Topic: Block # chart explained.
in Forum: C3 Engines
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This is a piece of the
Small Block Chevy Engine Block Identification sheet
Does anyone know what the highlighted (red) spec's at the bottom mean. I'm confused a little. In particular I am looking to figure out what the 185 370 means.
Does anyone know what the highlighted (red) spec's at the bottom mean. I'm confused a little. In particular I am looking to figure out what the 185 370 means.
Years Casting CID Main Caps Comments
1980-85 140029 350 - - 2 car
1973-80 330817 400 - - 2 car, truck
1975 355909 262 - - 2 car, truck
1976-85 355909 305 - - 2 A
1975 360851 262 - - 2 Monza
1976-79 361979 305 - - 2 car, truck
1980-85 140029 350 - - 2 car
1973-80 330817 400 - - 2 car, truck
1975 355909 262 - - 2 car, truck
1976-85 355909 305 - - 2 A
1975 360851 262 - - 2 Monza
1976-79 361979 305 - - 2 car, truck
Etc.......
1969-79 3970010 350 185 370 2 or 4 car, truck, Vette
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Frederick, MD - USA
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Vette(s): 1969 convertible L71 427/435 4-speed black interior
The 185 and 370 must refer to different horsepower ratings...370 would be an LT-1. 2 or 4 means the same casting was used for 2 and 4 bolt main bearing caps.
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
It only means that your block was the same casting that was used on an LT-1, not that necessarily it is one. There's a lot more to an LT-1 than simply what block casting it has...crank, heads, cam, lifters, intake, etc. are all specific to an LT-1.
Get all the numbers off the block and it can be decoded to what it is and what car or truck series it was intended for from the factory.
Get all the numbers off the block and it can be decoded to what it is and what car or truck series it was intended for from the factory.
not actually you need the suffix code stamped by the water pump to correctly determine engine date and hp. check this site out.
Thanks guys, I appreciate it. Doesn't look good for matching #'s, but I'm still not sure I have Identified the right ones yet either. Seems like every number I get doesn't make much sence except the standard block #. GM wouldn't mate the THM 400 to a 270 horsepower 350 would they?

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The 400 was the only 3 speed auto available at the time, so yes, they would install it an any vehicle. HP wasn't an issue. Even one of the two ZL1s had a 400 automatic in it.
Gunslinger's info is right on. The #3970010 block was used in many different configurations over the years, from the lowly 185hp to the mighty LT1(and even my anemic 195hp L48!). The main difference was the 2 or 4 bolt mains.
They didn't use the 350 trans until the late 70s in the Corvette, even tho it came out in 1969. The 400 came out in '64.Adams' Apple 2007-03-28 10:00:16
Gunslinger's info is right on. The #3970010 block was used in many different configurations over the years, from the lowly 185hp to the mighty LT1(and even my anemic 195hp L48!). The main difference was the 2 or 4 bolt mains.

They didn't use the 350 trans until the late 70s in the Corvette, even tho it came out in 1969. The 400 came out in '64.
Joel Adams
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FIND THE CODE NEAR THE WATER PUMP AND I'LL KNOW, GOT IT!


SO ON MY 71 BESIDES THE BLOCK CODE 3970010 ON THE BLOCK TOP DIRVER NEAR THE TRANNY AND THE NUMBERS NEAR THE WATER PUMP IS THERE ANY OTHERS I SHOULD BE LOOKING FOR AND IF SO WHERE ARE THEY?
THE TRANNY HAS A TAG BUT THE CODE SEEMS ODD AND I CAN'T LOCATE A GOOD EXPLAINATION 71CK8345/71K504/CK (ANYBODY?).

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