factory 72 340 pistons???

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Looks like aftermarket ones...all the low comp ones i have/seen are dished.
 
Looks like a replacement piston for the 1972 & 1973 340.
Which would be a low compression piston.
 
the 72-73 low compression pistons usually have 4 notches ....like the ones you have.

measure how far they are down in the bore at TDC
 
hi, original 72 -73 pistons have 4 small valve notches , about .110 deep. those are an after maket piston you have there. original 340 pistons are not dished, 360's are dished, depending on year . first 360 were flat tops.
 
That looks like an aftermarket piston. All factory 340 pistons had two valve reliefs. The 72/73 were flat tops, the earlier pistons were domed. Heights are different between how deep they set "in the hole", and from the wrist pin centerline to the top block. P/N 3004571 (std) 3004572 (+.020) and 3004573 (+.040) for the 73 pistons.
 
no factory oem 340 pistons had domes..all were flat tops..

correct compression height on the piston was dropped to lower compression 72+ had a compression height of almost .100 less then high compression pistons.
 
Early 340 pistons had 2 valve reliefs and stuck a little above the deck. 72-73 had flat tops with 4 valve reliefs that were .080 below the deck or so. Those pistons pictured are aftermarket. Measure and see if they come close to deck level or stick way below deck. They look like some pistons I put in one of my 340s. About 9.5:1 w open chambered heads or closer to 10:1 with some closed chambered heads.
 
I think they are bad pistons, and the block looks terrible. Give me your address and I'll come pick it up. Just kidding. But is this motor for sale? I also live in kansas and need a std 340 block.
 
swinger340 said:
Early 340 pistons had 2 valve reliefs and stuck a little above the deck. 72-73 had flat tops with 4 valve reliefs that were .080 below the deck or so. Those pistons pictured are aftermarket. Measure and see if they come close to deck level or stick way below deck. They look like some pistons I put in one of my 340s. About 9.5:1 w open chambered heads or closer to 10:1 with some closed chambered heads.
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the chamfer around the piston is in the hole (cannot really get a good measurement becuse of the chamfer) but across the center/top of the piston is at deck or out some. i will try to measure it tonight.
 
75dartsport said:
I think they are bad pistons, and the block looks terrible. Give me your address and I'll come pick it up. Just kidding. But is this motor for sale? I also live in kansas and need a std 340 block.
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sorry man its not for sale.. where are you located in kansas?
 
aaron68s said:
the chamfer around the piston is in the hole (cannot really get a good measurement becuse of the chamfer) but across the center/top of the piston is at deck or out some. i will try to measure it tonight.
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Look like the trws I used in one of my 340s. Mine were even with the deck with the 4 deep valve reliefs and with 63 cc heads I ended up with 9.8:1 static compression. Ran a comp XE284H .507/.510 cam and thing ran very strong and had 150 lbs of cylinder pressure. Was about rite for our crappy gas
 
swinger340 said:
Look like the trws I used in one of my 340s. Mine were even with the deck with the 4 deep valve reliefs and with 63 cc heads I ended up with 9.8:1 static compression. Ran a comp XE284H .507/.510 cam and thing ran very strong and had 150 lbs of cylinder pressure. Was about rite for our crappy gas
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thats the exact same cam i have. I know the pistons are at least even if not up some. which brings me to some questions. My original plans were to put MP thin gaskets (which i already have) and have .020-.030 taken off the heads. should i still do that????
 
aaron68s said:
thats the exact same cam i have. I know the pistons are at least even if not up some. which brings me to some questions. My original plans were to put MP thin gaskets (which i already have) and have .020-.030 taken off the heads. should i still do that????
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If they are stock iron heads, I personally would. In stock form they are about 70 cc. Get them down around 65 cc or less so you will have close to 10:1 compression. JMO Be able to build a nice stout 340 using the parts you already own
 
i got some measurements this morning. pistons are at deck height, valve reliefs are .200 deep. So with .030 off the heads and MP .025 gaskets where will i end up for CR? Thanks Aaron
 
Info i got on those pistons shows the valve relief at 10.0cc.

Applying to calc.....

4.04 B
3.31 S
.001 Deck
+10.00cc relief
.025 comp gasket
Along with a 65cc chamber........

Came to 9.64 to 1
 
aaron68s said:
i got some measurements this morning. pistons are at deck height, valve reliefs are .200 deep. So with .030 off the heads and MP .025 gaskets where will i end up for CR? Thanks Aaron
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Would need to know the ccs of the heads and I assume it is std bore. But I took .030 off of my J heads (ending up with 64 cc, found my machine shop slip), used a fel pro .039 head gasket and ended up with 9.8:1 so Im guessing you would be rite around there if not closer to 10:1 with the thinner head gasket. I wouldn't go through the hassle, just sell it to me. HAHA!!
 
Thanks Rick and Swinger for the info. My heads should be done wednesday, cam is in, waiting on my ARP head bolts and comp rockers. got any bench racing HP numbers I can look forwards to? LOL,,, air gap 750dp carb
 
Yes be sure to degree the cam. Mine had to be advanced like 8 degrees to get it @ 106 with my cloyes chain. The chains all vary a little so degreeing is very very important. My motor had 2.02 J heads with some gasket matching and some bowl porting and it made 398 HP with an LD340 and a holley 750. Very nice little motor. I just sold it 3 mo. ago and replaced it with my 428 aluminum headed 340. Guy put it in a 71 drop top cuda and loves the motor. I should have kept it, but unfortunately I cant afford to keep them all. Also keep in mind with planed heads you will need to run adjustable rockers or shim your rocker shafts.
 
If you are milling the head you will need to mill the intake surfaces of the heads (best option) or mill the intake (worse option). It would be best if you could take the block, heads, head gaskets, and intake to machine shop and mock it all up before heads are assembled and have intake side of heads milled so intake fits correctly. Or do what I did and get it all together and find out the intake does not fit and mill the intake. Now no other intake will fit and the milled intake only fits your engine. Not the end of the world but spending some time up front would be best.
 
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