So... What did I buy?

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Hellrats

Just another dumbass
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This will be a long story but follow along as I could use your help. I'm always looking for 340 small block parts. If it says 340 I'll go check it out. If it's a deal it's mine. I have always been a fan of it, the giant killer. So I found an ad a few months ago for some Mopar stuff in a barn find. It's a two hour drive but I'm retired now and it gives me something to do other than my part time job. Anyway, I get ahold of the guy and do the two hour drive. Turns out he is a Ford guy but he had to buy it all or nothing so he bought the lot. He has two 340 engines. One is a short block and it is rough to say the least. The other is just a block with main caps. But he has a crankshaft for it and that is it. I thought OK I have two sets of 340 rods at the house so lets make a deal. I bought the short block and bare block and the crankshaft for $500 bucks. I was thinking I did OK. I disassemble the short block, it looks like a boat anchor but you never know. Took both of them to my machine shop. They cleaned and mag them. Both check out OK but the rough one needs sleeves, now the other one will clean up at .040" on the bore. The crankshaft needs turned but is OK other than that. So I tell them do the better of the two blocks and the crankshaft. Also go ahead and rebuild the factory rods I dropped off. Everything goes as planned and I picked up the parts today. They look great! I'm happy!! Then I start looking closer and I'm like... WTF? These are some weird numbers on this block? So turn my attention to the crankshaft. I'm like bingo bango!!! Could it be? I think it is a 318-3 truck crankshaft or an old Direct Connection crankshaft? It has no part number on it at all but it most surely is forged. So I'm asking all you guys... WHAT THE HELL DID I BUY? The block numbers are crazy and it has no VIN. Doesn't look like it ever had one. They both were standard bore too. Both blocks was cast in 72 but the letters on the front say it's a 73. Is this last of the run of them?

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The block is genuine and the crank looks like a normal forged piece to me I have 2 340s and had 3 in my life. I cant explain why there are no numbers but i have had guys tell me some of the cranks don't have numbers. It makes me wonder if it is or was a replacement .
 
That's a heavy duty 318 crank, I believe. The 340 cranks had the front throw drilled all the way through if I remember right.
 
Yeah that's the plan. I'm really confused about the block numbers. Not like it makes a difference I just never have seen one like this.
 
Looks like forged crank. Where's the weird block #'s? In 5th pic I see "JM 340P". Nothing on vin rail?
340-6 stamping is normal. The numbers following the dash usually range from 1-8. I've never seen a dbl digit there.
 
I agree with 71GSSDemon, replacement blocks didn't have VIN numbers. That is a 318-3 truck crankshaft, I have one of those hard to find pieces. RRR is correct front throw is not drilled through, nice score! 65
 
There is nothing "odd" or "weird" about it. It's a 72 casting 340, would have came in a 73 model, or warranty block. And yes, that's a 318 steel crank. You got a nice score for sure
 
Hellrats said:
This will be a long story but follow along as I could use your help. I'm always looking for 340 small block parts. If it says 340 I'll go check it out. If it's a deal it's mine. I have always been a fan of it, the giant killer. So I found an ad a few months ago for some Mopar stuff in a barn find. It's a two hour drive but I'm retired now and it gives me something to do other than my part time job. Anyway, I get ahold of the guy and do the two hour drive. Turns out he is a Ford guy but he had to buy it all or nothing so he bought the lot. He has two 340 engines. One is a short block and it is rough to say the least. The other is just a block with main caps. But he has a crankshaft for it and that is it. I thought OK I have two sets of 340 rods at the house so lets make a deal. I bought the short block and bare block and the crankshaft for $500 bucks. I was thinking I did OK. I disassemble the short block, it looks like a boat anchor but you never know. Took both of them to my machine shop. They cleaned and mag them. Both check out OK but the rough one needs sleeves, now the other one will clean up at .040" on the bore. The crankshaft needs turned but is OK other than that. So I tell them do the better of the two blocks and the crankshaft. Also go ahead and rebuild the factory rods I dropped off. Everything goes as planned and I picked up the parts today. They look great! I'm happy!! Then I start looking closer and I'm like... WTF? These are some weird numbers on this block? So turn my attention to the crankshaft. I'm like bingo bango!!! Could it be? I think it is a 318-3 truck crankshaft or an old Direct Connection crankshaft? It has no part number on it at all but it most surely is forged. So I'm asking all you guys... WHAT THE HELL DID I BUY? The block numbers are crazy and it has no VIN. Doesn't look like it ever had one. They both were standard bore too. Both blocks was cast in 72 but the letters on the front say it's a 73. Is this last of the run of them?

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A mostly unknown issue...

Put the upper main bearings in place and take a look at how the hole on the bearing sit right over the intersection of the 2 feeds, cam and main. Notice the intersection is shallow...the web between is high and tight.. oil doesn't get through easy and not much to the main either...plus the bearings hole isnt open enough to expose the main feed completely.

Open the bearing holes, slot them... or counter sink the main saddle where the 2 feeds intersect. You're welcome !
 
No 318 cranks are drilled through the journals due to the smaller rods and piston lighter weight.

Crankshaft
The 273,318 and 340 all have the same stroke and use the same crankshaft. There are , however , several different crankshafts available. The 1968-1972, 340 engine used a different crank(PN2843868) than the 318 although both were forged. The 318-3 truck crank (PN 2843885) is a forged, hardened crank, but is no longer available. The 1973, 340 uses a cast crank (PN 3751162)and requires a special damper and flywheel or torque converter assembly. Do not use forge crank flywheels,dampers, or torque converters on cast cranks vice-versa. All 360 engines have cast cranks with larger main bearing diameters(2.81") than the (2.50")of the standard 318 or 340.
 
Nice score! The 340# Cast into the side of the block is what verifies the 340. The -6(or any number after the 340) simply tells how many casting cycles that the engine mold went through.
Some say the higher the casting number the more opportunity for core shift, but who really knows.
 
The ( -6 ) is the Pour number from that ladle. I believe they at sometimes they would get (13 ) blocks from one ladle. I have already seen a (-13) .

The (340 - 1) would be the hottest with the most bi-metal The higher numbers the pour gets colder and the flow is not consistent plus some slag. I have seen a -11 and the block was not that complete around the lifter bores who knows what it would have sonic tested at.

I don't think it is core shift as much as it is incomplete flow around the bores Also at the end of the shift QC is gone. They usually go home before the hourly workers.

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I just noticed something intresting...

The "4" is surounded by a circle. It seems to be in about the same location as the 273 Core Plug was????

same sand casting molds but with modifications?????


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The - with a number after is for any change that is associated with that mold .
Certain cores will get damaged or wear excessively and those get a replacement core or section inside the mold .
Or it can be from a revision level change for the mold .
They discovered that there were having failures or difficulties in the process.
So engineers redesigned a mold or core and that lets them know if it was effective,,,,,or months down the road when they are having warranty work,,,they know what that casting came from.
I remember years ago I bought two 440 ‘s from a guy,,,they were 68 models he had pulled from a pair of old cars he had .
These blocks were cast 6 months apart but were assembled only 2 weeks apart by the 10,000 day calendar,,,,1 was cast in March 67 , and the other was Sept 67,,,,both had 10-67 bearings in them
The cylinder heads were immaculate and the outside,,,crisp lines from the molds ,,,the blocks too .
I’m assuming because they were from new molds,,,,looked great !

Tommy
 
Oldmanmopar said:
No 318 cranks are drilled through the journals due to the smaller rods and piston lighter weight.

Crankshaft
The 273,318 and 340 all have the same stroke and use the same crankshaft. There are , however , several different crankshafts available. The 1968-1972, 340 engine used a different crank(PN2843868) than the 318 although both were forged. The 318-3 truck crank (PN 2843885) is a forged, hardened crank, but is no longer available. The 1973, 340 uses a cast crank (PN 3751162)and requires a special damper and flywheel or torque converter assembly. Do not use forge crank flywheels,dampers, or torque converters on cast cranks vice-versa. All 360 engines have cast cranks with larger main bearing diameters(2.81") than the (2.50")of the standard 318 or 340.
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Smaller rod's? I've always read that all the small blocks have the same length rod and take the same rod bearing. Please explain this
 
All of the bearings were the same size but the 273 and some early 318 connecting rods were lighter in weight. I have a set of bushed 273 rods and they are the same length just the beams are smaller. I did not get the rods with the crankshaft so I have no idea what they would have been. I would think they would have been the heavy ones being a truck but I do not know for sure. It all has to be balanced so at this point I'm just using the 340 rods I had rebuilt.
 
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