1972 340 Block vs 1970 340 Block

Author Topic: 1972 340 Block vs 1970 340 Block  (Read 771 times)

Offline soccernut43

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1972 340 Block vs 1970 340 Block
« on: January 10, 2018 - 10:57:03 am »
Are there any differences between the 70 block and the 72 block?  Original 70 block was damaged beyond repair and have a 72 block but all 70 parts.  The 70 block was punched out .30 over.  Looking to restore as a cruiser.  Thanks!!




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Re: 1972 340 Block vs 1970 340 Block
« Reply #1 on: January 10, 2018 - 12:05:12 pm »
Only difference is the date...
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Offline 70chall440

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Re: 1972 340 Block vs 1970 340 Block
« Reply #2 on: January 10, 2018 - 11:54:42 pm »
Only difference is the date...

 :iagree: Most of the time people defer to older engines as being better in construction but in this instance I do not believe this to be the case.
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Re: 1972 340 Block vs 1970 340 Block
« Reply #3 on: January 11, 2018 - 02:09:09 am »
:iagree: Most of the time people defer to older engines as being better in construction but in this instance I do not believe this to be the case.

It's just the block... A 70 has a better crank (forged vs cast) higher compression (10.2 vs 8.5) bigger valves (2.02 vs 1.94)... But the question was about the block..
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline soccernut43

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Re: 1972 340 Block vs 1970 340 Block
« Reply #4 on: January 11, 2018 - 07:10:16 am »
Thanks guys!  Yes, the only concern I may have is with the bore.  The pistons I want to use are from the 70 block that was bored 30 over.  I have to check and see if t his is possible with the 72 block and it's smaller bore.  I think I have 3 cranks, one is steel for sure.  I have a  set of Hamburger heads I purchased 30 some years ago that have never been on a car that I'd like to try and use.  Work in progress.

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Re: 1972 340 Block vs 1970 340 Block
« Reply #5 on: January 11, 2018 - 11:37:36 am »
Bore the block no biggie
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline Aussie Challenger

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Re: 1972 340 Block vs 1970 340 Block
« Reply #6 on: January 11, 2018 - 04:42:54 pm »
Thanks guys!  Yes, the only concern I may have is with the bore.  The pistons I want to use are from the 70 block that was bored 30 over.  I have to check and see if t his is possible with the 72 block and it's smaller bore.
The 340's all had the same bore size standard before boring, are you sure that your '72 is a 340?
Dave

Offline Locomotion

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Re: 1972 340 Block vs 1970 340 Block
« Reply #7 on: January 31, 2018 - 11:57:05 am »
It's just the block... A 70 has a better crank (forged vs cast) higher compression (10.2 vs 8.5) bigger valves (2.02 vs 1.94)... But the question was about the block..

(2.02 vs 1.94):nono:

(2.02 vs 1.88) ;)

If just swapping the original rotating assembly into the '72 block, keep it all together. Don't swap any cranks or rods around without rechecking the balance.


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Re: 1972 340 Block vs 1970 340 Block
« Reply #8 on: January 31, 2018 - 07:45:28 pm »
(2.02 vs 1.94):nono:

(2.02 vs 1.88) ;)

If just swapping the original rotating assembly into the '72 block, keep it all together. Don't swap any cranks or rods around without rechecking the balance.

Missed it by that much..... :roflsmiley:
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline jimynick

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Re: 1972 340 Block vs 1970 340 Block
« Reply #9 on: January 31, 2018 - 11:19:27 pm »
Missed it by that much..... :roflsmiley:
You just had a wee Chevy moment, that's all.  :cheers:

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Re: 1972 340 Block vs 1970 340 Block
« Reply #10 on: February 01, 2018 - 12:18:37 am »
Only 340's I've ever owned all have had 2.02 valves.... Been around Chevy guys my whole life.. Never owned one... Rarely driven one.... Lots of Fords, no Chevies... Worked on/for Ford for many years, It's how I paid for Mopar's in my early years...
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline Locomotion

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Re: 1972 340 Block vs 1970 340 Block
« Reply #11 on: February 01, 2018 - 07:13:05 am »
Only 340's I've ever owned all have had 2.02 valves.... Been around Chevy guys my whole life.. Never owned one... Rarely driven one.... Lots of Fords, no Chevies... Worked on/for Ford for many years, It's how I paid for Mopar's in my early years...

Well........OK, we'll let it go this time. :drunk: I'll put this away. :rofl:


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Re: 1972 340 Block vs 1970 340 Block
« Reply #12 on: February 01, 2018 - 11:23:00 am »
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...