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#14486 - 02/26/18 10:11 AM MGB rod bearing failures, here's my plan
Hap Waldrop Offline
Champion

Registered: 02/03/11
Posts: 802
Loc: Greenville, SC
For several years now it seems most MGB race engine builders have seen more rod bearing failure than ever before, mostly #3. Now e have reacted in many ways, a little more clearance at the rod bearing a little more side clearance at the rod, coatings, oil relief at the rod big end thrust area, but nothing seems to work. Now years ago we didn't seem to have this issue, my Huffaker MGB had unreal bearing life, so what has changed? For one bearing quality, back then we had Vandervell VP2 bearing, now we have the King CP tri metal bearings which is designed for the street not severe race duty. The Vandervell VP2 were rated at 12,000 psi, the King CPs are rated at 6000 psi, big difference. My latest bearing failure was #3 and it happen after a great weekend for acing where I went as fast in my vintage MGB as I ever had at the take easily in my class in Saturday feature against good field for cars. The Sunday morning I would just load up, and not race the Sunday race ans the fast guys I raced with the day before were packing up too. Long story short I could get any help to load the car, in a hurry I cnrak it up, cold morning, high 30s, and I think that cause me to turn #3 bearing nothing during that race led me to believe I had an issue in the race and I watch the OP gauge like a hawk, all my gauges for that matter, always have. Now I did have another #3 rod bearing issue a year earlier and I ruled to too tight of rod side clearance at .014" which I not run aprox .018". Now the last failure the bearing clearly had started to turn, and had flattened out an spilled over on to the side thrust are of the rod, but no sign of heat, no bluing of anything.

OK, a little more info for you unfamiliar with the MGB engine, #1 rod is fed off the the number #1 main, #2 and #3 are both fed off #2 main, #3 rod is fed off #5 main. This is the 5 main bearing engine, main bearing life is just fine, rods not so much so, and while #2 and #3 rods are the main culprits, I would not trust any of the of the rod bearing for more then 3-4 weekend tops. I run about .0023 on the rods and .002on the main, I mostly use Valvoline VR1 20/50 and 50 non synthetic oil and have for about 20 years with success, so I don't suspect an oil issue, but willing to try another oil, thought about Joe Gibbs Driven non synthetic oil, not a big fan of synthetic oil in these leakers smile

OK, so there's the spill. So when I think of the old days with the Huffaker MGB,and now the biggest change I can see is a lesser bearing. The King CP tri metal are half the load rating of the old VP2s. Now King does make a excellent racing rod bearing in the XPC line, which has 16,000 psi rating and comes from the manufacturer coated, pretty much everything any of us would want from race bearing. However they don't offer them for the MGB, but after some research I do find a Honda XPC rod bearing that can work with some effort. It require I turn the crank down about .090" under stock, Pauder Machine will make rods for me with the Honda bearing housing bore and bearing retainer notches but at the MGB's rod width, the width difference between the bearings is the Honda bearing is only .020" narrower. I will get the crank nitrided. The bearing size comes in std. .001 and .010, so two under sizes to work with.

Now I trying to convince King that making the XPC bearings for MG A and B series is a viable market, but until then I will go the Honda XPC bearing route. I am convinced this is a bearing quality issue, your thoughts?
_________________________
Hap Waldrop
Acme Speed Shop 864-370-3000
www.acmespeedshop.com
MG/Triumph Performance Street/Race Engines
The Vintage Production Car Festival
https://www.facebook.com/vintageproductioncarfestival

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#14487 - 02/26/18 12:46 PM Re: MGB rod bearing failures, here's my plan [Re: Hap Waldrop]
JimG Offline
Enthusiast

Registered: 02/01/11
Posts: 55
Loc: Aurora, CO
Hap,
We have the same problem with TR4 motors, 2 & 3 are fed from # 2 main.
We often see bearing clearances too tight and have to send them back for a minumum
.0025. On the rods I'm lucky I can get Clevite 77's for the Jag 4.2L motors.
I think I got my last set from Summit. We also have a company in town that applies a friction reduction coating that seems to help. I also had to open up the oil passages on # 2 main. If your going to lose a rod on a TR4 it will almost always be 2 or 3. Most likely to happen on stock cranks vs forged due to crank flex & 3 main blocks. Have you looked at Clevite/Mahle for a compatible size ?
jim g

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#14488 - 02/27/18 06:27 AM Re: MGB rod bearing failures, here's my plan [Re: JimG]
Hap Waldrop Offline
Champion

Registered: 02/03/11
Posts: 802
Loc: Greenville, SC
Originally Posted By: JimG
Hap,
Have you looked at Clevite/Mahle for a compatible size ?
jim g



They quit making MGB stuff a while back, I am sure they make the the same Honda application, but the King XPC is already coated form the factory and has 5,000 psi more load capacity than the Clevite/Mahle. This racing bearing is the cat's meow.


Here you can read about them here
http://kingracebearings.com/tech-lab-overview/


Edited by Hap Waldrop (02/27/18 06:29 AM)
_________________________
Hap Waldrop
Acme Speed Shop 864-370-3000
www.acmespeedshop.com
MG/Triumph Performance Street/Race Engines
The Vintage Production Car Festival
https://www.facebook.com/vintageproductioncarfestival

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#14495 - 02/28/18 11:25 AM Re: MGB rod bearing failures, here's my plan [Re: Hap Waldrop]
JimG Offline
Enthusiast

Registered: 02/01/11
Posts: 55
Loc: Aurora, CO
I will look in to that. Thanks Hap.
jim g

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#14531 - 04/25/18 10:59 AM Re: MGB rod bearing failures, here's my plan [Re: Hap Waldrop]
Hap Waldrop Offline
Champion

Registered: 02/03/11
Posts: 802
Loc: Greenville, SC
OK, a follow up on this. My approach to this is two fold.

1. Turning down the rod journal to use the King Racing XPC bearing to size that works for a Honda race bearing application.

2. Prepping a crank that drills #2, and #4 mains in the crank to double the oil feed to #2 and #3 rods.

We shall see. Thanks to all those who helped with ideas on this.


Edited by Hap Waldrop (04/25/18 01:52 PM)
_________________________
Hap Waldrop
Acme Speed Shop 864-370-3000
www.acmespeedshop.com
MG/Triumph Performance Street/Race Engines
The Vintage Production Car Festival
https://www.facebook.com/vintageproductioncarfestival

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#14532 - 04/26/18 01:22 PM Re: MGB rod bearing failures, here's my plan [Re: Hap Waldrop]
zuzulo56 Offline


Registered: 04/25/11
Posts: 2440
Loc: Hollywood
Originally Posted By: Hap Waldrop
Originally Posted By: JimG
Hap,
Have you looked at Clevite/Mahle for a compatible size ?
jim g



...the King XPC... is the cat's meow.




Let us also hope that they prove to be "the Bee's Knees"!...or, at the very least, "the caterpillar's kimono":


[767]


Edited by zuzulo56 (04/26/18 01:24 PM)
_________________________
Ronald James Michael Marin
Hristos Anesti!...So, Be cool and play nice!



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