1970 911T 2.2->2.3...worth it?

[Cbuckhout]

I am rebuilding my 1970 911T, and have to get new pistons and cylinders. I am wondering if I should stick with what I have, or use this as an opportunity to go bigger.

The stock size is 84mm, and I was told that I could go to 86mm to make my 2.2 a 2.3. My other option is stick to basically the size I already have - boring to 84.5mm and getting some custom forged pistons to match. With either option I would be keeping my compression ratio below 9:1 (right now it is 8.6:1). The difference in cost between the two options is minimal.

Even though the cost for the pistons and cylinders is similar, would I need to change/modify/buy other engine parts to accomodate this 0.1 increase in engine displacement? If I do, would it be worth the cost, time, and potential headache? Does a 0.1 increase really make that much of a difference?

I'm not changing anything else on the car - I'm using the same case, crankshaft, camshafts... I am also planning to use this car just to get around town (with maybe a little race here and there).

Any thoughts, opinions, suggestions, etc. are greatly appreciated!

Thanks!!

[burtm5]

I had the same question 30 years ago. I decided to bore case to 2.7 pistons and jugs to get to a 2.515 liter motor. 40 mm webers E cam. It only had 8.5 cr as this was what was available then. today you can get je with what ever cr you want. max for single plug would be 9.5. this was a good combination. getting 50 extra hp makes a significant upgrade. If you are only going up 10 to 20 hp then question the money. so either stock or make a real increase in hp to justify the price increase. best Henry

[Cbuckhout]

great! thanks very much for the advice! I'm going to stay stock for now, and upgrade down the road.