Mahle 98mm RSR quick help

[Alan.UK]

Hi all,

How many types of 98mm mahle style pistons are there for the 3.0 (70.4) crank ?

1) I know there are the 98mm Max Moritz style (which I have)
2) RSR high compression ones 10.2:1
3) ?
is there a 9.2:1 CR mahle 98mm piston ?
and if so will this clear an S cam?

Thanks

Alan.UK

[jpnovak]

I am not aware of any Mahle pistons other than the two types you mentioned.

There was a CIS version of a 98mm piston but that would definately not clear an S cam. The RSR type will.

[Carrera3.5L]

Basically 3 big bore versions of Mahle pistons available for the 70.4mm crank and 3.0L case. All have 22mm wrist pin diameter:

1) 98mm suitable for CIS - 9.8:1 CR

2) 98mm suitable for carb/mfi - 10.2:1 CR

3) 100mm suitable for carb/mfi - 9.8:1 CR (not very common)
this requires case machining and yields 3.3L in displacement

Ralph

[Brother]

When you say option number two is suitable for carbs/mfi? Do you mean that you can run that CR with carbs and pump gas or that you can run cams that will work with those systems and still clear the piston?


Learning as a I go. I'm thinking of putting PMO's on my 3.0 motor someday unless I can find the 3.7L kit from Andial.

[Carrera3.5L]

Originally posted by Brother
When you say option number two is suitable for carbs/mfi? Do you mean that you can run that CR with carbs and pump gas or that you can run cams that will work with those systems and still clear the piston? Learning as a I go. I'm thinking of putting PMO's on my 3.0 motor someday unless I can find the 3.7L kit from Andial.

What this means is that they are the "RSR" type piston dome which have large valve relief cut-outs that allow you to run more aggressive cam profiles.

I would think twice about a 3.7L CIS kit from a 3.0L unless you really want to go against the grain and be different from most everyone else, the 3.6L Varioram transplants will be cheaper, more reliable, and will produce more power with a few performance upgrades. I wouldn't ever build a 3.7L CIS, but I guess a 3.7L carbed motor would be definitely different and kind of interesting to see the results...I think the 102mm Mahle pistons/cylinders and Carillo rods needed are about $7K alone!!!

If you have a 3.0L, I would stick with 98's for a 3.2L. Would be a nice SC motor with carbs, suitable cams and SSI's as long as you don't have to pass emissions tests every couple of years. Many, many, many people have done these over the years.

Here is an image of an "RSR" style piston to give you an idea what they look like:



Ralph

[Alan.UK]

Thanks for the Info,

Ralph, that pic is the set I have a lead on. Do you know what CR they run at ? The pistons I was getting confused with are the RSR style ones in which the valve pockets almost meet in the middle of the piston.

Will those pistons pictured above work well in my engine (see spec below). If not I am just going to buy new 98mm 9.5:1 J&Es with new aftermarket 98mm barrels.

Engine 79 SC with 39mm inlet ports
46 PMOs
98mm pistons (currently have the MM style but these will not work with my cams
Andial S cams
Distributorless Ignition
SSI heat changers
Dual outlet exhuast

This will be bolted to a later 3.2 915 box which has an oil cooler.

Thanks

Alan

[Wayne 962]

There are several different types - all with different compression ratios. I have the 10.5:1 RSRs...

-Wayne

[Carrera3.5L]

Originally posted by Alan.UK
Thanks for the Info,

Ralph, that pic is the set I have a lead on. Do you know what CR they run at ? The pistons I was getting confused with are the RSR style ones in which the valve pockets almost meet in the middle of the piston.

Will those pistons pictured above work well in my engine (see spec below). If not I am just going to buy new 98mm 9.5:1 J&Es with new aftermarket 98mm barrels.

Engine 79 SC with 39mm inlet ports
46 PMOs
98mm pistons (currently have the MM style but these will not work with my cams
Andial S cams
Distributorless Ignition
SSI heat changers
Dual outlet exhuast

This will be bolted to a later 3.2 915 box which has an oil cooler.

Thanks

Alan

Alan,

The pic I posted is actually a 100mm piston with 23mm pin to turn a 3.2L Carrera motor into a 3.5L. The CR for this particular piston is only 9.2:1. This "type" of piston will work with the S cams that you want to use.

The advertised CR and actual CR's are sometimes different with Mahle Motorsport products. One advantage of JE's is that you can provide them the information so that they manufacture you a set with the CR that you would ideally like to run.

Ralph

[Alan.UK]

Thanks for the advice

I will let you know how I get on.

Alan.UK

[Brother]

Thanks Ralph.

I knew the price of the 3.7 kit was a little outrageous. In reality, I plan to do the 3.2 bump with PMO's. Not sure whether I would need 46's or 40's but I'd call them first. Of course SSi's and a dual out muffler would be in order there as well. Just line in Wayne's book.

Andial and RUF ads kept me focused in college. I'll have to thank them someday.

With a 176,500 on the clock, you would think I would be close to the rebuild but it still pulls hard and doesn't complain.

[cnavarro]

There is an alternative to the andial/mahle 3.5 & 3.7 conversion P&C kits. Although I typically don't stock them on the shelf, I have made a half dozen of these conversion sets in the last year; in every case the customer single-plugged the engine and kept the compression down at 9.3:1 (saw 9.5 and 9.2:1 being thrown around). Although still pricey at a little under $4k, it's readily available and with the use of JE's, total customizable for exactly what you need or want. My biggest concern with the 3.7 conversion is the fact that the case needs to be bored out to 106.5 or 107mm, which leaves minimal support around the head stud bosses. Has anyone tried to put case savers in a 3.0/3.2 case and opened the case up for the 105mm or 107mm register? That said, there are other applications with less support around the stud bosses. In every case i've seen, the 3.5 and 3.7 conversions have been in N/A applications and I would keep it that way too.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[Brother]

Thanks Charles.

When you come up with the budget big-bore kit, give us a call.

What kind of performance were your customers doing the 3.7 upgrade getting?

[cnavarro]

Budget kit. haha, that's funny Honestly, nothing yet as far as dyno #'s. Although I have quite a few sets out, everyone has been tight lipped I've had to go as far as to literally pay people for feedback and dyno results in the past and it looks like I might just have to do that with the 3.5 kit I currently have a customer who is doing a 3.0->3.5 (102mm bore) at Black Forest (San diego, ca), but it's still coming together. Waiting to hear on the #s from that.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance