Engine Re-Assy Problem

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blasphemous

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I bought a 440 that had been sitting for a while. It's a 76-ish (ext. bal.) motor home engine. I pulled the caps to check the barings in the bottom ends. All the bearing look fine, the crank went back in fine. I put the rod bearings back together (without spinning then engine over each time) and it was locked up tight.
I found the rod that was locking up on the crank. I removed all the pistons to clean and inspect. After putting them back in, now I have two rods/caps that are locking up on the crank. It's the #1 and #3 piston/rod assemblies. When torqued down to 45 ft/lbs, the crank won't turn at all. With those loose and the other 6 torqued down, it turns over fine.
I tried swapping piston/rod assemblies with one that turned fine after torquing. The problem stayed at the same position, #3. I tried swapping caps, no good and then just bearings, no good. Now, everything is back where it started, no matter what I tried, #1 and #3 always lock it up.

Does anyone have any ideas? When I torque those two down, it feels like it takes a lot more to get the to torque than the other rods. All caps are orientated correctly to the rods as well.
 
Did this engine turn over before you took it apart and it almost looks like from your text that you are reusing the old rod and crank bearings. Sounds like the rod big end is out of round.

Terry
 
Had a simiar problem with a buddys 340 about 20 years ago, if I remember right, the pistons were pressed on the connecting rods backwards. Just like you, six of the eight were fine, but two were backwards and it locked the motor.
 
The person I bought it from said it had been rebuilt not long before sitting it as he had it in his Power Wagon briefly before swapping in a built 440. He said this one had the crank cut (.010/.010) and new bearings put in and after opening it up, everything looks fine internally... other than it sitting a while.

Demon Seed - It turned enough to disassemble it. I probably turned some of the pistons around. They're in the same holes, but all orientated the same way and I didn't pay attention to that when I disassembled. I assumed... and we all know where that gets us.

340john - I'm thinking this may be the problem. Like I just said above, that's really the only thing that changed from turning it over before disassembly the first time. Thanks for the tip! I'm going to try that tonight when I get off of work. I'll let you know if it's the ticket or not.
 
did you try plasti guageing it? maby you need undersize bearings or the po put oversize bearings in is and only 6 or them needed them. for the price of plasti guage i would do it anyways
 
tyler_s18 said:
did you try plasti guageing it? maby you need undersize bearings or the po put oversize bearings in is and only 6 or them needed them. for the price of plasti guage i would do it anyways
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This is what I'm thinking, that not all the rod journals were cut. Pull out all the rod bearings and check the backside for part no/oversize markings.
 
I did check all the bearings to make sure they were all .010 bearings... and they are. However, I didn't plastigage every journal and I don't know why? I have some in my toolbox, I imagine the frustration made me over look it. It's good to take a step back and get an outside opinion, case in point.
 
I assume you have had the pistons out of the motor ? maybe the ones that locked are as mentioned above installed the wrong way. Check the position of the oiling hole on the rods for the pistons in question. The oiling hole should be pointing towards the opposite cylinder on the rod journal. My guess is that - or the crank was improperly sized for the bearings or the big end of the rods were not resized and are ovaled.
 
The pistons should all have a mark to designate front. More importantly, the rods must only face the correct way. Every rod has a tapered side, and a flat side. If you didnt dismount any pistons, then using the rods alone you can get it back right. The tapered side of each rod faces the crank radius. You will have 4 "forward" facing, and 4 "rear" facing. 1 and 3 both have tapered sides that face forward. If you mixed up the caps on other rods, this might be a problem too. Are both cap and rod stamped alike? So you KNOW the caps are on the right rods for all 8?
 
Well I got #3 fixed, the rod is on the piston backwards. I did have the pistons out, but I didn't take the pistons off the rods. I haven't been able to figure out #1 yet. It still locks up with the piston facing forward or backwards. I plasti-gaged all the rods and they're all .002" and the mains were .004". I'll have to check the tapered edge on #1 to make sure it's towards the radius.

It sounds like the only thing it can be now is that #1 is out of round. Is that something a machine shop can check and fix?
 
I bought these to check my crank over:

http://store.summitracing.com/partd...art=SUM-900014&N=700+-166796+115&autoview=sku

And I also bought one of these to check the bearing clearances:

http://cgi.ebay.com/ebaymotors/Parts-Accessories_Automotive-Tools__Dial-Bore-Gage-Gauge-Set-Precision-2-6_W0QQitemZ170298161002QQddnZPartsQ20Q26Q20AccessoriesQQadiZ2871QQddiZ2811QQadnZAutomotiveQ20ToolsQQcmdZViewItemQQptZMotors_Automotive_Tools?hash=item170298161002&_trksid=p4506.c0.m245&_trkparms=72%3A543|65%3A12|39%3A1|240%3A1318
 
Did you plastigage the other 7 rods on that crank? If it ran, and you didnt damage it by overtorqing, it should be fine. I dont think the rod will go out of round by itself. I have gottne myself so confused before that I've had to take it all apart and start from the beginning...lol before I started using my assembly form. I think i'd take all 8 out, beign very carfeul to not mix anything, quadruple check the installation of the rod, piston and cap, and plastigage each journal as you go. recording them all. Then if all 7 are good, but #1 is tight, it's the rod. Also, with stock type flat top pistons, that forward facing mark... really doesnt matter. I dont know of any piston manufacturer that is using the offset pin any more. So it looks neat and technically is correct to have them all facing front. But if they were reversed, it means nothing.
 
.004 on the mains is pretty loose. You might have oil pressure problems - be sure to use a high volume oil pump.

How did you "fix" #3, you say the rod was in backwards ?

And yes the big end of the rod can be re-machined.
 
Sorry, I didnt read the results on the plastigage... The mains are too lose. I hope you plan to run a HV oil pump.
 
All rod gauged out to .002" and like I said the main are .004". I'll get a HV oil pump to be safe. The rods on 1 and 3 are backwards, after flipping 3 it fit fine and I can turn the engine over. However, after turning 1 around to the correct direction (champfered side of rod to the crank radius) it's still tight. I'll going to remove it and take it to a machine shop. Actually, I'll probably take both 1 and 3 just to be safe.

Any other suggestions thus far? I wouldn't have thought about the oil pump. This is my first solo engine build.
 
blasphemous said:
All rod gauged out to .002" and like I said the main are .004". I'll get a HV oil pump to be safe. The rods on 1 and 3 are backwards, after flipping 3 it fit fine and I can turn the engine over. However, after turning 1 around to the correct direction (champfered side of rod to the crank radius) it's still tight. I'll going to remove it and take it to a machine shop. Actually, I'll probably take both 1 and 3 just to be safe.

Any other suggestions thus far? I wouldn't have thought about the oil pump. This is my first solo engine build.
Click to expand...

Are the main bearings brand new and if so how many times, that you know of, have they been loosened and tightened. I would buy and install a new set of mains, they're not expensive and recheck with the plastiguage.

Terry
 
Given what you found so far I would have that crank/rods/block looked over at the shop. Lot cheaper to fix it now then later.
 
Check to see if the rod caps were reassembled with the correct rod AND facing the propper way. I've seen more than a few engines lock up because the rod caps were installed incorrectly. Easy way to check is to remove the cap and look at the bearing tangs. They should be on the same side, assuming the rod was sized correctly.
 
The .004 mains kind of bothers me. I dont know what ind of cash you have, but it might be worth buying a set of .001" undersize bearings to tighten that up. I like tight mains and rods, or tight mains and lose rods. Also, I would have ALL the rods resized and the crank carefully measured (not plastigage... buy mic'd). I tend to be over cautious, but that's what I'd do to make sure it's all right.
 
Money's tight right now, I work in the auto industry :angry7:
I was hoping this would be a pull apart, clean up and reassemble job. I'm not going to throw it together only to have it lock up though. I'm going to call a machine shop down the road and talk to them about the rotating assembly. If it's not going to be a whole lot, I'll get it dropped off.
 
Save your pennies !

Do you have the correct vibration damper ? Is it in good shape ? If not, you might consider getting a forged crank if you have to regrind the journals. I guess it depends on what you want to do with it. Neutral dampers are pretty easy to find for the forged cranks.
 
At minimum, look into the undersize bearings. They are probably a special order, and a little more $$.. but they will give a bit more insurance to it as is.
 
moper said:
At minimum, look into the undersize bearings. They are probably a special order, and a little more $$.. but they will give a bit more insurance to it as is.
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Who would be best to go to for bearings like that? A decent product for not a whole lot of money. The engine is basically just a stock rebuild with a cam, intake and headers. Not a lot of performance, originally I was going to rebuild this as a stocker and get another to build as performance.
 
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