2-Bolt or 4-Bolt?
 

Okay, guys ... is there way, short of engine disassembly or revelation through Ouija Board, to tell if my L-48's a 2 bolt or 4 bolt main? Does the serial or block number indicate this?

It's beginning to look like bolt-on horsepower component selection choices are, reasonably enough, in large measure determined by this.

:cheers:

Mike

Decode your casting # at this site...

http://www.mortec.com/castnum.htm

Now why is # mains so important for bolt-ons? I don't totally agree with that, unless you are bolting on a Wieand Blower or something...

99% of L-48's are 2-bolt, cast main, cast pistons.

I have an all new rotating assembly in my 2-bolt but still decided to build a motor with a power range of 2000-5500 rpm. Fits how I drive and my cruise rpm.

2-bolt mains are good for probably 400 hp...just don't take 'em up to ridiculously high rpms!

If the engine won't be used at high RPM's for an extended period of time, a 2-bolt block should even be ok for up to 500 HP..

:iagree:

What is a safe RPM max for an L48 2 bolt?

One thing to remember is that Chevy did not produce a 4-bolt main small block until the 350 came out in '69. ALL of the 327's and 283's were 2-bolt mains.

tom...

A 2 bolt main is stronger than a 4 bolt main. One look at the 2 vs. 4 bolt webbing will make you agree.

A splayed 2 bolt block is the strongest with the exception of some aftermarket products.

How many of you know anyone that lost a 2 bolt main on the street? It doesn't happen very often.

2 Bolt Vs 4 Bolt
 

The only main failure I personally know of was a friends circle track racer and it was a 4-bolt main block.He also likes the 2-bolt blocks. :thumbs:

L-48s, which are 2-bolt mains, have the same casting # as L-82s, which are 4-bolt. Chevy used this 0010 casting for many years in "high performance passenger" applications.

Not many cranks falling out of small block chevies at the track. :thumbs:

The rods fail once in a while but the mains/cranks are not the weak link by any means. If you are worried about the bottom end you can install an ARP main stud kit. You can sleep well with that setup. Lots of track cars running that setup.

Add a set of good rod bolts and use forged pistons and forgettabouwdit :flag: Anthing you can drive on the street will survive fine with that.

Remember, GM never even built a 4 bolt main 327. I know the stroke is shorter by .23" but you get the idea.

-Mark.

This is not exactly true. While the webbing is thicker because of 2 less bolt holes, strength of this area is not what you have to worry about. At high RPM The caps can walk on a 2 bolt. So youll lose your bearings in a hurry. Splayed caps being stronger are only a myth! The only reason that splayed caps are significant in our hobby is that its the simplest way to convert a 2 bolt to 4 bolt block! But You are right that in a street application, your not going to lose a 2 bolt block. I beat the tar out of my the 2 bolt V8 in my mustang and no issues yet :)

Oops Just noticed Im on my dads account :) Noroofmustang is to blame for this post!

Personally I would not worry if it is a 2 bolt or 4 bolt unless as someone else mentioned you were going to turn High RPM lets say above 6500RPM. But if you are going to go above that and up to the sky of say 10,000RPM then only the best parts will do. Years ago I ran a 4 Bolt main with ARP bolts on everything daily into the 9000 to 9500 rpm range and tore the engine down about every 5000miles or less to inspect everything. You need to decide on what you want the engine to do. Once you know that there are many good people on this board that can give good information on the combo to run for the desired effect.

Also I would not worry too much about high HP it is good for bragging but beyound a certain point it just makes the car that much harder to handle. You want a balanced car.