Zero10

ow this stuff.Hi there!
I am hopefully starting the reassembly on my 951 engine shortly, and I have some quick questions....

I bought the 101mm pistons from Ski, and I presume the end gap specs should be the same as factory. I don't see why they would be any different, however I don't know how to align the ring gaps. A few people have told me have the top gap facing the front of the engine, the second gap 30* clockwise (looking down on the piston) from the first, and the top oil ring gap 60* from that, with the bottom oil ring gap exactly opposite.
Is this correct? In my head, it makes the most sense to have the top 2 ring gaps exactly opposite, but I don't really know this stuff.

Also, how can I measure the ring end gap? Don't I need a ring compressor just to get them fully compressed?... Don't know how I can fit a feeler gauge in there with the ring compressor on.

cruise98

Goetze recommends putting the top two ring gaps 180 degrees apart. The gaps are front and rear, not intake/exhaust. The oil ring goes 90 degrees to the exhaust from them. Align the oil ring gap and spring gap 180 degrees from each other. Others will recommend 120 degrees apart. I have done it both ways and cannot tell the difference with performance or compression/leak down tests. YMMV.

Stick with factory specs on the gaps, and yes you should check them. I install one piston in the bore without rings or rod and carefully slide it to the bottom of the bore. Lightly oil the bore first. Take the ring and carefully insert it into the bore about an inch or so. You can do this without a ring compressor, just use your fingers. Push the piston up to within 10 mm or so to square the ring up and measure it with a clean feeler gauge. The factory rings will probably be within spec and not need any attention.

What rings are you using?

Zero10

I am not certain. Ski included them with the pistons. They came in little baggies

What do you mean 90 degrees to the exhaust from them?
Do you mean align the cap with the exhaust side of the engine?

cruise98

You have three gaps. Top ring goes towards the front, second goes towards back. This makes a straight line from the front of the engine to the back. Place the oil ring gap 90 degrees from this line towards the exhaust (lower balance shaft). The oil ring has a spring, put the joint for the spring 180 degrees opposite the ring gap.

If you have a three piece oil ring, ask Ski what the proper arrangement is. Better ask to be sure.

Zero10

The Goetz oil rings are 3-piece, I'm not sure if mine are as well. If they are, I'll probably go 120* for each gap, starting from the top pointing towards the exhaust side.

Thanks for the info.

Ski

chris, weren't the instructions in the box for the gap placement?. jwl just did his car and I asked him to pop in here and give you pointer or two, since it's been so long since we did the track car. You should see the "dots" on the rings as they are your top/bottom guide and then you should have instructions for the oil ring. jwl...

David Floyd

Zero10

No ring gap placement specs, no ring end gap specs, just piston-wall clearance, and ring sizes.

I must be blind, I didn't see the dots, which way should they be? I'll make sure I get them right.

I'm a little concerned about the ring end gap. I measured far over the factory specs for new rings, almost at the wear limit. I checked out the piston fit, and it's perfect, it couldn't be any tighter without the pistons binding, so I don't think the cylinders are bored too big.

As for the oil ring, I tried assembling it, dropped in the big squiggly ring, then the 2 flat rings after it, after locking the ends of the squiggly ring together. Is there an orientation for the flat rings in the oil ring?
When I assembled the oil ring, it fit together very nicely. Did I do it right?

Zero10

So... dots up or down?
Installing the crank tonight, hoping to drop in the pistons, and install the head as well.

I looked at the rings again, and now I see the dots

Also, my ring gaps were slightly off, I had the rings right at the top of the cylinders when I measured the gap. Pushing them to about the mid-point of the cylinder, I get 0.5mm end gap on the top 2 rings, and 0.45 on the 2 oil rings. (can't tell on the squiggly one).

David Floyd

Up

jwl

Dots up! Squiggly ring gap over the wrist pin and use that as your referance. Rotate the bottom oil ring 135 deg ( 90 + 45 ) and the top oil ring 180 deg. from that. Rotate the secound compression ring 45 deg. and the top compression ring 180 deg from that. Basically all ring gaps should be 90 degrees from each...like a X.

Zero10

Damn!!
I looked at them, and turned the idea over in my head, and put all the dots down, lol.
I'll be pulling the pistons tomorrow.

I couldn't discern any tapered edge on the outside of any of the rings, although I found one tapered edge on the bottom compression ring on the inside.

That said, the outside corners of the rings are sharp!! I got my finger pretty badly on one, I was quite surprised.

This whole ring alignment thing has me a bit confused.
So, gap in the squiggly ring over one of the wrist pin circlips, top oil ring is 45* one way, bottom oil ring is 135* the other way (or I guess 225* the same way). Then, going in the same direction from the squiggly ring, as the top oil ring went, continue another 45 degrees from the top oil ring, then set the top compression ring exactly opposite?
In my head, that puts the top compression ring at either the front or rear of the cylinder, the bottom compression ring at the other side. Then the flat oil ring gaps only 45* from the gaps in the compression rings.

So, question of the second (or is it third, or fourth?...) How do I align the caps on the rods? There is a relief cut into the bearing surface of the rod, and of the rod cap, should the reliefs be on opposite sides (like the main bearings), or the same side, so the numbers match on the rods?
I wish I had paid a little more attention to that when I took them apart, I thought of it after I took the 4th one off...

jwl

Yes, the numbers should match... the reliefs of the rod and cap should be on opposite sides if not your bearings will bind.

Zero10

Hmm, on mine, if I line the numbers up, the reliefs are on the same side....
wtf? I as well thought they should be on opposite sides, like the main bearings, but then I thought, everywhere in the factory manual, they keep saying to line up the numbers on various parts, so I was torn.
I'll put the reliefs on opposite sides, that's more important
I'll be flipping all the rings over today, and installing the rods on the crank
Maybe, just maybe I'll get the head on as well. It's all starting to come together......

Zero10

Gah, more problems.
I torqued down the rod nuts, and I can't turn the crank anymore. I put my torque wrench on the crank pulley, and I can't even get the crank to rotate at 200lb/ft. I doubt the starter motor could turn it.....

The first time, I torqued down 2 of the rod caps, using assembly lube on the bearings, and I couldn't turn it. I figured maybe the assembly lube was too sticky, so I pulled the rod caps, wiped out all of the assembly lube, and replaced it with some mobil 1 10W30, torqued the rod caps down again, and this time I could turn it, although it took a lot of effort. Once I torqued down the other 2, it was stuck....

Have I done something wrong?

I already turned the rings over, so that's right now, and dealt with 100 other little problems, now this.... this just isn't funny anymore.