Main Bearing Replacement ?
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Senior User
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From: Seattle
Main Bearing Replacement ?
Alright, this may be a dumb question but I'm a bit disoriented about the size of replacement main bearings I need. I'm running a 1976 F100 with a 360.
The bearings I had are not marked as undersized or oversized so I am guessing they are standard size.
The lower (non-grooved/ported)bearing is numbered: G8AE-6A338-A-B
The upper (grooved and ported) bearing is numbered: C5AE-6333-AE-A?
I plastigaged the bearings I have in there. Used green plastigage. It compressed out to just UNDER the .003 marking.
This is my undersize... correct?
Also: "Contour Design" vs not?
This is the set I think I need...
The bearings I had are not marked as undersized or oversized so I am guessing they are standard size.
The lower (non-grooved/ported)bearing is numbered: G8AE-6A338-A-B
The upper (grooved and ported) bearing is numbered: C5AE-6333-AE-A?
I plastigaged the bearings I have in there. Used green plastigage. It compressed out to just UNDER the .003 marking.
This is my undersize... correct?
Also: "Contour Design" vs not?
This is the set I think I need...
Junior User
Joined: Jul 2010
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From: Cincinnati
I found it much more helpful to go to the specific engine forum for this type of question. I always look and look but no replies, or replies that don't help much when I post something like this in the dent forum.
Posting Guru
Joined: Jul 2009
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From: Schweinfurt Germany
No no no... But not to worry right idea wrong name. That is if I understand what you did.
Took the plastigage placed it on the bottom (i.e block side bearing) or on the top on the crank after you set it in there and torqued down the main caps took em off and read it there Yes?
Alright that is your bearing clearance and if I am not mistaken 0.003 is just fine although it is a little loose for a non-race engine I would have expected more of the 0.002-0.0025 range for a normal engine. But as long as you have enough oil pressure in your system 3 thousandths won't be a problem.
Now are you looking at undersized bearing because you had your crankground or there was excessive wear?
If you need standard size you will need to ship them in but I would recommend these instead.
King Engine Bearings MB559AM - King AM-Series Main Bearings - Overview - SummitRacing.com
Also there is a whole range of undersized bearings.
Do you have a mic? If so get a reading off of your crank and let us know I can be more help when I have that information as well.
Took the plastigage placed it on the bottom (i.e block side bearing) or on the top on the crank after you set it in there and torqued down the main caps took em off and read it there Yes?
Alright that is your bearing clearance and if I am not mistaken 0.003 is just fine although it is a little loose for a non-race engine I would have expected more of the 0.002-0.0025 range for a normal engine. But as long as you have enough oil pressure in your system 3 thousandths won't be a problem.
Now are you looking at undersized bearing because you had your crankground or there was excessive wear?
If you need standard size you will need to ship them in but I would recommend these instead.
King Engine Bearings MB559AM - King AM-Series Main Bearings - Overview - SummitRacing.com
Also there is a whole range of undersized bearings.
Do you have a mic? If so get a reading off of your crank and let us know I can be more help when I have that information as well.
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From: Seattle
No machining work yet. I want to wait until spring to do it all up right (when I can afford to pay and ride my moto while the block is down).
Yep: I put the plastigage under the crank (or, on top as it was upside down).
Since the crank is not stamped anywhere I am assuming it has never been machined. In that case do I just want standard bearings? Sorry I am being such a dumba$$. It's my first go-around with this.
Yep: I put the plastigage under the crank (or, on top as it was upside down).
Since the crank is not stamped anywhere I am assuming it has never been machined. In that case do I just want standard bearings? Sorry I am being such a dumba$$. It's my first go-around with this.
Posting Guru
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From: Schweinfurt Germany
Hey no problem we all had our cherry engine right guys. Ok here is what I want you to do for me. If you have a digital or mechanical micrometer go out to your garage and measure either all main journals or 3 oughta 5 on your crank. (I like averages better than assuming values off of one possibly outa whack measurement)
If you do not have a mic they are cheap enough to buy and you always can find uses for them. But if you have a clothish tape measure like the kind a tailor would use you can get circumfrence and we will calculate from that. Using that we will decide on what you should grab. =)
If you do not have a mic they are cheap enough to buy and you always can find uses for them. But if you have a clothish tape measure like the kind a tailor would use you can get circumfrence and we will calculate from that. Using that we will decide on what you should grab. =)
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Senior User
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From: Seattle
I do have one!
Measurements from front (timing) to rear (flywheel):
2.75"
2.749"
2.75"
2.748"
2.751"
Hope that helps?
Measurements from front (timing) to rear (flywheel):
2.75"
2.749"
2.75"
2.748"
2.751"
Hope that helps?
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Posting Guru
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From: Schweinfurt Germany
That is great so for all tense and purposes we are going to use 2.75 as your journal size
Now are you sure that you have a 360? that seems rather large for a 360 crank I am thinking you might a 390 let me check for you
Nevermind being stupid same family use generally the same parts. Here these should work.
http://www.summitracing.com/parts/KGB-MB559AM/
It would seem you are well with in tolerance so the ones you have would be fine as well.
Now are you sure that you have a 360? that seems rather large for a 360 crank I am thinking you might a 390 let me check for you
Nevermind being stupid same family use generally the same parts. Here these should work.
http://www.summitracing.com/parts/KGB-MB559AM/
It would seem you are well with in tolerance so the ones you have would be fine as well.
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Nominal journal size is 2.7488" so for all intents and purposes you have a standard sized crank.
Speed Pro Z125M - Speed-Pro Competition Series Main Bearings - Overview - SummitRacing.com
These are much better quality bearings.
Josh
Speed Pro Z125M - Speed-Pro Competition Series Main Bearings - Overview - SummitRacing.com
These are much better quality bearings.
Josh
Posting Guru
Joined: Jul 2009
Posts: 1,536
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From: Schweinfurt Germany
Pfft Maybe for backing material but the king bearing offer 5 times the actual amount of bearing material coming in at around 0.015 instead of the industry standard of 0.003-5
But your opinion and if you have had sucsess with them then you have not going to be a downer about parts I love em all.
But your opinion and if you have had sucsess with them then you have not going to be a downer about parts I love em all.
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