5.2 Build - main bearing size code identification

[engineermike]

FWIW, and these are just random Euro examples that I could find easily:

Minimum piston-to-wall clearance:
Gen3 Coyote: -0.0002" (interference)
Predator: 0.001"
BMW S38: 0.0011"
BMW S52: 0.0009"

Minimum main bearing clearance:
Gen3 Coyote: 0.001"
Predator: 0.0011"
BMW S65: 0.0012"

Looks like the American clearance are actually tighter, in these examples at least.

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[GregO]

Gen3 Coyote: -0.0002" (interference)

This one is hard to wrap a persons head around until one takes into account pistons are not machined perfectly round.
Coated aluminum cylinders are the greatest until stuff goes bad !

 

[engineermike]

@GregO i believe that negative clearance is due to the grafal coating, which is abradable and about a mil thick.

 

[GregO]

@GregO i believe that negative clearance is due to the grafal coating, which is abradable and about a mil thick.

Yep, lots of different skirt coatings in the 2 Stroke world where 80% of the cylinder is wide open.
I'm amazed at the GEN3 5.0 piston to bore when factoring two machined components with an ID & OD that's size on size and the force needed to press the shaft into the bore. Open the bore up .0005 and the parts nearly glide together, .0000 or less and it's induction heater or hydraulic press time.

 

[Strokerswild]

PS. This Sunnen Gage is like the one I just sold last year to a machinist for $200, Dam I got screwed. Good Luck

Ugh. Don't feel bad, I basically gave one away a few years ago too....

 

[WildHorse]

Looks like the American clearance are actually tighter, in these examples at least.

And ? Actually save it. Knew there's a reason why I'm tryna stay away from this forum.

 

[engineermike]

And ? Actually save it. Knew there's a reason why I'm tryna stay away from this forum.

Take a moment to read all of your contributions to this thread, then show me that a) they are factual and b) they are relevant to the discussion. Your answer lies there.

 

[WildHorse]

Take a moment to read all of your contributions to this thread, then show me that a) they are factual and b) they are relevant to the discussion. Your answer lies there.

Shots too. Give yer balls a tug big boy. Most of the 'factual information' here leads to confusion, bickering, etc., etc. Don't like my posts ? : Block user works really good. Have a great day.

 

[engineermike]

Mmmmk.

Anyway, I took yet another set of readings, 3 per main at 12/2/4 and got within a tenth of what I posted earlier. I can say with a high degree of certainty that main 2 isn’t larger than all the rest. I find that consistently mains 2, 3, and 4 are very close and main 5 is the smallest. This lines up with the INNMG code. Not to mention the crank and a spare gen3 coyote block I have both only have the 6 letters and a number codes. I’ll be ordering bearings tomorrow based on INNMG.

 

[engineermike]

Once I put it all together the main bearing grades required are:

1. 2/2
2. 1/2
3. 2/2
4. 2/2
5. 1/2

 

[GregO]

Once I put it all together the main bearing grades required are:

1. 2/2
2. 1/2
3. 2/2
4. 2/2
5. 1/2

Awesome work Mike.

 

[DougS550]

Once I put it all together the main bearing grades required are:

1. 2/2
2. 1/2
3. 2/2
4. 2/2
5. 1/2

Of course, you will not final assemble until reverification with micrometers/bore gages for actual ODs and IDs gaps/ clearances of each Rod and Crank Main bearings?

 

[engineermike]

Of course, you will not final assemble until reverification with micrometers/bore gages for actual ODs and IDs gaps/ clearances of each Rod and Crank Main bearings?

Yes, especially since I have all the tools and been practicing plenty.

 

[DougS550]

Yes, especially since I have all the tools and been practicing plenty.

Man, the good old days. Spending hours apon hours assembling, disassembling, measuring until your confident and can tell yourself, yep, that's it. Good Luck.

 

[engineermike]

Man, the good old days. Spending hours apon hours assembling, disassembling, measuring until your confident and can tell yourself, yep, that's it. Good Luck.

Well…the rest of the story is that I don’t actually plan to use this motor as-is. I bought the block and pistons with the intent of building a 10.2/1 5.4L stroker. I got the rods basically for free and found a good crank so I figured I’d go ahead and assemble a stock predator back-up and convert it to a stroker later. So yea, I’ll be going through this again in a couple months with a 3.840” crank without a ford size code to go by.

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