A little update on this project, it well under way, bascily this guy already has a 12G-295 head, and has decked and using it on another 948 bottom end, now I'm building him a a more robust 948 bottom end. The engine is using .060" over 998 piston, which make it .120 over the standard bore of 2.48 of a stock 948, so the bore size now is 2.60", which now make the engine a 1044cc, the 948 block took the bore szie with zero problem, plenty of meat left, the normal 948/1098 head gasket will work fine with even a little room left to spare. The AE 20950 998cc .060" pistons which are flat tops work fine and as for deck height, which no one seem to be able to give me a answer ahead of time, but they work out to about .016" on piston deck height, I was told everything from .060 down in the bore to .010 above the deck, so much for asking the experts
Oh it's worth mentioning that AE 20950 piston are a modern 3 ring design.
Another thing to talk about here is the fact we are using 1098 connecting rods, as the 948 pinch bolt I guess could be made to work with 998 floating piston, but using the 1098 rod just let me utilize the floating set up the 998 pistons were designed for. Now on to rod bolts, now i not much for using stock rod bolts, why go to all this trouble to make thing bigger and badder, and then use the stock bots and that silley tab washer set. I search the ARP catalog and found a gneral replacement rod bolt ARP #200-6207 which was perfect for the 1098 rods and would work with zero mods, and would also work fine in the 948 rods as well. The rod bolt look alot like the one that would be used in aftermarket racing rod, and have a 12 point head, they fit into this rods like they were desgined to be there all along.
I'm using the APT VP266 cam sahft with the normal pin drive oil pump set up. The combustion chamber number on this cylinder head, currently they are 24.0 CCs, and with that number, the compression ratio would be little above 10.5 to 1. Wee're deshrouding the combustion chamber a bit, and will be using the 1.31" 1275 intake valve, but staying with the 295 stock exhaust valve size. SO we'll target the combustion size to close to 25CCs and that will get us to the 10.0 to 1 target compression ratio.
I never know what path a customer will take me on with a engine, in the begining, I thought to myself, why not just build a 1275 and be done with it", but the customer wanted people to look under the bonnet of his Bugeye and see a 948, right down to the 950 on the side of the block.
There's ton more work to do, as the dummy build is done down and I know we're OK with piston deck height, and now off to take the rods and pistons back out, and prep the connecting rods, which the customer wanted fully race prepped, which mean the full kit and kaboodle, lathe lightening at the thrust sides and polishing the the beams and full rod body, resizing of the big end with the new ARP rod bolts.
In closing this is what make this job interesting the education never ends, and you always get to do new thing based on the curosity and imagination of your customers, and that makes coming to work everyday worthwhile.
I'll keep you guys updated and promise pictures in the near future.