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1G 1g tob noise & rpm drop - crankwalk

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
Jenkins motor parts. https://www.facebook.com/pages/category/Automotive-Parts-Store/Jenkins-Motor-Parts-600911010048851/

I use 20W50 also and always have, VR-1 at that, so I'm going to say that oil wasn't the problem, I am more prone to think that there was damage done when your balance shaft bearing came out and you lost oil pressure, at least to some extent although there could be other contributing factors, the thrust bearing is not pressure lubricated, it only gets the runoff from that main bearing as it acts like a controlled oil leak dripping onto that thrust area. I am from the camp that believes that part if not a large part of the issue in the 2g was the goofy clutch master cylinder that could go out of adjustment and keep pressure on the thrust bearing, effectively wiping away any lubrication like a scraper. In a 1g though, you wouldn't have that same issue unless your using a 2g master. I also was suspicious that the 2g crankshafts were not properly hardened. You want your main bearing clearance to be looser than your rod bearings, especially the thrust bearing, so as to not starve the thrust.
Thanks Matt! I’ll give them a call tomorrow. Idk if the crank I picked up is any good so I’ll have to bring it to the machine shop to see if it’ll polish out. Don’t think it will tbh so I may have to hunt down another crank.
 

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
Have you mic'd the thickness of the thrust bearing halves? I'd be curious to compare each, both inner (nearest the crank) and outer (nearest the block and girdle) parts of the thrust surface, to see if there's a difference between the halves. Could indicate that they weren't set flush correctly or if it wore at an angle.

Ever since I got that package of ACL Race bearings that had tool marks.. a gouge, rather.. on the bearing surface and the mains were too wide to fit the crank, and yet they were packaged like that, I never tried them again.
I measured both halves.

None thrust side is fairly even throughout, about .004mm variation measuring 5 areas on each half. My 0-1” digital mic sucks.

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Thrust side definitely wore uneven, 1.679- 1.757mm variation. One of the grooves is completely worn away.

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Crank definitely wasn’t rotating straight.
I was able to find a good crank so off to the machine shop here in a few days.

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There’s a local shop D&D that can align hone our blocks 🤞
 

T bags

Proven Member
209
136
Apr 9, 2022
Newark, New_Jersey
I measured both halves.

None thrust side is fairly even throughout, about .004mm variation measuring 5 areas on each half. My 0-1” digital mic sucks.

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Thrust side definitely wore uneven, 1.679- 1.757mm variation. One of the grooves is completely worn away.

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Crank definitely wasn’t rotating straight.
I was able to find a good crank so off to the machine shop here in a few days.

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There’s a local shop D&D that can align hone our blocks 🤞
I see the cup of rocket fuel in the background
Sucks about the crank but it’s almost getting their.
 

jed344

Supporting VIP
1,182
285
Jan 10, 2008
Waterville, Iowa
Interesting, in my 14 years of building dsms I have only ever seen 1 crankwalk. This car also had clutch adjusted wrong so kept pressure on TOB so I assumed that is what caused it. All the motors I have built end up around .0025-.005 when I check crank play. I also always anytime a girdle or ARP mains get used have machine shop check and align hone if needed.
 

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
Got my block align bored (not honed) which is more accurate from what I’m told, and also had the new/used crank polished.

I am convinced my error was from not seating the thrust bearing. Since our caps are not dowled, there is room for error.

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Also measured the 4 edges of the old thrust bearing and they’re all off by a few 10 thousandth which confirms my suspicion.

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Rookie mistake :ohdamn::ohdamn::ohdamn:
 

T bags

Proven Member
209
136
Apr 9, 2022
Newark, New_Jersey
Got my block align bored (not honed) which is more accurate from what I’m told, and also had the new/used crank polished.

I am convinced my error was from not seating the thrust bearing. Since our caps are not dowled, there is room for error.

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Also measured the 4 edges of the old thrust bearing and they’re all off by a few 10 thousandth which confirms my suspicion.

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Rookie mistake :ohdamn::ohdamn::ohdamn:
Glad you caught the error. That chair has seen many builds and looks like a veteran
 

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
Glad you caught the error. That chair has seen many builds and looks like a veteran
Haha yeah. She’s had many cameos. It happens when all my work space is full of other parts.
 

We're on Boost

15+ Year Contributor
1,602
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Aug 25, 2007
Seattle area, Washington
Up in post #55 where you are measuring, I think, 1.124" across the bearing from one thrust face to the other - do you have a number for what that dimension should be on a new bearing? I thought there would be a number for that in the regular FSM but I don't see it.
 

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
Up in post #55 where you are measuring, I think, 1.124" across the bearing from one thrust face to the other - do you have a number for what that dimension should be on a new bearing? I thought there would be a number for that in the regular FSM but I don't see it.
I was measuring the worn down thrust side. The non thrust side hasn’t been touched. I don’t have a new bearing yet (standard size is on back order) but I’d imagine it would be the same on both sides.

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We're on Boost

15+ Year Contributor
1,602
430
Aug 25, 2007
Seattle area, Washington
I don't see a number for that either, in the FSM. I mean, the main bearing thickness, and what the thickness of the thrust flanges should be. For new bearings.
For example, in the RB26 service manual they give a whole table showing the thickness of different bearing "grades" and what the resulting oil clearance would be on your measured journal diameter.
Do you have a number for what the thickness of the thrust flanges should be on a new bearing?
 

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
I don't see a number for that either, in the FSM. I mean, the main bearing thickness, and what the thickness of the thrust flanges should be. For new bearings.
For example, in the RB26 service manual they give a whole table showing the thickness of different bearing "grades" and what the resulting oil clearance would be on your measured journal diameter.
Do you have a number for what the thickness of the thrust flanges should be on a new bearing?
I do not. With the old bearings and new crank, these are oil clearance I’m getting. Only measure one crank and one rod since there’s no point in measuring all of them for now.
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DSMPT

DSM Wiseman
2,178
1,762
Jun 12, 2014
Japan / Mexico, Arizona
Just a little tip here, 6 bolt doesn't have "grades" for bearings like Nissan but 7 bolt does have. That's why OEM 6 bolt main bearings are sold as a complete set and OEM 7 bolt main bearings are sold individually as a pair. There are 5 grades for main and 3 grades for rod. Mitsubishi sort them by colors and IIRC thickness is approxi .0001"~.0002" different in each color. They don't show the thickness, so usually Mitsubishi mechanics have at least one or two pairs of sample in different color to check/calculate clearance and would determine what color they need by using the sample.

Here is the specs of 6 bolt main bearings from bearing manufacturers (1st pic is King. 2nd pic is ACL).
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T bags

Proven Member
209
136
Apr 9, 2022
Newark, New_Jersey
Just a little tip here, 6 bolt doesn't have "grades" for bearings like Nissan but 7 bolt does have. That's why OEM 6 bolt main bearings are sold as a complete set and OEM 7 bolt main bearings are sold individually as a pair. There are 5 grades for main and 3 grades for rod. Mitsubishi sort them by colors and IIRC thickness is approxi .0001"~.0002" different in each color. They don't show the thickness, so usually Mitsubishi mechanics have at least one or two pairs of sample in different color to check/calculate clearance and would determine what color they need by using the sample.

Here is the specs of 6 bolt main bearings from bearing manufacturers (1st pic is King. 2nd pic is ACL).
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😎 OG information right their
 

DSMPT

DSM Wiseman
2,178
1,762
Jun 12, 2014
Japan / Mexico, Arizona
Only for 7 bolt split thrust and it would cost about twice more than the standard ACL Race bearing complete set that we are normally buying, but if you want to set oil clearance accurately by adjusting bearing thickness on each journal, Tomei sell their main/rod bearings for 7 bolt split thrust in 3 different thickness as a pair (That's ACL Race or equivalent, anyways they are supplied by ACL).
 
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We're on Boost

15+ Year Contributor
1,602
430
Aug 25, 2007
Seattle area, Washington
Just a little tip here, 6 bolt doesn't have "grades" for bearings like Nissan but 7 bolt does have .........

Aha, thanks! That's the kind of info I wanted to find.

The 2 charts for 6-bolt King and ACL, I see they do give the thickness. Will the thrust flange thickness just be the same as the radial part of the bearing?

With 6-bolt bearings not being available in "grades" it seems like it would be pretty hard to dial in a specific clearance that you want. How would you do that?
 

DSMPT

DSM Wiseman
2,178
1,762
Jun 12, 2014
Japan / Mexico, Arizona
Will the thrust flange thickness just be the same as the radial part of the bearing?
To be honest I have no idea but I don't think that's exactly the same thickness as the journal part since usually the journal part thickness is not even as the center part is thicker and the side part is thinner. (If strictly speaking, it would be slightly oval after tightening main cap bolts)
With 6-bolt bearings not being available in "grades" it seems like it would be pretty hard to dial in a specific clearance that you want. How would you do that?
I use "production's accuracy difference". Prepare a couple of sets and take the one it fits better on each journal. Or by polishing journals at a machine shop.
 

ist dwa

10+ Year Contributor
603
371
Nov 5, 2009
Centerville, Ohio
The only way to Crank walk a 6 bolt is to mess with oil pressure which you did when you spun that stupid BS bearing. This is what caused all of this.

I think I posted to you about using balance shafts

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DSMPT

DSM Wiseman
2,178
1,762
Jun 12, 2014
Japan / Mexico, Arizona
One of the Real Street videos mentioned using a different size bearing on the cap side to tighten or widen oil clearance. Just curious if that’s an option for us.
Yes some people mix standard and .001" thicker or thinner bearings as half/half to adjust but that's only when you want to adjust less than .001", like when you want to remove or add .0005". Usually you don't wanna do that if the bearing size is .010" + or if the bearing thickness is different more than .0005”.
 
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AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
Yes some people mix standard and .001" thicker or thinner bearings as half/half to adjust but that's only when you want to adjust less than .001", like when you want to remove or add .0005". Usually you don't wanna do that if the bearing size is .010" + or if the bearing thickness is different more than .0005”.
That makes sense

The only way to Crank walk a 6 bolt is to mess with oil pressure which you did when you spun that stupid BS bearing. This is what caused all of this.

I think I posted to you about using balance shafts

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I think it’s from not seating the thrust bearing. Oil pressure never got seriously low when the balance shaft bearing came loose
 

ist dwa

10+ Year Contributor
603
371
Nov 5, 2009
Centerville, Ohio
"I think it’s from not seating the thrust bearing. "

That doesn't even make sense. I'll say it once more, crank walk is an oil pressure problem. You can't seat the thrust bearing incorrectly. Crank walk is not enough oil pressure on the thrust side of the main bearing, clutching a car is wildly hard on that bearing, not enough oil pressure allows it to move and destroy the bearing. This is also why I NEVER EVER start my own cars with a race clutch in it while depressing the clutch. Don't forget you were also messing with that clutch adjustment as well again which can have huge effects on the lateral pressure applied to the crank.

If you installed a bearing wrong you don't get 3000 drive miles, which is a lot, it would be done basically instantly.
 

AWD-Tony

Supporting Member
6,804
3,690
Sep 11, 2017
Cincinnati, Ohio
"I think it’s from not seating the thrust bearing. "

That doesn't even make sense. I'll say it once more, crank walk is an oil pressure problem. You can't seat the thrust bearing incorrectly. Crank walk is not enough oil pressure on the thrust side of the main bearing, clutching a car is wildly hard on that bearing, not enough oil pressure allows it to move and destroy the bearing. This is also why I NEVER EVER start my own cars with a race clutch in it while depressing the clutch. Don't forget you were also messing with that clutch adjustment as well again which can have huge effects on the lateral pressure applied to the crank.

If you installed a bearing wrong you don't get 3000 drive miles, which is a lot, it would be done basically instantly.
So you’re telling me you’d run an engine with main cap for thrust bearing this way?

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100% this is off and it can be centered. If there wasn’t enough oil pressure, #1 main and rod bearings would show some sign of oil starvation. Why would engines spin a bearing before crankwalking then?

This guy builds 1000+hp engine and breaking world records has no clue what he's talking about.
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You will not get proper endplay measurements without seating the thrust bearing first
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