961Half Way There

Here's a photo of where the valve hit #2 on the left hand side. Pushrod on this valve was pretty bent up.

I put on over 150 miles today taking the head to a machine shop in over in Alexandria, then back home for lunch, and then up to Bluffton to a fellow who will do the injectors. Only 1 injector cracked within the specified 2,700-2,800lbs. All the others cracked at between 3,300-3,500lbs.

I've got parts on order and if the head comes back okay with no cracks in it and the valve job complete, we'll begin reassembly. I should know on the head by the end of the week.

Colin, MN

So. four new injectors and keep the one that worked as a spare?
Keep us posted, hoping it all works out well!

did that piston that kissed valves have a broken rod?

No. The rod bent and the crank broke. Machine shop called this afternoon and the head is good despite the engine failure. Valve job is done. I should be able to run over and pick it up on Monday.

Colin

Actually he'll be able to put in new tips at about 60% of the cost of a whole new injector.

Colin

Wow!

At this point, we're suspecting injector pump timing as a possibility in causing the bent rod on #2, which then cause the crank to break into 3 pieces from the stress. But we'll probably never know for sure what happened.

The head on the damaged engine checked out OK, despite the piston hitting the valve. We need to use that head on the replacement engine. This gives me some hope that the block itself might still be usable. Though if I ever need it, I'll magnaflux it before putting any work into it. I had thought I might proceed with rebuilding the damaged engine now, but I need the $$ elsewhere for the upcoming farming season.

Colin

Do the diesels have a linger strike that causes valve interference when/ if timing is off?

I have never heard the term "linger strike", but I suspect you are asking about "longer stroke". I don't know about the stroke, I suspect the top of the piston goes up to the top of the block or just a bit higher (as in a 201 diesel). To get the compression high enough for diesel combustion, there is much less open volume in the cylinder area. The approximate compression ratio is about 18:1 on the diesel whereas it is somewhere in the 7 to 8 area for the gasoline version. On my 401 diesels, normal compression by way of battery turning the engine is about 400 psi, and should be about the same for the 201 engine. I suspect it may be a bit less on the earlier 172 engine. There are 2 common ways to get the higher compression: 1) use different pistons which extend higher into the head just a bit, and 2) use a different head casting which sets the top of the combustion chamber (and valves) closer to the piston top when at TDC.

Have you ever determined the volume of the head chamber in a gasoline engine by using water and a graduated cylinder? I have checked different heads from 8 & 9N engines to see which head will give me higher compression. It is real easy on the flathead because there are no valves. Just put the sparkplug in its normal hole and pour water into the combustion chamber area until it is flat with the gasket surface of the head. Of course the head is off and flipped upside down and leveled. Some call this process "C - C ing" the head. The less water volume in cubic centimeters, the higher the compression.

Long answer, but that is the thought process the engine designers go through.

Paul in MN

I type on a phone and lng messages just aren't practical as the phone keeps changing what I type, between that and small characters make typing rough.

Yes I'm aware of displacement issues and comp ratio differences. Just didn't know how much of it might be head. Gasser red tigers apparently are non interference, the oil burners must kick that.

Hi Paul,

The compression on this engine is about 17:1 as opposed to about 7:1 on the same version of the 172ci engine running gasoline.

If you bring the piston TDC, I would say that the piston is just a little proud of the top of the block. I did not measure it and my eyes could be misleading me. If it is proud, it is a thousandth or less.

Colin