Two bolt mains?
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Racer
Joined: Aug 2010
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From: Fresh Meadows New York
i have my 74 L48 for 20 years the number on the pad are gone.. all number match except the pad..alt,distributor,carb, tranny, intake, eveything correct, but its a 4 bolt main....it a 10 block
Safety Car
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From: North Easton Mass
Rick B.
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
They could also substitute a 4 bolt for a 2 bolt if they ran out of 2 bolts for any number of reasons. 2 bolts with ARP studs will handle upwards of 500HP, personally I wouldn't go much higher than about 400HP, I made ~300RWHP with a warmed over L48 with factory main bolts, caps and crank and rods 
Safety Car
Joined: Aug 2001
Posts: 4,883
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From: North Easton Mass
They could also substitute a 4 bolt for a 2 bolt if they ran out of 2 bolts for any number of reasons. 2 bolts with ARP studs will handle upwards of 500HP, personally I wouldn't go much higher than about 400HP, I made ~300RWHP with a warmed over L48 with factory main bolts, caps and crank and rods
Rick B.
Le Mans Master
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From: Butler Pa
The block may have been trashed for any number of reasons and replaced using original accessories, spun main bearing, frozen and cracked, broken ring scored cylinder.
Drifting
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Racer
Joined: Jun 2009
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From: Milton Delaware
Not being a mechanic or ever claimed to be...... so what is two bolt main.......four bolt main and just what is the importance? How does one tell if he /she has a 2 or 4 bolt main. Thanks for the explanation.
Team Owner
Joined: Jan 2006
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From: Crossville TN
An engine block with "2-bolt mains" has 2 bolts on each main bearing cap. An engine block with "4-bolt mains" has 4 bolts on each main bearing cap. 4-bolt mains are stronger than 2-bolt mains. 
Le Mans Master
Joined: Sep 2003
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From: eastern NC
Back in the day, before the General offered 4-bolt mains in a small block Chevrolet, a lot of 2-bolt blocks became 4-bolt blocks overnight with the help of a competent machinist.
It was also not unusual to spin those old 2-bolts over 7000 rpm's from time to time either.
Good luck... GUSTO
It was also not unusual to spin those old 2-bolts over 7000 rpm's from time to time either.
Good luck... GUSTO
Intermediate
Joined: Dec 2010
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Back in the day, before the General offered 4-bolt mains in a small block Chevrolet, a lot of 2-bolt blocks became 4-bolt blocks overnight with the help of a competent machinist.
It was also not unusual to spin those old 2-bolts over 7000 rpm's from time to time either.
Good luck... GUSTO
It was also not unusual to spin those old 2-bolts over 7000 rpm's from time to time either.
Good luck... GUSTO
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Four bolt mains for Gen 1 small blocks mean the 3 center mains have 4 bolt and the front and rear are 2 bolt,
You start getting into some serious stuff when you get all 5 mains 4 bolts and the center 3 splayed as well as being made of billet steel. The Motown 400ci block I have has this and will accept a 4 inch stroke crank with no clearancing
You start getting into some serious stuff when you get all 5 mains 4 bolts and the center 3 splayed as well as being made of billet steel. The Motown 400ci block I have has this and will accept a 4 inch stroke crank with no clearancing