340 questions - anybody recognize these pistons?

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pauly

pauly

MOPAR or no car!
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I started pulling the 340 apart that came in my 70 duster project. It's 0.030 over with these pistons in it............casting date 6-72. Has 1970 X heads on it. Appears someone polished the rods? What advantage would this serve? Are these stock rods? It did also have a windage tray in it.

Block info: Cast date: 6-7-1972, part number 2780930-340-2. Passenger side has 3B137371 stamped into it.

K Member: I'm thinking this a newer K frame based on the motor mounts. Do these take a motor mount more like a 70's and 80's truck would?

Just trying to figure out what I am starting with. Your help is greatly appreciated.

Thanks! Pauly
 

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standard k-member for 1970
pistons are low compression for the 1973 car that it was built for. should be cast crank damper.

polishing rods makes oil slide off - less resistance at high r's
 
Can't tell if the rods are stock. Polishing the rods reduces aeration of the oil (less fog, more in oil pan) which reduces internal friction and improves the efficiency of the oil system.

The pistons are very much in the style of the 318s. The part number in the block rules that out. The high compression pistons have the valve reliefs in the side closest to the plug and a dome or pop-up on the side near the carburetor. These pistons are not them. I've never seen the LC 340 pistons. The 360 pistons were dished. There was a rim around the top of the piston and the rest was sunken in, flat. My guess is those are aftermarket pistons. Hope some one who has opened a 72-73 340 can chime in.

The K-frame is clearly a pre-73 model. The tells are the flat engine isolator pads and the anti-sway bar that ducks around the brace.
 
It's got a wide casting line on it - wouldn't that be forged? Cast crank would be thin. Pistons appear to be afterrmarket - they are 0.030" -will see if I can find any numbers on it. Are the 340's like the 440's where they ran forged cranks in them until mid way through 1972?

I will have to get the rest of it apart to get the rest of the story!

Thanks for the help!!
 
68-72 used forged steel cranks. P/N 2532457 or 2843868.

The forged crank was internally balanced, the 73 crank was externally balanced.

Hope this helps.
 
In 72 and 73 some 340's had cast and some had steel cranks it depended on what they had left over and what plant the car was made at .
 
Yup, they look the same as mine. TRW forged 8.5 to 1 pistons. Heavy buggers but they are what I wanted for my particular build.

Jack
 
sounds like a nice crank & if it specs out and the block you have a nice start. you will want to get them checked out and the rods checked too before you buy any goodies though.

if you get the AOK, and the machine shop says they are in good shape, i'd recommend a set of pistions to get you to 10:1 and some aluminum heads.
it all depends on your goals.

the X heads are good for someone doing a numbers match restore so they would have good resell value, and would fund your aluminum heads.
the X heads were good in the day, but no match for current aluminum heads. (multiple benefits - weight, detonation resistance, run cooler, usually flow better unless the X heads are heavily ported by a pro, etc.) if you were restoring a car 100% you might need a set of those heads to make it "show ready" i would not recommend putting money into the heads for street/track use.

i've heard mention of these heads, if you were in the market for a set i'd ask around to see what kind of experiences people are having:
Airwolf 220 SB Mopar heads
http://www.j-performance.com/index.php?option=com_content&task=view&id=59
 
if you need to bore to.060 i have brand new pistons for sale rods were probly magnefluxed
when rebuilt if you need rods i got some for 80.00 a set but if you take yours off wich you should to check the bearings put new bolts back in the rods i have a set of arp"s for $50.00 + shipping with all pistons look like they came with a rebuild kit rods look like they may be stock 3418645 theres a few guys here that can tell you about any thing you want to know about that motor just by a peek thell chime in to help yah
 
there seems to be a mismatch of pistons in your engine. the 3 ones on the left seem to be CAST sealed power z428 hi compression pistons while the one on the right seems to be a stock low compression piston from 72-73 or a replacement for those engines. look at the valve notches to see the difference. weight is the same for both types so apart from the compression difference, both are interchangeable. the only way to know for sure is to measure the distance of the pistons from the deck at top dead center. if im right ,the 3 ones on the left should come out of the deck about .007 inches at tdc ( 1.829 compression height) while the other one would be about .082 down in the hole at tdc ( 1.740 comp. height). this is only by judging pictures so i may be wrong, measure to be sure.
 
Trw's usually have part#'s stamped on top, If you can find the #'s i have a TRW book and can tell you what you have.
Here are some TRW piston #'s, L2322F,L2322F-30,L2322F-60, These are forged ones.
Hope this helps some.
Ed.
 
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