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Any of the engines will easily handle a 1mm overbore. SCCA rules allow for it, and it is common practice to take the additional displacement. It isn’t unheard of to bore a 1750 to 82mm.
 

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A good 750 top frame may be more difficult to find than you imagine. But I agree that making an “abnormale” from a normale is better than making an “abveloce”!
 

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Rob, I have no idea if it is really required. But the machine shop I have trusted for boring liners always does so using a torque plate. When I get them back, they are labeled 1-4, and I put them in that specific hole. He claims that is the only way to ensure that they are perfectly round.
 

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Hi Koenraad,

Neat trick with the 10 mm spark plugs, I had never thought of it. I opted to use off-the-shelf parts on this build in an effort to keep the cost down. I used 1 mm oversize intake and exhaust valves with stock stem diameters so I could use stock guides, seals, retainers, locks, shims, etc. The 1 mm oversize valves fit on the stock valve seats as well. If the engine output on the dyno is disappointing when I am done, the first place I would turn to try to make more power is the head, but I hope it doesn't come to that.

FYI, my cylinder head man told me that he can get better flow out of a 1750 head than a 1600 head. I believe that Mike Sperry of Sperry Valve works told me the same thing 30 years ago. The guy I bought my used engine parts from told me I could have either one for the same price, so I picked the 1750 head. The better flow thing might just be an "old wives' tale", but I figure the chambers might be shaped better for matching up to my 80 mm bore.

Rob
I think you will find the 1600 and 1750 combustion chambers identical with the exception of a very small chamfer at the interface on the 1750.
 
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