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A-Series Rear Seal

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atm92484 Avatar
atm92484 Andrew M
Fort Worth, TX, USA   USA
What are your thoughts on removing the top half moon piece, machining the bottom half off of the bearing cap so the back side of the bearing cap is flush with the block, and making a new rear main seal holder that has both a smooth and precisely sized bore for the scroll seal and extends rearward some to hold the rubber seal for the crank?

The seal holder would be two pieces that split at the same line as the bearing cap and there would be two vertical bolts to attach the two. The top piece would bolt to the block using the existing three 1/4" bolt holes. Next you would have to slide the lip seal over the end of the crank, place the crank in the block, install/torque the caps, then install and torque the lower half of the seal holder. If there is enough room to get a wrench in there the rear cap would also have two 1/4-28 holes drilled/tapped into it to hold the lower half of the seal holder to the cap.

Thoughts?

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Billm Avatar
Billm Bill Masquelier
Santee, Ca, USA   USA
Talk to Gerard at http://www.gerardsgarage.com/ before you try to reinvent the wheel
BillM

atm92484 Avatar
atm92484 Andrew M
Fort Worth, TX, USA   USA
I think part of the reason why mine is leaking in the first place is due to larger than original clearances on the scroll seal. I did not have the block line honed for fear of making the clearances worse (and the bearing clearances were fine and the crank spun freely when the caps were torqued) but I measured over 0.006" of clearance during assembly. At that point I needed an engine and didn't have time to mess around - I'd like to fix it without having to find a competent local machine shop for LBC engines and pray they can stick to a schedule (from what other racers have told me...things tend to go long).

I also thought the consensus was that the rubber rear main seals don't hold on race engine anyways? I figured if I could at least get the scroll part working again the rubber would have less to hold back.

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Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
Andrew, you didn't say if you were using any type of rear seal now. If not currently using a rear seal, then Gerard"s kit looks a lot like the kit being sold by Mini Spares, Mini Mania, Moss over the years, that never seem to last and seal. Gerard's kit, while it looks very similar, has a couple of important mods, one the new three bolt upper piece that bolt to the blot instead of the stock piece is now ball milled on the inboard side to match main cap, and lets the slinger work as intended, and then two piece seal holder, has tow dial pins to positively align itself. Bottom line, I have worked with Gerard's kit maybe 6-7 times now over 5-6 period, and we had no big issues. Same deal as the other seal kits, when using an aluminum flywheel, you need to take some material off of the center section that registered over the end of the crank to make sure it does not contact the seal, and this is in addition to the supplied spacer washer, those using a stock flywheel, then this is not needed.

You wrote:
"What are your thoughts on removing the top half moon piece, machining the bottom half off of the bearing cap so the back side of the bearing cap is flush with the block, and making a new rear main seal holder that has both a smooth and precisely sized bore for the scroll seal and extends rearward some to hold the rubber seal for the crank?"

This is exactly how the rear seal kit is made for the BWR billet crank, it's flywheel hub is unique in it's design, it still allows a normal flywheel to be bolted to it, but the section where the seal rides is more like a MGB, then a oil seal kit like your above description custom made for this crank is used.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


Member Services:
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atm92484 Avatar
atm92484 Andrew M
Fort Worth, TX, USA   USA
No seal currently. Would having larger clearances on the cap side and tighter clearances on the top side be an issue with Gerard's kit?

Is there a gap between the back side of the cap and the front face of the aluminum for the seal holder or does that get sealed with RTV or a gasket?

Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
In reply to # 3494588 by atm92484 No seal currently. Would having larger clearances on the cap side and tighter clearances on the top side be an issue with Gerard's kit?

Is there a gap between the back side of the cap and the front face of the aluminum for the seal holder or does that get sealed with RTV or a gasket?

Gerards, and all the traditional rear seal kits have a replacement 3 bolt piece, yes you seal it with Halomar to the block, the top section of the seal holder then bolts to that piece. Sounds like Gerard's kit will fix your problem. However make no bones about the non Gerard seal kit do not work long term, the mods he made to his kit is difference in success and failure of these kits.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Free Tech Advice - Alloy wheels for British Sport Cars,and others
Tom Colby Avatar
SAN FERNANDO, CA, USA   USA
As Hap says, Gerard's just might work out well for you. No question that Gerard's is the best designed seal kit made. .006" scroll clearance is absolutely way too much clearance. Also make sure you have plenty of crankcase breathers.

Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
In reply to # 3495160 by Tom Colby As Hap says, Gerard's just might work out well for you. No question that Gerard's is the best designed seal kit made. .006" scroll clearance is absolutely way too much clearance. Also make sure you have plenty of crankcase breathers.

Hey Tom, good to see you here. smileys with beer



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Free Tech Advice - Alloy wheels for British Sport Cars,and others
atm92484 Avatar
atm92484 Andrew M
Fort Worth, TX, USA   USA
In reply to # 3494827 by Speedracer Gerards, and all the traditional rear seal kits have a replacement 3 bolt piece, yes you seal it with Halomar to the block, the top section of the seal holder then bolts to that piece. Sounds like Gerard's kit will fix your problem. However make no bones about the non Gerard seal kit do not work long term, the mods he made to his kit is difference in success and failure of these kits.

Thanks Hap - on the other hand the better option may be to try Gerard's first and see what happens. Pulling engines is down to a science at this point. smiling smiley


In reply to # 3495160 by Tom Colby As Hap says, Gerard's just might work out well for you. No question that Gerard's is the best designed seal kit made. .006" scroll clearance is absolutely way too much clearance. Also make sure you have plenty of crankcase breathers.

Thanks Tom - I currently have three 1/2" hoses (one in the bottom end, one for the front breather, and one for the valve cover). All three feed into the air-oil separator/catch-can which vents to atmosphere.

Going back to the original question - seeing as the clearances are what they are, is it worth coming up with a seal holder that will reduce it back to original and hopefully minimize the work the rubber seal would have to do?

From what I've gathered through various posts, 0.003" is the goal right?



Edited 1 time(s). Last edit at 2017-04-22 10:08 AM by atm92484.


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Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
In reply to # 3495679 by atm92484

Going back to the original question - seeing as the clearances are what they are, is it worth coming up with a seal holder that will reduce it back to original and hopefully minimize the work the rubber seal would have to do?

Gerard's kit already does this.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Free Tech Advice - Alloy wheels for British Sport Cars,and others
Tom Colby Avatar
SAN FERNANDO, CA, USA   USA
Two ways to go here. Either try Gerard's kit, or disassemble the engine and have the block align-bored. Period

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Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
Yep to what Tom said.

I have dealt with many of the stock three bolt pieces on the block, and they have a bit of wiggle room, literally in the bolt holes that are slightly oversized. a racing buddy, Jim Crieghton show me years ago, to try to move the bolt on piece to achieve the same clearance you have the main cap side, using feeler gauges to check, not easy as you have to go around the corner with the feeler gauge, so to speak, but still very do-albe. In my case the cap side had .002" clearance at the scroll, so we positioned the three bolt piece to do the same. Sometime this even put the bolt-on piece proud of the block, in which case I filed it to flush with the block. If you do this, a reverse scroll will be as good as it can get, which means minimum leakage when running, and still marks it spot when parked. Using the Payen lower gasket set is crucial, as it comes with the half circle rubber pieces that go in the oil pan, like the factory used, the other gasket set have cork for here, which has expiration date on how long it will seal.

OK, now again looking at the rear seals kits, Gerard kit keeps the reverse scroll working as it was intended to, and this was the fault of the other design, it did not, and would flood the front side of the seal eventually causing a major failure of the seal. The whole idea is to keep the reverse scroll doing it's job to pull oil back to the crankcase and then the seal is the back up for that. If you did what you talked about in your first post, about milling the rear cap to be flush with the block, then making a seal kit for that design, it might work, but you have to modify the crank as well as the main cap, Gerard's kit is way easier to do with the stock rear scroll crank.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Free Tech Advice - Alloy wheels for British Sport Cars,and others
Tom Colby Avatar
SAN FERNANDO, CA, USA   USA
While doing the engine R/R on a street Spridget is a bit time consuming, on the racing Sprites we build here, we can do R/R pretty damned fast. We had a real problem several years back with a leaking rear main on a customer car/customer built engine. None of the seal kits available would stop this particular pretty bad oil leak (about a 6 inch diameter puddle after 15 minutes of idling.) Pride made me want to try one thing before doing a complete tear down & align-bore. So here's what we did. It takes some skill, and a lot of patience.
Yank the motor, the flywheel, and rear engine plate. Important thing here is that the customer DID HAVE the 3 bolt horseshoe from this particular engine. We very slowly flat sanded the three bolt where it butts down on the rear main cap a tiny bit at a time and kept installing on the block until we could hear it barely scraping the crankshaft scroll. Gotta have the radio off and tell everyone around you to shut the hell up so you can hear it. Once we had it barely scraping, I took a can of semi-flat black spray paint because in my mind, it isn't as thick as gloss black, and thicker than flat black when applied. Shook the can up real good, and made one quick, full pass over the three bolt where the crank scroll rides. Then I let the paint dry real good. Then I lightly flat sanded the area again where it butts the rear main to get any possible overspray off. Used the gasket with Hylomar and ran in the 3 bolts using AN flat washers (not lockwashers!) Again, really take your time, gotta have complete silence around you. Just going by "feel" and slowly tightening up the bolts, making sure the 3 bolt does not move around all the while pushing down on it firmly. Spark plugs out, rocker assembly off - so you have some feel as to what's going on. My theory was the thickness of the paint allowed the 3 bolt to not actually touch metal-to-metal, and then, just spinning the crank by hand would then rub the paint off, leaving the clearance just about perfect. Put it all back together, installed the engine, cleaned the shop floor real good, lit the engine up and just let it run for a half hour. Shut it down, and waited for a couple hours. The floor was dry. I drove it home - 16 miles, 10 of those miles @ 70 mph - over 4000 rpm.
Pulled into my driveway, slid a fresh piece of cardboard under it, made a cocktail, walked the dog. Two or three drops of oil! Went and made 3 more cocktails, went outside with the flashlight, and there was maybe now 4 drops (total!) I did a jig, howled at the moon, and patted myself on the back. Customer says he can drive it 2 - 3 hours at a shot with nothing more than a nickle size puddle - Quarter size if it's one of our 100 degree So Cal summers. If any of you here wanna bitch about a dime sized leak from an A-Series after hours of driving at 4000 rpm................................Ha. Hell, I've had worse from an align-bored block! Was a truly stellar moment for me. So then, I just shared a major secret. Takes time, patience, and 'feel", but it worked unbelievably well.

atm92484 Avatar
atm92484 Andrew M
Fort Worth, TX, USA   USA
Thanks for the advice Hap and Tom. I ended up ordering a kit from Gerard - I'll pay attention to clearances while I'm installing it. There are a few events I'd like to do but I've been nervous about nicer tracks being more strict about leakage; hopefully this is the fix.

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