Ralph, sorry to here you are having a little trouble with the C/R. It will still be a fine motor though. Good luck. I think you will be safe with the .80ish deck height with those pistons. And with the .015 off the heads, things should be just fine. Just remember, There are a very few things that a couple of pints of Granville Island's finest can't cure!!

Cheers, Jeff

Hmm...I don't know much about about this, but why bother with Mahle's at all when you can order custom forged JE pistons in almost any dimension/shape you want? They are lighter to boot...

Mahle rules.

Well I understand that we have huge purist population here with lot's of myths, legends and history floating around but frankly, Mahle doesn't rule any more than 80's KKK K27 turbochargers compared to modern Garretts...

It's 2004 for god's sake...there are better pistons to be had than some shelved "gold plated" pistons from 20 years ago.

JE's are stronger and lighter than 20 year old Mahles, and probably priced the same or less. I don't see the point of building low comp race motor just to say it "has Mahles in it"...it doesn't show when you look at the engine.

There is lot's of mumbo-jumbo around which piston-design to use, but my anectdotal expirience is that JE'swill withstand more horsepower than OEM ones in most cases. I have a friend with 680 dynoed HP from a 2L engine, using JE pistons.

Wayne:
http://forums.pelicanparts.com/911-engine-rebuilding-forum/161373-je-pistons-vs-mahle.html?highlight=forged

You guess 235 rwhp?? You are LOW!:)

A friend has a 3.2 that has been chipped, cam timing advanced, your headers and a Flowmaster - 213 RWHP. Stock cams. Do a rough projection to 3.2 liters and viola, 234 hp - WITHOUT your internal mods and internal attention to detail!http://www.pelicanparts.com/support/smileys/smash.gif
(Guy working)

Mahles/JEs:

This is so controversial.....
My 2 cents, no comments on this plz, just a data point:

Mahles are proven and rarely have problems; JEs have had some weird issues in the past with reliability in 911 engines.

FWIW. And from what I've read on this and the Rennlist boards.

Ain't that the truth! All I will say on the matter is many of the most respected engine builders and machine shops here on the West Coast use Mahle products exclusively for their street engines. The ones that I am familiar with are Andial, Vision, Rennsport Systems and Ollie's Porsche machining. Steve Weiner from Rennsport has posted on these forums many times why he doesn't use JE's in a street application. Do a search as there is plenty of info, you just have to decide for yourself whose opinion you trust. I defer to the experts above who do these motors on a regular basis. If I am a sheep for blindly following then so be it.:)

Just for the record, there are also many tricks available to further raise up the compression ratio. Unfortunately, you start spending serious money on custom machine work and you can open up a whole new can of worms with respect to the width of the motor and potentially having to use custom sprockets, chains, etc. For a basic street motor, I don't feel it is worth the extra effort. We'll mill the heads .010"-.020" and whatever the CR ends up being after this work will be what we run.

My problem with Mahle is that they advertise one CR (and know it is wrong) when in reality it is something completely different.

Jeff, thanks for the vote of confidence. Steve feels the same way. I miss sitting on the couch on Saturday nights watching HNIC with a GI in one hand and some Indian Candy in the other.SmileWavy Damn NHL.

Ralph

What is the main difference between the Mahle US version and Euro version? Why can you acheive 10.3 CR with a Euro stock 3.2l set up and only 9.3 (or close) with a US set up? I know PAG originally did it because of the lower quality/octane fuel avaliable in the US.. But I am wondering why Ralph is having trouble acheiveing a 10 CR with Mahle pistons.

Ralph:
Do the chain sprocket boxes have to be machined with the cylinders to keep the cam line in sync??
Regards,
J.P.

Don't confuse the original Mahle 95's found in the US and Euro spec 3.2L engines with what I have. Those CR are supposed to be pretty accurate.

The problem seems to be with the 98's and 100's carb/mfi type pistons that Mahle Motorsports makes for the 23mm wrist pin. Someone at Mahle must have measured something incorrectly when these sets were designed or produced. From what I understand, the Motorsport 98's and 100's that retain the original wedge dome top for Motronic are accurate with their stated 9.8:1 CR.

Ralph

In my particular instance, no. In other situations depending on the massaging done then yes other factors can come into play. This is what I want to avoid at all costs (figuratively and literally).

The width of this motor really is not changing much where I will have these additional worries. Ollie's opened up the spigot bore but didn't really remove any material from the case that would make the width narrower. Machining the relatively insignificant amount of material from the heads also narrows the width somewhat (which increases the compression), but that will be compensated for to a degree with the thicker base gasket to get the deck height in spec (which will lower the compression).

It truly is a game, isn't it? Trying to increase compression without ruining the deck height or losing proper piston to valve clearance or having to modify other parts.

At this point, I just want to compromise and get back to a stock 9.5:1 CR without custom machine work that will affect other components. At the end of the day, it is still a street motor.;)

Ralph

"Someone at Mahle must have measured something incorrectly ..."

- That is not possible. They are German!

Let's hope that it is them that has miscalculated and not me! Anyone want to double check my math?

The heads were milled .020" and we are using a .5mm base gasket for a final deck height of .75mm. Here are the numbers for the CR formula listed above in a previous post:

1. 7.85
2. Head CC is now 88.8
3. With .5mm base gasket, deck height is .75mm
4. 5
5. 5.75
6. Cylinder CC is 71
7. 45.14
8. Dome CC is 25.86
9. Swept CC is 584.04
10. Deck CC is 5.89
11. CR is:

584.04 + 88.8 + 5.89 - 25.86 divided by 88.8 + 5.89 - 25.86

Compression ratio is now the original 3.2L US spec 9.49:1. You can see that milling the heads changed the head cc volume a full 3 ml from 91.8 to 88.8 and gained back .36 in compression.

I'm happy, would have liked to had it up a bit higher but not willing to go through additional gyrations to make it happen. The CR is conservative enough that I won't have any problems with 91 octane and it won't potentially knock itself into a million pieces next summer when things heat up again.

Not much else to report tonight. The cylinder heads were obviously reassembled since they had to be taken completely apart to be milled. I also loosely assembled the conical bolts and nuts on the rocker arms and installed the RSR o-rings onto the rocker arm shafts in preparation for the coming nights. Organized the cylinder deflectors and sheet metal and brought home all the old parts that I will not be using but may need for something or someone else down the road.

If everything goes according to plan, the pistons & cylinders, heads and cam towers will all be fitted tomorrow night. We hope to have the longblock fully assembled by Thursday night or Friday night at the latest. Next week will be the electrical and injection components put back on and routed nicely and then it should be ready to go back in the car. Will have to install the Andial signal splitter under the seat next to the DME unit, install Steve Wong's new chip and install a bracket to hold both ignition coils.

It's getting closer!:p

Ralph:
With your final compression figure of 9.49:1, do you still need twin ignition with 91 pump gas? How much volume increase does the second spark hole add (cc's)?
Regards,
J.P.

As to the Mahle brand name controversy...

in all high-level ...or high quality...or "difficult" applications with "no worries"...I've seen only 2 brands consistently show up:

- Mahle
- Cosworth

OTOH......the west coast hot-rod sub-industry has ...over the years...produced some mighty fine stuff..and I always wondered, for example, when Porsche goes shopping world-wide for suppliers, why names like Carillo ( rods), ARP or Raceware ( bolting) , and such....don't figure into the equation. Some of this is indeed historical inertia....and some may be that these specialist suppliers may not be able to ( or want to) produce in the overall quantities necessary.

Wil

Ralph
Are you then saying that 3.5 mahle c.r. is allways low, but 3.4 will be close to 10.3? If you had know this before would you have gone to twin plug?

J.P.,

Yes and no. I still need twin ignition because of the high-dome piston design (see pics) and the fact that 100mm is a very large cylinder. If the above weren't the important facets, then no I would not need it for 9.49:1 because that is the same ratio as standard. I just wanted a higher CR to be able to kill two birds with one stone.

Unfortunately, we never cc'd a head with single plug for comparison. I have to go to Andial/PMNA again today and will ask but I am sure someone may be able to chime in here and provide the difference in cc from single to dual plug.

Ralph

I can only base this on my own personal experience, my friend Steve's 3.4 and from what I have been told by Andial regarding others. The 3.4 and 3.5 sets that use the carb/mfi piston type are indeed lower than claimed. Figure about 9.2:1 rather than 10.3:1 for these sets in twin-plug format.

From what I understand from them as well, is that the Motronic wedge dome shaped piston in 98mm or 100mm does indeed measure to the advertised ratio of 9.8:1. I do not know if the standard 95mm in 9.5:1 US spec and 10.3:1 Euro spec are completely accurate. Can anyone who has done a stock rebuild or upgraded to the Euro spec pistons confirm?

Interesting question that you brought up. I probably would still have proceeded along the same path, as I planned on twin-plugging regardless of using 98's or 100's as an extra safety margin with our poor fuel quality and hot weather. If twin-plugging, the extra machine work to bore the case spigots for 100mm is relatively inexpensive. I only ended up with 100's because they were actually much cheaper for me then 98's so it kind of made it a no brainer as far as I was concerned.

Ralph

Update for 10/26:

Made some good progress tonight. Steve and I were able to put pieces together in "chunks" tonight before things will slow down again.

We started by attaching the cylinder heads to the cam towers. We used Yamabond/3 Bond 1104 as the sealant.

http://forums.pelicanparts.com/uploa...1098844689.jpg


Completed assembly:
http://forums.pelicanparts.com/uploa...1098844781.jpg


We then sprayed/prepped the (6) .5mm 100mm base gaskets with Permatex High Tack Sealant in preparation for installing the piston/cylinders. Rod bolt torque (35 ft./lbs. per ARP) and bolt stretch (.0117-.0122 per ARP) was checked one last time before installing the pistons. The 3 oil ring gaps were lined up 120 degrees apart from each other before the ring compressor helped slide the pistons into the cylinders.

http://forums.pelicanparts.com/uploa...1098845245.jpg

http://forums.pelicanparts.com/uploa...1098845317.jpg


Next came the cylinder deflector tin, beautifully powdercoated semi-gloss black by Specialized Powdercoating in Huntington Beach, CA.

http://forums.pelicanparts.com/uploa...1098845407.jpg

Last, the oil return tubes and cam towers w/ the heads already bolted on were installed as a unit, leaving us with this:

http://forums.pelicanparts.com/uploa...1098845719.jpg

The ARP head stud nuts w/ washers are torqued down to 38 ft./lbs. per ARP's recommendation and will have the night to "settle". Steve likes to give them a night and then double check the torque before proceeding further.

To get an idea of how much time is involved, we have spent approximately 12 hours on the assembly since the parts came back from the machine shop. Combined with tear down time and cleaning/prep time, we are around 27 total hours right now. Many shops charge around 40 hours for a normally aspirated engine teardown/rebuild and I think that we will be close to that figure (either slightly higher or lower).

What do you guys think so far?:confused:

Ralph

It's a thing of beauty Ralph, I can't wait to see the article in European Car magazine. I subscribed when they did the early 911 series of articles and am glad to see they're doing more 911 articles. I'm thinking of building something similar eventually for my '72 911 "rsr" project, so I'm following this thread very closely!