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I.C. Engine Main Bearing Housing Bores?

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Long shot here. Working on a project and i need data that seemingly no longer exists!
Short version:
Need to line bore engine block main bearing housings.
Original housings have been reworked several times poorly. Original housing size can not be derived from current bores.
Rear main has been welded up to repair previous blow up....(crank failure) Housing is oversize for oversized bore (thicker wall shell)

Specifics:
Engine:3 liter, V 12 BRM Gran Prix purpose built racing engine (circa 1974 type 202 i believe). No factory specs. available.
7 main bearings.
1-6 standard housing bore (as far as i can tell) .0755 wall bearing shell
#7 housing over bore (repair of damage from previous crank failure). .087" wall bearing shell

Have a set of original bearing shells (NOS)
Vandervell.
Shells have numbers, but shell numbers don't relate to anything in any catalogue i can find.
Std housing shells: #5674 .005
Oversize housing shell: L8986/1 .0005

Contacted the shop that supports these engines in the UK and they supplied housing bore info, but the numbers don't work....Bore less shell thickness does not come close to std crank
sizes....

Have in the past when confronted with this sort of problem made test bearing housings and test assembled bearings...
Shells will tend to "pinch in" at the parting line if the bore is too small...Have started underside and incrementally increased the test bore till the shells give even bore...(these shells are not5 tapered on wall).

Looking for a better way at getting the dimensions i need....Perhaps a smart guy method of accurately measuring the real length of the bearing shells, edge to edge so i could calculate the installed
circumference...
Open to ideas.....

Cheers Ross
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
Ross, If you're stumped, what help can we be?? :eek:

OK, maybe a tiny bit. Only good way I can think of to get the proper circumference of the shells is from a really good CMM (and operator!) doing a sweep of the OD and ID. That should allow for a model that then gets "circularized" to a nominal that you can start your test bores from, as long as there's some adjustment made for nominal crush at the shell ends (we don't know what Vandervell designed for, do we?).

Other possibility is the bearings you have are not the right ones. Or, maybe just say F'it, and get custom bearings made using actual block and crank geometry?
 

eKretz

Diamond
Joined
Mar 27, 2005
Location
Northwest Indiana
Assemble the bearings as if they're in the housing and use a small pi tape would be my approach. Make your test housing based on that measurement. And yes, pictures would be awesome!
 

CITIZEN F16

Titanium
Joined
May 2, 2021
Assemble the bearings as if they're in the housing and use a small pi tape would be my approach. Make your test housing based on that measurement. And yes, pictures would be awesome!

+1 on the pics, is someone restoring a vintage race car?
 

barbter

Diamond
Joined
Oct 27, 2007
Location
On Tour...
As Milland said, CMM but ONLY if you can trust the operator....
I would go your old school route of turning up a tube in the lathe to trial/test fit the shells.
And I would still do that, just to double check a CMM result....
 

bastarddsm

Aluminum
Joined
Feb 18, 2014
Location
Southern Illinois University
I think I would start with the crank, and work backwards. Make sure the crank journals are sreviceable, and work with a bearing supplier to find shells for that journal. Then work to get the bore id.

Maybe you grind the crank to use a known and easy to get bearing shell, and rework the block.

It really depends on what the goal is. is this so it'll run and move around under its own power? Or is it going to be vintage raced? The repair strategy changes a lot.

I worked a lot with a shop that was doing a lot of top fuel block work. Those move the mains over like 0.002-3" PER PASS! So after like 5 passes they machine out the block to take a "spacer saddle" that fits between the cap, upper bearing and block, and new caps. Then re-machine the main tunnel. I think they do that 2x and then it's off to alcohol use. Most don't make it that far before being windowed repaired and sent to alcohol teams.
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Some shots of the engine block.
Don't have the heads. I am only doing the lower end repairs.
Sorry only upside down shots at present....
Block setup on my FP4NC Deckel to take advantage of the horizontal spindle...Doing some rough machining to get the rear main ready for line boring.
Needed thrust locating surfaces renewed, along with the oil feed groove cut in...and the oil feed drilling (not done yet)

Setup with sump fitted to rough out rear bore....Note no access to the interior with the sump in place,,,sump carries mains 1,4 & 7

attachment.php


Fixture was made for another job, different setup (another BRM) ...Needed spacers to get clearance for the clamping nuts etc....

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Other side view...looking toward the rear main....

attachment.php


Shot of the rear main...weld repairs prior to any machine work...Block was cracked up the "V" through the oil feed drilling.
Peening is there for stress relief...

attachment.php


attachment.php


Cheers Ross
 

magneticanomaly

Titanium
Joined
Mar 22, 2007
Location
On Elk Mountain, West Virginia, USA
Looks like Mahle bought Vandervell...Can they not make sense of those NOS numbers?

ISTR long ago I got a list of engine bearings from Federal-Mogul, indexed by journal size. You could start with such a list and develop a list of shells that might work, and the bores that they would fit, and choose waht size to finish your block to.
 

McClure Machine

Aluminum
Joined
Mar 22, 2018
Long shot here. Working on a project and i need data that seemingly no longer exists!
Short version:
Need to line bore engine block main bearing housings.
Original housings have been reworked several times poorly. Original housing size can not be derived from current bores.
Rear main has been welded up to repair previous blow up....(crank failure) Housing is oversize for oversized bore (thicker wall shell)

Specifics:
Engine:3 liter, V 12 BRM Gran Prix purpose built racing engine (circa 1974 type 202 i believe). No factory specs. available.
7 main bearings.
1-6 standard housing bore (as far as i can tell) .0755 wall bearing shell
#7 housing over bore (repair of damage from previous crank failure). .087" wall bearing shell

Have a set of original bearing shells (NOS)
Vandervell.
Shells have numbers, but shell numbers don't relate to anything in any catalogue i can find.
Std housing shells: #5674 .005
Oversize housing shell: L8986/1 .0005

Contacted the shop that supports these engines in the UK and they supplied housing bore info, but the numbers don't work....Bore less shell thickness does not come close to std crank
sizes....

Have in the past when confronted with this sort of problem made test bearing housings and test assembled bearings...
Shells will tend to "pinch in" at the parting line if the bore is too small...Have started underside and incrementally increased the test bore till the shells give even bore...(these shells are not5 tapered on wall).

Looking for a better way at getting the dimensions i need....Perhaps a smart guy method of accurately measuring the real length of the bearing shells, edge to edge so i could calculate the installed
circumference...
Open to ideas.....

Cheers Ross

Ross, first you need to get the finished size of the crank either as it is or after grinding. Then you will need the deck hight of the engine this is from centerline of crankshaft to top of deck surface. If you move the crank up in the block too far piston is going to hit the head. Then you will need the diam that your main bore will clean up to. Give these dim to a bearing mfg and they will be able to provide you with correct bearings.
Make sure you line hone as this is how the bearings dissipate heat.
Your welcome to contact me if you have any questions.
Mike
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
The real cuplrit is that BMW, like most/all Teutonic makers, is stingy with the information. Shame on them.

I can pick up a factory manual for a 1962 Plymouth and the main bore specs are listed.

Looks like you have a nice shop and setup, BTW.
 

boslab

Titanium
Joined
Jan 6, 2007
Location
wales.uk
The studs caught my eye too, elegant, reminded me of tensile test specimens I used to make on a myford ml7 years ago, the whole shop is beautiful, a hint of green in my otherwise bloodshot eyes, such a nice place to work.
The only contribution if at all using rollers to determine the ID of the shell, but if it’s elliptical that’s going to be useless, a trial plug as mentioned seems the only rational course,
Mark
 

Brett W

Aluminum
Joined
Jan 10, 2014
Location
Huntsville AL
Why not call King and Mahle. Give them dimensions of the crankshaft and existing shells. Get specs for a current bearing that is available and common. Then machine block to use those shells, which theoretically they could give you. Maybe work from a production engine?
 








 
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