TOPIC: One for the Professer

I read with interest about your comment having bored a 89 cube V4 .060" over and fitting it with pistons from a 115. I need a little help here -

In both the blocks I have, the No 4 cylinder has deep scoring from the rings getting stuck. I'd guess that .030 would be needed to clean up the deepest cuts. NOS pistons would be nice - but the price is out of the question. I could put a sleeve in the No. 4 hole, but that's expensive too. I could just overbore the bad cylinder - but I don't like the idea of just one overbore, though I have been told by many old timers that it would be fine.

What is the bore dia. for a '74 V-85? I found a cheap NOS Std. set of pistons. If the bore is 3.44" I believe these will work with a .060 overbore? If they are 3.50" then they won't.

Also - I'm guessing the wrist pin Dia & location are the same on the 3.44" pistons you fit into that engine. ???

I'd just go find another powerhead - but the one's I keep finding all seem to have at least one bunk cylinder.


Thanks for your help

BG

The bore for a 75 - 85 HP is 3.375

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Fitting the standard 115 HP pistons into the 66 -100 HP was not easy.

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It required machining some material from bottom of skirts and also from the top for clearance on the cylinder head.

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All rods were selected to weigh the same and pistons machined to weigh the same.

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That engine ran at over 6000 RPM effortlessly.-I could not find / nor could I afford the proper props for it -19" 2 blade bronze is all I had ( still have 2 or 3 of them )

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I have a number of 100-HP blocks , but no interest in shipping them anywhere, pick-up only.

Thanks for the response.

What is the bore on a 1974 V4 85 HP? Is it still 3.44 or is it 3.58? I have heads from a 1971 V100 the combustion chambers have more room for the deflector. They go straight up at the cylinder walls, where the 1968 and earlier heads had an angled area that comes closer to the defelector. I have a NOS set of pistons & rods for the 1968 V100, so a good block would be the smartest option. I wonder if there are any members near you who would be willing to ship one of those blocks you have to me????


Thanks for your help - I have plenty of parts to put a couple of these together, just no good blocks. If necessary, I'd put in the pistons for the 1974 engine if they are 3.44

Thanks again.

As stated the standard bore for a 74---85 HP OMC is 3.375

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I am not sure where you get your numbers

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The standard bore for the short lived 115 HP motors of 69 thru 70 was 3.437