While disassembling one of the p400's I found this, going to require new rod bearings, and these motors are 'select fit" bearings.. this motor has 2 different bearing halves in each rod...
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Never trust a crate motor
- Thread starter Twisted Steel Performance
- Start date
Big T
Well-Known Member
Are the middle #s date stamps? 5 09 vs 8 07?
Were they just clearing parts off the shelves on the final engines?
Were they just clearing parts off the shelves on the final engines?
I'm not sure if those are dates or not yet but will find out...
The defect is the first pic, something embedded into the bearing, I can catch a finger nail on it and their is a score line in the bearing, only on that bearing half, not on the mate and nothing on the crank journal..
The pics of the backs are just showing how to tell what half was used to fit everything, the mains are select fit also... this is true with ALL 6.x motors...
The defect is the first pic, something embedded into the bearing, I can catch a finger nail on it and their is a score line in the bearing, only on that bearing half, not on the mate and nothing on the crank journal..
The pics of the backs are just showing how to tell what half was used to fit everything, the mains are select fit also... this is true with ALL 6.x motors...
3500GMC
What T F, over
A standard size half mixed with a 26 thousandths under for the other half? For one rod? Jeez what a mess.
Last edited:
No, every rod had the same mix, standard in the top & .026 in the cap... it's common from what I have seen in the past motors...
3500GMC
What T F, over
Wow. What a hack job they/somebody is doing. Never trust a crate motor is right.
JayTheCPA
Well-Known Member
A guy I know who races, never trusts a crate motor, always tears them down first, and then puts them on a dyno.
This makes me wonder if it has something to do with my experience. And given that observation, will let out more detail on the P-400 issue that I had.
At 500 miles I had to pull the oil pan as the custom franken-pan leaked. I got a call from the shop as their Master ASE was freaked-out by all the metal he saw. When I got to the shop, some of the stuff was so fine that it was suspended in the remaining layer of oil and kind-of looked like an art painting of brown with gold flecks layered into it. A magnet pulled up a *lot* of visible chuncks. The shop owner got the idea to pull the oil pump which was a good idea as there was scoring visible to the naked eye. Also, by this point I was on the 3rd batch of oil, so who knows how much more was generated in the first two batches.
That motor was sent back to the vendor whom was not able to find the metal source but did buff the crank and IIRC replaced the oil pump. Damage was contained to the crank, and below, where everybody felt confident that the dual filter setup saved the rest of the motor.
While waiting for the motor to come back, I got another oil cooler, and lines.
After we got the motor back, the shop was highly suspicious of that motor (and the vendor) and decided to idle it for an hour before they would let me near the truck. In that hour, they got an excuse to drop the oil pan again as the 'repair' to franken-pan made it leak worse than before the 'repair'. At the bottom of the pan was nearly as much fine metal as before the motor was sent back to the vendor for 'repair'. Ordered another oil cooler but this time the shop decided to clean-out the lines as they were highly confident in their abilities to do so . . .
After we got a good franken-pan from the vendor, the vendor was cut-out of the loop and I got a direct contact at AGM whom reported that the P-400 did create a lot of metal during break-in and the oil analysis reports looked normal for the stage of break-in.
Roll forward 20K miles and I never got confidence to take the oil past 3K miles due to the reports of high metal content. But it did start to drop-off.
This makes me wonder if it has something to do with my experience. And given that observation, will let out more detail on the P-400 issue that I had.
At 500 miles I had to pull the oil pan as the custom franken-pan leaked. I got a call from the shop as their Master ASE was freaked-out by all the metal he saw. When I got to the shop, some of the stuff was so fine that it was suspended in the remaining layer of oil and kind-of looked like an art painting of brown with gold flecks layered into it. A magnet pulled up a *lot* of visible chuncks. The shop owner got the idea to pull the oil pump which was a good idea as there was scoring visible to the naked eye. Also, by this point I was on the 3rd batch of oil, so who knows how much more was generated in the first two batches.
That motor was sent back to the vendor whom was not able to find the metal source but did buff the crank and IIRC replaced the oil pump. Damage was contained to the crank, and below, where everybody felt confident that the dual filter setup saved the rest of the motor.
While waiting for the motor to come back, I got another oil cooler, and lines.
After we got the motor back, the shop was highly suspicious of that motor (and the vendor) and decided to idle it for an hour before they would let me near the truck. In that hour, they got an excuse to drop the oil pan again as the 'repair' to franken-pan made it leak worse than before the 'repair'. At the bottom of the pan was nearly as much fine metal as before the motor was sent back to the vendor for 'repair'. Ordered another oil cooler but this time the shop decided to clean-out the lines as they were highly confident in their abilities to do so . . .
After we got a good franken-pan from the vendor, the vendor was cut-out of the loop and I got a direct contact at AGM whom reported that the P-400 did create a lot of metal during break-in and the oil analysis reports looked normal for the stage of break-in.
Roll forward 20K miles and I never got confidence to take the oil past 3K miles due to the reports of high metal content. But it did start to drop-off.
If I am the one responsible for the modifying like in these cases I take nothing for granted, my name and shop is on the line and I am anal about what I send out the door no matter how large or small the job is.
When someone wants a motor built, I always give my recommendations, questions always go back and forth pertaining to some mods or parts the customer thinks they want.. sometimes I don't agree to a part someone wants to use, If a customer wants to save money and use something I don't I always have them make the purchase and send it, and that will be in writing on the final invoice along with my concerns, and their are times I refuse to do something I know will jeopardize the project. Normally this has all been discussed prior to taking the project so nothing comes up during the build.
The case of odd bearings is nothing new with any built motor, I want the clearances a certain way, I have even applied certain coating products to the back of bearings that needed snugging up, with some coated parts a tighter clearance is desired.
In the case of a 6.x when people just start taking the motor apart they should take the time to check bearings and not take for granted they are all the same size, even new gas motors are built this way but few people know this or bother to check.. even if a crank is ground or polished, the bearings should be fitted for each rod & main location..
Enough of the rant, the different bearings is a very common thing...
When someone wants a motor built, I always give my recommendations, questions always go back and forth pertaining to some mods or parts the customer thinks they want.. sometimes I don't agree to a part someone wants to use, If a customer wants to save money and use something I don't I always have them make the purchase and send it, and that will be in writing on the final invoice along with my concerns, and their are times I refuse to do something I know will jeopardize the project. Normally this has all been discussed prior to taking the project so nothing comes up during the build.
The case of odd bearings is nothing new with any built motor, I want the clearances a certain way, I have even applied certain coating products to the back of bearings that needed snugging up, with some coated parts a tighter clearance is desired.
In the case of a 6.x when people just start taking the motor apart they should take the time to check bearings and not take for granted they are all the same size, even new gas motors are built this way but few people know this or bother to check.. even if a crank is ground or polished, the bearings should be fitted for each rod & main location..
Enough of the rant, the different bearings is a very common thing...
MrMarty51
Well-Known Member
Wow, and I have always been to the thinking that if there is a .026 bearing on the one side, there should be a .026 bearing on the opposite side.
That just does not make circumferential sense to Me to mix them like that.
That just does not make circumferential sense to Me to mix them like that.
Will L.
Well-Known Member
The terms of fitting all bearings to the exact clearance size is originally “blueprinting” later more appropriately named “clearancing”.
Bearings are not perectly round. Crankshaft is. Adjusting the clearance by using different size bearings is not just common, it is the only affordable way to get the clearance to the optimum fit. The idea that a huge fat bearing on top and tiny skinny bearing on bottom seems to be a recipe for disaster. The truth is the slight difference between them is far less than the flex of a crankshaft or flex of the block even.
0-100 scale numbers for concept:
If you have a varience say where a bearing needs a 100 top and 0 bottom to get the gap between the bearing and the crankshaft that is optimum, yes you would be better to replace them both with a 50. However the next journal of the crank now may need a net result of 20, so you now need a couple 10 bearings. What about the next journal that need a 35? Or a 37? You basically need a complete setnof bearings in every size available to accomplish this, so since 5 main caps, with 10 sizes you need 50 sets of main bearings. Rod bearing- 8x 10 so you need 80 sets of rod bearings to rebuild your engine.
Now this is real, and engine buliding shops have a massive inventory on hand to deal with it when they are repeatedly building blue printed engines. Not to those numbers and variety obviously, but you get the idea.
Even when you spend the money and have a block line bored and cut the crank, the skillset of the machinist to get it as close as possible almost always results in the need to use different bearing sizes to gain optimum fit. Deciding to pay $700 on top of the normal price of boring the mains to get them all hand finished to as exaclting a fit as possible is up to you to decide it’s worth it. But if doing that, it isn’t worth it unless after having the crank turned, you pay the extra $2,000 to hand polish the crank to exact sizing. Which of course leads to another $2,000 for the rod big end. Now, you can have the same exact bearings top& bottom front to back and achieve perfect clearance. Btw that was iirc the actual price I paid doing a 400 cid sbc back in the 90’s. I convinced myself it would really make a difference since the big boys in racing were doing it at the time. Nowdays you can talk to most any of the builders at the track on topfuelers and they just mismatch the bearings, within as close a range as possible. So put the cost and difference into perspective.
I am not surprised on the bearing damage btw. Crate motors are no different than the engine as it came factory in any rig. It is mass production folks. Stacks of people buy crate motors or brand new vehicles and run them as is and have no problems. Many are fine, and a certain percentage of them have flaws that shorten life, some by a lot.
My new optimizer had a toasty cam bearing (also stamped gm btw). Luckily for me it argued with the cam and the block is perfect. I did not remove the cam bearings when I got it. I didn’t crack the pan or the valve covers. I did flush the hell out of the oil and coolant system. Uao tested at 250 mile
Intervals up to 2500 miles then at 1,000 mile intervals up to 10,000 because at the time, i was getting them for $15 each! Later at full price Only at 10,000 mile intervals when my pricing went away as the local lab closed. That is how I caught it, combined with the drop in oil pressure, which was still way within limits. Really the engine would have been fine with that bearing and cam for probably 200,000, so damaged is a subjective term.
New car manufacturing has had millions upon millions of practice runs and learned over time what they get away with and what they cant. Any engine that is built and has a long shelf life, or gets handled by multiple people before being sealed up and started is always more likely to have issues.
No question, that if someone is a better than average up to amazing level mechanic, it is far better for them to completely disassemble a new engine and reassemble it.
A keen eye like Chris’ won’t allow small imperfections to continue. But his customer will pay more for it than just having an engine dropped in and ran. Imo, yes absolutely worth it. If someone is buying an $8,000 engine and can afford $300 worth of insurance or $2000 worth of insurance to get the most out of the engine is up to them. How much this customer paid or who they are I obviously have no idea. I do know the insurance money they paid - they just got a return on that investment.
When my engine goes together again, my garage is large enough with enough contamination possibility I tent off a clean room for it zombie movie style.
Some say: paranoia will destroy ya!
I say: just because you’re paranoid doesn’t mean they aren’t out to get you. haah In this case- contamination.
Chris- keep up the paranoia style watchful eye and keep that reputation intact. Atta boy!
Bearings are not perectly round. Crankshaft is. Adjusting the clearance by using different size bearings is not just common, it is the only affordable way to get the clearance to the optimum fit. The idea that a huge fat bearing on top and tiny skinny bearing on bottom seems to be a recipe for disaster. The truth is the slight difference between them is far less than the flex of a crankshaft or flex of the block even.
0-100 scale numbers for concept:
If you have a varience say where a bearing needs a 100 top and 0 bottom to get the gap between the bearing and the crankshaft that is optimum, yes you would be better to replace them both with a 50. However the next journal of the crank now may need a net result of 20, so you now need a couple 10 bearings. What about the next journal that need a 35? Or a 37? You basically need a complete setnof bearings in every size available to accomplish this, so since 5 main caps, with 10 sizes you need 50 sets of main bearings. Rod bearing- 8x 10 so you need 80 sets of rod bearings to rebuild your engine.
Now this is real, and engine buliding shops have a massive inventory on hand to deal with it when they are repeatedly building blue printed engines. Not to those numbers and variety obviously, but you get the idea.
Even when you spend the money and have a block line bored and cut the crank, the skillset of the machinist to get it as close as possible almost always results in the need to use different bearing sizes to gain optimum fit. Deciding to pay $700 on top of the normal price of boring the mains to get them all hand finished to as exaclting a fit as possible is up to you to decide it’s worth it. But if doing that, it isn’t worth it unless after having the crank turned, you pay the extra $2,000 to hand polish the crank to exact sizing. Which of course leads to another $2,000 for the rod big end. Now, you can have the same exact bearings top& bottom front to back and achieve perfect clearance. Btw that was iirc the actual price I paid doing a 400 cid sbc back in the 90’s. I convinced myself it would really make a difference since the big boys in racing were doing it at the time. Nowdays you can talk to most any of the builders at the track on topfuelers and they just mismatch the bearings, within as close a range as possible. So put the cost and difference into perspective.
I am not surprised on the bearing damage btw. Crate motors are no different than the engine as it came factory in any rig. It is mass production folks. Stacks of people buy crate motors or brand new vehicles and run them as is and have no problems. Many are fine, and a certain percentage of them have flaws that shorten life, some by a lot.
My new optimizer had a toasty cam bearing (also stamped gm btw). Luckily for me it argued with the cam and the block is perfect. I did not remove the cam bearings when I got it. I didn’t crack the pan or the valve covers. I did flush the hell out of the oil and coolant system. Uao tested at 250 mile
Intervals up to 2500 miles then at 1,000 mile intervals up to 10,000 because at the time, i was getting them for $15 each! Later at full price Only at 10,000 mile intervals when my pricing went away as the local lab closed. That is how I caught it, combined with the drop in oil pressure, which was still way within limits. Really the engine would have been fine with that bearing and cam for probably 200,000, so damaged is a subjective term.
New car manufacturing has had millions upon millions of practice runs and learned over time what they get away with and what they cant. Any engine that is built and has a long shelf life, or gets handled by multiple people before being sealed up and started is always more likely to have issues.
No question, that if someone is a better than average up to amazing level mechanic, it is far better for them to completely disassemble a new engine and reassemble it.
A keen eye like Chris’ won’t allow small imperfections to continue. But his customer will pay more for it than just having an engine dropped in and ran. Imo, yes absolutely worth it. If someone is buying an $8,000 engine and can afford $300 worth of insurance or $2000 worth of insurance to get the most out of the engine is up to them. How much this customer paid or who they are I obviously have no idea. I do know the insurance money they paid - they just got a return on that investment.
When my engine goes together again, my garage is large enough with enough contamination possibility I tent off a clean room for it zombie movie style.
Some say: paranoia will destroy ya!
I say: just because you’re paranoid doesn’t mean they aren’t out to get you. haah In this case- contamination.
Chris- keep up the paranoia style watchful eye and keep that reputation intact. Atta boy!
@Twisted Steel Performance More educational rants please.
- Staff
- #13
Another thing is that .026 may be the mm size, not in inches. .026 in mm is .010 in inches iirc. So they may have had a batch of cranks that were .005 under size after finishing. Instead of scrapping them or trying to turn them furthur(they would have to go to .020 because there is no way you could turn them and polish them .005), they just used a standard in top, and the 1st undersize in the bottom to achieve a .005 undersize. I've seen this done in other engines.
I still remember working for Chrysler/Dodge/Jeep and all the engines had a letter hand written in white at each cylinder. This was the variance from standard bore. Instead of tightening machining tolerances, they decided to have pistons made in .0005 increments so they could keep piston to cylinder fit as tight as possible to reduce cold engine noise. Bearing sizes from the dealer were also availible in increments of .001 up to .003 +/- standard. It made engine work in house a nightmare because everything had to be torn down and checked before parts could be ordered, hence why we did very little in house engine work, and put short/long blocks in everything.
Husker6.5
135' diagonal 16:9HD, 25KW sound!
No different than our old 6.5 blocks having the stamped mark next to each offender to indicate factory oversize lifter bore(s)
MrMarty51
Well-Known Member
I once rebult a 400 Dodge V8.
Got the block and pistons back from the machine shop. I was double checking piston clearance, iirc it was a .015 feeler gauge. whatever size it was, I went to pull the feeler gauge and man was it tight. I called the machinist, He said yeah they are tight, take a look at the foot note, oh, yeah, a foot note, the clearance was with a nine pound pull on the feeler gauge. WOW, never ever set one up that tight before.
I had big time concerns of it seizing, never did, at least not within the first 100,000 miles, I figured after that, the warranty was off. LOL
Long Brown Train
New Member
Good thought, but it is actually 0.001". Putting a 1 thou bearing on one side would be adjusting clearance by a half thou. It seems very likely this is what is going on. Good - that they are checking clearances this accurately. Bad - that there is imbedded crap in the bearing.
- Staff
- #17
Just went and did the conversion, and you're right, it's .001, so a .0005 change.