[Verdoro 68]

I finally received the Butler balanced rotating assembly for my 464 build last week. I started measuring rod bearing clearances while the block is getting machined. Since this is the first time I've done this I could use a gut check.

These parts are out of the box from Butler. I have no idea if Butler does anything other than balancing the assembly, but the bearings were new in the box so I assume not.

Eagle cast crank rod journals are measuring 2.1994-2.1995. The Eagle forged h-beam rods torqued to the recommended 63 ft/lbs with Clevite 743-HN bearings is giving me .0019-.0020 clearance. This seems on the tight side to me. For what it's worth, I believe these are coated bearings.

Just curious what others experiences are with Butler rotating assemblies? Based on what I've read, want to be in the .0022-.0025 range, correct?

[Mr Twister]

Seems right on to me, I'm sure some pros will chime in, but I would run it.

[prostreet64]

What is the intended use? For a street car 19 to 20 sounds good but for racing where you will see sustained higher rpm compared to street I would say 25 is more in line.

[Verdoro 68]

It’s a street car. Might see very a rare Wednesday night bracket drag night.

[Singleton]

.0019-.0020 is fine. My 495 engine is in the .0017-.0019 range. For comparison, the factory specs for rod bearing clearance is .0005-.0026

[Verdoro 68]

I figured with the old rule of .001 per journal inch, I’d want to err on the side of .0022. Sounds like tighter is ok on a street engine.

Overall, the journals are all in the same ballpark:
1/2: 2.1994
3/4: 2.1995
5/6: 2.1992
7/8: 2.1993

Bearing thickness is uniform at the middle as well at .0685 so the clearance is pretty close to .0020 for all of the journals give or take a ten thousandth.

[Formulajones]

.002 is perfectly fine on the rods. I would not even worry about a ten thousandth either way.

One machinist I used for years always set up his clearances .003 on the mains and .002 on the rods no matter what brand engine it was. He built fantastic engines for decades.


Run it

[hurryinhoosier62]

Ken Crocie had what I call the Crocie rule: .002 clearance on both the mains and rods for street Pontiacs. You should be fine.

[track73]

I've always done ,0022 on both with zero problems

[HWYSTR455]

First thing to do is call Butler and ask. When you're talking about that small of a variance, it could be fudge-factor on tools, temp of parts, etc.

My understanding is that aftermarket rods like the .0022-.0026 range (or more), which also allows for a certain amount of out of round. Worse case, when it's a little on the big side, you should run a little thicker oil. On the tight side, there's no 'adjustment' or 'compensation'.

And that's regardless if it's a 'street' engine or a 'street/strip' engine. (or even a bracket race engine)


.

[mgarblik]

Like others have stated here, .002" is fine. Coated bearings, street, strip use, 10W-30 quality oil= good to go. Final clean everything the very best you can and put it together IMO.

[srmmmm]

My engine builder (Len Williams) also indicated the rotating kit from Butler that went into my engine was on the tight side for clearances, but he preferred that anyway for a street engine. I was surprised at the oil pressure on the dyno after running over an hour with 10W-40 it was never below 50psi even at 600 rpm.

[Verdoro 68]

Heard back from Butler. Their recommendations are .0020" - .0025" on the rods and 0025" - .0030" on the mains so it looks like I'm in the ballpark. Agree about the "fudge-factor". I measured the crank and bearings 10 times already to ensure the numbers I had were consistent. This exercise is definitely highlighting my need for a set of reading glasses.

I ordered some .001 undersize bearings over the weekend thinking I could use a 1/2 shell to get me to .0025, but it doesn't sound like I need them.

[Formulajones]

Originally Posted by Verdoro 68

I ordered some .001 undersize bearings over the weekend thinking I could use a 1/2 shell to get me to .0025, but it doesn't sound like I need them.

I wouldn't even bother with that. Run it at .002 and enjoy a long healthy life.

[Jay S]

Undersized .001” would for tighter clearance, not looser

[Verdoro 68]

Originally Posted by Jay S

Undersized .001” would for tighter clearance, not looser

Good catch. I stated that wrong and ordered “extra clearance” which would be oversized. Will be sending them back anyway. Hope the rest of the build goes this easy.

[Verdoro 68]

I got the block back from the machinist today and started fitting the crank. I’ve got an average of .0015 clearance on the mains which isn’t nearly enough.

In this case is it best to find a set of extra clearance main bearings or have the crank machined? Maybe I’ll give Butler a call tomorrow and see what they recommend.

[70GS455]

Originally Posted by Verdoro 68

I got the block back from the machinist today and started fitting the crank. I’ve got an average of .0015 clearance on the mains which isn’t nearly enough.

In this case is it best to find a set of extra clearance main bearings or have the crank machined? Maybe I’ll give Butler a call tomorrow and see what they recommend.

I would try to find some 1X or extra clearance bearings for your main size

Sent from my SM-G991U using Tapatalk

[Verdoro 68]

Have some on the way!

Started a new thread for this build since I’m sure there will be lots of gotchas….

https://forums.maxperformanceinc.com...d.php?t=861242

[HWYSTR455]

Did the machinst fit the caps and hone the saddles? Could have opted to lean towards the tight side of the spec. Measure the saddles, and check for out of round.

How did you mock it up for clearance measurement? Did you use the crank when you torqued the caps, or just the bearings?


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