FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 63.5xl on July 30, 2016, 07:34:37 PM
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Putting engine together and crankshaft cannot be turned by hand, cannot grab ahold of a weight and spin it, have to have some leverage. Crank is a 390 .020 main crank in a 68 block. Do not have any employ either. Using Clevitte ms683 P-20 bearings. Put the crank and bearings in a 66 410 block I have here and same thing. They plastigauge at .001 and a couple at .0015. Beginning to think it is the Clevitte bearings because the crank was previously a .020 .010 crank that was fine before. Could spin it before like a wheel of fortune by grabbing a weight. And
Also is the thrust bearing the only different main bearing between early and late blocks? Tried these in a c3 block first before I put them in the 66 410 block and all the bearings fit the saddles except for the thrust bearing, it was way to tight.
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Early blocks take a different thrust bearing so that explains why your thrust bearing is tight in the C3 block.
Now, I'd imagine your thrust bearing is giving you fits. This happens once in a hand full of engines and you just have to sand the thrust surface of the bearing until you have end play. Start by just putting the top half of the thrust bearing in the block, lay the crank in, and check play. If you have none, sand the front side of the bearing on a flat surface until you get the appropriate clearance.
If you have clearance with the upper bearing but don't have any with the cap bearing, make sure the bearings are set and if you have to clearance it as well, do it.
Not an uncommon problem....
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Thank you Brent
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After I took the crank back out, here are some photos of the new bearings that were just installed using Brad Penn assembly lube. It was only turned over by hand a few times.
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I think you might have damaged your thrust bearing if you forced it into an early block. The flanges may have been spread. I would assemble everything without the thrust bearing to see.
Also....I'm not a fan of Plastiguage but if your only coming up with .001 clearance I would be taking it all back to the machine shop for measuring/blueprinting. .001 is too tight IMHO.
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A 68 block is not an early block though, it's a late block and should use the big bearing
Also, .001 is not too tight for a stocker, but it does require everything to be very straight
Questions
- Do you have access to a micrometer to measure the journals?
- If you put the bearings in order, to the wear marks have a pattern that might show a bad main alignment?
- Are the small slots for the tabs clean? (I did a Poncho 389 a LONG time ago that wouldn't turn, the tab slots were gunked up, used a small screwdriver to scrape clean)
- Any chance you put caps on backwards or mixed up? Remember "tab to tab" for bearing caps, I say it to this day
- Is it a small bearing crank? The way to check if its the thrust is assemble with no bearing in the thrust and see how it turns
- Did you measure thrust clearance?
My hunch, caps backwards or in wrong place, or small OD crank with big OD thrust is holding the crank up
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I think you might have damaged your thrust bearing if you forced it into an early block. The flanges may have been spread. I would assemble everything without the thrust bearing to see.
Also....I'm not a fan of Plastiguage but if your only coming up with .001 clearance I would be taking it all back to the machine shop for measuring/blueprinting. .001 is too tight IMHO.
I did not force it onto the earlier block, I was just going to use that block to try and it was obvious it would not fit on the early block so I used the 66 block I had to try it.
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I had the line bore check and it was fine, also it does the same thing in my 6 410 block. I stuck the 410 crank with its used std size bearings back into the the 66 block and it is fine. This crank was fine in this 68 block when I tore it down 3 years ago. It was a .020 .010 crank then also and it only needed a polish. So same crank, same block it came out of the only difference is new clevitte 77 bearings.
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The thing about Plastigage is that it's basically just a ballpark visual indicator.
I wouldn't be too confident that your clearance is what it is and as Ross suggested, it's best to check with a bore mic. But with only .001" clearance, everything has to be straight, round, and not tapered. I've seen cranks that have had over a half thou of out-of-roundness, or more than in journal taper. Could very well be what you're experiencing.
I would try and verify what your clearances are if you can.
I experience the thrust bearing problem on 1 out of every 5-6 engines. It's not uncommon at all to have to add clearance where there was none.
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But Brent why was things ok before and the only thing changed was the bearings. I will sand the front of the thrust down to get end play, but that will not affect the wear that the other 4 bearing already had on them, will it? Could it be the clevite 77 bearings.. for future reference is that the brand to use or some other brand?
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Bearing clearances vary from brand to brand. For example, you may find that you would have an extra half thou of clearance with a King versus a Clevite. The new block could have also been align honed on a specific side of spec. It could be that the mains are on the low side...
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Dropped crank and rods and block off last Monday at a machine I just found that knows the FE's as good as he knows the other guys. He is booked up a couple weeks so will wait and see. He did say after looking at new bearings there is something wrong so he is going to start with checking the line bore that the other shop said was good.