what type of new pistons for 3.0 cis

[carl74344]

i have been putting off getting new p&cs. i was going to use my old ones. but do not want to take a chance and have to do it all over again.

my question is posche replacement 9.3:1 or 9.8:1. or LN with je pistons.
if not 9.3:1 what do i need to do for 9.8:1 or the LN/Je.

thank for any help.....

[Sub8]

9.8 euro spec Mahle P&C nothing else needed. Buy and fit. OEM spec, quality control and durability. Slight performance increase vs 9.3.

LN may offer same quality and durability etc but are nearly $2000 more than Mahle. Great if you are considering custom capacity or CR.

You might be able to get your current P&C repaired / replated for marginally less than new parts.

Hope that helps..

[carl74344]

thank you. so the 9.8 is a plug and play? no special shims?

[Sub8]

Yes afaik. Valve to piston clearence is usually checked during build, just in case.....

[VFR750]

Doing it all over again is not that hard. You get better each time you do it.

Mahle p&c are very expensive, but in retrospect, you get what you pay for.

Although my replated cylinders and JE piston are currently working well, it took three tries. I would say the $3400 Mahle p&c likely would have sealed the first time and would have ultimately cost me less than the $1750 I originally spent.

However, the deep valve pockets on the JE pistons saved me when I mistimed the RHS cam. Although I might have found the problem during assembly if I had the Mahle CIS pistons.

There you go: a lukewarm recommendation for aftermarket p&c to save money.

[Sub8]

Mahle available for 2950 delivered.......

[carl74344]

where did you find them so cheap? do I need to dry fit everything including rockers?
or do I just do the check with the # 1 with the solider between the piston and head?
thanks for the help....carl

[carl74344]

well big change. i found 9.3:1 set. so back to factory. thanks to everyone for the help. now i can get started. thanks for everything...carl

[Sub8]

P a r t s g e e k, of all places.

[Trackrash]

Wouldn't it be nice if Mahle sold just the pistons?

[Dan J]

Mahle 9.8 Euro pistons are known to have issues with ring lands cracking if using street gas
so I wouldn't call them a perfect solution.

[carl74344]

well back to the begaining. the P&C set i ordered was discontuned. and the replacement was $300 more per cylinder.
not sure witch way to go...... re-ring what i have or LN/je pistons or 9.8:1 set.
HELP!!!

[Trackrash]

Show us a picture of what you have now.

['76 911S 3.0]

I went with JE 9.5:1 and re-plated cylinders from EBS Racing. Albiet, I went with 98mm bore, the JE & EBS combo works well. No smoke, no piston slap and the EBS cylinders are specifically machined for the JE pistons.

[Josh D]

Originally Posted by '76 911S 3.0

I went with JE 9.5:1 and re-plated cylinders from EBS Racing. Albiet, I went with 98mm bore, the JE & EBS combo works well. No smoke, no piston slap and the EBS cylinders are specifically machined for the JE pistons.

^ This.

If you are going to replace P&C's, might as well increase displacement. Keep your eyes peeled for a set of used 3.2 Carrera cylinders ($500) that don't have the head gasket groove (Mahles or KS will do). Have them bored and re-plated by EBS ($1100). 98 mm JE's or Mahle "Max Moritz" pistons ($900-$1200) and you're still all in for P&C's for under $3K and get a nice power bump to boot.

[arbita1]

Originally Posted by Josh D

^ This.

If you are going to replace P&C's, might as well increase displacement. Keep your eyes peeled for a set of used 3.2 Carrera cylinders ($500) that don't have the head gasket groove (Mahles or KS will do). Have them bored and re-plated by EBS ($1100). 98 mm JE's or Mahle "Max Moritz" pistons ($900-$1200) and you're still all in for P&C's for under $3K and get a nice power bump to boot.

Is it really that simple to increase displacement. Are there no fuel injection system upgrades required for this?

If your having the cylinders replated why can you not just use your original 3.0 cylinders and have them bored to 98mm and replated?

[Josh D]

Originally Posted by arbita1

Is it really that simple to increase displacement. Are there no fuel injection system upgrades required for this?

If your having the cylinders replated why can you not just use your original 3.0 cylinders and have them bored to 98mm and replated?

For K-basic CIS (78-79 US & 78-83 ROW), it's simply adjusting the CIS mixture screw. For Lambda CIS such as yours, I believe they plugged the hole to the adjustment screw to prevent tampering, and the O2 sensor, along with the control computer and frequency valve make the adjustments. It might self adjust enough, or you would have to drill out the plug to access the mixture screw.

3.0 cylinders use a compression head gasket that sits in a groove on top the cylinders. When bored out 3 mm, the inside ridge of the groove gets thin and could possibly break off, so it's recommended not bore them out. 3.2 Carrera cylinders don't use a head gasket, but have a slight taper on the sealing surface.

European tuners such as Max Moritz and RUF were doing this back in the late 70's and early 80's using custom P&C sets from Mahle that have a unique wedge piston dome for increased compression with single plug. Claimed 217 hp. I have a set. Porsche even did a factory upgrade using 97mm turbo cylinders and a custom Mahle 97mm piston for a 3.1L that made 210 hp. Do a search, interesting history on that one because no one seems to know how many were built