2 bolt or 4 bolt main in a 74 L48 engine

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2 bolt or 4 bolt main in a 74 L48 engine

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Corvette Forum >> Corvette Models >> Corvette C3 Forum >> 2 bolt or 4 bolt main in a 74 L48 engine

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2 bolt or 4 bolt main in a 74 L48 engine - 11/29/2007 10:59:06 AM

1974corvetteowner

Posts: 215
Joined: 8/11/2005
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Does anyone know if a 74 L48 engine is a 2 or 4 bolt main?
Is there any way to tell using the casting numbers? or do i have to pull off the oil pan and look?

Post #: 1

RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/29/2007 3:21:11 PM

78buckshot

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From: Michigan
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Hi '74, you'll have to drop the pan to know for sure but here is a little info from my own experience. The factory L48 in my '78 has block casting #3970010, the books all say this block was cast from 1968 thru 1976. GM installed these in everything they turned out. I've torn down three engines with the same casting number and they have all been four bolt's. I have not pulled my L48 apart so I can't say for sure but my money is on it being a four bolt.

(in reply to 1974corvetteowner)

Post #: 2

RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/29/2007 4:11:08 PM

1974corvetteowner

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Thanks Buckshot and my Engine's cast number is also 3970010

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RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/29/2007 8:37:22 PM

73shark

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Saw a '73 L48 that was a two-bolt. I believe from some of the old mag articles that the L48s were all two-bolt mains.

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RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/30/2007 5:25:26 AM

C3 Starship

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Check your number through www.mortec.com , should get an answer there.

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RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/30/2007 8:25:41 AM

Rich G.

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Joined: 1/12/2007
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If I remember correctly most of the 4 bolt main engines had a 1/8" pipe plug on the top of the block in front of the intake just behind the timing cover.

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Post #: 6

RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/30/2007 9:05:53 AM

1974corvetteowner

Posts: 215
Joined: 8/11/2005
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Thanx starship but it didnt really help becuase for the casting number i have (#3970010) it is listed as 2 or 4 bolt

(in reply to Rich G.)

Post #: 7

RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/30/2007 11:06:09 AM

Wedge

Posts: 223
Joined: 11/3/2005
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Yeah... L48's were 2 bolts. But that same block was used for the LT1's in '70-72 in the 4 bolt set up... no difference in the oil galleys on that one.

(in reply to 1974corvetteowner)

Post #: 8

RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/30/2007 3:14:37 PM

78buckshot

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From: Michigan
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I'm hoping to pull the factory motor out this winter and replace it with a stroker, I'll be pullin' the pan off for sure 'cause I'm curious as to what GM had left over and stuck in the late '77's. I'll let you know as soon the last pan bolt is out.

(in reply to Wedge)

Post #: 9

RE: 2 bolt or 4 bolt main in a 74 L48 engine - 11/30/2007 3:21:01 PM

1974corvetteowner

Posts: 215
Joined: 8/11/2005
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Would you be able to tell by the size of the harmonic balancer?

(in reply to Wedge)

Post #: 10