650SS half time pinion

This is going to be a very interesting thread. The symbols, on these pinions, suggest advancing or retarding of the valve timing. I've not seen it done on the half-time pinion before as generally it is the Camshaft sprocket that has a vernier to permit adjustmenton a Dommie engine. Otherwise the ignition timing has to be reset, as well, each time a change is made. Somewhere on this website are details about how by playing around with the sprockets and pinions the valve timing can be changed.

I have a feeling that you are going to have to assemble most of the engine, on a bench, and then check the valve opening times using each of the different pinions. There will be a bit of careful measuring required here plus a table of the opening times.

An alternative route might be to ask advice from some of the lads that rebuild race engines for a living. eg Norman White, Mick Hemmings etc.

I have 4 Half Time Pinions, marked -3 -5 +1 ?1 ( please see photo ) I am building a 650ss engine, can you please advise me on which one to use.

All help will be greatly appreciated. Owen.

The one to use is +1 is the right pinion

yours anna j

Other than the one marked -5, the original dot seems to be in exactly the same position in relation to the slot for the woodruff key. I would need a degree disc to check accurately. I have a suspicion that the later numerical marks are spurious, unless someone has gone to the trouble on machining slots a degree or so out - which seems unlikely. So my guess is that any of these 3 should be OK if assembled by the book. Can't see the slot on the -5 pinion to check.

Anna, could you explain why "The one to use is +1" ? Just interested in how you come to that conclusion.

I'm with Gordon, unless someone went to the trouble of obtaining pinions without a keyway & then machining their own a degree or so out, even then, it doesn't make much sense, as Phil quite rightly says, you would usually make any alterations at the cam sprocket. The -5 pinion seems to have a sleeve protruding, never seen anthing like that before & certainly not part of a normal half time pinion

Regards, Tim

Anna, could you explain why "The one to use is +1" ? Just interested in how you come to that conclusion.

I'm with Gordon, unless someone went to the trouble of obtaining pinions without a key-way & then machining their own a degree or so out, even then, it doesn't make much sense, as Phil quite rightly says, you would usually make any alterations at the cam sprocket. The -5 pinion seems to have a sleeve protruding, never seen anything like that before & certainly not part of a normal half time pinion

Regards, Tim

well if you count the teeth on pinion you get 6 from the key-way the the punch mark dot on 3 and +1 and on 5 you 7teeth my spare Pinion as 6 teeth from the key-way so the one mark one and its marked with other 1 on this side then crossed out with a other mark looking like a cross , this one is there nearest to the original pinion been 6 teeth from the key-way to the punch mark dot and there other pinions do not belong any where

Previously anna jeannette Dixon wrote:

well if you count the teeth on pinion you get 6 from the key-way the the punch mark dot on 3 and +1 and on 5 you 7teeth my spare Pinion as 6 teeth from the key-way so the one mark one and its marked with other 1 on this side then crossed out with a other mark looking like a cross , this one is there nearest to the original pinion been 6 teeth from the key-way to the punch mark dot and there other pinions do not belong any where

Sorry Anna, not with you there? On the pinion marked with a 5, (bottom left in pic) you canât see a keyway, or a clear timing dot. On the other three, starting at the keyway, counting anti clockwise toward the timing dot, Iâm counting seven teeth on all (including the marked tooth). The timing dots all correspond with a tooth & the keyways all look to correspond with the gap between two teeth & with the exception of the number markings, all three look to be the same. Perhaps Owen could tell us if, with the pinions laid one on top of another with the keyways lined up, do the teeth line up also?

Regards, Tim

Previously owen_green wrote:

I have 4 Half Time Pinions, marked -3 -5 +1 ?1 ( please see photo ) I am building a 650ss engine, can you please advise me on which one to use.

All help will be greatly appreciated. Owen.

The above thread question is from nearly a year ago. I had never coma across such markings before and then just today............while searching through my spare intermediate pinions, I came across one with similar markings. See attachments. I am fairly certain that this pinion came off a 1950 model 7 engine. Note also the extra markings on the front of the pinion to help locate the timing position.

Owen might I suggest you assemble the engine (and rotate a few times) with any one of the three (with keyways) and then try replacing with each one at at a time to see if each will go on without turning the engine (at all) they may all be the same. Even better to start with a genuine standard one on loan from someone.

Cheers from downunder - Patrick