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Old 12-17-2019, 10:30 PM   #1
RalphM
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Default This, is why you pull the clean out plugs on a crank!

This is a 4 inch mark crank that I pulled out of a 1940 engine. It was set up for racing, running full floaters. Bearings look pretty toasted and you can see why.
I stuck a Q tip in the right side and pulled out a lot of crap.
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Old 12-17-2019, 10:33 PM   #2
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Default Re: This, is why you pull the clean out plugs on a crank!

Certainly not a clean block either... i'm guessing
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Old 12-17-2019, 11:17 PM   #3
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Default Re: This, is why you pull the clean out plugs on a crank!

I'd say that engine has had a bit of water/rust in it! Good that you decided to clean it out!
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Old 12-18-2019, 10:26 AM   #4
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Default Re: This, is why you pull the clean out plugs on a crank!

Crank measures .020 under on the mains and .017 under on rods.
These are the bearings
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Old 12-18-2019, 05:37 PM   #5
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Default Re: This, is why you pull the clean out plugs on a crank!

Ay our shop we grind lots of crankshafts. The plugs have to come out so the oil passages can be cleaned thoroughly to remove years of deposits.
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Old 12-18-2019, 07:09 PM   #6
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Default Re: This, is why you pull the clean out plugs on a crank!

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Ay our shop we grind lots of crankshafts. The plugs have to come out so the oil passages can be cleaned thoroughly to remove years of deposits.
Exactly! And then on these cranks, tap the holes for screw-in plugs (especially the larger Merc cranks).
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Old 12-18-2019, 07:11 PM   #7
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Default Re: This, is why you pull the clean out plugs on a crank!

Quote:
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Crank measures .020 under on the mains and .017 under on rods.
These are the bearings
I'm sure it will need to go to .030 and .030. Before you grind it, make sure you have both the rod and main bearings in hand -- and hopefully the block you might put it in. The only real way to size the mains is with the block and bearings you're going to run . . . as clearances tend to vary a bit, so I always do it the right way on my race engines. Also, "loose" is better than tight! LOL
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Old 12-18-2019, 07:12 PM   #8
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Default Re: This, is why you pull the clean out plugs on a crank!

What size are the rod journals???
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Old 12-18-2019, 07:22 PM   #9
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Default Re: This, is why you pull the clean out plugs on a crank!

The crank pin bores are a last chance filter of sorts on a lot of old engines. The centrifugal forces will usually hold the particles in the throw end of each crank pin. They sort of get stuck there in a sludge mix of crud. Eventually, they can get like that if too much crud deposits in there. That would generally be a sign of poor maintenance or not properly warming the vehicle up during operation. Little old ladies that only drove to the post office or store and back for all of a 5 minute ride had engines just full of sludge like that.
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Old 12-18-2019, 08:45 PM   #10
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Default Re: This, is why you pull the clean out plugs on a crank!

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What size are the rod journals???
Measured 2.121”,
My book says standard is 2.138”.

I have some NOS .030 over full floating rod bearings.
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Old 12-18-2019, 09:02 PM   #11
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Default Re: This, is why you pull the clean out plugs on a crank!

Not sure what was going on with this engine, but I have seen engines run on salvage yard oil. They drain the oil from old junked cars and reuse it! I rebuilt a 460 that I later learned had been through this. The inside was a mess, it was unbelievable what all needed replaced!! So do a lot of checking, even on parts or surfaces that you would suspect on a normal rebuild.
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Old 12-18-2019, 09:25 PM   #12
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Default Re: This, is why you pull the clean out plugs on a crank!

In the 80’s my sister had about a 8 year old Oldsmobile. It had a popping through carb, I suspect that it had an issue with the valve train so I pulled the valve cover, and there was a perfect mold of sludge in the shape of the valve cover. Once I got it all cleaned out I found a broken pushrod. The car was a cheap runner so I cleaned the sludge out of the other side as well as drain the oil and ran Diesel through it a couple times. Then put oil back in it. She ran it for a while before she finally got rid of it. In 40+ years of working on cars I’ve never seen another one with that much sludge buildup.
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Old 12-19-2019, 07:15 AM   #13
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Default Re: This, is why you pull the clean out plugs on a crank!

Quote:
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Measured 2.121”,
My book says standard is 2.138”.

I have some NOS .030 over full floating rod bearings.
Sounds like it is using the 29A rods - which you already have. So, it would not be a problem in going the route of full-floater. The other approach is to switch over to the 8BA 49-53 rods (regular insert bearings) - they are cheap and much easier to install (don't have to do all the hand fitment work you have to do with floaters).

There is nothing wrong with full-floaters (I use them in my traditional stroker builds - with 91A/21A rods), just that most folks don't take the time to correctly fit them to the crank/rods. I like Ole' Ron's idea of opening up the big-end of the rods a bit (like .001) to make them a bit "loose" - as loose is fast in my book! (Of course I build high-end race-type engines). If you have any questions on full-floater fitment, feel free to PM me (if you've never done it before).

Good luck and STAY WARM - was about 10 degrees this AM . . . probably about 20 degrees warmer than your world! LOL
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Old 12-19-2019, 12:34 PM   #14
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Default Re: This, is why you pull the clean out plugs on a crank!

Thanks,
Not bad now, but supposed to get cold this weekend, -35 by Saturday.

Yes,full floating rods.
So what would the finish measurement on the big end of rod be?
Or is it better to measure rod bearing thickness to determine these clearances?
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Old 12-19-2019, 02:21 PM   #15
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Default Re: This, is why you pull the clean out plugs on a crank!

I don't have the spec off hand, but just lookup the current ID of the big, end - have them hone the ID to .001 larger than spec. If they are resizing the rods, then they're going to hone them anyway. Also, make sure they know the ID is a bearing surface - you want a highly polished surface. If they don't know how to do that - find somebody else. I would always have the rods checked anyway - chances are they'll need to be resized.

You can figure out what your rod journals need to be by doing a bit of mic work - starting with the ID of the rod (using a precision 3-point bore gauge), then add the bearing thickness, then add another .002 or so. You'll probably find that you'll want the crank grinder to make the journal size about .001 smaller than they're used too. You want to end up with .0025 or so of total rod journal clearance. After all this, you'll probably have to hand fit the rod bearings anyway - using a rubber mallet, scotchbrite and lacquer thinner. You want to make sure the bearing shells actually FLOAT - in the rod and on the journal. You can't just drop them in and go - that can be a fatal mistake.

On the mains, buy the bearings FIRST - then have them install them in your block (torqued to spec) and then use a precision 3 point dial-bore gauge (they better have one!) to measure the exact ID of the bearings, then you want to have them grind the mains for a final clearance of about .0025 to .00275 or so.

By having the actual main bearings and grinding the crank to FIT THEM (for each main), you'll end up with the right clearances. I've seen many cases where the main bearings fluctuate a bit and I can't get the correct clearances without doing it this way (which is always the best way anyway). We don't have the luxury in our Flathead world of ordering bearings that are .001+- the standard sizes.
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Old 12-19-2019, 09:45 PM   #16
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Default Re: This, is why you pull the clean out plugs on a crank!

I'm wondering how do you guys get the plugs out of the rod journal ends? I've tried different ways, but this would be interesting to hear from different people. What size plugs or thread size do you tap the holes when putting them back in?
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Old 12-20-2019, 11:51 AM   #17
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Default Re: This, is why you pull the clean out plugs on a crank!

After today I’ll be off till the day after Christmas. I’m going to pull those plugs and I’ll take some pictures and post them on here. I’ll see if I can try a couple different methods.
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Old 12-20-2019, 12:25 PM   #18
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Default Re: This, is why you pull the clean out plugs on a crank!

I use an appropriate size thread tap and tap some threads in there. I have a matching threaded fitting for my slide hammer to pull them.
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Old 12-20-2019, 12:50 PM   #19
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Default Re: This, is why you pull the clean out plugs on a crank!

Quote:
Originally Posted by RalphM View Post
In the 80’s my sister had about a 8 year old Oldsmobile. It had a popping through carb, I suspect that it had an issue with the valve train so I pulled the valve cover, and there was a perfect mold of sludge in the shape of the valve cover. Once I got it all cleaned out I found a broken pushrod. The car was a cheap runner so I cleaned the sludge out of the other side as well as drain the oil and ran Diesel through it a couple times. Then put oil back in it. She ran it for a while before she finally got rid of it. In 40+ years of working on cars I’ve never seen another one with that much sludge buildup.

My sister was famous for killing cars. The problem was that she only put like 1000 miles a year on her cars at the time. Short trips and she drives like someone's grandma.
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Old 12-20-2019, 12:52 PM   #20
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Default Re: This, is why you pull the clean out plugs on a crank!

Same as rotowrench but many are peened in some fashion if so I use die grinder to remove peened area first.
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