BritishV8 Forum: Main Bearing Cap Bolt Reuse

BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: Main Bearing Cap Bolt Reuse

Posted by: BlownMGB-V8
Date: May 19, 2022 03:33PM

I thought those went away with the intro of roller cams.

Jim

MGBV8
Carl Floyd
Kingsport, TN
(4513 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: Main Bearing Cap Bolt Reuse

Posted by: MGBV8
Date: May 19, 2022 06:47PM

'Cept Rover didn't use those fancy cams. :)

Don't think they were for the cam, as Chevy & Ford quit using con rod squirt holes in the 60s.

BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: Main Bearing Cap Bolt Reuse

Posted by: BlownMGB-V8
Date: May 20, 2022 10:07AM

I believe they will only squirt when the big end goes below the main bearing parting line about 20 degrees or so. Not sure how much oil that puts in the cylinders.

Jim

MG four six eight
Bill Jacobson
Wa state
(324 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Main Bearing Cap Bolt Reuse

Posted by: MG four six eight
Date: May 20, 2022 10:09AM

Yeah, almost all modern "V" engines don't have them. Some of the newer stuff uses spray nozzles off of the main oil galleys to lube/cool the pistons. This is particularly true with high performance and boosted engines.

It was a bit of an eye opener after seeing the pistons. It tells me a couple of things though,
1, the 215 needs those squirt holes and that they do indeed have a purpose.
2, "A" likely the replacement rod bearings being sold for 215/3.5L also fit another application which doesn't have squirt holes. "B" they probably combined the part #'s to save costs and streamline manufacturing.

I believe that I still have the old pistons somewhere, If I think about it, I will try and remember to post a pic.

Bill

roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Main Bearing Cap Bolt Reuse

Posted by: roverman
Date: May 20, 2022 01:38PM

Brian, you torqued 3.5L mains to 100 ft/lbs , with studs ? Where did you find that spec. ? If so, I'm totally surprised you
didn't pull the threads out of the block ? When using .500" studs, you should reduce torque by 35% ! 20 tpi. vs. 13 tpi.
Good Luck, Art.

MGBV8
Carl Floyd
Kingsport, TN
(4513 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: Main Bearing Cap Bolt Reuse

Posted by: MGBV8
Date: May 20, 2022 07:31PM

Honda was pretty serious about oil squirters to keep the S2000 pistons cool. What does it do to the oil temp?

MG four six eight
Bill Jacobson
Wa state
(324 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Main Bearing Cap Bolt Reuse

Posted by: MG four six eight
Date: May 20, 2022 09:10PM

I would think that it increases it slightly, after all the heat has to go somewhere ;-). Not sure if the S2000 uses an oil cooler, I know that a lot of GM engines do.

Edited 1 time(s). Last edit at 05/20/2022 09:11PM by MG four six eight.

BriansMGBV8
Brian Macmillan
Seattle
(61 posts)

Registered:
09/26/2008 12:39PM

Main British Car:
72 MGB Roadster Rover 4L

Re: Main Bearing Cap Bolt Reuse

Posted by: BriansMGBV8
Date: May 20, 2022 10:43PM

Art,
ARP directed 110 lbs. The directions were specific to the 3.5 Rover. My courage only took me to 100lbs. Machinists did initial torque and recommended I retorque to the same as the studs require stretch to hold. They were solid to 100 lbs.

I appreciate the guidance on the squirt holes. I inspected and they’re definitely there. Neither manual I have talks to these feature though both manuals tell you to put the dimple on the rod forward for right bank and aft for the left. This puts the squirt hole at the top. I notched the bearing to match the hole.

Edited 1 time(s). Last edit at 05/20/2022 10:44PM by BriansMGBV8.

BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar

Re: Main Bearing Cap Bolt Reuse

Posted by: BlownMGB-V8
Date: May 21, 2022 09:37AM

If you look at the oil holes in the crank, of course they follow the throws, unless cross drilled. The top main has the oil groove. So pressurized oil is only available on about the bottom 140 degrees or less of crank swing. That means the only oil available to the squirt hole is what remains in the "wedge" as the rod comes around the top, meaning also that the squirt hole is depleting the oil cushion available for the bearing on the power stroke.

Everything has a cost.

Jim

Edited 1 time(s). Last edit at 05/21/2022 09:40AM by BlownMGB-V8.

MG four six eight
Bill Jacobson
Wa state
(324 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Main Bearing Cap Bolt Reuse

Posted by: MG four six eight
Date: May 21, 2022 01:41PM

This is actually one of the better (least scored) pistons and it's difficult to photograph the scoring and have it show in the pic. In the pic they look like scratches, but you can actually drag your finger nail across them and feel that they are fairly deep. Also disregard the corrosion as they have been laying outside in my scrap metal recycle pile!
All 8 pistons have it and the thrust side is worse than the non-thrust side. Upon tear down it definitely caught my attention as it is something that I do not usually see on a low mileage engine.

roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Main Bearing Cap Bolt Reuse

Posted by: roverman
Date: May 23, 2022 11:49AM

One problem is the 60 year-old design. Fortunately, piston/ring designers evolved.

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