Forward Engine Knock

[P Browning]

The H Engine Problem -- Here is the best I can describe it:

1. The crankshaft & mains plus rod & piston units had just been received from a well-founded engine rebuilder -- fully readied to go. The cylinder head just overhauled to include new valve guides by yet another well-founded shop -- a man who rebuilds race car engines and has worked with me for several years. There is no reason for me to doubt workmanship.

2. The valve train was fully installed (crankshaft, piston & rod units, head, pushrods, tappets installed and adjusted - no magneto). My next step is to perform a compression test yielding 60 on each side. Here is the anomaly -- as each piston passes over compression TDC, I hear a prominent knock appearing to emanate from the forward end of the cylinder block. I hear the knock to the same intensity on each side. Never in all my days have I heard this before!

3. Thinking it was due to dryness up front, I continued assembly and engine closure. During run-up lasting well over an hour, the knock was consistent and is awesome. Using a long screwdriver cupped to my ear, I determined once again that it IS from up front that the knock is happening. Thinking a possible flywheel issue, I switched flywheels with my HN tractor. The HN runs fine, and the knock remains in the H engine.

4. Wondering if I erred in setting operating clearance, I took the engine down far enough to access the rod journals and plastigaged the No. 2 side -- come out at 0.0025 - 0.0027 (Just under 0.003) and so I felt that was as good as one can be! This is where I am at now.

5. In chatting with an engine parts rebuilder, the notion of how the connecting rod pin bushings are oriented come up in the discussion. If for some reason that piston pin is at an angle which IS NOT orthogonal (exactly 90°) to the piston's line of travel, there could be a sudden slap back & forth of the rod bushing inside the piston -- and if this travel is far enough, I rather imagine we could hear it!

6. At this point, I do not have a solid plan of action other than to remove the cylinder head and extricate the rod & piston units for a closer look. Your thoughts?? If you have some suggested tests I can do, I will be most anxious to hear; no -- to listen! (PatB)

 

[Paul_IN]

Perhaps a quick test would be to remove the rocker assembly so the valves can"t move and turn it over again. It would be a quick way to determine if valve seats are not at right height possibly allowing valve to piston contact. If knock is still there then go inside the engine to try and find something not right. Good luck, I hate problems like this when everything should be right.

 

[F-I-T]

I agree with Paul here. Eliminate the valves. If it were on one side only, I'd say a valve is hanging up and "snapping" closed at the last moment (I don;t think on an "H" that an open valve can contact a TDC piston). But, if you check where the flywheel is everytime the noise occurs, see if it happens exactly at the same flywheel position, regardless of #1 TDC or #2 TDC. If so, it's in the flywheel side and not the half-the-revolutions-of-the-flywheel camshaft side.

Then again, it could be as simple as an oil line that is getting bumped by the crank motion and going "Proing!?!" each time.

During running, if you short one side, then the other to kill the cylinder, does the noise move or diminish?

I've forgotten from your post, but are the pistons new? Are the wrist pin bushings new and were they honed straight and true? Boy, they'd have to be off a ton, probably so much that you could see it by leaning the rod one way and then the other. On a layout plate it would be really apparent.

I would still look down in from the top plate to see if there is possibly something contacting the rotating parts as the engine is walked over. A noise can transmit itself pretty handily up a pushrod. Look over the rocker shaft for steps to. Maybe a rocker arm is waling itself sideways, then snapping back its original position, agasint the side-spring pressure. That would make for a "clack"!

Frank

 

[P Browning]

Good Morning Paul -- I failed to mention that with the valve train fully intact and both sparkplugs removed, the knock noise IS NOT there -- as in preparation for the compression test! She rolls over quiet as a church mouse. As you suggest, however, may tell us another factor. Thanks so much for your note. (PatB)

 

[F-I-T]

Pat:

Just for clarification, if you were to "belt" it over at a decent speed, but without ignition, compression, fuel, etc., it doesn't make any moise? I'm confused. I thought you said it made the noise while you were just turning it over by hand as well as running.

On either cylinder, if the wrist pin bushing axis is not parallel to the crank pin axis, and/or the wrist pin bushing bore is not concentric to that wrist pin axis, and/or the wrist pin bushing is out-of-round, all of this could stack up to cause the wrist pin to wrist pin bore to enter an interference and then possibly snap back into position. I hope that is not the case. I can't recall if you mentioned replacing and finish honing the wrist pin bushings. I know a lot of people overlook those and in the old Deere's that is where a ton of wear is stored.

 

[P Browning]

In prep for the initial compression testing following valve train installation & adjustment (no plugs in and no magneto installed), I was able to whip the engine over quite well, and NO -- the noise is not there! She rolls over so quietly.

The pistons are the ones that came with the tractor & I have no history before that other than to say the engine made lots & lots of noise upon arrival! At the engine rebuilder's, the wrist pin fit into the pistons was judged superior. The rods are rebuilt and new bushings were installed and honed as needed to fit the pins. I too think they would have to be terribly skewed to cause the knock.

During Run Up, I also found the knock about as strong on one side as on the other -- this by way of removing first one plug wire -- one-side fire, and then reversing the sides.

At this very time, the No. 2 journal is opened, head remains installed, and the tappets are removed. (PatB)

 

[F-I-T]

Pat:

THe only thing tha tI would do now would be to remove the rocker shaft, and rap each valve to see that it returns with a snap, and isnpt hanging up in static mode. If it runs well, but just with the noise, it could be a slow to return valve that is not slow enough to cause a misfire out the exhaust or a backfire up an intake. It's fairly common to have anew guide be just a bit tight, especially after it runs for a few minutes and the valve stems start to heat up and swell. Without hearing it, that's about all I can think of to check. Still, shorting out one then the other cylinder to see if the noise while running moves or dimishes might tell you more.

Frank

 

[Mike M]

You mentioned something about it not being there with the plugs out. Do you have JD pistons in there or some other kind ? and are they hitting the spark plugs ?

 

[P Browning]

Mike -- at this stage, it is time to regroup. I made an initial assumption that the pistons were okay, and I don't think that was a wise one. The previous owners installed new rings and had this beast in the local tractor pulls where it did well but made a pile of noise.

The assumption I made (and should not have) was that the pistons and block were okay because on tear down, I had fair compression -- in the 60's and so far as I was concerned, that would have been okay for me. Being naive, the issue of severely worn pistons escaped me, and this is what I think I am facing -- piston skirt slap!

The pistons are JD pistons and plugs are Denso L14-U so I am okay there.

Tomorrow, I will finish the take-down. From there, we make measurements that should have been made from the git-go -- that is to observe pistons and bore for wear and wear patterns. I rather imagine the outcome will be to oversize and we then will have a new engine! 'Will advise.

Thanks for your come-back. (PatB)

 

[F-I-T]

I would rather think that the rear of the bores are worn so that the low end is furhet out of spec than the top. As the pistion tracks down, the rods are pulling or pushing against the piston from above or below at the highest angle available as compared to "straight ahead". This rubs the top and the bottom of the cylinder at the trail skirt until it is tapered from wide at the bottom to tighter toward the top. Using a new ring and a feeler gauge to check the end gap at top/middle/bottom of the cylinder would have shown that if it was present. Many times folks just try to judge the top cylinder ridge to determine wear, and don't go down further to check total "taper" and cylindricity.

Once you know the total taper, out of round, and total diameter wear, you can stack this 3-D polygon into a cylindrical sketch, and after 60 years, I find most cylinder bores will fail this test, requiring rebore. After all this time, and equipped with a decent quality dial bore gauge, I never seem to find a block in current and continuous use to ever be in that spec. It's quite often not the pistons that I throw away, but rather the pistons won't fit the new bore that the block decides you need.

 

[P Browning]

Thanks Frank -- We (Me, the block and the rod & piston units) are off to the engine rebuilder tomorrow for analysis -- 'will advise. The session should be enlightening.

I must provide guidance to all out there willing to cut a corner so far as piston versus bore wear is concerned. Even if one chooses not to deal with this problem, at least having it measured gives you some data in event it comes to bite you in the rumpus at a later point in time. (PatB)

 

[F-I-T]

Once again, though, you can tell yourself a ton without going to the machine shop if you use an engine ring and measure the end gap with a decent feeler gauge set. It will show up taper and wear right away. If you have a large micrometer, you can set the mike to a given length, say stock bore diameter, then squeeze the ring into it, measure the end gap that remains when the ring is compressed into a standard diameter, and using this "calibrated" ring as a cylinder gauge, determine to within a few tenthousandths, the degree of taper and wear. Just in case you want to save a trip to the shop, but I'm supposing that you'll be there anyway for some boring mill time. One of the most revealing tools I ever bought was a decent dial bore gauge, good up to 9", and it was not nearly as expensive as people think.

 

[P Browning]

Yes -- I must do this. The procedure appears simple enough and the priciple quite sound. I am betting it won't take too much time to see the problem! Thanks again (PatB)

 

[P Browning]

In measuring variance of bore using a piston ring, I found the ring gap to measure from .090-inch up front reducing some to 0.050-inch at the back of the block. From tech data, ring gap should be 0.015 to 0.025-inch (0.020 nominal). Using 0.020-inch for analysis, one may reasonably assume an excess gap of 30 thousandths at the rear of the bore and 70 thousandths up front.

Dividing each gap excess by 22/7, we observe (no regard to ovality) oversizing to the tune of nearly 0.010-inch at rear and 0.022-inch at the front of the bore. Most assuredly, measuring with a micrometer would reveal opening distance greater than 0.022-inch over due to a non-uniform (egged) wear pattern. We shall see -- perhaps 0.030-inch oversize will do the trick! (PatB)

 

[Mike M]

Did you check for standard size pistons in a .030 overbore block ?

 

[P Browning]

Mike -- not completely just yet, but I am gaining on that one. I do not have an accurate micrometer but using what I think is a fairly new standard sized ring, I found ring gap of from 0.050-inch at the back on up to 0.090 up front. Considering 0.020 a nominal ring gap and doing the math, this illustrates bore oversize of from 0.010-inch (rear) on up to 0.022-inch up front -- far in excess of what should be. I am on the way to a friend's place -- a fellow with the right stuff to measure and then we plot the course to recovery. At least I am confident that it is a poor relationship between piston and bore is causing the racket I am hearing. Thanks for the word. (PatB)

 

[Mike M]

Just slide a feeler gauge in between the piston skirt and the cyl. wall at 90 degrees opposite the wrist pin and see how much clearance you have.
You don't even need to pull it apart.

 

[F-I-T]

Better check that "tech data" on the ring gap, Pat. Deere followed Hasting's advice for all the years that I've worked on their stuff, and the Hastings adage is "3 or 4 per inch of bore" meaning .003" to .004" per inch of bore for ring end gap, so an "H", at least MY "H" will have from .011 to .014" end gap. Be careful you don't end up with a rebored engine that still has the compression of a 4,000 hour motor.

Since you didn't force the ring into an known circle so that you know what the end gap would be for that ring in a standard bore, you only know relative to this, relative to that. Once you establish what the true end gap when held in a standard bore is for that ring, you have a gauge, and I bet you have a block that is even bigger than .010" top, .022" bottom. I hope .030" covers you at the top!

If the ring were perfect for a standard bore, say a .012" end gap, and your cylinder bore measures .090 gap at the top, you would have .078"/Pi to get closer to .025" O/S. Add a few scratches, some out-of-round, (machinists never call it "ovality" or eliptical unless it is a true form and this is just a shape with no guaranteed symetry) and you could exceed .030". See, I wasn't joking about it wearing beyond .030". Now if the cylinder tilts in any way, and the boring mill will show that, you might be over .030" for a total clean up. It depends on what the end gap truly represented.

Do check that end gap standard you are using. I think it is way too wide. I'm not a fan of the royal "We" unless you have a helper type for you, so "I", hope you make it at .030"!

 

[P Browning]

Frank -- so right you are. The oversizing I sensed was totally without regard to any particular axis or direction. As you say -- the 0.022 over may be only a smidgen in one direction and well over 0.030 in a direction 90° away. My engine rebuilder has seen this many times and will advise me by day's end the minimum overbore that will be needed.

And so far as specified end-gap goes, DIR214 (Feb 39) calls out 0.012 to 0.016 end gap for the H tractor. Field Service Bulletin 95-S (3-15-39) calls for ring gap of not less than 0.015 for all rings in the H tractor! And so YES, the service manual data departs from these guidelines and from those of the industry -- why, I do not know. But this issue is of little bearing on my case anyway other than as a basis for a swag. It was the variance in bore diameter from one end to the other that blew me away -- a variance of approximately 0.012-inch with the largest diameter at the combustion end!

Thanks again for your guidance. You see -- I can learn something after all now and then. (PatB)

 

[Mike M]

Bottom line --- new chapter for restoration guide-- never rebuild an engine without access to an inside and outside mic.

You give me accurate ID measurements of bottom of block and top of ring travel and back in about an inch, and only really need the vertical from installed in tractor as this is where the most wear occurs. Then we can advise farther.

 

[F-I-T]

I don't know why they "departed" from that spec either, but as for advice, I would tend to go with the 3 to 4 per inch of bore. That engine even at operating temp won't see the heat that a NAQSCAR engine will do, so it needs enough end gap to ensure that the ends never meet under heat and break a ring, but too much just lets that much more compression out. As the engine warms up and the ring gaps close a bit you get more compression and more efficiency and more power, all good things. I know Clooney and I had a lengthy discussion years back about the amount of compression that goes even behind the ring, through the groove and out the other side, which is an other reason to look piston lands over very carefully. A lot of folks do not and it will let them down as time goes by. There are a lot of places to lose compression, as as we both know, keeping the compression is a good thing on these old engiens. I always say that if you treat these JD's like lawn mower engines, you can't go wrong. They turn relatively slow, but in order to start nice be able to run well towards lean so as not to foul up, they need decent compresion. A JD is not air-cooled, so the expansion factors can be reduced back to a common slow turning ignition engine.

I sure hope you can save that block. I have not looked around, but I soon need to for my "H" project, at the available sizes for O/S pistons. I know JD offered STD and .030". I just stepped away and went on a search and found Sharp's offering .060"/.090", and they say they have a .125" kit. I guess the .030 is a thing of the past? Not sure who else has those, but that goes a long way in allowing those "H" blocks to be saved. Is someone making a .045" now? Heck, maybe there are 10's and 20's. At those small overbore increments, they can most likely use the same casting and just machine it just a bit more/less. There is probably more meat in an "H" block than any other, 'cept maybe a "D".

Good luck on it!

Frank

 

[Mike M]

I have always found Deere's ring set to be gapped maximum and the same with their presized bushings. Some are even over the max.wear spec. when new ! I guess if they error to the side of loose they will have far fewer problems then if too tight.