Overbore

[Myetball]

What's the most anyone has or feels these engines can be overbored? .040? .060? Got another crazy idea and want to know if it will fly.

[biosehnsucht]

.040 = ~1mm over, or 84mm. I recall hearing stories of some crazy 84.5's but I wouldn't try it myself. if you did 85 (~0.060) you'd likely be using the cylinder walls as paper cups at that point.. if there was any left.

[Jezz_s13]

I've never heard of anyone having problems with 1mm oversize, and I've never heard of anyone running anything bigger.

[Myetball]

I chatted with a guy going .060 over but lost touch before he got it all back together and running.

I'm working with a non-turbo engine. The crazy idea is to bore it out to 84.5mm and drop in a stroked CA20 crank. Stroke would be 94.35. I'd run 11:1 compression and stage II cams with upgraded valvetrain. Custom rods and pistons would be a must. The CA20 crank is a tough forged unit but the rods are like toothpicks compared to the CA18DET.

[Jezz_s13]

2.11L CA, sounds interesting.

I'd have thought with not turboing it that the extra 0.5mm wouldn't be *such* a big issue.I've just looked on takakaira at the main Jap companies and 84mm seems to be the biggest they do.

[Myetball]

It occurred to me today how to get an 89mm bore. Take a CA20E block (88mm) and bore it out 1mm over. Shave the necessary 3-4mm off the top of the deck so the CA18DE head fits on without the need for a special timing belt. Custom length rods and pistons and perhaps custom main cap bars and girdle. So what's the displacement of an 89 x 94.35 engine?

[biosehnsucht]

~2348 (rounding) cc( volume of cylinder is pi * r^2 * h .. then * 4 for total displacement, and divide by 1000 for cc's displacement)

thats gettin a bit large there.. and whats the deck height on a CA20? after taking those few mm's off and shoving the customs bits in there, even with raising the wrist pin height chances are with that kind of stroke you'd have a rather bleh stroke/rod ratio..

[Myetball]

Apparently I can't read a shop manual. The CA20E is 84.5x88 stock. So I'd be looking at 85.5x94.35. Stock rod length is 149.3mm so compensating for the deck trim...let's say 3mm for the sake of argument...I'd end up with 146.3mm rods on a 85.5 x 94.35 bore/stroke. The added 6.35mm stroke would be compensated for by relocating the wrist pins 3.175mm upwards.

[biosehnsucht]

2116cc, 1.55 R/S ratio can't recall how-if to factor wrist pin into RS so thats just plain old R/S, not the worst but not the greatest either.. the wrist pin relocation should help tho..