Four bolt main

Reply Subscribe

Thread Tools

Search this Thread

Feb 13, 2006 | 09:49 PM

canucbuck

Thread Starter

Instructor

Joined: Dec 2004

Posts: 198

Likes: 0

From: Newmarket Ontario

Four bolt main

Over the past year I nave read alot and learned alot about vettes. But I would really like to know what the real definition is between a four bolt main and a two bolt main????

Feb 13, 2006 | 09:52 PM

2th farmer

Melting Slicks

Joined: Nov 2004

Posts: 2,540

Likes: 1

From: Pineville Kentucky

CI 6-8-9 Veteran

UHHHH! 2 bolts

Feb 13, 2006 | 09:56 PM

2th farmer

Melting Slicks

Joined: Nov 2004

Posts: 2,540

Likes: 1

From: Pineville Kentucky

CI 6-8-9 Veteran

Sorry about that, I'm such a smart azz sometimes. There are 4 bolts holding the main bearing caps vs 2. I for one question how valuable this is for the average driver and hot rodder. My 454 build is a 2 bolt main and I am sure if something fails it likely won't be that.

Feb 13, 2006 | 10:47 PM

carl a

Safety Car

Joined: Jun 2002

Posts: 4,135

Likes: 1

you'll probably hear a lot of people hear say how much better 4 bolt mains are compaired to 2 bolt, remember the 327/350 h p motors or the 60's ---------2 bolt

Feb 13, 2006 | 11:03 PM

jerrylee

Pro

Joined: Jan 2006

Posts: 599

Likes: 0

From: New York

2 or 4

is there an easy way 2 tell if u have 2 or 4...thanx....

Feb 13, 2006 | 11:06 PM

LIQUIDDRAGON

Melting Slicks

Joined: Aug 2004

Posts: 2,063

Likes: 1

From: Beverly Massachusetts

Quote:

Originally Posted by jerrylee

is there an easy way 2 tell if u have 2 or 4...thanx....

yep just pull the oil pan

actually most people say you can tell by the engine stamp number but i have seen to many cases where that has not been the case so to say for sure the only way is to pull the oil pan and see for your self.

Feb 13, 2006 | 11:16 PM

Cory1970

Pro

Joined: Jan 2002

Posts: 624

Likes: 0

From: Marietta ga

Quote:

Originally Posted by canucbuck

Over the past year I nave read alot and learned alot about vettes. But I would really like to know what the real definition is between a four bolt main and a two bolt main????

4 bolts are stronger than 2 bolts. 2 bolt mains are fine for anything up to the 400- 450 hp range. 2 bolt blocks that are splayed for 4 bolts are even stronger than 4 bolt mains.

Feb 14, 2006 | 07:20 AM

Tom454

Le Mans Master

Joined: Apr 1999

Posts: 6,134

Likes: 46

From: Raleigh North Carolina

Quote:

Originally Posted by canucbuck

Over the past year I nave read alot and learned alot about vettes. But I would really like to know what the real definition is between a four bolt main and a two bolt main????

On a factory Chevy smallblock, the crankshaft is held in by 5 saddle positions. Each saddle position is two parts: the block side, and the cap. The block side is a cast part of the block, the cap side is removeable so the crank can be installed/removed. On a small block Chevy, the middle 3 caps can be held in by either 2 or 4 bolts, depending on application.

Truck blocks and high performance passenger car blocks were commonly fitted with the "4 bolt" blocks.

The best way to tell for sure is to drop the pan & look at the main bearing caps. Yes.... some 4 bolt main blocks can be identified by reading the casting information, but I've seen exceptions even then. So if you really want to know for sure, the best approach is to drop the pan & take a peek.

This is only for the factory SBC.... others (e.g.- some factory BBC) have all 5 mains with 4 bolts.