Righty; there is something wrong with your numbers. The standard size for a 318 rod journal is 2.125. Crankshafts and bearings come in .010, .020, and .030 undersize. --- So, 2.125 less .010 =2.115 -------- 2.125 less .020 =2.105. So, neither would work according to your dimension of 2.110 ! They make 'standards' which are highly accurate pins which are used to calibrate [zero in] micrometers.
318 LA rebuild after losing a valve seat
- Thread starter Righty Tighty
- Start date
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Yes, trying to figure out what is wrong here.
^^^^^
Righty should look over the paperwork on his reman crankshaft that he says is a
.040 /.040 undersized reman. Also should remeasure his rod journals again.
Kind of starting to look like it is a
.040/.020 from reading this post.
.040 oversized bearings on a .020 crank rod journal is going to lock that rod to the crank when assembled.
Definitely something going on here with the wrong bearing sizes.
I'll double check, but I measured both with my digital caliper and micrometer. They are VERY well cared for and cailbrated Starrett and Mitutoyo tools. I do have standards, just for kicks I'll calibrate the mic again.
My crank is .030 under, I apologize if I said in an earlier post that it's .040. This was mentioned a while back in this thread, and I had .040 on my mind because my cylinders are .040 over. Either way, I'll dig up the paperwork and check. Maybe it's .030/.020? My guess is that even a .030 bearing on a .020 journal would still have problems. Ten thou is a lot.
Wait a second.....EUREKA! I just remembered I accidentally bought a set of .020 bearings and I still have them. I work today, but I'll try one and see how it fits.
And George, I have been installing them dry and applying lube afterwards. I did however notice during one of my cleaning sessions, that some of the thick lube made its way between the bearing and rod. I cleaned that very well before proceeding. Also, when I mentioned the bearings sitting proud, it was actually just one, and that problem was rectified when using the correct cap, in which the bearing was sitting low. When assembled, they mated properly.
Thanks for all the help, guys. Apologies if I seem like such a mess here....
And George, I have been installing them dry and applying lube afterwards. I did however notice during one of my cleaning sessions, that some of the thick lube made its way between the bearing and rod. I cleaned that very well before proceeding. Also, when I mentioned the bearings sitting proud, it was actually just one, and that problem was rectified when using the correct cap, in which the bearing was sitting low. When assembled, they mated properly.
Thanks for all the help, guys. Apologies if I seem like such a mess here....
nm9stheham
Well-Known Member
If you have 2.109" + or - measured with 2 good measuring tools, then it sounds like the crank was turned wrong. Sounds like the .020" bearings are not going to do it either, but it is worth the try, plus checking the mic vs standards. (My mic's are ancient and still are within .0005".....)
Where did this crank come from?
Where did this crank come from?
^^^^^ Trying to remember if the actual size of the oversized .020 rod bearings are actually made to .018 to allow the .002 oil film clearance between the bearing and crank when assembled ??
nm9stheham
Well-Known Member
If you have 2.109" + or - measured with 2 good measuring tools, that agree with each other, then it sounds like the crank was turned wrong. .020" undersized bearings will still be an interference fit by at least .003" if this is true.
Check the mic against standards. Dropped mics usually read high, not low. But since your tools agree, I doubt this is the issue. BTW, I'd put the piston in with the .020" under bearings with no rings on it to eliminate the ring drag and leave only the bearing drag. it ought to spin as free as the crank that way.
Where did this crank come from?
Check the mic against standards. Dropped mics usually read high, not low. But since your tools agree, I doubt this is the issue. BTW, I'd put the piston in with the .020" under bearings with no rings on it to eliminate the ring drag and leave only the bearing drag. it ought to spin as free as the crank that way.
Where did this crank come from?
I’ll check again. There’s always the factor of user error to be considered, but the instruments themselves aren’t the issue. I’m confident in that. They’re both practically new and have always been in their cases.
I got the crank from AutoZone. It’s a reman for a 71, this is before I discovered the block is a 73. I remember someone mentioned 71 and 73 cranks are the same, so I put that to bed.
One thing I don’t understand is why it won’t turn when the plasti-gauge said there was .001”. Reading KK’s build tutorial and the service manual, specs are .0005-.002”. If it’s within tolerance, shouldn’t the crank be able to turn?
Think about it if you have too much bearing in there and you start drawing it up snug, you can push the bearing insert out of round giving you an inaccurate reading of your plasti-gauge clearance test.
Different opinions on this but the .001 clearance is too tight, .002 is ideal.
Even online there are some that say .0015 is less than ideal for a street engine. Others say .003 for the racing community is OK as they are using the high volume oil pumps to feed them efficiently.
Sure there are lots of opinions on this.
.002 ths. clearance would be my choice for a basic street engine
Different opinions on this but the .001 clearance is too tight, .002 is ideal.
Even online there are some that say .0015 is less than ideal for a street engine. Others say .003 for the racing community is OK as they are using the high volume oil pumps to feed them efficiently.
Sure there are lots of opinions on this.
.002 ths. clearance would be my choice for a basic street engine
nm9stheham
Well-Known Member
Are you using the green plastigage?
Once reason I can think of that explains why you get .001" with the plastigage but the crank is locked: the rod ends and bearings are getting the crap distorted out of them with this very high degree of interference fit. If you have .030" under bearings, meant for a journal size of 2.094-2.095", and are tightening the rod ends onto a 2.109" journal size, then who knows in what direction(s) the rod ends and caps are going to have to give when you torque them down, and how the rod cap will distort. So the bearings and rod end/cap can be clamped hard at the sides where the parting line is located, and the rod cap bowed up with a bit of a gap where you are placing the plastigage.
If you do determine that the journal is indeed 2.109" + or -, then I'd be getting a bore gauge, torque down each rod and cap pair outside the engine without the bearing shells, and carefully checking the rod ends for roundness. (Or take them to the shop and ask them to check the ends.) I'd be concerned that some permanent distortion may have been put in the rod ends and caps.
OK on the source. Hard to say on the quality control there; never heard of issues (but I sure don't hear everything!). And yes the cranks are the same for those years; that's not the issue.
Once reason I can think of that explains why you get .001" with the plastigage but the crank is locked: the rod ends and bearings are getting the crap distorted out of them with this very high degree of interference fit. If you have .030" under bearings, meant for a journal size of 2.094-2.095", and are tightening the rod ends onto a 2.109" journal size, then who knows in what direction(s) the rod ends and caps are going to have to give when you torque them down, and how the rod cap will distort. So the bearings and rod end/cap can be clamped hard at the sides where the parting line is located, and the rod cap bowed up with a bit of a gap where you are placing the plastigage.
If you do determine that the journal is indeed 2.109" + or -, then I'd be getting a bore gauge, torque down each rod and cap pair outside the engine without the bearing shells, and carefully checking the rod ends for roundness. (Or take them to the shop and ask them to check the ends.) I'd be concerned that some permanent distortion may have been put in the rod ends and caps.
OK on the source. Hard to say on the quality control there; never heard of issues (but I sure don't hear everything!). And yes the cranks are the same for those years; that's not the issue.
nm9stheham
Well-Known Member
FWIW.... I've raced hard and long (rallying, with sustained high RPM's) with rod bearing clearances around .0015". Nary an issue. Ima thinkin' that is the least of the OP's worries....
And I agree 100% on the rod distortion.
nm9stheham
Well-Known Member
More likely .019" under GJ. The rod journal diameter spec from the AERA manual is 2.124-2.125" for stock size. So the the bearing is only about .001" larger than the nominal.
I am using the green, I'll try the red tomorrow as well as the .020 bearings JUST to satisfy my curiosity.
The rods were checked for roundness and straightness, one was out of round and corrected by the machine shop.
nm9stheham
Well-Known Member
I just asked the color as the red would be too large to give accurate readings down at .001". No need to change now as you have been using the right size.
My point on checking the rod end roundness is that it absolutely needs to be done again if the rod journal and rod bearing sizes were so badly mismatched as is suspected. You have no way whatsoever to know that, once they have been so badly distorted, that they will return to round when the distorting forces are released. They may be fine or they may be 'bent'. Sorry for the bad news......
Please recheck your tools and re-measure to find out if the rod journal is truly 2.109" + or -.
My point on checking the rod end roundness is that it absolutely needs to be done again if the rod journal and rod bearing sizes were so badly mismatched as is suspected. You have no way whatsoever to know that, once they have been so badly distorted, that they will return to round when the distorting forces are released. They may be fine or they may be 'bent'. Sorry for the bad news......
Please recheck your tools and re-measure to find out if the rod journal is truly 2.109" + or -.
Do a 2 point inside diameter measurement of the bolted large end rods with caps installed at 90° to one another, using your calipers.
Good place to start, you will know right away if they are stretched.
Good place to start, you will know right away if they are stretched.
BEARING MYSTERY SOLVED
Okay, instruments checked and they were spot on. I measured the journals again, this time much more carefully. After multiple measurements, the decided 'new' average was 2.105 with the digital calipers, then confirmed by the mic. So, I went on to see what the crankshaft kit paperwork said, then it dawned on me. I had forgotten it was a KIT that included ALL bearings. That explains where the .020 under rod bearings came from...because I never did remember ordering .020 under rod bearings, yet there they were.
So there you have it, it's a .030/.020 crankshaft and all is well. I am however going to heed the advice to take the rods in to ensure roundness, since there was some mixing up of the caps. For a split second I considered just going with what I have, but I want to be absolutely sure. The shop I go to isn't lightning fast, but he's a straight shooter and does quality work from what I've seen.
I've learned this is not a fast process, at least not for the novice. The good news is I have some work I can be doing on the instrument cluster in the meantime.
Okay, instruments checked and they were spot on. I measured the journals again, this time much more carefully. After multiple measurements, the decided 'new' average was 2.105 with the digital calipers, then confirmed by the mic. So, I went on to see what the crankshaft kit paperwork said, then it dawned on me. I had forgotten it was a KIT that included ALL bearings. That explains where the .020 under rod bearings came from...because I never did remember ordering .020 under rod bearings, yet there they were.
So there you have it, it's a .030/.020 crankshaft and all is well. I am however going to heed the advice to take the rods in to ensure roundness, since there was some mixing up of the caps. For a split second I considered just going with what I have, but I want to be absolutely sure. The shop I go to isn't lightning fast, but he's a straight shooter and does quality work from what I've seen.
I've learned this is not a fast process, at least not for the novice. The good news is I have some work I can be doing on the instrument cluster in the meantime.
nm9stheham
Well-Known Member
Well that is all sounding a lot better and more logical !
Let's hope the rods are fine... but as you say, no point in ignoring a possible issue at this time. Explain to the shop all the why's to re-check the rods so they will best know what to be looking for.
Let's hope the rods are fine... but as you say, no point in ignoring a possible issue at this time. Explain to the shop all the why's to re-check the rods so they will best know what to be looking for.
Rods are back from the shop and all is well. Pistons, cam, and timing set installed. Measured bore and depth of the cylinders to calculate compression ratio while I wait for the timing cover gasket to arrive. Also drilled out one of the cam thrust plate bolts to give it the oiling hole it needed.
Gonna hit up some engine shops tomorrow to see if they have any junk solid lifters I can have to check piston to valve clearance, since I’ll be using hydraulic lifters.
Looking Good !
Looks like you are ready for a set of these next:
Put a tack of weld on a old hydraulic one, make sure it is pumped up.
Or take a old one apart and add a stack of washers in it.
Are those the 302 casting heads?
Well crap. I already tossed my old hydraulics. Otherwise I’d definitely do that.
nm9stheham
Well-Known Member
So everything plastigaged out good and it's all turning well? That's good news!
You're gonna get this licked yet. Good work!
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