Rebuilt 310 B. Immediate compression issues See pic.

Ok. Spent some bucks doing an in-frame rebuild on my 310 B. The machine shop completely redid the head with new valves and the works. Put in piston liners with new pistons and rings. Fairly quickly started with blow by. Compression test showed subnormal compression. (350 recommended, all shooting 280 to 325. Tractor seemed to run ok but oil from breather soon became a torrent. Tore head off today and found a 5 mm indent on all aluminum cylinders in exact location of exhaust valves. Exhaust valves sat proud of the head surface 4 to 5 mm as well.
Of course machine shop saying not my fault. Had 3 different professional opinions today from Deere certified mechanics. All say machine shop error. Few explain blow by. One says the pistons, connecting rods, and bearings should be replaced.
Your thoughts????

(quoted from post at 13:22:50 05/31/23) machine shop completely redid the head with new valves and the works. Put in piston liners with new pistons and rings.

Click to expand...

compare an old (taken out) piston with one of the new ones. are they identical in terms of wrist pin height and dome dimensions? if so, you'd have to suspect the head. there are specifications (I believe in your service manual) for the valves (how far above/below the head surface.

Pretty much a dimension issue. Could be the pistons, the head planing, the valves, the pushrods or the cam. We don't know exactly what you've changed out. You've got to get in there and measure everything. Looks like from the valve impressions on all the pistons, that the problem is consistent in nature.

Who purchased and installed the liners and pistons?

I did the cylinder sleeves with Piston embedded. All John Deere parts- no aftermarket stuff. Block was level and true. Sleeves below required tolerance as per manual. did not touch front end or timing links. Machine ran well prior to rebuild but was a cranky start. Turns out all the valves were bad on the head, so the machine shop did a complete head redo including planing. Machine actually ran well immediately after rebuild, but started with oil from breather tube. Did a compression test. Spec was above 350. Reporting 1 to 4: 320- 285- 315- 320. Over a few weeks noticed more oil from breather tube and loss of power.
ALL these pistons have this 3 to 5mm indent below the exhaust valve. Machine shop guy acknowledges these valves are bent, but says the intake valves were jammed higher in the head- also uneven wear. IE BENT.
Have a range of professional opinions that go from just redo the head to replace pistons, connecting rods, bearings, and check crankshaft.
These opinions come from John Deere mechanics and the head guy at Deere.
So far NO explanation on how I have oil pouring from valve cover except pressure excaping from the valve guides.

Well thats the mark made when it drops a valve although I think thats the first time Ive seen it all the way across consistently on all four!! John Deere parts but were they specific to the block casting number? That would be the main question. Im assuming connecting rods were reused. If so then yeah that kinda leads toward what others have been saying take a real good look at the piston.
It would be a pretty big stretch to think machine shop error caused this actually as it would take some extreme shaving. Im assuming perhaps they also installed the new valves like mine does while they are machining anyway. They are very unlikely to get that wrong also because if stem length was wrong you would assume the intake valves would be doing it too as they are generally the same stem length. Pushrods for simplicity are usually the same length rockers are usually the same shape just left and rights and this leads me to the final question...if the only difference between the two is spec on valve adjustment and possibly cam lobe height what is your intake and exhaust spec? What is the specific engine model?everything to this point has suggested and I am assuming you have a Diesel engine in a backhoe but I know the gas specs on Dubuque 4 cylinders valve adjustment can be different by up to .007 tighter...that would do it. And keep them open a tic causing your low compression.
So valves need replaced machine shop probably will do it for free as mostly labor. Piston needs verified and adjustment spec needs to be known for certain. Then you asked if down below and issue could be caused...unlikely that aluminum piston is nice and soft and should be what needs replaced and it does need replaced as it could be a little out of round. I mean if you go the route that they are telling you where do you stop? Wrist pin and clips since they are out sure but connecting rod and bearings being replaced you could make the argument that if it caused stress on the connecting rod it caused stress on the crank.
So to completely prevent the possibility of ventilating the block a new engine is required and that is how you sell a 15000 engine to a farmer just trying to fix his tiling backhoe.

So IMO whats needed is 4 pistons with rings same as what came out look on the bottom should be a number on the old ones if deere
4 wrist pins 8 keepers
4 exhaust valves and inspection of the guides probably free labor from the machine shop to check it out again since there was a problem. New head gasket and away you go.

Last thing I almost forgot. Your blow by question. Its possible its the guides but even with all that happened I bet they are going to be all right but the machine shop will know. Its very possible your pistons are no longer round being smacked like that while hot. That would cause a good amount of blow by into the crankcase

Thanks for the reply.

When I pulled the head, all exhaust valves were proud of the cylinder head by same distance as indent. Why is this not simply a case where the exhaust valves were too long, or when he planed the cylinder head, he did not take a corresponding amount off the valve stems?

As for all the potential issues with the pistons and related parts, you are correct. Where does one stop on part replacement?

What if I just put the head with correct valves back on and see how she runs. It's an 84, and mostly used to push snow these days.

Its tempting to try it but you could possibly score a liner Im afraid if that piston is out of round. The thing that gets me is the intake side isnt doing it. And so if they got that right on the intake valve stem length it stands to reason they got it right on all since they would do them all at once assuming they werent waiting for the exhaust set to arrive...you could check the top of the stem and see if intakes were ground and exhausts werent but length wise I suppose matters a little bit but whats more important is the gap created by your valve adjustment. As long as thats there and correct the valve could be a hair long and still be just fine. One of the reasons to pull the cover and adjust once in awhile under normal conditions and to double check spec now

You could have someone mill you some custom piston pockets ... prb not the machine shop you went to.

Thanks again for the many thoughts. Yes, the intake valves did not indent, so that's a mystery. The tappet clearance was adjusted correctly twice. After the initial breakin all head bolts had to be retightened which means removing rocker arm and redoing the tappet clearance yet again.
When I removed the head, all the exhaust valves sat proud of the head plane, not recessed. I know the valves were bent, but suspect this was the initial problem. My mistake was taking the head back to the guy who originally did it. He has since removed all the valves, and I expect all evidence to the nature of the crime will disappear. He is obfuscating greatly, and only after I told him my attorney wanted to open a liability claim did he say he'll redo the head.All I want is a head back that has correct valves. I'll take care of the bottom half.
I am about to test the piston clearance by placing a level on the block and hand rotating the crankshaft. If the pistons do not clear that plane, then the bottom clearance is fine. I will also look at liners closely, and if any scoring, replace them.
Push rods were not replaced. Bought 4 more just in case some are now bent. Deere parts were matched to the engine number.

pm me ... I am curious as to your area and the machine shop that did this work ... I would like to avoid them if possible ... I don't find stories like this amusing, especially their lack of accountability ... thanks!

Follow-up. After reading a few technical articles about valve damage to pistons I decided to take apart the lower and take a look. (of interesting note, opinions of local mechanics were evenly divided on whether this was necessary, with 50% saying that everything in the cylinders should be fine, and 50% suggesting there might be issues.)
ALL pistons had broken compression rings, and 2 of the 4 had both compression rings broken (remember that these were sleeved pistons and rings in inserts that were correctly placed into the block).
The technical article correctly alluded to broken rings from these kinds of valve impacts.

She's back together and runs beautifully. Guy that did the head still assures me he did everything correctly. He did re-do the head with proper valve clearance (recessed) and did not charge me for the head redo. But with pistons, rings, gaskets, fluids, another 1000 bucks bites the dust. Good thing I'm retired and had time and curiosity to figure it out.