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31 buick 50 engine


my31buick

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Going to church Sunday and my 31 started to make noise. I Just spent over 7k totally going thru this engine. fresh babbiting. rocker assy. rebuilt. cam bearings. This thing sounded awesome. Till now. It started knocking. Towed her home and pulled the pan. No. 7 Rod bearing beat out. I had 40 lbs oil press. at all times. even after knock. Is it possible That connecting rod nuts were torqued way too tight? I ask because they seemed extremely tight when I loosened them. I need help guys. Incompetent engine shops are killing me. Im seriously depressed about this and I thought I spent the extra time and $ to make this a dependable driver. Almost want to give up on it.

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Tightness of the rod bolts is unimportant provided the rod cap is shimmed so the bearing has proper clearance. It may be that the mechanic set them up to tight.

Dont blame the engine - it is not its fault.

If you can, pull an adjacent rod cap, check the shimming and use "plastigage" to check bearing clearance to insure it proper.

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I really hate to hear that this is what you get after investing a lot of time and money into a project that you're supposed to be enjoying. There's not too many things that could have caused this; I'll list the ones I know, in the order of my opinion of probability:

1. Crank was a few thousandths flat and the rod cap was fitted based on the flat side measurement.

2. Shims were inadvertently left out leaving things too tight. Bearing clearance should be around 1.5-2 thousandths.

3. Rod was installed backwards. I know the rods have a front and back but what I don't know is if it is physically possible for one to go in the wrong way.

4. Oil passage clogged.

Pretty much all of these can come from careless workmanship. I have all my machining, head work and cam bearings done at Usave in Tulsa but I do the assembling myself.

If I remember correctly, there may be a remote chance to repair this without removing the crankshaft. There are others far more knowledgeable about this and hopefully they'll speak up if I've got this wrong. Here are the steps:

1. Somehow, loosen the wrist pin bolt on the rod - a small handed contortionist would be handy.

2. Pull the head.

3. Push No.7 piston out as far as it will go, rod will not come through cylinder.

4. Remove the wrist pin and pull out rod from the bottom as crank is turned to make room (I hope someone here knows for sure if there is clearance for this)

Lastly, fix this as soon as you can so that you have it behind you. Also, while it is always nice to know the cause, recognize that it is water under the bridge.

Good Luck

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If it is like the '34 50 Series, the harmonic balancer between the 1st and 2nd cylinders might have to be removed if one of those pistons have to come out - otherwise pistons MUST be removed from bottom - The bottom of the piston rod is bigge than the cylinder bore, as I recall from my 34-50

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Well that will be much better than I thought. For some reason I recall I was not able to do this with my 31-67 and it may have had something to do with getting the ring compressor on when the crank was in but I thought it was a matter of clearing the crank with the piston.

Thanks for the correction!

Joel

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Don't try to remove the wrist pin with the piston in the car. They are pressed in and you will waste your time. The piston and rod will come out the bottom with the crank in the right position. I made a ring compressor out of aluminum, much like the modern ones used on the top. taper the inside bore so it compresses the rings as you push the piston through. There is a bevel on the bottom of the cylinder wall that is supposed to aid in installation, but I had bored my block .040" oversize and had lost s good portion of the bevel. The spring steel compressors are difficult to use with the crank in place.

Your problem could have come from an improper babbit casting. or lack of correct oil hole placement. Generally with babbit bearings, you are less likely to have damaged the crank journal. A damaged insert bearing will definitley damage the crank journal.

Bob Engle

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It has been over 40 years since I did my '31 - so I dont remember the clearance. The spec should be in the service manual. However, I'd imagine the clearance would be between .0015" and .0025".

Be sure to check other rods to establish their condition and clearance.

The unfortunate thing about a babbited engine is when it pukes a bearing, often babbit metal pieces will be circulated through the oil system, so clean carefully.

If you stopped the engine quickly enough, you may be lucky and no damage will have been done to the crank.

The nice thing about a babbited engine is that it could survive a failure like this without damaging the crank - not so with an insert engine (usually).

Dwight makes a good point.

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Thanks for all the in put gents. Tonight I plan to remove the piston and rod thru the bottom without removing the head if I can. I have talked to the Babbitt guy and he said he will rework the bearings. As far as engine shops go I am starting to have a huge lack of trust in their work. The first engine shop in Tulsa (southwestern) eng builders. egg shapped one piston trying to drive out a wrist pin without taking out the pinch bolt. This cost me 2k to have all new aluminum pistons made by Arias because I could not find a stock cast iron piston. Then after the Babbitt was done the same engine shop called saying the crank will not go in the engine because the Babbitt guy messed up on bearings. So I go investigate and find they are trying to put the crank in backwards. they thought the generator hole at the front of the engine was the starter hole. So I Picked up everything and took it all to another engine shop. Although this guy is nice enough, I have had to take things back several times. I insisted on being there on assy. of the engine and he was ok with that. But I was discouraged when I realized the assy. guy does not double check ANYTHING. no plastigauge of bearings to double check tolerance. I also caught a rod being installed that had the oil hole plugged with Babbitt. I caught that and pulled the rod back out and drilled the hole out. A person would think that knowing this is a hard to find engine with parts not available they would take time and effort to make sure its done right.

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Lots of the new mechanics do not understand the older engines, especially those engines with babbit bearings.

Today on a modern engine,, you can mike the crank, buy suitable insert bearings and just throw the engine together since there really isnt anything you can do about the bearing clearnce anyway.

The old babbited engines, the clearance is adjusted both by machining and shimming. You have to check clearances.

On the old engines, I have always done everything myself - including pouring and machining the babbit, then fitting things - I did have mains and cam bearings align bored by a real machine shop after my initial machining. I assembled everything myself.

Finding an old fassioned engine machine shop these days is hard. Many modern mechanics dont even know how points work.

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We have built a couple of these engines, and there are a number of ways to really screw them up. The rods are offset, as the cylinder bores are spaced differently than the rod journals. If the rods are not correctly installed, there will be trouble. There is a hole drilled in the rod and bearing that directs a jet of oil up at the cylinder wall when it lines up at the proper moment with the hole in the crankshaft. If this hole has not been redrilled by whoever did the bearings, the cylinders and also the camshaft and starve for oil. Check your rods to make sure the hole is there. Also, a bent or twisted rod can place severe stress on the bearing. Rods must be aligned after they are bored. Run a plastigage check on another bearing, about .002" is good, and see what the bearing looks like. Bright spots on the sides of the bearing indicate alignment problems. Look at your failed bearing and see if large chunks of babbit are falling off of the bronze shell. This would indicate poor bonding of the bearing to the shell. I hope you can avoid that, as it means bad news for the rest of your bearings. Since your oil pressure is good, there must be some other problem. Good luck and let us know what you find.

Regards, Roger & Erik

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Roger thank you for all the information. I Try to pay close attention to the engines when I disassemble them. I did catch that the rods are offset. I also noticed on assembley of the engine that the one of the holes you ar e talking about was plugged. I was actually upset that the engine shop did not catch it. but I was there while they were putting in the rods so I noticed that and drilled it back out. However you lost me on the part about the rods need to be aligned after bored? Do u know what the limits are on the rod journal being out of round. If im measuring correctly it looks like .003. but I'm not regular at using precision instruments. Rod Gaffrey of Gaffrey babbitting in Deadwood South Dakota did the babbit work. super nice guy and he only works on pre war stuff. He said there could be slim chance he did not get something just right when he poured babbit. But that he will fix the rod again. I like him because he is always helpful to answer questions and that he is a one man pop shop. anything done with rods and bearings is done by him alone.. He has some cool pics. on his website. It sounds like you know this engine well. May I ask what torque you recommend for the rods and the mains?. .Thank you for all the help.......Shawn.

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Alignment of the rods means that the wrist pin hole in the small end of the rod is exactly parallel to the big end journal bore. If it is not, the rod bearing, wrist pin, and piston fit in the bore will all be subjected to undue stress. I use a Sunnen rod alignment tool to check them. If they need adjustment, the large end is placed in a soft jaw vise and appropriate tweaking is made to the small end. Then it is rechecked. Sounds crude, but that's how it is done even on the newest engines. When your engine is assembled, the small end of the rod should not be in contact with the wrist pin boss of the piston, you should see the wrist pin on both sides between the rod end and piston.

The rod journal on the crankshaft should be less than .001" out of round. If it is not, the shaft was not reground or it has suffered wear beyond what is acceptable. Torque specs are not available for many older engines, but a 3/8" rod bolt should have 30 ft lbs and then tighten to the next available cotter pin slot. If the mains are 1/2" bolts, they should be 75 ft lbs or better before lining up the cotter pin hole. Many aspects of babbit work are more art than science. Things do go wrong, work with your babbit vendor and get it straightened out. Please let us know what you find.

Regards, Erik & Roger, Rumble Seat Garage

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There is no bearing left on the one that failed. Also I have not learned how to load and post pics on here. Walk me thru it and I will gladly load some of the bearing, rod, crank, and just the car. Found out tonite that a crack repair done where the lifters are is still leaking coolant directly onto the rod that failed. So I think I have found the culprit. Engine is about to come out and get block crack fixed, crank machined, rod re babbitted and then I think I will assemble it myself this time.

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Ok guys, got the engine out this morning and head removed. Anyone that is familiar with the 31-50 buicks figure out to remove the engine you have to take the rear end and transmission out to get the engine out. all just to get those pesky little flywheel nuts ? Have any of you considered welding the nuts to the flywheel? Most engines I have dealt with the crank is threaded and the bolts go in from flywheel into the crank. If the nuts were welded to the flywheel on the 31 buick I think you could simply drop the oil pan and the rear main bearing cap then take out the flywheel bolts leaving the transmission in place. Am I right or missing something? Im just thinking if future engine removal was necessary this would make things a little simpler.

a

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I have a partial answer to the engine removal question.

The last time I worked on my '31 and '32 was in 1969. However, I am definitely sure you can remove and replace the engines without pulling the rear end and transmission.

I also remember that it wasn't easy

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i just did this,easy to side the rearend back slide trany out, then secure motor for lifting,raise a bit ,lift bell off,because wont clear steering.or you will fight and swear.

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Ok guys. Got the engine tore down. There were two crack repairs done. Each one was just above the lifter assy and each one about 6-8 inches long. This really brings in to question if the block is worth trying to fix. It just so happens that the leak was dripping onto the rod that failed. Now the guy who babbited the bearings in suggesting trying to modify the rods to accept insert bearings. I am sure we discussed this before babbiting the first time and was urged to stick with the babbit . Also brings to question another thought. If I get another block, Will I be able to just install my main bearings, my crank , cam bearings and cam into new block? Or will I have to have it align bored/Honed again? Mark Shaw will you message me about the spare block you have? Is it definitely A good block? Has it been bored any before? and how much are you asking? Im thinking my block is questionable. Waiting to hear from machine shop that I dropped it off at this morning on if they think it is repairable.

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ok guys, Got the engine tore down to bare block this weekend. There were two crack repairs done on this block. Both just above the lifter assy. Each crack repair is about 6-8 inches long. this brings into question weather the block is worth fixing. its at the engine shop now so I'm waiting on their opinion. It just so happens the leak was dripping directly onto the rod that failed. So my bet is that's what caused bearing failure. Also the babbit guy is talking about re fitting the rods with insert bearings. This is something I thought we had discussed prior to him babbitting the rods the first time. And I was sure I was directed not to do this. Have any of you done this before? How did it work out? Mark Shaw it looks like I may need that spare block. What can you tell me about it? message me if you can about it and what you need to have for it. Thanks guys.

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