340 questions

[abodyjoe]

so this is for sale near me. was thinking about maybe picking it up if the price is right.

so he says its a 1972 340 engine out of a 1972 Barracuda.. not sure if that's true or not but I'll post a vin pic.

do those look like the early pistons? i thought by 72 they were lower compression. this from what i remember look like the 68-70 higher compression pistons. or am i totally wrong?

would a 72 have a steel or cast crank. the guy says he isn't sure.. he thinks its steel but says he looked it up and is getting conflicting information.

he thinks its std bore but obviously i'd have to measure it when there in person.

obviously i have to go see it in person but what do you think it may be worth? 340's seem to be all over the damn place price wise...

 

[crackedback]

72 model year.

Those look like the higher compression units. Low compression usually have 4 eyebrows

Crank look at the casting/forging parting line. Hard to see in the picture.

Std blocks are $600+ easy all day long or more.

 

[abodyjoe]

thanks. thought they looked like higher compression.. when did they lower the compression? guess i'll have to go look at it now..

 

[Professor Fate]

Sometime in mid to late '72 they changed to the externally-balanced/cast crank/lower compression motors. So, a '72 could be either way depending on date of manufacture, and possibly by assembly plant.
A better pic of the crank would help determine if it's cast or forged. The balancer would also be a dead giveaway, as the cast crank unit is plainly labeled as such.

 

[crackedback]

It's a fairly early vin so anything is possible with hold over parts from 1971

I'd guess a forged cranks with that piston assembly.

 

[Scody21]

Looks like some machining will be in order, might be able to just hone it. It is taken apart for a reason, who knows why. Unknown block, without a sonic check, pressure check and measuring, is a gamble until it hits the machine shop. If machining is necessary, pistons could be worth what someone with a stock block will pay ya.

To me, no more than 500 for as it sits.

 

[abodyjoe]

i'll go look at it and see for sure.. thanks for the info.

 

[Bodyperson]

Sometime in mid to late '72 they changed to the externally-balanced/cast crank/lower compression motors. So, a '72 could be either way depending on date of manufacture, and possibly by assembly plant.
A better pic of the crank would help determine if it's cast or forged. The balancer would also be a dead giveaway, as the cast crank unit is plainly labeled as such.

If its the correct balancer for the crank. I've been mistaken that way once. Cast balancer on a forged crank.

 

[Scody21]

i'll go look at it and see for sure.. thanks for the info.

Take a set of calipers and notes on bore, rod and crank journals sizes.

That crack looks rusty as hell, the journals will most likely have to be cut.

 

[Bodyperson]

Do the cast cranks have the journals drilled like that crank does? I think just the forged 340 cranks got those.

 

[krazykuda]

What's the casting date on the block???

 

[abodyjoe]

can't see in the pics

 

[Professor Fate]

If its the correct balancer for the crank. I've been mistaken that way once. Cast balancer on a forged crank.

Of course, and the same goes for the rest of the internals- crank, pistons, etc.- "assuming" they are original to the block. Who can be sure at this point.

 

[ch1ll]

Yes, measure the journals on the crankshaft. I bought a 72 motor and it was.020/.020 from the factory. Crank will be marked if it was under from the factory, but offhand I don’t remember the markings. My book at home will tell what they are. Bearings go to .03 under unless you by china bearings. I have seen them.060 under, but at that size you risk grinding off the hardened part of the journal.

 

[ch1ll]

Get a better picture of the crankshaft and we will know if its cast or forged.

 

[jimmer]

I have had 1 stock 72 340 that was a factory forged crank and another that was cast.
So as stated it could have had either depending on date and or assembly plant.

 

[ch1ll]

These are the factory markings for undersize engine components including crankshaft journals.

 

[RustyRatRod]

The compression drop and cast crank came in some time around April of 1972, so it's entirely possible it's a forged crank, 10.2:1 motor.

 

[abodyjoe]

ok he sent me crank pics.

 

[mopowers]

Looks like a forged crank to this untrained eye.

 

[crackedback]

Forged. Look at the parting line next to first journal on left. It's wide and ground flat. A cast crank would have a thin line where the two casting box halves came together.

 

[abodyjoe]

ok, thanks

 

[RustyRatRod]

Most definitely forged.

 

[crackedback]

Cast vs forged ID

 

[abodyjoe]

ok/ that helps a ton