to do it. No cost for another plate, no time cost of capital, no retail markup. Depending on how much you pay for machine work, and how much you think your time may be worth, this one-off route may cost $75-$200, and you don't have to worry about it being commercially available now or in the future. You could buy and modify another seal any time you might need a replacement.

Once you have the installation kit in hand (as described above), installation time is not too much. You still need to drill two holes in the rear main bearing cap, just a hand drill job if you're careful. Tap the slip ring onto the crankshaft flange and shove it into position using the flywheel and bolts as a pusher. Remove flywheel and use a hand drill to install the small roll pin to assure the ring stays put. Carefully glue and screw the seal in place before proceeding with normal installation of the flywheel. All that might add about 1 hour to engine assembly time, which you can do yourself, or you might pay the auto shop to do it for you.

So if you can barter and/or do most of the work yourself, you might get it all for under $100. If you want to pay a Brit car mechanic to do it all for you, maybe $250 or thereabout, completely installed. Just don't try to use me as a crutch if the bloke quotes a higher price, because I'm not a service broker. This of course does not include the time or cost to R&R the engine. But it's still cheaper than shaving and line boring the block and main bearing caps, not to mention tearing down and reassembling most of the engine to do that.

I hope this puts it in perspective for you. If you actually do install one of these rear seals, please let me know how it goes, what you pay out of pocket, and who did what. So far I have feedback from several people who have done this, and I know at least a couple dozen have been installed (that I know about). For a one-off job a machine shop might want to charge $100 for a slip ring, another $100 to modify the rear plate, and maybe $50 or more to modify the seal. If you have some friends with some machine tools you may get it done for a couple of personal favors and the cost of the standard Viton seal.

Addendum, April 2021:
Good news. Since December 2019 Kent Prather (Prather Racing) has been supplying this parts kit for this rear seal installation.
On Dec 15, 2019, Kent Prather wrote:
"Since I introduced this advanced mga, mgb 3 main real engine seal solution at the GT44 in Iowa, I have had considerable questions and interest in this kit. Most comments include the fact that there are a few steps that are very hard to achieve by the non machinist. I have since started to sell a kit to make this available to everyone. The hardest part is to manufacture the sleeve needed to adapt the rear of the crank to the new seal. The other hard part is to adapt the seal from a cup seal to a flat seal. I have taken the time to make a new batch of these parts. This kit includes: Complete instructions, the modified seal, the adapter sleeve, the 4 button head screws and shipping and handling. Complete, easy to do, yes it still takes time, plus I will answer all your questions. This kit is ideal for the new engine build and take your engine into the positive rear seal world, or adapt an older engine to a positive seal. It will slow down the rear engine of a worn engine, but is not a substitute for a proper engine rebuild". -- Price: $220 -- Location: Wakarusa, KS, USA