opinions please 2.0S P/C

[ajwans]

My engine reconditioner yesterday told me that my pistons and cylinders
are out of spec:

bores 80.15 - 80.19
pistons 79.89 - 79.90

Anybody have an opinion about how to remedy this. I'd like to keep stock
appearance and the ring grooves are good. It has been suggested that
the cylinders (biral) could be sleeved to first undersize, pistons milled a
little and ring ends filed.

This isn't going to be a race motor but I do want a quality rebuild which
won't have to be torn down again, ever.

Pros/Cons vs getting 80.5/81mm pistons from JE and boring the cylinders?

andy

[Steve@Rennsport]

Hi Andy,

First, Biral cylinders are in effect, an iron sleeve in an aluminum barrel so sleeving them is not a good idea at all. I would either get another used set thats better than yours or have them bored .020 oversize (using torque plates) and have a JE made to fit.

Now,....if your statement "won't have to be torn down, ever", is to be true, then your only choice would be new Mahle P/C's. Its NOT cheap, but quality never is,...

[ajwans]

I am confused, I thought biral was iron bore with aluminium fins cast
into it. I am amateur so please excuse my ignorance.

andy

[Flieger]

Yes, iron cylinder bores/liners with Aluminum fins cast around them to make up the body of the cylinder and take the rest of the stress of compression/combustion

[Eagledriver]

I think what Steve is saying is it wouldn't be a good idea to put a sleeve inside another sleeve. I'd get a set of 2.2 pistons and cylinders that are within spec. The look will be identical but the engine will be a 2.2 instead of a 2.0. Other options are to bore the cylinders oversize and use custom pistons.

-Andy

[304065]

Andy,

Started typing you an email but I figured I would post here.

Yes, the Biral cylinders are a cast-iron sleeve inside cast aluminum fins. I don't believe it is possible to remove the existing sleeve. The trouble with Biral is that while the cast iron makes a good wear surface, it doesn't transfer heat that well. Hence the introduction of Mahle Nikasil in 1971 (917). Putting a sleeve inside the sleeve would just make the heat transfer problems worse, to say nothing of the difficulties of anchoring it mechanically.

Anyway, there aren't any meaningful negatives to a 1mm overbore and custom pistons. This is exactly what I did-- the pistons were made by JE in 81mm size with a 9,5 compression ratio, which is about the limit for the reformulated Panther Pee passed off on the cash-strapped American consumer as "gasoline." You can go higher compression if you wish but remember that the higher the bump on the piston, the more you effectively divide the combustion chamber in half, meaning the flame front has to travel over the bump.

There is much chin music here about the limitations of JE but even the stalwarts admit that for a street engine they will be OK.

[ajwans]

Where do you get rings for an 81mm piston?

andy

[304065]

Andy,

Mine came from JE along with the pistons. The ring package specified is thinner than the factory, they are low tension rings that do a better job of sealing to the cylinder. See my thread called "Jugs and Slugs" for more details about antidetonation grooves and the ring sizes.

[ajwans]

JE can do pistons in any size, no? How about a set of 80.5mm pistons?

What options should I ask for, there seems to be a great deal available.

andy

[304065]

Andy,

If you want 80.5, sure. Remember the math:

81 x 81 x 66 x 3.1416 / 4 x 6 = 2040cc

80.5 x 80.5 x 3.1416 / 4 x 6 = 2015cc

At 160 hp for 1991cc stock, that's .08hp/cc so 81s would get you an extra 3.2 hp!

But seriously it doesn't make much difference although they do have an 81 forging, that is what I used.

[911st]

Not an expert but I hear boaring these things is a real risk.

The less material the better. Can they just be honed to square and or the first size over for J&E's?

[304065]

Originally Posted by 911st

Not an expert but I hear boaring these things is a real risk.

The less material the better. Can they just be honed to square and or the first size over for J&E's?

Where do you hear that? Boring to 81 has been done for years with no problems. There is a limit to the extent you can bore, of course. It's a cast-iron liner inside an aluminum fin package in a low specific output application (80bhp/liter), certainly not as good as a Mahle nikasil but not going to be a liability for a street engine.

[BURN-BROS]

81's are the way to go and pose no problem as John has stated. I would be hard pressed to find 80.5mm rings.

[911st]

Originally Posted by john_cramer

Where do you hear that? Boring to 81 has been done for years with no problems. There is a limit to the extent you can bore, of course. It's a cast-iron liner inside an aluminum fin package in a low specific output application (80bhp/liter), certainly not as good as a Mahle nikasil but not going to be a liability for a street engine.

15 year old info from when I had my first 2.4S motor rebuilt. I was told that the liner was a bit on the thin side and that once in a while there would be a break through. The machinist that told me did a lot of Porsche. I guess I was poorly informed. Thank you for the correction.

[BURN-BROS]

Originally Posted by 911st

15 year old info from when I had my first 2.4S motor rebuilt. I was told that the liner was a bit on the thin side and that once in a while there would be a break through. The machinist that told me did a lot of Porsche. I guess I was poorly informed. Thank you for the correction.

You may be correct with the Biral. The 81's that I have done are the normal cast Iron cylinders and have had no problems.

[911st]

Again my info is old but I think the factory may make up the blanks w the alloy cast around the liner. Then they are machined. The liner may not always be the same thickness or centered in the casting after the machining. Again, not an expert on this.

I was told no risk w the T cylinders, it was the S like I had that once in a while would be to thin in places but not alwas.

I'd go for it is a substantial savings but when I did mine J&E did not have to reputation they do know and a factory set was not so out of site.

Also not that LN Engineering's Nickies might be worth looking at. They are all alloy and come in larger slip in sizes. I'd build a 2.5 long stroke at 9.5 C/R.

[304065]

Here is a picture of a Biral 80. You can see how thick the liner is, probably 4mm. Removing 0.5mm is not going to make it too thin.