How important are the Pistons?

[trbig]

2.1" is close enough to 2.8"??? You realize that's over 1/2 an inch.. right? Might be jussssst a touch of piston slap going on.. lol. Probably a little low on compression numbers also.

Hopefully you meant 2.185

Tod

[randy]

Hastings shows 2.185 diameter rings, but what is the width of our rings and what is the width of the ring groove? The 2.185 rings on Hastings' site come in three widths, .0775, .0760, .0620.

[Crazcnuk]

So we need to know not only bore diameter, but:

land width, ring thickness, chamfer types and directions, plus ring material.

From looking at my rings, I would say Yamaha used a cast iron top ring and a Chrome moly 2nd ring? Is there any reason to go with different materials?

What about oil rings?

Now you see why I said it may take a guru or two to go through the choices!

I do believe that Hastings will be cheaper thean Yamaha.

[randy]

Yes, our top ring is a standard straight edge, the second ring is a scraper. Hasting also shows oil rings in the same diameter. Critical is the clearance top/bottom between the ring and the piston groove. Someone care to measure? The specs are not in either of my OEM manuals.

[b.walker5]

2.1" is close enough to 2.8"??? You realize that's over 1/2 an inch.. right? Might be jussssst a touch of piston slap going on.. lol. Probably a little low on compression numbers also.

Hopefully you meant 2.185

Tod

Actually my typo was with the 2.184*** measurement , should have been 2.814952 , which is imperial for 71.5, so 2.815 inches is what your'e looking for. So, back to the drawing board for all those looking at 2.185. Sorry for the confusion

While I think of it, there's another error in my post about this, I've listed 2.835, or 72.00mm, as 1st over size which is incorrect, it's actually 2nd over. 1st over is 71.75mm, or 2.824795 inches.

[Crazcnuk]

I wonder if it is possible to simply send hastings a set of rings and see if they would make them?

[b.walker5]

They do say they'll make to order, but there's probably a minimum order requirement, I doubt that 1 set would be an option. With the vast number of sizes and style's they list in their 400 something page catalogue I'd say it's a safe bet they've already got something that'll fit. Sending a set for matching up to get part numbers and style of rings is a good idea though, anyone got a spare set? Once the style is established, it should be a simple matter of getting the standard and oversize sizes matched up. Oversizes are in .25mm increments from the base size of 71.5.

[Crazcnuk]

I have ordered 4 sets, of 1st over, off of Ebay, once they show up I will have a set of standard and 2 sets of 1st over extra left over.

[jfmerk]

Standard Ring Dimensions

Yes, our top ring is a standard straight edge, the second ring is a scraper. Hasting also shows oil rings in the same diameter. Critical is the clearance top/bottom between the ring and the piston groove. Someone care to measure? The specs are not in either of my OEM manuals.

I've got ring dimensions since I'm in the midst of a 78E restoration project. Bear in mind these rings have 44K miles on them and probably didn't see as many oil changes as they should. The first and second rings and grooves were so jam packed with baked oil and carbon, I broke a few of them trying to dig them out of the grooves!

I did however salvage a nice set that are within the factory range for the standard bore by checking the ring gap and side clearances. My cylinders are right at 2.815" ~ 2.816" and within allowable wear limits.

The piston ring measurements are as follows:

Top Ring: Width = 0.046", CS = 0.115"
Middle Ring: Width = 0.0583", CS = 0.1175"
Oil Control Ring: Width = 0.1075", CS = 0.108" (square CS)

I'll check with our Federal Mogul Rep at work and see if he can help me identify these. Quantity may be an issue again but I'll find out.

[randy]

Please define the 'CS' measurement? Thanks

[Crazcnuk]

Cross Section maybe?

[jfmerk]

Yes: CS = Cross section, sorry that comes from years of measuring and sourcing hydraulic cylinder seals.

[TopCatGr58]

Hey JF,

Thanks for finding the thread and posting the measurements.

But I don't want to be THICK, but your CS measurements are larger than your "width"? I think you mean the width is actually the height, since they lay FLAT and are actually wider than they are taller!?

And so your CS would be the longer WIDTH measurement across the ring??

Just want things to be clear for everyone, we're not all engineers or mechanics here!
T.C.

[jfmerk]

Ring measurement clarification

Hey JF,

Thanks for finding the thread and posting the measurements.

But I don't want to be THICK, but your CS measurements are larger than your "width"? I think you mean the width is actually the height, since they lay FLAT and are actually wider than they are taller!?

And so your CS would be the longer WIDTH measurement across the ring??

Just want things to be clear for everyone, we're not all engineers or mechanics here!
T.C.

T.C.
I agree, I'm all for making sure we're all on the same page. I looked at the ring measurements as if you had a piston in your hand, and measured how wide the piston ring grooves are. The Cross Section and this is just me, was the difference between the diameter of the bore and the inside diameter of the ring divided by 2.

You are right in looking at them laying flat they would measure as you described.

So if we lay the rings flat on a table the measurements would look like this:

Top Ring: Height = 0.046", Width = 0.115"
Middle Ring: Height = 0.0583", Width = 0.1175"
Oil Control Ring: Height = 0.1075", Width = 0.108" (square CS)

Hope that helps,