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Registered
Join Date: Sep 2000
Location: Bournemouth, England
Posts: 1,099
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Mahle 98mm RSR quick help
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 |
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I would rather be driving
Join Date: Apr 2000
Location: Austin, TX
Posts: 9,108
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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.
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Jamie - I can explain it to you. But I can not understand it for you. 71 911T SWT - Sun and Fun Mobile 72 911T project car. "Minne" - A tangy version of tangerine #projectminne classicautowerks.com - EFI conversion parts and suspension setups. IG Classicautowerks |
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Doesn't want/need a 3.6L
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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 |
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Registered
Join Date: Aug 2004
Location: San Antonio, TX
Posts: 1,814
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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.
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Paul 1980 911SC Targa - Sold 1972 914 - Sold |
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Doesn't want/need a 3.6L
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Quote:
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 |
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Registered
Join Date: Sep 2000
Location: Bournemouth, England
Posts: 1,099
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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
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Author of "101 Projects"
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There are several different types - all with different compression ratios. I have the 10.5:1 RSRs...
-Wayne
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports |
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Doesn't want/need a 3.6L
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Quote:
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 |
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Registered
Join Date: Sep 2000
Location: Bournemouth, England
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Thanks for the advice
I will let you know how I get on. Alan.UK
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Join Date: Aug 2004
Location: San Antonio, TX
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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.
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Location: Momence, IL 60954
Posts: 1,911
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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
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Charles Navarro President, LN Engineering and Bilt Racing Service http://www.LNengineering.com Home of Nickies, IMS Retrofit, and IMS Solution |
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Registered
Join Date: Aug 2004
Location: San Antonio, TX
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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?
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Paul 1980 911SC Targa - Sold 1972 914 - Sold |
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Join Date: Oct 2001
Location: Momence, IL 60954
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Budget kit. haha, that's funny
![]() ![]() ![]() Charles Navarro LN Engineering http://www.LNengineering.com Aircooled Precision Performance |
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