For the love of a tractor engine: The life and times of the 18R-G

[checksix]

Steve, sounds like a good plan. Any idea as to what years it was in this configuration?

[Steve M]

As far as I can tell e flame trap was only on 88210ish vintage engines.
88230 engines (the ones I've seen) had the casting for mounting it but not the opening or tapped bolt holes.
88250 and later engines did not have the casting for this feature.

[7t5-27]

While the engine types are not the same TG has the same setup, I was under the impression it was to relieve crank case pressure. In both cases the hose connects to the balance tube so that the vapor can be rerouted into the intake system, also the the later T series blocks do not have the hole into the block but do have the bosses for the holes. Be Safe
Greg

[Nevakikamukau]

[QUOTE=Steve M;1192204]Run the lines from PCV lines to a catch can and then vent the catch can back to the main air filter. This way you won't be defected for having an open air filter.
The little filters ontop of the cam cover are not legal and having a filter on a catch can would not be legal either.

QUOTE]

Mmmm ... but then I will still need a PCV valve in the system for the flashback issue.

[o_man_ra23]

Nevakikamukau, although you are using what is on the outside fair reasoning in wanting to use a one way valve in your PCV system, your logic is flawed. What you need for combustion of the gasses in the crankcase is a suitable mix of combustable gas to oxygen. Too much combustible gas and the mix is too rich to ignite. Not enough, and you don't have any explosive force.

Quite simply the crankcase gasses aren't very conducive to explosion on their own. Combustion pressure puts a generally positive pressure in the crankcase, so it doesn't suck oxygen rich air in from outside, and that same combustion pressure (otherwise called blowby) also feeds the inert Carbon dioxide and carbon monoxide in, which on their own can be used to extinguish flames (carbon dioxide is commonly used to extinguish electrical fires when the dry powder will damage sensitive equipment).

What I ran in my early 18R-G was the block breather into the balance tube, then valve cover breather into the air filter just before the carby. Seemed to work fine, and even with the many backfires I had over the years, never once did the engine explode or have any flashback into the crankcase.

[checksix]

I agree with O-mans logic, and would like to confirm that as he described it, is the exact set up shown in my green book. Unfortunately most green books and many motor blocks don't show the flame trap under the exhaust manifold as this was an early configuration. But every block will have a vent, and an intake. The intake as I've always seen depicted is into the air filter (so clean air is drawn into the block via the valve cover), and the exhaust of the block always finds its way back to the intake manifold to be burned.

[Nevakikamukau]

I agree with O-mans logic, and would like to confirm that as he described it, is the exact set up shown in my green book. Unfortunately most green books and many motor blocks don't show the flame trap under the exhaust manifold as this was an early configuration. But every block will have a vent, and an intake. The intake as I've always seen depicted is into the air filter (so clean air is drawn into the block via the valve cover), and the exhaust of the block always finds its way back to the intake manifold to be burned.

I don't think so. With four slugs operating at great speed there is only one place that the air through the filters is going, and that is down the throat of the carbies and into the combustion chambers. There will be no clean air drawn into the block via the valve cover, at least whilst the engine is running. The pistons function as a strong vacuum pump drawing the air into the combustion chambers.

[Steve M]

The air in the crank case should just be recycled because as two pistons go up, the other two go down. The air mass inside the crank case should remain the same.

However, gasses that bypass the rings (through the ring gaps) need a place to escape, which is where the PCV system comes in.
This is the way that I see it functioning, but that is purely my brain working, I have had no education on this matter from book or other official source.

[o_man_ra23]

Steve M, that's the system in a fairly simplistic nutshell. Actually that's a pretty well written description too, as it isn't too confusing.

[Scoobzd]

+ rep for Steve M !

In a nutshell there Steve !

[thdevilshands]

So a bit of an update:

Got the head off finally. In the green book in the engine service bit for the 18R there's a tip showing where to jam a screwdriver (we used a cold chisel) and it just pops the head straight off.

Now we're trying to work out why it was blowing smoke. The head gasket was fine and the head looks pretty good too almost no corrosion. Anyone mechanically minded have an opinion on the valves? I have nfi what to look for.



The bores look pretty smooth, no major scratches and most of the pistons look A1, what should I be looking for to see if the rings are stuffed?

For example Cylinder Bore for #1



This was the cam timing before we took the head off.



Looks a bit off yes??

But the bottom end looks timed up properly.

In this pic the dixxy rotor is at lead for Number #1 spark plug



And here you can see the timing marks at the same position




Any ideas on what to do?

Cheers, Jon

[checksix]

I had to go back to try and pick up what's going on here. You posted low compression:

35, 60, 60 ,60.

You also posted that the cams didn't seem timed right.

From my experience, since the compression numbers seem somewhat consistant, I wouldn't be thinking valves or pistons. Generally if a valve burns, it is more localized to a single cylinder. A broken piston or ring would also be localized. Most likely the issue is the valve timing.

Have you been able to find any part numbers on the cams so it can be confirmed what cams they are, in case they require odd timing?

The next 2 questions will shape up all the rest of the response: How much money is in the budget, and how much time are you willing to spend turning wrenches?

[o_man_ra23]

To check the rings properly, you have to pop the pistons out. They only come out the top, you can't pull them out the bottom. The rings should all spring away from the pistons and you should be able to swivel them around easily.

In the photo you showed, just to the right of the bottom of the piston as pictured, it looks like you can see the top ring, and there is a large gap. The ring gap should be quite small. It 'looks' like that pison is quite sloppy in the bore actually. I would suggest pulling them out and having the pistons and bores measured, as the bores may be excessively large for those pistons, which would cause a huge amount of smoke.

To test valve seating, clean out the ports and combustion chambers so they are all dry. With the cams off, and the head oriented with the combustion chamber down, use a syringe or otherwise to get some kerosene down on top of the valves. You should do one side at a time, and tilt the head so that the valve is pretty well vertical. Kerosene shouldn't leak through into the combustion chamber. If you get slight seepage, this is fairly normal and just requires a re-seat. If it pisses through, you may want to look at replacing that valve and seat.

Keep stripping the motor, it doesn't look as though you have found the cause with 100% certainty yet.

[o_man_ra23]

Checksix, you are correct that the symptoms of ring and valve failure are normally localised, however if ALL piston/ring sets have issues, then it will show on all cylinders. Also, No. 1 is almost HALF the compression of the others, which indicates there is something more than cam timing at fault.

Cam timing should be set with a dial gauge and degree wheel anyway to negate re-grind inconsistencies. I think I did a writeup on how to do this a number of years ago - would still be in the forums. If not, a book called "21st century performance" has a detailed section on setting cams properly.

[checksix]

O-man your powers of observation are amazing. In going back and looking down the bore of #1 (bottom of the stroke) I agree, there does appear to be an excessive ring gap. The difference of compression for the #1 was troubling, but with all of them so low, I focused on explaining that. My next recommendation would be budget and work focused depending on his response. If he's pinching pennies, time the cams, and button it up and see what happens. If it goes badly, he's out his time (considerable), and the cost of the gaskets, (not much). If the budget has the money, then do a full valve job, pop the pistons and if possible limit it to a ring job by just honing the cylinders (provided there is no ring ridge on the cylinders). A full rebore may be needed after seeing the ring gap however.

I liked the valve leak advice, hadn't thought of the check you suggested, but it would be a good idea.