Main Bearing Clearances / Tolerance

[jake197000]

i work on pacakards all the time and own a 1941 formal sedan.way over built.my dad always said packard never made a bad car.

[earlymopar]

OK Fellas. I'm finally back with some measurements. I had (a lot) more setbacks than just the main stud nuts and deep socket issues that I mentioned earlier. I lost my brother and have been suffering all that loss of very close family brings. I've also been helping my sister-in-law with a lot of details as you may expect. It's a tough road and especially with today being Thanksgiving, a day he and I really enjoyed celebrating together....

Hopefully I can communicate my measurement values and locations well without a diagram but of this is not clear, please let me know. I picked up my engine from the shop that did the initial work with the idea that they would have a chance to "correct" their previous errors. So, these measurements are from the latest short block. Leaving #1 and #5 main caps in place and removing #2, #3 & #4 to check run out I measured 2 locations per journal; 1 on the block front side of the journal and one on the block rear of the journal (each side of the oil hole). With that in mind; #2 = +.0004" (left side) / .0005" (right side), #3 = +.0001" (left side) / .0004" (right side), #4 = +.0001" (left side) / .0008" (right side). After assembly and using plastigauge, I found the following clearance numbers; #1 = .0025" to .003", #2 = .0025" to .003", #3 = .003" to .0035", #4 = .0025" to .003" and #5 = .003 to .0035".

It would seem that using a +.001" bearing on the lower bearing half or main cap only (.0005") would be a good idea on numbers 3 & 5 . Your thoughts?

[earlymopar]

I forgot to mention what I believe the machine shop did to "correct" the original issue (too little clearance on the #5 main bearing) is that they re-cut the #5 saddle. Again this is a guess on my part as the shop owner wouldn't tell me specifically what he found and what he did to "correct" things. Since #3 shows similar clearances to #5, I'm questioning whether they re-cut #3 as well.

Of course my engine was all done cosmetically before I had to take it back it so the paint was ended up getting stripped again after they re-machined and re-hot tanked. The problem is that all of the soft and threaded pipe plugs had also been installed. I'm (now) really leery of whether any debris from the last machining was left in the passages. I'm about to order a set of gallery brushes and go over everything but if any of you have recommendations (short of a full disassembly of the block and re-tanking again), I'd like to hear your suggestions.

[ProPower engines]

OK Fellas. I'm finally back with some measurements. I had (a lot) more setbacks than just the main stud nuts and deep socket issues that I mentioned earlier. I lost my brother and have been suffering all that loss of very close family brings. I've also been helping my sister-in-law with a lot of details as you may expect. It's a tough road and especially with today being Thanksgiving, a day he and I really enjoyed celebrating together....

Hopefully I can communicate my measurement values and locations well without a diagram but of this is not clear, please let me know. I picked up my engine from the shop that did the initial work with the idea that they would have a chance to "correct" their previous errors. So, these measurements are from the latest short block. Leaving #1 and #5 main caps in place and removing #2, #3 & #4 to check run out I measured 2 locations per journal; 1 on the block front side of the journal and one on the block rear of the journal (each side of the oil hole). With that in mind; #2 = +.0004" (left side) / .0005" (right side), #3 = +.0001" (left side) / .0004" (right side), #4 = +.0001" (left side) / .0008" (right side). After assembly and using plastigauge, I found the following clearance numbers; #1 = .0025" to .003", #2 = .0025" to .003", #3 = .003" to .0035", #4 = .0025" to .003" and #5 = .003 to .0035".

It would seem that using a +.001" bearing on the lower bearing half or main cap only (.0005") would be a good idea on numbers 3 & 5 . Your thoughts?

Back in the days before most good shops had a line hone we used to custom grind the cranks to fit the blocks needs.
Depending on what size the crank would end up I would just install the bearings to be used in the block and tighten the caps as needed then gauge the housing bores 1 at a time. Note the size calculate the clearance needed and grind the mains to suit the block.
Now in your case it seems like who ever did the line hone work did not measure all the bearing bores when torqued up then pick the tightest bore then reduce the size by say .003 and make all the rest the same size before line honing.
As well as they most likely did not dial in the mandrel before honing as well. I have seen the results of this many times

[earlymopar]

Thanks ProPower. Those seem like definite possibilities. Another I thought about is that they possibly didn't line hone to begin with (even though that was a request when I dropped the block off, when I raised the issue of inconsistent bearing clearances), they may have gone in on this 2nd time and "cleaned -up" only saddles #3 and #5.

[PackardV8]

Hopefully I can communicate my measurement values and locations well without a diagram but of this is not clear, please let me know. I picked up my engine from the shop that did the initial work with the idea that they would have a chance to "correct" their previous errors. So, these measurements are from the latest short block. Leaving #1 and #5 main caps in place and removing #2, #3 & #4 to check run out I measured 2 locations per journal; 1 on the block front side of the journal and one on the block rear of the journal (each side of the oil hole). With that in mind; #2 = +.0004" (left side) / .0005" (right side), #3 = +.0001" (left side) / .0004" (right side), #4 = +.0001" (left side) / .0008" (right side). After assembly and using plastigauge, I found the following clearance numbers; #1 = .0025" to .003", #2 = .0025" to .003", #3 = .003" to .0035", #4 = .0025" to .003" and #5 = .003 to .0035".

It would seem that using a +.001" bearing on the lower bearing half or main cap only (.0005") would be a good idea on numbers 3 & 5 . Your thoughts?

Agree, try a half and then a whole set of .001" in #3 & 5 and see what Plastigage tells you.

As well as they most likely did not dial in the mandrel before honing as well. I have seen the results of this many times

For the good of the order, how do you dial in your line hone mandrel? What is the evidence/result of not dialing in the mandrel?

[earlymopar]

Thank you. Will do. My bearings are due end of day on 12-1 so I should have answers on 12-2.

[swampbuggy]

Earlymopar, there is an old saying concerning insert bearing clearances and it is appropriate in this thread. A little bit TOO tight and everybody knows it "was", a little bit loose and most likely nobody knows it. This is a quote from David Reher of Reher-Morrision Racing Engines about clearances ( I have come to the conclusion that a little extra clearance is indefinitely better than not enough. Mark H.

[Steve.k]

When dealing with situations where our bearing clearances are a half to a full thou looser than target, we have calico coat the bearings and problem is solved. We always use coated bearings on all race engines and the performance of the coating is excellent. Not bad money and turnaround is quick.

Not to take away from original poster.
Bill what would one of those engines make for power

[ProPower engines]

As well as they most likely did not dial in the mandrel before honing as well. I have seen the results of this many times

For the good of the order, how do you dial in your line hone mandrel? What is the evidence/result of not dialing in the mandrel?
[/quote]


If you read through the set up instructions it shows the use of a mag base dial indicator being used to check mandrel run out.
This is checked at the drive end which should be the same at the other end unless there was damage to the mandrel and it has a slight bend in it.
Since we know there is not any factory engine with the main line we deal with that is dead center of the housing bores it requires checking the runout of the mandrel. Rather then just using the center pins to set the shoe height till the pins slide out the runout of the mandrel must be set as well..The instructions are available on line but it would take 10 pages for me to type them out to fully explain the way and reasons for doing/checking.

For me it makes it a simple check during the mandrel setup before I start line honing.
Once you get used to it the check just comes natural after that but just think of those PITA line hone jobs that you never seem to get perfect and may have to cut a cap or two a couple times. This helps stop that PITA by proper setup.

The details were posted up here a few years back but as we all know the transition of owners of ST has been alot of work and it seems to be lost from the search function but the OP may post it again

[modok]

If the mandrel is not centered the you will wear the shoes unevenly.

But this type of hone with one set of stones and two shoes.... ARE prone to developing fourth order harmonic shape, (like a four leaf clover) ANd if it begins doing that, about the only cure is to retract the shoes enough that it quits, then center it again.

[BILL-C]

When dealing with situations where our bearing clearances are a half to a full thou looser than target, we have calico coat the bearings and problem is solved. We always use coated bearings on all race engines and the performance of the coating is excellent. Not bad money and turnaround is quick.

Not to take away from original poster.
Bill what would one of those engines make for power

A recent one made 1660 hp with 2 stages of nos on chassis dyno with no issues. That translates to close to 1800 at flywheel.

[earlymopar]

Understood swampbuggy. But I wonder what someone like Reher would consider "a little extra" and "too much". Sure, it depends on a number of of factors but in the case of a street-strip engine, what's too-loose?

Earlymopar, there is an old saying concerning insert bearing clearances and it is appropriate in this thread. A little bit TOO tight and everybody knows it "was", a little bit loose and most likely nobody knows it. This is a quote from David Reher of Reher-Morrision Racing Engines about clearances ( I have come to the conclusion that a little extra clearance is indefinitely better than not enough. Mark H.

[n2omike]

0.0020" only leaves 0.0010" on each side of the bearing when running. Most machine shops are happy to be within a half thou when grinding cranks, rods, etc. This means out of round, taper, simple accuracy to the size they want, etc. Stack a few of those tolerances while trying to run tight clearances is a recipe for spun bearings. ALWAYS err on the side of loose.

Many guys will grind it down to the big side of the clearance and done... and don't bother grinding it down to the middle or low. When I was using a local shop (when they still did good work) I would always ask them to grind it down to the low side of the tolerance for extra bearing clearance... and had very good luck with that.

Modern ISO 9000 and robotic/laser production methods, along with MUCH stiffer blocks/cranks allow new stuff to have tighter clearances. Do NOT try this at home. lol. There is zero benefit to 'tight'. A little extra clearance is ALWAYS better than not enough.

[swampbuggy]

Earlymopar, i certainly can not speak for Mr. Reher but personally i would be ok with up to .001" total extra clr. on a Main of 2.500" diam., .0025 + .001 = .0035 if it takes a high volume pump, so be it. Mark H.