connecting rod direction

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racyroy1

racyroy1

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Hey guys just a quick question, I tore my 340 down 5-6 months ago and I thought i wrote down which way the con rods went in, as in "stamped rod number should be on the passenger side of the block" type of thing but I can't find my notes and it's been a loooooooong time since i disassembled it. Can any of you remember and help me out with this? I'm ready to stuff the pistons back in and for the life of me I can't remember.

thanks in advance

kevin
 
The notches for the rod bearings, to keep them from spinning, go towards the outside of the motor.
 
The chamfer for the crank filet clearance is cut on one side of the rod only. So the rods need to be oriented so the two rods touch each other on the side with no chamfer. The bearings are offset in the rod to clear the crank's filet so getting that backwards usually means it will be hard to turn over and will have no side clearance on the rods.
 
Ditto to what moper said. I have never heard of the bearing retaining notches having any relationship to the orientation of the rod. You can't have both since the rods chamfered edge needs to point in opposite directions to ensure they are facing the outside of the journel where the chamfer is.

Kevin, stamped numbers on rods are not a factory thing. It was done by someone when they tore the engine down to keep the caps and rods from being mixed up. It was very likely they were stamped while still in the engine and the only convienent way would be on the side facing the outside of the block. BUT, that is no guarantee, use the position of the chamfer and the slight off set of the bearing in the rod to decide the orientation.

Also, if you are installing new pistons with valve reliefs (other than the rebuilder specials with 4 reliefs) there are right and left pistons and the notchs have to be orientated so you have E,I,I,E,E,I,I,E. So for each cylinder you need to have the correct piston orientation along with the correct rod orientation.
 
Thanks guys you've jogged my memory and the common sense factor has kicked in. I should have known most of what you all said but hey, it's been a loooooooooong time LOL. Again gentlemen thanks. Oh yea I'm running kb 243's on stock rods and i know about the bearings but thanks for the refresher. I just finished filing the ring end gap and am ready to drop in the slugs...

I knew I could count on ya'll

thanks.

kevin
 
Dont forget the extra gap needed on the top ring with those pistons...
 
dgc333 said:
Kevin, stamped numbers on rods are not a factory thing. It was done by someone when they tore the engine down to keep the caps and rods from being mixed up.on.
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Are you sure??

My 340 with the stock 1972 bearings still inside were stamped. Hard to believe they were done by anybody outside the factory but maybe?..
 
Yes, they were stamped from the factory..... thats why sometimes you find them stamped half a number, or I saw a crank once, with a nice "3" stamped right onto the journal..... Hard to believe the factory did that.
 
"connecting rod direction"

Let's see, is it up then down...no wait, it's down then up. aw hell it's up and down up and down, etc.

Sorry could'nt resist a little humor.
 
Actualy is as much side to side as up and down.... and if you park sideways on a hill, some are side to side, and some are up and down.......
 
dodge freak said:
Are you sure??

My 340 with the stock 1972 bearings still inside were stamped. Hard to believe they were done by anybody outside the factory but maybe?..
Click to expand...

I have never seen a stock connecting rod with cylinder numbers stamped on them. Why would they? They are not specific to a cylinder and are all the same. It would require the factory to stock 8 part numbers when one would do. Plus the guys building them in the first place are using new parts so there is no need to keep track of a specific cylinder the a piston rod combo is installed into.

I would have to say some one was in the engine after it was orignally built.
 
thanks again guys, I got the rotating assembly put to gether last night and it's all smooth and once i looked at the rods closer it all came back to me. The funny thing about this whole thing is, is that I've rebuilt 400 hp diesels and up to 3500 hp engines and when i started to put this little 340 together I got scared cause it was so small i was afraid i was gonna make a mistake. I've been to school for this stuff and know it quite well but it seemed like when started this project I forgot everything and didn't use any of the knowledge that i have. You guys all gave me a kick start.. I just find it kinda funny and embarassing. Anyway off to the races

kevin
 
dgc333 said:
I have never seen a stock connecting rod with cylinder numbers stamped on them. Why would they? They are not specific to a cylinder and are all the same. It would require the factory to stock 8 part numbers when one would do. Plus the guys building them in the first place are using new parts so there is no need to keep track of a specific cylinder the a piston rod combo is installed into.

I would have to say some one was in the engine after it was orignally built.
Click to expand...

I have torn down MANY Mopar engines that were numbered from the factory, many.
In fact, this little 89 318, that I just finished, was a 56k motor that had never been apart. Some of the rods were marked with numbers, and some with symbols barely recognizable. I made it a habit a long time ago to lightly scribe the top of the piston, including direction. It makes it so much simpler.
 
when i bought the engine in question, the owner had said it was a virgin and had never been rebuilt, and everything i observed in the engine led me to believe the same thing. The caps and rods were stamped. and the clean up at the machine shop said the same thing it was minimal to clean it up, in fact everything i ordered ( bearings ) were at .010 over and rings were .020 were not commonly carried and it took extra time to get them. I measured the bores and they came up almost 4.04. I've read that the factory had stamped depending on the situation and had even put in reground cranks up to .020.
 
I have opened up factory builds that have had non standard sizes, very unusual though from my experience. If my memory serves me, they used "maltese cross" stamp to identify such a motor.

I have never been informed how the factory actually balanced these motors, but they didn't just throw a bunch of parts together.

The counter balance weights on the internal balanced motors, have always had lightening drill holes that I have seen. I always thought that is why they had the rods numbered, after coming from their balance operation.
 
All it would take would be the guy doing the machining at thye factory to "zone out" for a second, and whoops! Oh well, we'll just take it to the next undersize/oversize.
Or a crappy casting for that matter.
 
racyroy1 said:
Hey guys just a quick question, I tore my 340 down 5-6 months ago and I thought i wrote down which way the con rods went in, as in "stamped rod number should be on the passenger side of the block" type of thing but I can't find my notes and it's been a loooooooong time since i disassembled it. Can any of you remember and help me out with this? I'm ready to stuff the pistons back in and for the life of me I can't remember.

thanks in advance

kevin
Click to expand...
i picked up a smallblock mopar from a guy (all new parts) everything right down to the gasket to put it together he had all the mich. work done i gave him $150.00 bucks he set the crank started putting piston and rods turned over with each installed all was good he put number 7 and 8 in bolted them down and the motor locked up he walked away from it and it sat in he shop for a year when i picked it up he even tossed in the motor stand got it home started to check it out and found he had put 7 and 8 in the wrong holes rods turned the wrong way i push them out put them in right and low and behold it turns feely LUCKY ME lol for once in my life
 
dgc333 said:
I have never seen a stock connecting rod with cylinder numbers stamped on them. Why would they? They are not specific to a cylinder and are all the same. It would require the factory to stock 8 part numbers when one would do. Plus the guys building them in the first place are using new parts so there is no need to keep track of a specific cylinder the a piston rod combo is installed into.

I would have to say some one was in the engine after it was orignally built.
Click to expand...

The numbers on the rods are stamped at the time of assembly.
Every B/RB engine I have disassembled has been numbered and most of the LA motors too, but the last 2 318s (86+87) were not.
On those 2, I used punch marks just like I do on Navel engines.
 
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