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Old 01-22-2007, 05:01 PM   #1
John 65
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Default Anyone know this block GM 41 3970010

I know its a 350, (I believe), has a drivers side dipstick and a "8" for its build year. I would think 1978 cause the small pad in the front of the engine is the smaller square shape not the longer more narrow older style pad for 1968. The pad is smooth so theres no engine codes. Its cast GM 41 by the 3970010. I thought it was an L-48 but I know they had a rh dipstick. Thanks for any help.
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Old 01-22-2007, 05:11 PM   #2
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Yes, it's a 350 cid block, hi-performance application. Those ones were manufactured by GM between '68 - '76, but were being manufactured after that in Mexico. The Mexican blocks have the "Made in Mexico" raised letters next to the casting number.
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Old 01-22-2007, 05:21 PM   #3
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Quote:
Originally Posted by mts7900 View Post
Yes, it's a 350 cid block, hi-performance application. Those ones were manufactured by GM between '68 - '76, but were being manufactured after that in Mexico. The Mexican blocks have the "Made in Mexico" raised letters next to the casting number.
Thanks for your help, It dont have the Made in Mexico script on it, but with the 8 for the year it was cast (78 I would think cause of the smaller pad so it cant be a 68) and the lack of the mexico script I am still a little confused. Date on rear of rh side of block says J 7 8 Thanks

Last edited by John 65; 01-22-2007 at 07:02 PM.
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Old 01-22-2007, 07:30 PM   #4
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Quote:
Originally Posted by John 65 View Post
Thanks for your help, It dont have the Made in Mexico script on it, but with the 8 for the year it was cast (78 I would think cause of the smaller pad so it cant be a 68) and the lack of the mexico script I am still a little confused. Date on rear of rh side of block says J 7 8 Thanks
The lack of "Hecho En Mexico" (Made in Mexico) means it wasn't made there and most likely was cast in Flint, MI. As for the date, it's either a '68 or a '78. My info tells me it would have been a service replacement block if it's a '78.
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Old 01-22-2007, 07:35 PM   #5
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HI GUYS

Looking through my 1965-69 chevrolet by the numbers book this block came into production sometime in late april or early may of 1969 and was used through 1975.It was produced in 2 and 4 bolt application except for 1969 which were all 4 bolt main.They also explain that the date should have three digits,is there a digit that maybe you don't see.Or maybe not everything in this book is true.
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Old 01-22-2007, 07:36 PM   #6
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J 7 8 is an October 7, 1978 Flint block (the 3970010 block was only cast from 1969-1979 - about seven million of them); it was used in every conceivable car and truck application.
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Old 01-22-2007, 07:39 PM   #7
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I guess while i was typing you added j 7 8 which means j=october 7=7th day 8=1968
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Old 01-22-2007, 07:48 PM   #8
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There should be an engine code stamped on a block pad located immediately forward of the right hand cylinder head.Then maybe we can figure this out.

Sorry if i caused confusion
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Old 01-22-2007, 08:02 PM   #9
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Thank you all for your replys, unfortuntaly the pad is smooth, no codes. I guess I dont have anything special out there under the hood I questioned it cause I would have sworn the dipstick was on the other side for that year. Appreciate all your help.

Last edited by John 65; 01-22-2007 at 08:04 PM.
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Old 01-23-2007, 12:35 PM   #10
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Quote:
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I guess while i was typing you added j 7 8 which means j=october 7=7th day 8=1968
Nope, it's 1978 - none of those blocks were cast until mid-1969.
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Old 01-23-2007, 06:07 PM   #11
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In my experience, the "010" block is the most common pre-87 block. They were used in the last 302 and 327 motors, as well as hundreds of thousands, if not millions, of 350s. I have a 69 4-bolt version as well as a 77 2-bolt.

Some had a higher tin and nickel content, designated by 010 and 020 cast into the block to the left and right of the front and rear cam journals. I believe these were mostly used for the 302 and LT1 350s, but some may have been used in trucks.

BTW, one of David Vizard's books says the 010 block was made from 68-79. Mortec.com shows 69-80.
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Old 01-23-2007, 06:17 PM   #12
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Thanks everybody for your help.
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Old 01-23-2007, 06:32 PM   #13
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I just blew up one of these blocks (2 bolt main version). I am pretty sure the 2-bolt main versions were used in low performance applications, 4-bolt mains used on high performance.
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Old 01-23-2007, 08:11 PM   #14
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Quote:
Originally Posted by tangel2 View Post
I just blew up one of these blocks (2 bolt main version). I am pretty sure the 2-bolt main versions were used in low performance applications, 4-bolt mains used on high performance.
4 bolt was also used in trucks. The bigger trucks (1 ton and bigger) also had forged crankshafts.

I am sure they are not "high performance".
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Old 01-23-2007, 08:11 PM
 
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