A stock 87 2.8 never been rebuilt.
I developed a rod knock a while ago and finally got around to taking off the pan and investigating and fixing.
I stopped driving when it started. The crank looks as if it is okay but when i used the micrometer on it it measures 1.983 on one side and 1.9825 on the other. Measuring like and X.
I have only looked at that one crank journal where the rod connects so far. Is that to bad it cant work? Is it out of specs? Will i have to buy undersized bearings? What are specs?
Any Help appreciated.

It's actually a metric crank so the specs in the service manual are given in mm's:

A connecting rod journal should measure 50.750 mm (or 1.998"), with no more than 0.095 mm (0.0037") and no less than 0.035 mm (0.0014") bearing clearance for your oil film.

Your current journal diameter is 50.750 - 50.355 = 0.395 mm undersize (or 1.998" - 1.9825" = 0.0155" smaller than stock) so if you were to use a standard size bearing, your bearing clearance would be about 4 times larger than the maximum permissible (0.0155" divided by 0.0037" equals 4.1).

Undersized bearings come in 0.25 mm increments which means if you installed a 0.25 mm undersized bearing, you'd still end up with a 0.132 mm clearance which is still too large (max 0.095 mm), and if you installed a 0.50 mm undersized bearing you would end up with zero clearance.

Bottom Line: You need of a crank regrind. Besides, I would wager that your problems aren't only limitied to that one rod journal anyways.

That was the worst bearing.
Is it possible to just band aid it for a couple weeks while my dad and i rebuild our other motor?

You can just buy a little shim stock and shim the bearing. You will have to fit the bearing shells into the rod cap with the shim under it and then file a little off the end (of the bearing shell) so the cap will fit properly with the proper amount of bearing crush. Used to be done all the time. use some plastigauge when you are done to do a reality check on your clearances and life will be good. Larry

[This message has been edited by trotterlg (edited 04-22-2012).]

I tired a band aide temp fix with shims, lasted and 30 mins, the shims spun. Didn't mater though as I had planed on going with a steel crank anyway. I found a brand new Eagle steel crank for about $120. They may still be a few around -discontinued items- , do a web search.

[This message has been edited by Francis T (edited 04-22-2012).]

A Steel crank would be awfully nice.
So to band aid it should i get an undersized bearing? Would that help?

In a pinch, it'll help, but it won't last long before it's either knocking again or before it's spun the bearing.

So should i buy the .25 or .50 mm undersized for just that one?

I'd buy the 0.25 mm undersized bearing since you won't have to mess with shims and trying to file the bearing (personally, I don't see that option working out very well given the tight tolerances and crude tools available to file them). The 0.25 mm bearings would leave you with a clearance of about 5 thousandths of an inch (0.005") which is around 0.0013" larger than the max permissible. You definitely want to use some plastigauge to check the actual clearance possible try several bearings to get the one with the best fit. Running heavier weight oil will help a little too.

No, just buy a standard bearing and use shims to make it fit, you will be much better off. Put the new bearing in and plastigauge it, then buy shim stock to make it fit, remember it takes clearance off both sides, so if you have .010 clearance then buy .004 stock, put it in, file the bearing halves to match the cap and you will have .002 clearance. I would say up to .004 or 005 would be OK and not less then .002 because you have an out of round journal by at least .0005 or so. Larry

[This message has been edited by trotterlg (edited 04-23-2012).]

quote Originally posted by trotterlg: No, just buy a standard bearing and use shims to make it fit, you will be much better off.

You should explain how he should make accommodations for the bearing tangs, make a hole in the shim stock for the oil passage, and somehow try to keep the hole in the shim stock lined up with the matching oil holes in the bearing and the block. To do otherwise would be to condemn his engine to a much shorter life than using the 0.25 mm undersized bearing.

(Edited for spelling)

[This message has been edited by Bloozberry (edited 04-23-2012).]

Alright thank you guys so much im going to be buying a .25 since i don't want to mess with shims.
You all offered great help.
And for the record i was planning on doing the 15w-50 in it is that okay? Synthetic alsp.

He only needs it to run for a month or two, forgit the oil holes, main thing is to get the clearance right, if he buys an under size bearing and it is tight then he is SOL. Put a shim under the bearing shell in the cap, just cut the shim short so it does not go under the tang, then press it down and file it so about .002 higher than the cap on the end without the tang with the tang end even with the cap. Then do it again with the other bearing half. I am thnking you will find it a lot more out of round than you have measured, just don't get the tight spot any less than about .002 and life will be good. The oil hole just squirts a little oil on the under side of the piston, you really won't need this for a short term fix, if you feel you really need to do it just use a paper punch and put a hole in the shim to let oil to the hole. Make the shim shorter than the bearing shell bout abotu 1/8 inch on each end and not quite as wide as the bearing is. Life will be good. Larry

The 15W-50 should help prevent metal to metal contact in the journal, at least for a little while.

What are the shims i've never heard of or used them?

quote Originally posted by trotterlg: ...forgit the oil holes... The oil hole just squirts a little oil on the under side of the piston, you really won't need this for a short term fix...

Hunh? We're talking about the connecting rod bearings at the big end here... not the wrist pins. The oil holes in the connecting rod journals are extremely important... they're what keep the connecting rods from seizing to the crank. Even if you had a momentary brainfart about the oil holes, the fact is that even dust between the bearing shell and the rod cap or connecting rod can impact the clearances, so taking a hole punch to some shim stock is going to stretch the shim stock around the hole significantly more than the thickness of dust. (Edit to add: By the time he torques the bearing cap to spec, the bearing will have deformed so badly around the raised hole of the shim stock that the bearing will be as good as toast.)

quote Originally posted by trotterlg: if he buys an under size bearing and it is tight then he is SOL

Did you even read my first post? A 0.25 mm undersized bearing is not going to be too tight.

[This message has been edited by Bloozberry (edited 04-23-2012).]

I shimmed a rod bearing on my 88 duke back before I rebuilt it, using aluminum foil. I ran that way for several thousand miles with no problems.

quote Hunh? We're talking about the connecting rod bearings at the big end here... not the wrist pins. The oil holes in the connecting rod journals are extremely important... they're what keep the connecting rods from seizing to the crank. Even if you had a momentary brainfart about the oil holes, the fact is that even dust between the bearing shell and the rod cap or connecting rod can impact the clearances, so taking a hole punch to some shim stock is going to stretch the shim stock around the hole significantly more than the thickness of dust.

Lets see some engine basic things. The shims go under the rod bearings, rod bearing are oiled from the crank journal, so they do not need holes in them to be oiled. Any holes in rod bearing are for oil squirt holes to put oil to the under side of the piston, there is a lot of oil flying around in the crank case anyway, so for a short term fix just don't bother with them, lots of engines don't even have them at all. By using shims he can fine tune the clearance, he will likely have to do this because his rod journal is not round any more, so he needs to adjust it so that it is as tight as it can be on the small spots and as loose as it can be on the high spots. Doing it the right way and doing it as a bandaid fix are very different things and take differerent skill sets. Larry

quote Originally posted by Francis T: I tired a band aide temp fix with shims, lasted and 30 mins, the shims spun.

Then you (he) used the wrong skill set. Bearings have been shimmed for as long as there have been machines, it is very common and works very well if done properly. Larry

[This message has been edited by trotterlg (edited 04-23-2012).]

quote Originally posted by trotterlg: Lets see some engine basic things. The shims go under the rod bearings, rod bearing are oiled from the crank journal, so they do not need holes in them to be oiled.

My fault... I am wrong. I was thinking the connecting rod bearings were fed the same way as the main bearings, but the oil for the con rods does not come through the bearing shell but rather from directly to the inside of the journal from the mains.

That said, I still don't believe he will get as accurate nor as reliable a fix by using shims than he will by using an undersized bearing unless he has the experience and tools of an engine builder.

But the flaw in your plan is that he will not be able to adjust the clearance to ballance the clearance between the egg shaped sides of the journal. Larry

If he had the skills and tools to solve this problem more accurately with shims than with an undersized bearing, he would not have asked the question in the first place.

I supposed he asked the question to learn how to do a proper patch to it. Larry

Perhaps so. I too am willing to learn the proper way in this scenario as well then. I am unclear from your earlier description whether you use a shim under both halves of the bearing or just under the cap. It would make sense that you'd need one under both but that would be difficult to do with the engine still installed as in this case. Also, how do you file the bearing to ensure that it's square? How do you gauge that you've left roughly 0.002" above the cap? You must have to take an iterative approach to the filing to get the correct clearance... shaving off a little, assembling with plastigauge, and repeating the process until you've got it right. (Please don't take my questions as being sarcastic, as they surely can be read that way.)

OK, you need to use the shim under both halves of the shell. When you put the shim under the bearing half it effectively makes the shell longer in the rod bore, so you need to file off the extra. About .002 to .004 inches high on both sides, makes for a good crush fit when you tighten down the cap, this and the tabs keeps the bearing from spinning in the rod. Put the shim in, then the bearing shell, put somethig flat on the cap over the end of the shell with the tabs on it, push the end of the shell in so that the tab end of the shell is flush with the rod cap. Now file the other end down until it has about the thickness of one or two thicknesses typing paper sheets sticking up over the rod cap surface. Do this again with the other rod bearing half. A little more crush is probably better than too little, so leave enough so you can feel it with your finger. Then do a reality check with plastigauge. If you file too much off one side just file less of the other side, all that matters is that you get a good tight fit in the cap when you tighten it down. The shims do not have to cover 100% under the bearing half, just most of it leaving a little space on the sides and ends with the tabs. When you do the final assembly make sure you can move the assembled rod on the journal from side to side for a final check, if it is binding at all it will spin right away. Larry

Okay i have done some research on shims now and read all your posts.
One questions so far do you know how much we can shim because i need something like .2 millimeters is that to much for a shim?

The filing process sounds a lot easier to do on the unistalled cap than it does on the rod with the engine installed. I suspect you could do the filing on both shell halves by installing them one at a time in the cap and then transferring one onto the connecting rod to keep the filings away from the engine internals, and so you're not filing upside down. I'd still be wary about getting the ends filed squarely on both shells since they must contact each other very precisely or there will be uneven crush.

Sorry for all the questions, but in my mind to do this more accurately than the undersized bearing method, there has to be more info:

1. obviously you can't use just any file since they're all made with different widths and coarsenesses... what do you recommend to get the best results?

2. What material do you use for the shim stock?

3. How do you cut the shim stock so that it doesn't micro-warp along the cut edges? Seems to me that shears or scissors would bend the shim stock slightly so it wouldn't lay in the rod cap with the precision needed to file the bearing. We're only talking about several thousandths so it seems to me that advice on a good method to cut the shim stock would be really useful.

This definitely falls in the category of "learning new stuff everyday".

You are way over worrying the problem. Yes, fit both bearing halves using the rod cap. any file will work, just try to get it square. This is not going to be perfect, so close is good. Any shim stock will be fine, if the thickness of a pop can works out right use it, or a pop can and tinfoil. You can even buy proper thickness shim stock at auto parts stores, (they sell it there because people use it to shim bearings with). Don't worry about the edges, it is so thin that it will flatten out. This is dead easy to do if you don't think too hard on it. Just don't file too much off the bearing shell, or if you do, file less off the other one, you need a good crush fit on them. On one engine (a chevy sprint) I had a rod journal turned down a lot because it was really toast, I used a portion of a main bearing formed to fit the rod and then shimmed a little, probably shimmed and thicker bearing was about .100 inch or more smaller than stock. It is stil running. Larry

[This message has been edited by trotterlg (edited 04-23-2012).]

What if I used one half of a .25 and one half of a .50 undersized bearing?
My shop teacher just told me of this that they used to do this somethimes in the 50's 60s' and 70's.
What is bad about this or is it perfectly safe to take up the existing slop from just a .25 undersized bearing?
I have shyed away from the shims my dad told me to not do that.

I wouldn't because you don't have enough clearance for even half of the 0.50 mm undersized bearing shell. That side would not leave enough room for the oil film and you'd have metal to metal contact. You would almost certainly spin the bearing if you did this, in my opinion.

If you don't want to use shims, then the best course for a temporary fix is to use both halves of a 0.25 mm bearing. This should leave you with about a 0.005" clearance, which is only 1.3 thousandths of an inch larger than max permissible on a rebuild. In-service tolerances on the other hand will be larger especially on engines with average mileage. I don't believe you have to worry much about regarding the out-of-round condition of the journal... afterall, it's only half of one thousandth of an inch, and you've stated it's a temporary fix.

If you use half of an under sized bearing it will make the bearing tight on the ends of the shell and loose from top to bottom. Not a good plan at all. Shimming it is so easy I cannot see what is bothering you about it, just not a problem at all. If you really think you need to not shim it, use the under sized bearing, I do think that when you get it on that you will likely find that your journal is not what you have measured it to be and it will either be a little tight in spots or a little loose and you will have to shim it any way. Too tight is way way worse than a little loose. Larry

What are the rod caps torque specs?

34 - 40 lbft according to the service manual.

Alright thanks.
Just wondering. You know the notches on the bearings right? Well what happens if you don't put them back notch to notch?
I'm just curious.

That would be bad because it woud mean the rod cap is on backwards. Larry