Engine block decode help
Thread Starter
Drifting
Joined: Jul 2012
Posts: 1,255
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From: Slovenia, EU
2017 C3 of Year Finalist
Engine block decode help
We removed the heads from the engine today to refresh them. The engine is as far as we can tell all original.
All the numbers match the vin.
MY car is 71 with base 270/350 engine.
The engine code on the front is V0505CJK.
ON the casting I have a casting number 3970010.
Beside that are the letters GM ans a number 28 next to it.
The arrow on the top of the engine points to letter D ( other letters are T and N).
Then there is a cast the following: 3 E 41.
What do these castings mean?
I figured out the rest of them but the last one is an enigma to me.
All the numbers match the vin.
MY car is 71 with base 270/350 engine.
The engine code on the front is V0505CJK.
ON the casting I have a casting number 3970010.
Beside that are the letters GM ans a number 28 next to it.
The arrow on the top of the engine points to letter D ( other letters are T and N).
Then there is a cast the following: 3 E 41.
What do these castings mean?
I figured out the rest of them but the last one is an enigma to me.
Last edited by Primoz; Oct 22, 2021 at 08:43 AM.
Team Owner
Joined: Feb 2003
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From: Sitting in his Nowhere land Hanover Pa
2024 C2 of the Year Finalist - Unmodified
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the 3 E 41 sounds like the casting date which would be March 3 but you sure the 41 is not just a 1 for 1971
Melting Slicks
Joined: Nov 2006
Posts: 3,393
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From: Apple Valley, MN
The block casting date is on the right aft “shelf” and typically has a letter (for the month) then 1 or 2 digits for the day, then 1 digit (for the year).
Your 0505 in the stamping indicates the engine was assembled on May 5 so presume you have a May 1971 VIN.
The block, if original, would have been cast in late April or very early May. GM was pretty efficient with engine production in Flint in this timeframe so it is not unrealistic to expect a short duration between block cast date and engine assembly date.
I suspect you are interpreting the left screw head that held the cast date tag in the mold as a 3 and the actual block casting date is E 4 1, meaning May 4, 1971.
Your 0505 in the stamping indicates the engine was assembled on May 5 so presume you have a May 1971 VIN.
The block, if original, would have been cast in late April or very early May. GM was pretty efficient with engine production in Flint in this timeframe so it is not unrealistic to expect a short duration between block cast date and engine assembly date.
I suspect you are interpreting the left screw head that held the cast date tag in the mold as a 3 and the actual block casting date is E 4 1, meaning May 4, 1971.
Race Director
Joined: Oct 2000
Posts: 12,651
Likes: 3,110
From: Shamong, NJ
The date is "E 4 1", May 4th, 1971, which works perfectly with the "0505" May 5th assembly date. I'm not sure what the "3" is, but it's not part of the block's date code, unless it was the shift. The 3970010 is the block casting number, and is just about the most common block ever used by Chevrolet. It was used from around 69-79 mainly for 350's, but I've also seen "010" 302's. I'm not sure what the "28", "T" "D" and "N", etc are, but they're on most Chevrolet blocks, and could be the mold number, or something else not all that important to identifying the block as original to your car.
Melting Slicks
Joined: Sep 2004
Posts: 3,223
Likes: 666
From: Northeast
My understanding:
Clock, 4th hour of the 1st shift (flat head screw)
"3" is the conveyor
"28" is the cope pattern
D: day
N: night
T: third shift
FWIW, if you notice the screw heads on the tags
2 flat head is 1st shift
1 flat and 1 round 2nd shift
2 round head 3rd shift.
Clock, 4th hour of the 1st shift (flat head screw)
"3" is the conveyor
"28" is the cope pattern
D: day
N: night
T: third shift
FWIW, if you notice the screw heads on the tags
2 flat head is 1st shift
1 flat and 1 round 2nd shift
2 round head 3rd shift.
