I'm not really in a rush, and I already bought a big caulking gun tube of permatex, so I'll just stick with that. Is there any risk to putting permatex in conjunction with a gasket that has the red stripe on it?

 

By far the cheapest insurance to prevent leaks. I even use the stuff on the newer aluminum gaskets with silicone beads already on them. Never had a come back like this

Just remember the oil pan came factory with silicone and if you try to use a gasket it's not going to stay sealed for decades

 

That's what I've been reading. I have a pan gasket, but I don't plan to use it. I'm still not sure why the gaskets have a bad reputation, but since I have plenty of permatex, I'll be sure to use it liberally.

 

So I got the crank in with new main bearings. Pressed the front and back seals into their respective plates. And I swapped the '94 pistons on top of the '88 rods. I was going to toss the pistons into the block today, but I got all paranoid checking my piston ring gaps.

Now I'm waiting for rings. I was kinda hoping to have the bottom end wrapped up today and start putting the heads on. Instead, I have a 2-business day wait for rings, that will likely still arrive Wednesday. Ugh. Maybe it's time to ..... paint.

 

Well.... Piston Ring issues....

The spec for ring gaps are:

Top: 0.013"-0.023"
2nd: 0.062"-0.072"
Oil: 0.010"-0.020"

I measured my pistons a few days back and they fell into the "standard" ring size category. I ordered a set of "standard" size, and they arrived today. Here are the results:

Cyl 1 Top: 020, 2nd: 076, Oil: 020
Cyl 2 Top: 022, 2nd: 071, Oil: 020
Cyl 3 Top: 022, 2nd: 076, Oil: 020
Cyl 4 Top: 022, 2nd: 082, Oil: 020
Cyl 5 Top: 022, 2nd: 076, Oil: 020
Cyl 6 Top: 022, 2nd: 076, Oil: 020
Cyl 7 Top: 022, 2nd: 076, Oil: 022
Cyl 8 Top: 022, 2nd: 076, Oil: 020

I was hoping my rings would have fell into the low end of the spec, but all of them fell into the upper end. I'm tempted to order a 010 oversized version, and file them down to the low spec, but I'm having a hard time finding it. Anyone know where I can buy a set of 010's?

RockAuto has a set of 020's and 030's. How much more meat would I have to file off if I went up to that size? If it's a lot, I don't really want to go that route. I just have files, and not the fancy electric filing device.

Also, Is this kind of a waste of time? Is trying to obtain the tightest set of rings really worth all this effort? Or should i just run these upper-bound standard rings?

 

This is the guy I remember custom filing rings to fit!

It's all pretty much shown on page two here,

www.ford-trucks.com/forums/1470656-the-crewcab-project-2.html

All credit goes to him. I will probably go this route myself someday

As to the question as to weather it's worth it, imagine an idi with no blow by, zero oil leaks, I feel like I'm dreaming now but with a small second ring gap it is a possibility, less loss from adding extra boost as well.

 

As Mac stated in the thread: "I'll be really interested to see what happens with those ring gaps. I'd /never/ run them that tight, considering the factory tolerance. Remember, this is a high pressure, high temperature engine, and rings expand when hot. If the EGTs can safely hit 1100F, the ring temps have to be pretty hot, even cooled with oil as it is." and "Have you done calculations on how much a ring will expand when exposed to, say, 300-400F?"

Mac is right. That guy shaved his rings down to 016 and 018 for top and 2nd, respectively. 018 is outrageously smaller than spec. He did do some calcs on the rates of expansion for a few hundred degrees, but that custom turbo setup is going to push EGTs over a grand for sure. IDK. lots of work on that truck done after gambling on the ring gap.

 

I've never understood the fascination with trying to eliminate the blowby. It's there by design and hurts nothing.
In fact, not having to rely on sensitive tolerances is probably one of the contributors of the engine's longevity.

 

So, should I order a larger set and file it to the low end of the spec, or should I keep the set I have?

 

I'd run the standards myself; but do what you feels best.

 

I'm installing them on a "worn" engine, so i'm tempted to buy the 020's and file them down. But I ain't going down to 016 and 018! Maybe just under the spec...

I got time to wait for the parts cuz I'm heading out for a business thing for the next week, but I wanted to check this stuff before I departed.

 

Id say it goes both ways. Yea IH designed them with blow by, but does that make it a better design than all the other engine manufacturers that dont smoke like a locomotive? I compared IH gaps to cummins, cat, JD, and IH is way bigger on the tolerance. If i was putting rings in an IDI, performance or otherwise, i would go .018" and .022" General rule is .005" per 1" of bore. .013" seems unreasonably tight.

 

Not saying it's the better design, but since it is how it's designed I think it's best (to me) left alone. Caterpillar tolerances work well in a Caterpillar, but will they work in an engine not designed for those tolerances? I don't claim to know so I defer to the knowledge of the engineers that made the engine.
I don't see how the blowby in an IDI would cause them to roll coal? Unless you're running a road draft tube; then yeah, I could see an issue with that.

 

For one I think having no blow by would drastically keep oil consumption to a minimum, also wouldn't have oil puking down your intake from the cdr, there is so much oil vapor coming from the crank case on these rigs not even a 4" diameter catch can will pull enough out to clean it up.

Secondly, from the 6.9, 7.3, 7.3 powerstroke, 6.0, 6.4 and even Ford's 6.7 use a large secondary ring gap. Now this may be there preference for whatever engineering reason, so be it. But they are not the only diesel manufacturer out there. Here are the ring specs for the famous Cummins 12 valve that is easily good for 400k with routine maintenance. Some have even made it a million miles similar to several international motors.

Ring End Gap
Top Ring 0.400-0.700 mm
(0.016-0.0275 in)
Intermediate Ring . . . . . . . . . . . . . . . . . .0.250-0.550 mm
(0.010-0.0215 in)
Oil Control Ring .0.250-0.550 mm
(0.010-0.0215 in)

Here is another spec for the cummins N14 big rig engine.

MIN
0.017
MAX
0.027

Ring 2
MIN
0.020
MAX
0.030

Ring 3
MIN
0.019
MAX
0.029

Ring 4
MIN
0.010
MAX
0.025

How about some random Scania 16 litre engine from Scandinavia

1st ring
0.35 - 0.60 mm or .013" to .024"

2nd ring

0.45 - 0.65 mm or .018" to .026"

Since these three were direct injected engines let's try a fellow idi

Mercedes om617. It's in all those old Benz diesels

Ring 1 .008 - .016
Ring 2 .006 - .014
Ring 3 .008 - .018


My conclusion to this is they are plenty of diesel engines that have either small or large ring gaps. I would assume a larger lower ring gap would allow better oil to the top ring, but there is plenty of manufacturers who use a small second ring gap.

I would definitely suggest .020" over rings and to file them to internationals spec at the least since cylinder wear on the engine will not throw off the gap of standard rings.

Personally I would vote for a smaller second ring gap. At least .020 smaller but it's your motor and I welcome any decision you make. At least your willing to go with new rings. They would be my first thing to replace regardless of main/rod bearing wear on an idi. The bottom end is a tank on these things, minus the secondary ring gap that is.

 

What I found is that on a healthy engine, you get plenty of oil vapor... but it doesn't 'use' much oil(still within the normal range after 2500 miles). One quart of oil makes a massive amount of vapor droplets.
On a worn engine, well... it's burning the oil as well, which is probably where most of the oil usage is coming from.

Personally, I don't care that much about a little oil usage as long as it's less than a quart every 2500 miles. If it's more than that(on a new engine), that's cause for alarm. On a used engine, well, I finally got tired of adding oil once it was using a quart every 100 miles...