opposite rotation camshaft


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By aussiebill - 13 Years Ago
Been looking for my Interceptor book for years until today, funny enough was among 1st editions of Y block magazines. if you can read the 3rd paragraph down it shows the firing order of the cam and rotation direction of the marine engines, they are opposite to car as they are viewed from the back. i dug through some old cams and although i could of taken a bit more time and clearer pics you can see the 2nd cam from left has lobes everywhere except 1 & 6 which remain constant. the left cam is older normal regrind with small base circle due to wear, next is the boat cam, 3rd cam is normal cam with "Stellite" hard face lobe tops and one on right is old Potvin eliminater #27. Hope this shares some interest. regards bill.Smile

Doesnt look real clear, the opp rot cam firing order is ;12736845

By Hoosier Hurricane - 13 Years Ago
If you read that firing order backwards, it is the same as the forward rotating firing order.
By aussiebill - 13 Years Ago
Hoosier Hurricane (8/14/2011)
If you read that firing order backwards, it is the same as the forward rotating firing order.

yes john, its seems confusing to me.

By pegleg - 13 Years Ago
Bill, I hate to admit it, but you must be right! Number 1 and anything 180 degrees to it will be the same in either direction. Anything at 90 degrees will have to be reversed to be in the right place at the right time. Or in the wrong place at the wrong time. interesting!w00t
By aussiebill - 13 Years Ago
Frank, it was only that i finally found the manual and the page with the firing order etc that i put it up. On reflection, the crank is turning backwards but due to timing gears being used, the cam still turns in normal direction, hence the distributor idrive s normal etc.Smile
By Hoosier Hurricane - 13 Years Ago
That backward turning crank has me wondering.  Is the marie crank different?  What about the oil hole location in the journals in relation to the compression/power stroke load on the journal?  If the cranks are the same, do the marine engines show more crank and bearing wear than their landlocked brethren?  I seem to remember reading in YBM about the misplaced oil holes in one of the journals of the 239s and resulting accelerated bearing wear on that journal.