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Charlie Butterworth
Posted on Friday, 08 June, 2001 - 18:55:   Edit PostDelete PostView Post/Check IP

I am looking for advice and/or parts.

About 6 years ago I decided to put a B80 engine into a Phantom III to get a more reliable car.
(Note that the original engine has been preserved with the hope of rebuilding it later.)

The work was almost completed but after a few starts in the testing phase the gears inside the end of the starter motor were stripped off.
On closer inspection there were signs of earlier damage and it looks like the new load was too much considering the earlier damage.

To fit the B80 engine into the PIII a bell housing from a mark 6 Bentley was fitted to the B80 then a short universal shaft to the PIII gearbox. A Lucas starter motor suitable for a mk6 Bentley was used. This starter motor has 2 pairs of gears either side of a central one which give about a 2 to 1 reduction. (actually 23 to 11 or 21 to 13 or something like that)

The first question that I have is. Would a starter motor for a Mk6 Bentley that had its gears in good condition be adequate to start a B80. If so I will need to consider options of replacing the gears or getting another starter motor with good gears.

If the 'Mk6 Bentley' starter motor would not be adequate then I am open to suggestions of what might be a suitable alternative.

Note also that I have rejoined the RROC in Western Australia recently.

Thankyou in advance for your help

Charlie Butterworth

E&P IT Solutions
post: 3 MacArthur Street, Cottesloe, WA, 6011, Australia
voice: +61 (08) 9385-0391 facsimile: +61 (08) 9385-0413
mobile: +61 041 99 777 00
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Larry Ross
Posted on Sunday, 24 June, 2001 - 10:19:   Edit PostDelete PostView Post/Check IP

I am just completing the installation of a B81 engine into my 1947 Silver Wraith. I am having the starting shaft of the starter motor lengthened so that it is in the same position relative to the flywheel starting ring-gear as the original B60 engine.

As you know, the engine, gearbox, bellhousing are the same, more or less, in the Mk6 as in the Silver Wraith. The Mk6 starter motor will fit to a Mk6 (of course) or Silver Wraith bellhousing. The important thing is, this bellhousing will also fit any B-series engine. Anything from a B40 to a B81. You will need a thick 25mm spacer between the two.

Although I have not yet started my engine, one must remember that the PIV engine was started by more or less the Mk6/Silver Wraith Starter Motor. The PIV engine being more or less a B80. The Mk6 starter motor has 14 teeth. The ring gear on the B80/81 I believe is 128.

If you use any other starter motor on the B80, it might turn the engine for a while, and it might seem the the gears mesh ok, but it will either be too tight, or too lose. And sooner or later, you will damage the gears. Contact your local gear cutter, they will verify this. Also the starter motor gear must have the same 'lead-in' as the flywheel gear. This is a slight cut to one side of both gears, so the when the starter motor gear flys foward, it does not hit the corner of the opposing flywheel gear teeth. This allows the gears to 'bruise' past each other, on the way to meshing fully.

A lot of people looking at used gears have mistakened the 'wear' at the leading edge of both gears as real wear that requires refurbishment, when in fact this was always a deliberate cut from RR.

I could go on all night. If you have any further questions, email me. 'Am in England. I have over 1300 photos so far of my restoration, and am not even half way there.

Good Luck
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Bill Coburn
Posted on Tuesday, 24 July, 2001 - 18:10:   Edit PostDelete PostView Post/Check IP

I would be approaching the P III Society on this one as the conversion is a very common one and surely they would have the gen on the starting requirements.