trying to decide on P&C for single plug

[Trakrat]

My original pistons are Alusil and have some damage on the piston heads due to floating valves.

I have no desire to go with a twin-plug setup, so I need help in deciding on the best P&C setup.

Any suggestions on what I need to get?

(FYI... I've read Wayne's books, and unfortunately there is some contradiction written in his Engine Rebuilding book)

Can I go with 98mm 3.4, even though Wayne's book says 98mm needs dual plug? Can I go with the Euro spec P&C, even though Wayne's book says compression above 10:1 needs dual plug?

I'd rather not stay at 3.2 if I can find something better. Now's the time to upgrade while the engine is getting rebuilt.

(Everytime I research more, I'm just more confused and start doubting I'd make the right choice)

[emcon5]

The Max Moritz style piston is designed for a single plug, the dome shape is a wedge, compared to the traditional dome which would split the cylinder and can block spark propagation.

Since yours is a 3.2. you can bore out your cylinders to 98mm and have them replanted fairly inexpensively.

[Trakrat]

Originally Posted by emcon5

The Max Moritz style piston is designed for a single plug, the dome shape is a wedge, compared to the traditional dome which would split the cylinder and can block spark propagation.

Since yours is a 3.2. you can bore out your cylinders to 98mm and have them replanted fairly inexpensively.

I was thinking this as well.. but would have to get new cylinders... not using mine due to Alusil.
However... I came across a page on Patrick Motorsports site that sells the Max Moritz style 3.2 to 3.4 but they claim it is a 11:1 compression. That seems too high for a single plug setup.

[Flat6pac]

Onche you plate nikisil on the alucil cylinders you have what you need at98mm
Bruce

[emcon5]

Originally Posted by Trakrat

I was thinking this as well.. but would have to get new cylinders... not using mine due to Alusil..

You use your cylinders as cores. There are a few places that can bore them out to 98mm, and replate them with Nikasil.

I would give EBS Racing a call, I know they do it, and can probably sell you the pistons.

[Cory M]

You're fine going to 98mm just don't go high compression, that when you need the twin plug. I ran a single plug 3.4 with JE 9.5:1 pistons for several years.

[Lyle O]

I rebuilt my engine to 3.4 with Max Moritz style pistons. I shipped the cylinders to EBS and they had them bored and replated. They also supplied the Mahle Max Moritz pistons (9.8:1 CR), single plug. Great set up here in Michigan, though we have 93 octane gas. Steve Wong did the chip to match everything. Been running flawlessly for over 3 years now.

[Trakrat]

Originally Posted by Lyle O

I rebuilt my engine to 3.4 with Max Moritz style pistons.

Just curious... but does anyone make a 3.2 to 3.4 piston that isn't a Max Moritz style?

As far I can find... since 3.4 isn't a factory size option, it seems ALL the pistons have the Max Moritz style cut to them.

The bigger question is... are JE and Mahle pistons identical in measurements?
Meaning... is there a determined standard on what makes a piston a Max Moritz style??

I looked at EBS Racing and it looks like they use JE pistons. I had planned on buying Mahle pistons, only because I'm familiar with that brand.
What makes JE pistons better than Mahle?

[sp_cs]

Some info here - looks like JE do a single plug piston:

Want a JE forged 3.2 to 3.4 max mortiz style pistons?

[sp_cs]

Maybe use the search facility for a JE v Mahle discussion:

Mahle vs JE

[Trackrash]

There are these.... https://www.fvd.net/us-en/10010303304/mahle-30-liter-32-liter-rsr-piston-and-cylinder-set-1031-98-mm-big-bore-for-911-30-l-cis.html

[emcon5]

Originally Posted by Trakrat

Just curious... but does anyone make a 32. to 3.4 piston that isn't a Max Moritz style?

Yeah, I have 98mm Mahle RSR pistons. They have a traditional dome with valve pockets.

[Trakrat]

Originally Posted by emcon5

Yeah, I have 98mm Mahle RSR pistons. They have a traditional dome with valve pockets.

So does this piston provide a higher compression? I saw an RSR style design for a 3.4, but the compression was something like 11.3:1 which seemed really high for a 98mm piston.

The RSR style I saw had a slight concave center

[T77911S]

you need to start with what octane of gas you have and want to use.
last thing you want to do is have to retard timing because of fuel.

[emcon5]

Originally Posted by Trakrat

So does this piston provide a higher compression? I saw an RSR style design for a 3.4, but the compression was something like 11.3:1 which seemed really high for a 98mm piston.

The RSR style I saw had a slight concave center

I don't remember the exact advertised compression, but I remember it was pretty high, but a factor in the compression ratio of the volume of the combustion chamber. It measured at 9.8:1 with my 3.0/late SC heads. My engine is twin plugged though, so not a concern.

[3rd_gear_Ted]

For comparison:
Wossner Pistons, Huntington Beach CA

[darrin]

trakrat - since the single spark plug in your 3.2 is off center (dictated by valve placement), you need a wedge-style piston to facilitate flame propogation from the single plug across the wider 98mm 3.4 piston width. Regardless of whether it's referred to as a "max moritz" etc., assuring that the piston's designed to work with a single, off-center plug is key.

Although I recognize that you have no desire to go with a twinplug setup, I presume that you're going to need to have machine work done to your heads (valve guides, etc.) -- I'd strongly suggest at least inquiring into the cost of drilling the heads for a second plug (and capping the tapped holes). That way, if your build does have detonation issues, etc., you could convert to twinplug without disassembling the engine to have the heads tapped. Keep in mind that the 3.2 motronic system lacks a knock sensor and that by changing the design of the engine, you're introducing the potential for knock.

[Trakrat]

Originally Posted by T77911S

you need to start with what octane of gas you have and want to use.
last thing you want to do is have to retard timing because of fuel.

100 octane... or the equivalent of 100 octane.

[Trakrat]

Originally Posted by darrin

trakrat - since the single spark plug in your 3.2 is off center (dictated by valve placement), you need a wedge-style piston to facilitate flame propogation from the single plug across the wider 98mm 3.4 piston width. Regardless of whether it's referred to as a "max moritz" etc., assuring that the piston's designed to work with a single, off-center plug is key.

Although I recognize that you have no desire to go with a twinplug setup, I presume that you're going to need to have machine work done to your heads (valve guides, etc.) -- I'd strongly suggest at least inquiring into the cost of drilling the heads for a second plug (and capping the tapped holes). That way, if your build does have detonation issues, etc., you could convert to twinplug without disassembling the engine to have the heads tapped. Keep in mind that the 3.2 motronic system lacks a knock sensor and that by changing the design of the engine, you're introducing the potential for knock.

so if detonation could be an issue... could I go with an aftermarket ignition system to allow for a hotter spark plug to be installed and used?

[Trakrat]

Originally Posted by Cory M

You're fine going to 98mm just don't go high compression, that when you need the twin plug. I ran a single plug 3.4 with JE 9.5:1 pistons for several years.

so WHAT is considered high compression then?

I'm told that anything above 10:1 compression needs twin plug... if so.. then did Porsche twin plug their Euro spec cars from the factory to support the 10.3:1 compression that their factory spec P&C?

I was planning on buying the Mahle 3.4 P&C set... but then I noticed the weight of the 3.4 is heaver than the 3.2... which made me wonder if I would be gaining anything worth the price of going to 3.4