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View Full Version : WTH is a 2bolt & 4bolt main?



psycho72
03-30-2005, 01:36 PM
Just like the title says, what is this. Got any pics? What is the diff? I was told 4 is better. Is this true? Can I convert a 2 into a 4?

cheeseburger35
03-30-2005, 06:17 PM
the bolts refer to your main caps... some main caps use 4 bolts some use 2 bolts to attach to the block.... the 4 bolts are stronger.. and if you intend to build a motor that will have some power get a 4 bolt main block...

Polecat
03-30-2005, 08:19 PM
true...unless it's a 400 SBC, then a 2 bolt is better....but for most street performance, any 2 bolt will suffice.

psycho72
03-30-2005, 08:36 PM
I am asking is because I am getting a caprice with the LT-1, only problem is the caprice LT-1 is a 2 bolt main. So my alternatives are be happy with a max 400 horse beater (I read that a 2 bolt is good for a max of 400 ponies), swap engines or ???? Oh and all of this is on Fantasy Island right now. I am gonna get the car real soon but won't have money to dump into it for a while because I am dumping all my current funds into the stereo, rims and a drop.

Acidburn
03-30-2005, 08:38 PM
I am asking is because I am getting a caprice with the LT-1, only problem is the caprice LT-1 is a 2 bolt main. So my alternatives are be happy with a max 400 horse beater, swap engines or ???? Oh and all of this is on Fantasy Island right now. I am gonna get the car real soon but won't have money to dump into it for a while because I am dumping all my current funds into the stereo, rims and a drop.

even a 400hp B-body will be smoking fast, and i know people with over 400hp on Impalas so i dont think it makes that big of a difference

soundstreamer
03-30-2005, 08:58 PM
hey polecat, doesn't 400 sb chevys only come with 2 bolt mains...
there is an option some machine shops will do where they turn a 2 bolt( l o l ) main into a 4 bolt angled ( \\ o // ) main, which is stronger than the normal 4 bolt( ll o ll ). i think it's an rpm based upgrade mainly.

cheeseburger35
03-30-2005, 09:18 PM
have you heard about the upgrade to a 6 bolt ?? the outside extra two go at an angle into a thicker part of the block..

also the new gto's.. and the upcoming LS7 vettes will both have six bolt mains.. the LS7 will be a 427.. with an amazing bottom end..

Polecat
03-30-2005, 09:51 PM
hey polecat, doesn't 400 sb chevys only come with 2 bolt mains...
there is an option some machine shops will do where they turn a 2 bolt( l o l ) main into a 4 bolt angled ( \\ o // ) main, which is stronger than the normal 4 bolt( ll o ll ). i think it's an rpm based upgrade mainly.
no, there were two different castings, 509's were better...there were:
casting 3951509, came out in 70-71 and they all were 4 bolt mains, then castings 3951509, from 74-80, were two bolt, these are the years to have, then in 70-73, casting 3951511, were 4 bolt, but some from the factory outlets had some 2 bolt mains.

My 406 I built was a 509 casting, 74-80, 2 bolt...and I had an eagle rotating assembly, crank, 6" rods, JE forged pistons, etc...11:1, dart Pro 1 aluminum heads, 1.6 Comp roller rockers, RPM inatke and Holley HP series race carb...man, I miss that engine. :(

zane
03-31-2005, 02:34 PM
To make this easier to grasp have a look at the following page for pictures of 2 bolt and 4 bolt mains:

http://johnmonnin.netfirms.com/4boltPictures.html

psycho72
03-31-2005, 10:13 PM
Looking at those pics would be of any use to simply purchase some hardcore titanium or magnesium alloy whatever bolts. I mean the concern is bolt right? Just a question, not that I will actully do it but I am curious if uber bolts would make a diff.

Polecat
03-31-2005, 10:30 PM
Nope..not really, they are grade 8 bolts from GM, about the strongest you can get. But I wouldn't hesitate to make 450 HP on a 2 bolt main...

MSSOKC
04-18-2005, 10:03 PM
A stock LT1 block will hold more than 400 ponies. They're good for over 500 at the wheels. I know plenty of people than ran in the 450+ range on the stock block and didn't have any issues.