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Topic: 2 Bolt or 4 Bolt Mains

in Forum: C3 Engines


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2 Bolt or 4 Bolt Mains (1/8)
 10/22/09 10:09pm
jp75vette
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Bloomfield Hills, MI - USA

Vette(s):
1975 Corvette coupe, 4 speed manual, 383 ci 9.5:1,Edelbrock dual plane Air Gap intake, Alum Heads,Comp Cam, roller Rockers, PS,PB,Tilt


Joined: 6/29/2008
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Recently replaced the oil pan and also my oil pump. My engine has 2 bolt mains. I thought all Corvettes had 4 bolt mains.
 
The serial number on my engine matches the vehicle VIN.
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2 Bolt or 4 Bolt Mains (2/8)
 10/22/09 10:57pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
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Corvettes have never used a 4 bolt main engine exclusively. Most base/lo horse engines were of the 2 bolt variety...only the higher horse engines were 4 bolt, tho some low horse engines did get built with 4 bolt blocks if there was a shortage.

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2 Bolt or 4 Bolt Mains (3/8)
 10/23/09 11:26am
VetteSpecialties
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Mounds View, MN - USA

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70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe


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Joel is right.  The correct 010 block was available in either two or four bolt configuration, so you needn't worry.

Larry
2 Bolt or 4 Bolt Mains (4/8)
 10/23/09 10:49pm
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
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I'll throw in a bit of trivia here...
The 4 bolt main small block wasn't even "born" until '68 or '69(I fergit), so even the high output fuelie('57-'65) engines were 2 bolt mains...
This only proves that you can build a hot rod engine with a 2 bolt block.


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2 Bolt or 4 Bolt Mains (5/8)
 10/24/09 10:25am
VetteSpecialties
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Mounds View, MN - USA

Vette(s):
70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe


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You are right.  I had forgotten that.  I had a 283 that made over 500 HP and turned 9,000 RPM.  It lasted for years of abuse.  I finally gave it to a friend in Vegas.  He built a sand rail around it and abused it for several more years before it finally went bang.

Larry
2 Bolt or 4 Bolt Mains (6/8)
 10/24/09 10:32am
lukesvetteLifetime Member
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HOWELL, NJ - USA

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1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.


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A lot of 400 ci in small blocks used in the roundy-rounds are 2 bolt mains and they are on the upper end of the RPM range for the whole race. My buddy has had the same 2 bolt block in his race car for over 10 years - rebuilt several times with different rotating assemblies and heads, but she's still turnin left!! Thumbs UpLukesVette2009-10-24 07:34:28
2 Bolt or 4 Bolt Mains (7/8)
 10/26/09 1:14pm
VETTERBOBLifetime Member
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DUNEDIN, FL - USA

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1969 COUPE CORTEZ SILVER, BRIGHT BLUE INTERIOR 383 cu. in. 512 HP. Hooker headers w/ side pipes PS PS AC AM FM STEREO. 68,000.MILES C5 5oth Anniversary Coupe , auto.350hp


Joined: 10/22/2004
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MY BASE 300 ENGINE WAS BUILT WITH 4 BOLT MAINS.
2 Bolt or 4 Bolt Mains (8/8)
 10/26/09 11:30pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20128

There's no way of knowing what the main configuration is without looking at the mains. Casting numbers won't really tell the whole story. Sometimes, the stamped suffix numbers can point to a 4 bolt configuration, but not always.
On a 400(early, '70-'76 or so), it's a little easier...just look for three freeze plugs on the sides of the block. Three freeze plugs on a 400 block means it is 99.9% certain to have a 4 bolt main. Some 400 blocks only had 2 freeze plugs...those were almost always 2 bolt mains. All 400 blocks had three bosses for the freeze plugs, but on some of them, mostly the two bolt kind, the center boss was not machined for a freeze plug, so they only have two actual plugs in them, altho there were also some 2 plug blocks that has 4 bolt mains....confused yet?Confused
Lots of earlier, "base"/ low HP engines did have 4 bolt mains, even into the mid '70s.
Adams' Apple2009-10-27 05:05:17

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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