3.2 to 3.4

[david.avrahami@]

1987 carrera, I am contemplating doing this conversion by enlarging my own 9.5mm cylinders to 98mm (Mahle) and getting the max moritz (mahle) pistons 98.1 compression.
i AM TOLD THAT THIS CONVERSION IS A PLUG AND PLAY SET UP and i would like to know if any changes or adjusments have to be done to set it all up.
option 2 is to buy brand new 3.4 cylinders instead of the rebore and plate matching it also to the max moritz pistons (both mahle). is this set up require any head work to set up?
i would appreciate your proven answers especially from pelicans that did one of the two options above.

[LakeCleElum]

I have a Max M. 9.8 compression that went from 3.0 to 3.2......Plug and Play enough that I still use the CIS.....Highly recommend. Fine with 91 octane by setting total advance to 29 degrees on mine.

[911 Rod]

I just did this and it is plug and play, but you will need a new chip.

[darrin]

right -- since the sparkplug's off center on our engines, one needs to retard timing a bit to allow for full combustion with the wider piston on a 3.4. Going with a twinplug setup allows for more advance and power.

Question -- since I presume the OP would have his heads machined (valve guides replaced, etc.), how much sense would it make to have holes for second spark plugs added to each head during the process so that a dual plug setup could be more easily added in the future?

[86 911 Targa]

DRACO A5OG
^^^^^
Send Jim a pm.

Best,

Gerry

[Jgordon]

Why have your P&Cs machined? I bought a set when I had mine done. They weren't extravagant, and you get the added bonus of keeping your original set (for resale or posterity depending) and less likelihood of something going wrong.

There's a list of stuff to look at while you're in there; I have a thread I'll post, but others have done a better job.

Good luck! The added torque is sweet.

[Jgordon]

You all suck

3.2 to 3.4 - what else?

Again, good luck.

[jons911]

The Max Moritz pistons are designed to be plug and play for single plug engines. The piston dome is asymmetric to aid the flame front propagation. You may have to adjust your advance and upgrade to the 91 octane, but no significant engine upgrades are needed. If you go with a twin plug setup, you might as well get the higher compression JE pistons.

[david.avrahami@]

Jons911... "You may have to adjust your advance and upgrade to the 91 octane, but no significant engine upgrades are needed."
What do you mean by significant engine upgrades??? any head work? please be more specific if possible...thanks

[jons911]

I'm not a great resource for what work is needed for the heads. I would guess there may need to be some work to match the heads to the wider bore (I searched through some old threads, and I'm now pretty sure you have to get the heads matched), but you should probably send the heads to a shop to be checked out anyways during a rebuild. As far as the rest of the engine, it is my understanding you can continue using your stock components (cams, connecting rods, ignition, injection system, intake, exhaust). As others have pointed out, since you have a 3.2, it would be an easy upgrade to swap your current chip for a performance chip that is designed for your setup. Steve Wong chips have an excellent reputation on this forum.

The key is the Max Moritz pistons though. They are specifically designed for single plug. It's kind of a toss up on whether boring out to 98mm really requires the Max Moritz pistons to stay single plug or if you can get away with other pistons on higher octane gas and a bit more advance. You'll find people on both sides here. I personally would twin plug if not using the Max Moritz pistons (but I also love the twin plug distributor look). However, twin plugging leaves some potential untapped. You can use higher compression pistons, which would probably benefit from different cams. Performance improves even more when EFI is added on top of that. And the slippery slope continues.

But back to your case. I would get the Max Moritz pistons, and then send them with your cylinders to get rebored and plated. This way the shop doing the work on the cylinders can match the pistons to the cylinders with the proper tolerances. Then, get your heads matched to the cylinders. Finally, plug and play. I wouldn't waste money on buying new cylinders unless you feel the need to keep your original cylinders in stock form. The 3.2 95mm cylinders are just fine to be bored out, and you are not doing anything overly strenuous like running high boost or very high compression, so they will be just fine.

Kind of rambling, but I hope that helps a little bit. Keep asking questions if you have them, and also try google searching 3.2SS and 3.4SS (SS stands for short stroke) as that is the common name of the upgrade you are doing. That should pull up a bunch of threads which will give you a much larger information pool to pull from.

[Flat6pac]

Economics..find a set, or 6, alucil cylinders and have them opened up. Your Mahle s have a value that the alucil s don't have. Deck height will be reset as the work is being done on the cylinders.
Scratched alucil doesn't matter.
Bruce

[faapgar]

Hi,I have done around 20 conversions to 3.4 with the Max Moritz setup.You have to bevel the cylinder head for 98mm at the head gasket surface or risk contact as it is close.If you resurface the head use the 930-104-381-01 repair head gasket as it is 0.50mm thick.Your machinist can open up the inside from 95-98mm then no problems and the heads will never sweat.Fred

[archnraft]

Hi David,

I have a very nice set of 3.2 to 3.4 Max Moritz pistons with a new ring set. This is the plug and play set up you are looking for as Fred mentioned.

PM me if you are interested... I'm going with custom higher compression twin plug pistons...

Best,
Anna

[david.avrahami@]

Hi Anna,
I sent you a pm...but so far no response....