BC

I have run into a problem. I woke up this morning thinking about the piston rings I am re-using, and I am now thinking I have forgotten the order of the compression rings.

The stuff you can buy NOW, has a Positive-twisted (looks like a champher on the back of the ring at the top) chrome faced 1st, and a square non-twisted second ring.

The rings I am re-using (second guessing this now) are not like this. They still have the three piece oil ring, but the two compression rings are square Fronts (non-chrome face) and one of the rings is Positive-Twisted (Top Rear Champher).

I may have reversed those two. Champher on the second ring and Square first. I think it may have to be different.

Any ideas?

http://xtremecarzone.com.au/lofivers....php?t449.html

http://underthehood.mahleclevite.com/?p=815

BC

I seem like I am talking to myself here, but I figured it out.

The two top rings cannot be interchanged anyway. The rings are different thicknesses, and I installed them properly. For some reason, the pack has the complete reversal of the newer packs.

The top ring is block faced (possible taper, but I don't see it)

The second ring is Positive twist with the champher on the top back part so it will twist up when going down the bore - thereby adding additional oil shedding.

The new set is basically the reverse. Strange.

BC

Does anyone have any knowledge on that above? Why is the new set with the Barell face chrome top ring also have that top ring as a positive twist ring? The Oil ring and Second look right....

Public Service Announcement:

1) Using the Oil Pump Body to center the block halves DOES make a difference.

2) Always keep your pin in the rotational hole in the engine stand. The engine can fall out of the yoke.

3) Follow GB's advice on the 574 sealant.

Rob Edwards

I don't know how different S3 rings are from S4 rings, but I have a pile of un-disassembled '91 S4 pistons sitting here, would it be helpful to have pics of cross-sections +/- measurements of what is located where? Since you're using 'old' rings presumably they're comparable to what would be on these pistons I have (?)

Can use this as my hide-in-the-garage time tonight, just say the word.

BC

Full Disclosure that I would very much appreciate the info but I probably won't change the plan for this rat motor. So Yes!

The engine these came out of had very low miles. It may have been rebuilt, as the S3 heads had S4 chain tensioners (that I am re-using), and all the hardware inside the engine was like golden-colored newness. The bores and pistons were essentially untouched. All of that has been socked away for when there is more room to build more engines.

Just pictures would be really helpful of the cross section and front face of the two compression rings.

Those two sites I linked make me wonder if we have been remiss (I have been) in looking for new ring technologies even for the stock bores.

New wording in documents related to what rings are being designed today to work with today's Alusil seems to indicate that ONLY barrel-faced rings are used. The second ring is now known to be mostly about oil control, and the top ring shape is not positive-twist like the 951 ring packs we use on the 928.

Rob Edwards

Lots o' pics:

Damn pistons aren't even round!

Above the top ring:

Width 99.38 mm


Height 99.47 mm



Most of the way (62mm for S3 and S4 pistons, 50mm for GTS pistons...) down the skirt, 100 mm tall:



But still only 99.41 mm wide, at the bottom of the skirt.



Rings in situ:



Top Ring 1.45 mm thick, 4.09 mm wide, small chamfers on upper inner a edge, rectangular at the outer edge, to this untrained eye:








2nd ring- thicker, bigger chamfer on upper inner:









2 scraper rings are identical:





Oil pack expander:

BC

We, thanks Rob.

So on those pistons, the top and second compression ring is positive twisted. They both have chamfer on the top back.

That is a third separate design for s3 and s4 pistons.

How many miles are on those?

Rob Edwards

IIRC the engine came from a '91 with 87K miles. The last 100 miles or so were pretty hot and heavy, though.

BC

I think they changed the Rings because of the oil burning problems.

BC

Short block is done basically. Bearings with most clearance were put onto 2 and 6. Turning short block over with no heads takes about 20lb of torque or so. Less to keep it going. Chevy guys seems to use this metric to see how much tension the rings have and if there is anything binding.

Initially I felt the engine was too hard to turn over with just the crank in, but I remembered that the torco assembly lube is VERY sticky.

So I have an S3 bottom end with coated pistons, coated rod bearings, used mains and rings, and a polished crank that was at the bottom of the measurement range for the rod journals.

This is the only reason I was able to use the coated Glycos. Otherwise they would have been under .002 clearance in some places for sure.

BC

Couple Pics from today.

Disassembled and partially cleaned one of the 1R heads I will be using for this engine. S4 heads from a rennlister in Sykesville I believe.







These are pictures from the head's oil pressure valve.

It seems that the ball has worn away some of the valve? Has anyone ever seen this? There is some wear above the seat, but not directly on the seat.

I will replace this, and update that other thread about the head oil flow.

Any suggestions?

BC

I'll just create a link here for the Head work thread I opened many years ago. I will be working on another set of heads for this rat motor:

https://rennlist.com/forums/928-foru...hroughout.html

BC

More "headwork" (really just cleaning and prep).

I bought a new toy.

With that toy I will be measuring valve springs to see where I should go for this.







Seems like these springs are low tension. They are used, from an S4 head of unknown mileage. The head looks like it did not have a hard life though.

BC

What I am trying to show in the same pic is the approx spring height (I suppose that is not installed height, especially since there are very beefy spacers under the springs on this set of heads.

BC

http://speedtalk.com/forum/viewtopic.php?f=1&t=37604

http://www.yellowbullet.com/forum/sh...d.php?t=414628