Hey Gents,

Just wanted to see if anyone can explain what additional work would need to be done to upgrade my 3.4L turbo to a 3.6L. I currently have a 3.3L engine fitted with 98mm P/C's. I'm considering upgrading to 100mm P/C's.

I know that the case will need to be machined to accomodate the larger pistons; however, I'd like to know if there are any additional considerations that I need to be aware of.

Thanks,

Jitters

 

To go to 3.6l, you will need to upgrade from the 74.4mm 3.2/3.3 crankshaft to a 76.4mm 964 993, or GT3 crankshaft. If you go the 993 or GT3 route you will need new connecting rods too. It has been my experience that you don't gain as much from the bore increase as one might think. The 100mm cylinders are also weaker than the 98mm and do not last as long.

 

Hey Geoffrey!

You are the man...Thanks! That is exactly the kind of information I'm looking for. I was just curious. I don't want to get into any major modifications with regard to the upgrade.

Thanks again!

Jitters

 

Or another option is to do what I did... My crank needed to be turned as I had spun two rod bearings... I went with 98mm P&C's and then had Armundo at CCR offset grind my crankshaft. I now have a 78.8 mm stroke, which ,with the 98mm P&C's gives me something like 3589cc's or something like that. I also had the crank "croos drilled" for the center main oil mod while I was at it...

Just another option for ya....

I also forgot to add that this option will also require new custom rods, which use the chevy 2" bearings....

 

You have to be careful with cross drilling the crankshaft. For the low engine RPMs a modified turbo with a common plenum manifold cross drilling hurts more than it helps. When you cross drill the crankshaft you lose main bearing support and since the engine delivers enough oil to the #2 and #5 connecting rod I'd advise against it.

If you offset grind the crank to provide for more stroke, you'll need to be aware of the rod to oil pump clearances.

 

Thanks Guys,

I really appreciate the information. Again, as I mentioned earlier, I'm not looking to get heavy with modifications. My interest are to maintain streetability. My current setup with the 98mm P/C's is yielding just above 500 RWHP @ 1.3 bar on 103 Octane. Which is plenty for me...especially on the streets.

The only racing I do, if you would call it that, is AutoX; which doesn't require 1000hp to enjoy the experience.

But who know's what the future holds....



Have a great day!

Jitters

 

sounds like you have what you need then

 

You would also need to go to twin plug with 100mm.

 

Well, not quite...you see I've been looking for a set of 98mm pistons because I have to replace a bad one. Unfortunately, Mahle only sells the complete piston/cylinder set, which I don't need. I have been looking for quite some time now and have had no luck. My only other alternative is to use....(Don't curse me out) JE pistons. I know, I said the J word...

So, because 100mm pistons have been much easier to locate, I thought I'd see what the possibilities were to upgrade.

Well, I'm just gonna keep looking and hopefully something will happen real soon...

Thanks again...

Jitters

 

Have some JE pistons mande up then.

 

We will agree to disagree on the loss of main bearing support.... and Yes, There will be a clearance issue with the rods and oil pump... however with the Pauter rods i used, it was a very, very small amount that needed to be taken from the outer casing of the oil pump.... There was a very small patch of about 1/2 inch wide ....and only about 2mm deep... and only for two rods... I didnt think that was that bad at all....

As far as the JE pistons... I have them, DonE has them..and others... If you want to have a custom C/R and size....it is one of the only solutions out there...

 

Hey Thanks again. I've looked on the Bird and they have two sets available: 9.5:1 and 10.5:1. My question now is which one to use? Is there a way to determine what C/R my current JE pistons are?

Jitters

 

Forgive me if I'm wrong, but I thought DonE has gone through more sets of P&Cs that miles...I wouldn't use JE Porsche pistons in my lawnmower...

You can determine the compression ratio by measuring the net dome volume of the piston and the cylinder head volume with the spark plugs you are going to run.

 

Seems most people don't like JE pistons in air cooled motors.
FWIW, I just want to say they work very well in water cooled engines.
I've used them in BMW motor's I've built and they work great.
They make a faint ringing noise from mild piston slap as you accelerate for the first few minutes of driving with a cold motor before they expand to the correct tolerance, and in a sports car that doesn't bother me at all.
Once the engine is hot they have expanded and are perfectly quiet.

They are forged and because of that molecular structure they are stronger, lighter, and transmit heat faster than cast pistons to the cylinder walls which lowers chances of detonation when running as high a compression ratio as possible with street gas.

You see the JE sticker on most of the Nascar cars so they're good enough for them.

Lots if not all good Porsche engine builders prefer the origonal Mahle pistons though so they must be right.

 

And in today's level of available technology, that is unacceptable to me!!!