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What/how to inspect an engine bottom end

tdskip

Yoda
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About - hopefully - to pull the engine with low oil pressure from the TR3. Since I'll have it out it would seem that, despite it clearly not being healthy, exactly how bad off it is.

I've never opened up the bottom of an engine before, used a dial gauge, or plastigauge before but I'm game for learning. I'd like to ask for some help on this since I want to quickly figure out if she is cost-effective to repair vs going a different route as Randall has generously offered (you guys are great).

So, what background learning can you guys get me going on and then what should I start assembling in order to check her out?

Thanks!
 

Brosky

Great Pumpkin
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Tom,

Having the engine out is abig plus, so use it to your advantage. Get it on an engine stand and pull the pan so you can remove the bearing caps and do a visual inspection of the crankshaft and main and rod bearings. That will determine what to do next there. I never trust an old oil pump, or a new one for that matter, so get a new one and check the gear clearances BEFORE installing it.

And also look at the color of the rods and crank to see if anything ever got really hot in there.

No sense in doing all that without pulling the front cover and checking the timing chain, tensioner and gears. Of course then you will want to check the cam and that will require removing the lifters, so you might as well pull the head........ya-da, ya-da, ya-da...........

Some pictures will help a lot in moving you forward.
 

TR3driver

Great Pumpkin - R.I.P
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Almost anything can be rebuilt, especially when it comes to TRactor motors. I once had one that had been so badly neglected that the bearings were worn into the copper backing, and it ran great after having the crank turned and replacing bearings (including cam bearings), pistons & pins, liners, timing chain & gears, camshaft, valves, valve guides, valve springs, & the rocker shaft. In fact, I wish had that motor back, as the "3/4 race" cam & cheap header from JC Whitney really woke it up.

For the bottom end, the most important consideration is the crankshaft surfaces, so start there. Any scoring or wear big enough to feel with a fingernail means it needs to be turned, so you can stop right there and shlep it off to the nearest machine shop for attention. I'd suggest National Crankshaft in Anaheim, but I understand they have changed hands and no longer take retail business directly. Clark's Discount auto parts in Bellflower would send it out for a good price, but I don't know where they send them. Whoever you go to, ask them to Magnaflux it first.

Plastigage only reports what the actual gap is; it won't tell you if the gap is the result of worn bearings or worn journals. So it's really only useful as a final check before assembling with new bearings. You'll need calipers or (much better) a micrometer to actually check the journal diameters; but using a micrometer is something of an art in itself. Don't know if it's still true, but it used to be that a "full service" auto parts stores (like NAPA) would measure it for you.

Otherwise, at least for an initial inspection, I would just look for any obvious signs of damage or excessive wear. If it has spun a bearing, or a thrust washer fallen out, the damage will be obvious. Check out the bottoms of the lifters, any visible wear or damage here will probably mean replacing (or regrinding) the cam & lifters. If the cylinder bores look nearly perfect, they can probably be reused. To get a better idea of bore condition, remove a piston ring from one of the pistons, and use the piston to push the ring to the bottom of the bore. Measure the end gap to get an idea of the ring condition; then repeat the process at the middle and the top of the bore to judge the bore condition. The worst bore wear is always just below the top, where the top ring is when the cylinder fires; there will be almost no wear whatsoever at the very bottom (where the rings don't run at all).

There's more, but I'll let others fill that in.

Oh yeah, having a copy of the factory workshop manual (or Bentley reprint) is a must, IMO. Let me know if you don't have one and we can work something out. The Haynes manual is a close second best, IMO, but watch out for misprints.
 

TR3driver

Great Pumpkin - R.I.P
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Oh, one other thing, if you do want to buy and learn to use a micrometer, Enco has a 2-3" mike on sale for under $25 or a 0-3" set for under $50. Some will sneer at their quality (and it is certainly nowhere near that of Starrett, Mitutoyo or any other recognized brand) but I have found them to be adequate for working on TR motors. But be sure to use the supplied gauge(s) to adjust the zero first.

https://www.use-enco.com/CGI/INPDFF?PMKANO=222&PMPAGE=48&PARTPG=INLMPA&PMCTLG=01
 

martx-5

Yoda
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Brosky said:
... I never trust an old oil pump, or a new one for that matter, so get a new one and check the gear clearances BEFORE installing it...

After some of the horror stories I heard about new oil pumps, I sent my old pump for my TR3 to Ken Gillanders at British Frame & Engine and had them re-do it. Ken is also a wealth of information about the TRactor motors and offers quality parts for them.
 

TR3driver

Great Pumpkin - R.I.P
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martx-5 said:
After some of the horror stories I heard about new oil pumps,
:iagree:
However, I've been lucky. All of my oil pumps were within spec after lapping the housing a bit (as described in the workshop manual).
 

angelfj1

Yoda
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Tom: I know this will seem like an obvious issue, but be sure you have a good service manual, like a Bentley or equivalent. That way you know the min and max specifications for the critical components that you intend to measure. good luck
 

Don Elliott

Obi Wan
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If you decide to replace the oil pump you remove, check to see if it has a cross pin to secure the 4-lobed thingy to the drive shaft. See how they were originally in the S-T parts manual for item 4 on PLATE D facing page 11 in the maunual. If your pump doesn't have the cross pin, try to obtain a new pump which has the cross pin. Talk to all the suppliers and get one to to confirm this.

If the present pump has the cross pin, check the diameter of the main shaft for wear. If none and the 4-lobes all look straight and not too worn or scratched, lap the bottom of the body of the pump to get back to the tolerance specified in the manuals. Then re-install this pump when you finish rebuilding your engine.

If you can buy a new pump with the cross pin, check it for the end tolerance and if it's out, lap the body of the new pump.

If you can't buy a pump with a cross pin and you must buy a "new" "retro" pump without a cross pin - WELL - GOOD LUCK !!!

The pumps without a cross pin have a mild steel drive shaft (not hardened like the ones with the cross pins) so they will wear oval in a few 1000 miles. This will cause sloped wear on the lobes that do the pumping.

Finally all the repro pumps with no cross pin have been impressed with a straight knurling on the mild steel drive shaft. This is to so-called "secure" the lobed thiny to the drive shaft. They can't do a straight knurl on a hardened shaft. Also the knurling which is only about 0.005" high/deep might slip at any time. Even if it's 3 AM and you are mid-way between the desert and no-where. Many have reported that "all of a sudden, the oil pressure dropped to zero". This was later found out to have been caused because the knurling had not secured the two parts and the lobed thingy slipped.
 
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