Thoughts on using a 911/01 vs 915 gearbox in front of a 2.8 twin, in a '68 SWB 911

[jmz]

Can any of y'all with a keen eye and experience tell from these photos what was done on the 1968 912/6 that sold on B.A.T. a few months ago? https://bringatrailer.com/listing/1968-porsche-911-9/

[gled49]

If I had to guess I'd say those were VW type 2 CV joints that have the same bolt pattern as 100mm drive flanges in eather coarse or fine spline. I'm not sure how the axle spline to type 2 CV is handled. G

[raspy2point2]

Hi JMZ-- I assume you are doing JE pistons or something. Because if you are using 92mm RSR pistons on standard heads, you compression ratio would be about 12 to 1. Also if you are using a aluminum case--that's fine. If you are using a MAG case, my tech says it cannot take the high stresses of a 92mm x70.4 crank. He showed me a 2.8 engine made with a mag case and it had a crack and was useless. Although the owner was racing with it. I guess if you are just on the street and not keeping the rpm's at 6000 all day, you might be OK. Chris

[jmz]

Hi JMZ-- I assume you are doing JE pistons or something. Because if you are using 92mm RSR pistons on standard heads, you compression ratio would be about 12 to 1. Also if you are using a aluminum case--that's fine. If you are using a MAG case, my tech says it cannot take the high stresses of a 92mm x70.4 crank. He showed me a 2.8 engine made with a mag case and it had a crack and was useless. Although the owner was racing with it. I guess if you are just on the street and not keeping the rpm's at 6000 all day, you might be OK. Chris

I get it. I've got some pros working on the engine and yes I've got all the bad stuff. ...RSR pistons, mag case and standard heads. I had concerns and they've got the details worked out and have the compression ratio down to something that works with pump gas etc. I think it's going to be a fun little toy.

[Frank Beck]

Frank, those flanges are for CV joints with 94mm bolt circles, not 94mm diameters. They're basically aftermarket 108mm 85> flanges that use six M10 bolts.
Maybe I don't understand the fix you're suggesting?

Jon B.
Vista, CA

You're correct Jon; Martin doesn't build the 78mm bolt circle flanges. I like Gordon have drilled out 914-4 flanges and installed inserts. But that's only if one has the course spline diff.

[gled49]

Raspy, one of my 2.8's with Mahle's, Mag case, S cams, twin plug and MFI, just came off the dyno with 252hp. Comp was 10.2, done it many times, takes a little work, but for a street motor there's nothing like Mahle P&C's. G

[geneulm]

I second this. Not as strong as a sandcast case (absolute best choice) but can be made pretty durable. I’ve got a 7r that has been dowel pinned, 70.4 by 92 rsr w a little work to get the compression within workable bounds. Twin plug, ge60, mfi HB and is a fun motor. Take it to 7800 all the time.

An early mag case would be far from my first choice, but there have been plenty of them out there that have made them work and last under tough conditions.

[tfiv]

You won’t need to put on plastic door handles, or hole saw your wooden floor boards if you run the type 911 trans

[jmz]

You won’t need to put on plastic door handles, or hole saw your wooden floor boards if you run the type 911 trans

Hadn't thought about weight, That should come into play too I suppose.

[tfiv]

Ollie’s gets about $3500 now for a full meal mag case deal. Guys are pretty proud of those sand cast cases these days too though. If memory serves there’s nearly a 30 lb difference.