2.2 Heads on 81mm 2.0 litre cylinders

ix0ifan · 09-05-2009, 03:38 AM

I am trying to find enough information to be confident about building a 2.0 litre Twin Plug Motor with 2.2 heads.

I have searched the prvious threads on this subject and can't quite form a 'definitive' spec and I put this down to being a bit dim so I need to spell out my concerns and try to understand more about what to do.

It seems to me that there are two basic approaches that have been taken.

1. Supertec seem to use a spacer to lift the head slightly and I imagine this is to ensure that valve to piston clearance is adequate.

If this is the case does this mean that you could achieve the same result by shimming up the cylinder at the crankcase end?

Does the use of this shim allow 2.0 litre pistons to be used? and if so do they have to be re-cut to deal with the different valve angles?

I guess that there are significant differnces between this problem with 68 'S' pistons and 69 'S' S pistons.

I also see that Supertec have a 906 style Nikasil Barrel to use with these heads and I assume that they must be longer than the 2.0 litre Biral as apparently they don't need spacers.

I assume that the same piston issues exist.

2. I have seen the posts where Rennsport weld up the perimiter of the heads to remove the 'step' which I believe can cause detonation. They them re-machine to suit the 81mm bore.

Does this solution use a standard 2.0 litre head gasket or a Sealing Ring?

The Supertec solution doesn't seem to deal with ths issue or have I missed something? (Quite likely)

Again what to do about pistons.

I would like to use 906 size valves and ports as well as 906 cam profiles which must make these problems worse rather than better.

Is it best to have some custom pistons made and can I just use an 81mm version of the 2.2/2.4S piston or are there other issues?

I hope that I have made these questions clear as I would like to 'get it right first time'

Thanks

gestalt1 · 09-05-2009, 05:23 AM

good questions. from what i know, the 906 heads and pistons have more dome volume and porsche reduced the dome volume with the 2.2 and on heads. if you match the 906 or S pistons with 2.2 heads the different dome shapes would create a bad combustion shape - basically the middle of the piston and head would be close to each other and around the perimeter of the cylinder there would be a greater gap. overall you want the opposite where the combustion is focused in the center of the cylinder so it is pushing directly on the center of the piston. shimming the cylinders or adding a shim at the top does lower the CR and add valve clearence but the deck height would likely not be good. i would match henry's cylinders and pistons to 2.2 heads - it is the cheapest and best combo. the extra machining required to get the 2.2 heads to work on original cylinders would cost a lot and be less than optimal. also keep in mind that valve clearence is very difficult to predict on paper - 906 cams really don't have large amounts of lift, the valve is just open a long time with a lot of overlap. additionally the cam timing is very important to determine when the valves are at full lift in relation to where the piston is. there are many modern cams that have much more lift. this is why you have to build the engine to see if there is a problem.

BURN-BROS · 09-05-2009, 07:13 AM

Supertec's Cylinders Are already set up for the 2.2 head So no spacer needed. Henry has/had JE pistons made up for 81mm with the Valve angle for the 2.2 head. Nice product!

The 69S piston is literally identical to a 906 piston. The 68S has less compression and smaller dia. valve pockets(IIRC).

You should have the perimeter of your 2.2 heads welded to match a 81mm bore instead of the 84.

Why don't you give Henry a ring?

kenikh · 09-09-2009, 06:58 AM

the supertec spacers decrease the bore and fill the recessed mating surface in the 2.2 head to allow the use of the earlier style cylinder and gasket without increasing deck height. no need to weld the heads.

stownsen914 · 09-10-2009, 06:53 AM

That's a nice trick. I may give them a call them a call regarding a project I hope to undertake -- using SC/Carrera heads to make a 2.5L motor.

Quote:

Originally Posted by kenikh

the supertec spacers decrease the bore and fill the recessed mating surface in the 2.2 head to allow the use of the earlier style cylinder and gasket without increasing deck height. no need to weld the heads.

kenikh · 09-10-2009, 07:18 AM

they don't solve the head stud spacing issue.

BURN-BROS · 09-10-2009, 08:52 AM

Quote:

Originally Posted by kenikh

the supertec spacers decrease the bore and fill the recessed mating surface in the 2.2 head to allow the use of the earlier style cylinder and gasket without increasing deck height. no need to weld the heads.

The area that I am referring to is the head sealing area, not the height. The head would still need the perimeter welded to bring it from 84 to 81mm. But when you are done you have a very nice small bore motor.

As far as 3.0 liter heads, I would stay with 2.2-2.7 heads as I cannot come up with any benefits where the heads would be beneficial for such displacements.

aws · 09-10-2009, 06:08 PM

Aaron: The 3.2 cylinder heads with very little work will flow as well as a set of new Extreme custom 2.2 to 2.7 heads at a much lower cost. (260cfm at .500) The problem is the combustion chamber volume makes getting any compression problematic. The flow numbers support 300 plus for a 2.5.
aws

kenikh · 09-10-2009, 06:27 PM

Quote:

Originally Posted by aws

Aaron: The 3.2 cylinder heads with very little work will flow as well as a set of new Extreme custom 2.2 to 2.7 heads at a much lower cost. (260cfm at .500) The problem is the combustion chamber volume makes getting any compression problematic. The flow numbers support 300 plus for a 2.5.
aws

They may flow AS MUCH AIR, but they will not flow AS WELL. Xtreme heads (or any modern CNC port job) maintain air velocity at low RPM at speeds the 3.2 heads can only dream of on a small displacement motor. The 3.2 port profiles were not designed with small displacement as a consideration.

aws · 09-10-2009, 07:22 PM

Kenik:I think we need to differentiate between street and race engines. Aaron obviously felt there was no benefit to the 3.0-3.2 cylinder heads being run on the small displacement engines. I feel there is, in a race application. Bill's Xtreme cylinder heads are a work of art and make big horsepower, but close to the same results can be obtained with a set of 3.2 heads at a much cheaper price.

aws

kenikh · 09-10-2009, 07:31 PM

Quote:

Originally Posted by aws

Kenik:I think we need to differentiate between street and race engines. Aaron obviously felt there was no benefit to the 3.0-3.2 cylinder heads being run on the small displacement engines. I feel there is, in a race application. Bill's Xtreme cylinder heads are a work of art and make big horsepower, but close to the same results can be obtained with a set of 3.2 heads at a much cheaper price.

aws

Fair enough - if you don't care about non-race RPM, the difference is nil. Nonetheless, torque down low will be better on the CNC'ed heads.

stownsen914 · 09-11-2009, 08:07 AM

Quote:

Originally Posted by BURN-BROS

The area that I am referring to is the head sealing area, not the height. The head would still need the perimeter welded to bring it from 84 to 81mm. But when you are done you have a very nice small bore motor.

Do the Supertec spacers not fill the void at the perimeter of the combustion chamber where the head meets the cylinder? Is that the issue that requires perimeter welding of the head?

Quote:

Originally Posted by kenikh

they don't solve the head stud spacing issue.

True, this would need to be machined for sure.

Quote:

Originally Posted by aws

The problem is the combustion chamber volume makes getting any compression problematic.

Custom pistons would certainly be needed to make such a project worthwhile.

I've been bouncing this idea around for a while, and it seems like the various challenges could be overcome. Curious to hear others' thoughts though.

BURN-BROS · 09-11-2009, 08:55 AM

Quote:

Originally Posted by aws

Kenik:I think we need to differentiate between street and race engines. Aaron obviously felt there was no benefit to the 3.0-3.2 cylinder heads being run on the small displacement engines. I feel there is, in a race application. Bill's Xtreme cylinder heads are a work of art and make big horsepower, but close to the same results can be obtained with a set of 3.2 heads at a much cheaper price.
aws

I realize the flow numbers and cost may be tantalizing, but a cheap 300 horse 2.5 is a contradiction. I see too many build conflicts that you wouold have to overcome.

Seems like oversized seats, valves, and a good port job on a set of 2.2 heads would be a more prudent route.

BURN-BROS · 09:01 AM

Quote:

Originally Posted by stownsen914

Do the Supertec spacers not fill the void at the perimeter of the combustion chamber where the head meets the cylinder? Is that the issue that requires perimeter welding of the head?

I believe that the spacers are only for height. Give Henry a call, I am pretty sure he can set you straight on the matter.