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MG MGB Technical - camshaft identification OEM

MGB camshafts are identified (to some degree), by the number of grooves on the rear of the cam, past the rear journal, what does 1 groove mean, 2, etc.
Len Fanelli

Len,

A few weeks ago Dimitri Elgin of Elgin Cams (http://www.elgincams.com/campaper.html) explained to me that there were three camshaft grinds. The first (one ring) had a duration of 244 degrees intake and exaust; the second (two rings) had a duration of 264 degrees intake and exaust; the third (three rings) had 244 degrees intake duration and 264 degrees exaust duration.

Jim
J Brownell

Len,

I made a mistake. Mr. Elgin identified the grooves you asked about as slots, not rings as I called them.

Jim
J Brownell

As far as I understand, three rings on the rear denote an MGB camshaft and one ring denotes a Morris Marina camshaft.

However I believe that either can be reground to MGB specs.

I have never seen a camshaft with two rings in the UK.
Chris at Octarine Services

Part Number: 342-0002 Grind Number: 88G 303
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1957 1980 MGA-MGB 4 REPLACEMENT FOR FACTORY 88G303, CAMSHAFT (1964-80 "2 GROOVE") BASIC RPM 1000-4500
Engine Size Configuration
1598 C.C.

From crane cams for a "stock" replacement.
I have a 1 & 2 groove (OEM worn out).
Len Fanelli

Len,

Very odd figures - it was only the MGA 1600 that had a 1598cc engine and that camshaft carried a drive gear for the tacho on the end where the rings are normally to be found on camshafts.

My guess is that any cam from a 1598cc engine with rings on the back end will have come from one of the BMC saloon cars which were not fitted with a tacho.
Chris at Octarine Services

Just looked at the crane website -

http://cranecams.com/pdf/Page175.pdf

it says engine 1598 - 1798!

also it says 2" groove ?

still no real idea where a 2 groove cam comes from though!
Chris at Octarine Services

The plot thickens!

Just out of interest, I have been through the stock of reground and used cams I have on the shelf.

6 have 3 rings

3 have 1 ring

2 have no rings at all!

Chris at Octarine Services

Chris, et al. I wonder why this all matters? Unless one is doing a tear down inspection of an historical vehicle which, for some reason, must be all perfectly original?

By now, some twenty nine years after the last MGB was made, I would suspect that a significant number of those with working engines will have had the engines rebuilt. In such cases, the camshaft is frequently replaced and, even if it is not, we have no idea whether the camshaft found in any particular engine is original to that engine.

We do know that there were quite a number of B series engines built, only a few of which went into MG sports cars. These camshafts were, physically, interchangable. The factory may have used the number of grooves on the rear journal as an indicator of which type of engine--van, auto, sports car being the obvious choices, or they may have used a painted on number, letters or some other method of designation. Today, unless we can document that the camshaft is "factory, new-old stock" we are not likely to find out. We do know, however, that all of the various versions of the B series camshafts can be reground, to quite a number of different specifications, by a number of different companies.

I have only one camshaft remaining in my collection of "believed original" parts and it has a single groove on the rear journal. But, I would not bet money on it being an original camshaft installed in a BMC engine that was the first engine used in an MGB. The odds, without very good documentation, are against it.

And, it does not really matter today.

Les
Les Bengtson

Les, It does matter if one wants to have a regrind of a stock OEM cam,as there might not be enough material on a 230 duration cam, for a particular grind, in good condition, and for historical information.
Len Fanelli

There was only one grind of MGB camshaft in the UK and it had a duration of 252 degrees, inlet and exhaust.

In Dec 74 a new camshaft was introduced on US cars with an inlet duration of 230 degrees but retaining the exhaust duration of 252 degrees.

Generally, if selecting a cam for other than a stock application, I would always advise a cam ground on a new blank and cross drilled.
Chris at Octarine Services

This thread was discussed between 05/02/2009 and 09/02/2009

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