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> Jensen Healey & Jensen GT Tech > Engine & Transmission > 907 Main Bearing Shells - Conversion to Run Chrysler 318 V8 Shells

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Esprit2
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Many years ago, comments on this forum by JH racers who converted the 907 engine to run Chrysler 318 V8 main bearing shells. The idea was that for racers who rebuild the engine often, the savings on the dirt cheap Chrysler bearing shells compared to expensive Lotus shells quickly offset the initial machining costs and then became a significant on-going cost savings.

The +0.015" oversize bearing shells are no longer available from Lotus or JH sources. Vandervell, the original manufacturer, stopped making the Lotus OEM shells many years ago. Then JAE stepped-up, developed an aftermarket source, and also supplied bearing shells to other JH & Lotus suppliers. Now that source has dried up as well, and JAE's in-stock inventory is no longer insufficient to put together one complete set of +0.015" bearing shells. Owners of 9XX engines with oversize main bearing bores can no longer get bearings from any source. Perhaps a few lingering pieces getting dusty on a shelf somewhere, but not a steady, on-going supply.

As I recall, the first step to converting to Chrysler bearings was to align-bore the block assembly oversize. How much oversize? Was it (hopefully) +0.015" or more oversize? Are Chrysler 318 bearings a solution with a positive history?

Does anyone know the machining details? Preferably down to the 4-place decimal tolerances necessary to convert the block and main bearing panel assembly to accept Chrysler bearings?

Does anyone know how to reach any of those old racers who ran Chrysler bearing shells in their 907 engines? Any leads would be appreciated.

This affects all 9XX owners, JH and Lotus (907, 910, 911, 912, 920), whose block assemblies have been bored +0.015" over-size. In some cases, the blocks were bored oversize at the factory, so this can also affect 'virgin' engines. If a block was bored over-size at the factory, then +15 was stamped on the bottom of the Main Bearing Panel's 4th or 5th bearing web.

I've also posted this message over on the JensenCars mailing list on GoogleGroups. I think it's in the collective's best interests to figure out a workable solution.

Thanks & Regards,
Tim Engel

Last edited on 07-21-2017 05:10 pm by Esprit2

Esprit2
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I'm not sure, but I believe Ron Earp was one of those who converted to Chrysler bearings. Is Ron still on this forum? If not, does anyone know how to reach Ron?

Regards,
Tim Engel

Last edited on 07-20-2017 06:16 pm by Esprit2

Jensen Healey
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Try GT40s.com forum. I think he runs it.

Esprit2
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Thanks for the lead... I'll check it out.

Edit -- A friend who subscribes tGT40s.com is attempting to ping Ron for me; but to date, I've not made contact with him.

Tim

Last edited on 07-21-2017 05:18 pm by Esprit2

Esprit2
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Here's a few dimensional data-points for starters.

Crankshaft Main Bearing Journals:
CHRYSLER 318 V8 ................................. LOTUS 9XX Engines
2.4995 - 2.5005" -- Journal Dia ............... (2.4995 - 2.5005")
0.0005 - 0.0020" -- Clearance ................. (0.0005 - 0.0032")
#3 ................... -- Thrust Bearing .......... #5
0.0020 - 0.0070" -- Crankshaft End Play ... (0.003 - 0.008") ... Spec Dimension
?? .................... -- Crankshaft End Play ... (0.012") .............. Maximum Service Limit
?? .................... -- Block Main Bore Dia ... (2.6652 - 2.6660") Std Bore ID, Esprit
?? .................... -- Block Main Bore Dia ... (2.6655 - 2.6660") Std Bore, All Others
?? .................... -- Block Main Bore Dia ... (2.6802 - 2.6810") +0.015" Oversize, Esprit
?? .................... -- Block Main Bore Dia ... (2.6805 - 2.6810") +0.015" Oversize, All Others

Regards,
Tim Engel

Last edited on 07-21-2017 05:16 pm by Esprit2

subwoofer
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Maybe Garry Kemp or Mike Taylor would know?

--
Joachim

Esprit2
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Joachim,

I've not talked with either of them myself. However, this subject started over on the LotusExcel forum, and the fellow needing the bearing shells had already talked with Kemp, Taylor and Steve at SJ Sportscars. None of them had the +15 bearing shells, and they all said +15 shells were no longer available from Lotus, Vandervell or JAE... whose aftermarket supplier has been the source in recent years.

To be clear, he's looking for the revised shells for a cross-drilled crank (bottom shells are plain, no groove or hole). I have talked with Mike at Delta, and they do have a couple of sets of +15 bearings for the non cross-drilled 907 (bottom shells are grooved). But only a few sets, and no more coming. When they're gone, they're gone. So while JH owners may have a little more time, the problem is close enough that it would be wise to push for another option before you need it.

Regards,
Tim Engel

Last edited on 07-22-2017 03:52 am by Esprit2

jcdean
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Judson Manning did the build up for Ron. I have not a clue who Judson's machinist was. Ron Earp is very active on gt40s.com. Drop a line over there.



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