Thoughts on a 225 rebuild
I have 3 Super Six Engines in my shed and I'm currently toying around in my head with rebuilding 1 of them as a Long Rod 225 with EFI.
Creating a Long Rod 225:
you use your 225 block and crankshaft. And then you use the 7 inch 198 connecting rods and late 80's early 90's 2.2 Turbo pistons like Sealed Power W533P. The Pros of this combo are light, strong pistons and a very long connecting rod. This combination produces 1.7 rod ratio *which is really good* and will push the piston close to the top of the bore. (.040ish negative deck height). A stock 225 rod/piston setup stops somewhere around 0.175" down in the cylinder (negative deck height). Bringing the piston closer in turn raises the compression and also a increase in torque. With unmilled components and a fel-pro gasket. You would be looking at around 9.0:1 - 9.5:1 compression. If you start milling decks, then all bets are off as compression shoots up quickly
So whats the difference? Lets break out the old math:
225 rods and 225 pistons
Stroke - 4.125
Rod Length - 6.700
Deck Height - 10.680
Piston Compression Height - 1.918
225 Pistons have a Compression distance of 1.740
That puts the piston 0.178 down in the hole
-Boring
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198 rods and 225 pistons
Stroke - 4.125
Rod Length - 7.005
Deck Height - 10.680
Piston Compression Height - 1.613
225 Pistons have a Compression distance of 1.740
That puts the piston 0.127 out of the hole
-YIKES!
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198 rods and 2.2 Turbo pistons
Stroke - 4.125
Rod Length - 6.700
Deck Height - 10.680
Piston Compression Height - 1.613
2.2 Turbo Pistons have a Compression distance of 1.573
That puts the piston 0.040 down in the hole
-The Sweet Spot
So for a cheap upgrade in pistons/rods you can increase efficiency of the motor and the compression from 8ish to 9ish
If you go the Slant 6 route, I would encourage you to gasket match the intake and exhaust components and run 2.25 pipe to help out where you can.
