3.2 to 3.4 Conversion Kit for '87 911
 

New to Rennlist; I have an '87 Carrera that is just about ready for some valve guide work; I am considering the 3.2 to 3.4 'kit' that my local wrench has suggested. Has anyone any experience with this 'kit'? What are the upsides/downsides for this upgrade?

RT:

Nice upgrade and highly recommended. :)

Aside from the costs, there are no downsides. Just make sure that your compression ratio is less than 9.7:1 due to the 91 octane CA premium fuels.

I think the standard Mahle 98mm Motronic conversion kit is 9.8:1. I think that compression ratio is pretty much the standard for the Mahle Motronic 3.4 conversion kits with pistons and cylinders. I like Mahle. Anyway, I think that is the same compression ratio that came in the euro cars. What I am sure of though, is that 9.8:1 is the standard compression ratio on the 80-83 european 911SC with the 930/10 engine code. I have a couple of friends that run those at the track with me, and they haven't had problems yet. They, like myself with 9.5:1, run the mixture on the rich side. With Motronic, you should not have any problems. Of course, to be on the safe side at the track on a hot day, run a little race fuel mixed in or some sort of octane booster. And maybe also disconnect the oxygen sensor. For the street, you should have no problems. The advantage to building a 3.4 from a 3.2, when compared to an SC, is the fact that you already have a 74.4 crankshaft. So all you need are the pistons and cylinders. I like this conversion a lot. It is bolt on, looks stock, no rigging involved and you will still have matching numbers on the car.

Just curious, what is your expected P/E (power/expense) ratio?

I (dimly) recall Bruce Anderson in Excellence saying this wasn't a cost effective upgrade. I think he said that the extra .2 liters was less than 6% displacement increase and would therefore only increase power by approx 6% (13hp). The cost (according to BA) was pretty major. Are you replacing the P/C anyway?

No replacement for displacement, though.