What exactly does "4 bolt main" mean? I think I get the "4 bolt" part, but what about the "main"? Main what? Does this describe the junction of the engine to the transmission?

Same question about the "rear"? Is that just describing the number of bolts attaching the rear differential housing?

What exactly does "4 bolt main" mean? I think I get the "4 bolt" part, but what about the "main"? Main what? Does this describe the junction of the engine to the transmission?

Same question about the "rear"? Is that just describing the number of bolts attaching the rear differential housing?

4 bolt main describes the Main Caps that hold the Crank Shaft in place. Most motors are 2 bolt. Performance motors are 4 bolt. It's to help deal with the additional torque.

Yes and no on describing the rear end. A 12 bolt rear does have 12 bolts on the differential cover but it's also suppose to give you an idea the Horse Power and Torque that it is able to handle. For the most part from weaker to stronger its: 10 bolt (7.5" rearend), 8.5" rear end (can't remember if it's a 10 bolt also (long day at work)), 12 bolt, and the Ford 9 inch. I know there are others that I'm spacing on but this should give you an idea.

What exactly does "4 bolt main" mean? I think I get the "4 bolt" part, but what about the "main"? Main what? Does this describe the junction of the engine to the transmission?

Same question about the "rear"? Is that just describing the number of bolts attaching the rear differential housing?

Here look at these articles. It should help with some understanding.

http://www.popularhotrodding.com/enginemasters/articles/chevrolet/smallblock/

They are some Chevy build up articles but each one describes a lot of the parts of the engine and a bunch of the whys.

I'd suggest several of these technicial articles. Popular Hot Rodding's Tech Sections are full along with Super Chevy, Chevy High Tech performance and this little gem for first timmers and other newbie engine builders

http://auto.howstuffworks.com/
They have sections on :

> Automatic Transmissions
> Car Engines
> Fuel Cells
> Manual Transmissions
> Turbochargers
Good Luck and good reading. :D

What exactly does "4 bolt main" mean? I think I get the "4 bolt" part, but what about the "main"? Main what? Does this describe the junction of the engine to the transmission? While the answer to your question has been taken care of above. One thing to consider when looking for a core short block is although a 4 bolt main is more desireable, they are also harder to find and more expensive. 2 bolt blocks can be found everywhere and with a little addional machine work to add 4 bolt slayed main caps your better off....just food for thought. :cool:

From some of the stuff I have looked at 2 bolts webbing is thicker than the 4 bolts are. Thinner webbing is one of the reasons for splayed 4 bolt journels also from what I have read.

The cost issue is another factor. Mine are two bolts. I don't actually need the Mouse Motors to be 4 bolts I am not planning on that much HP and torque. When I go with a full race engine turning over 7000 RPMs then I'll look into the 4 bolts but then I'll be using Big Block.

Anyway I feel perfectly comfortable right now with my "Weak" little 2 bolt block. Neither are putting out, on pump, gas over 450 Horses. From several articles I've read GM's blocks 4 or 2 bolts mains are not the best to go with when considering all race anyway. But I suppose everyone has an opinion or example of why or why not.

Pete/Pete/Rob,
Thanks for your answers.

If you were going to build a blown, turbocharged, or nitrous injected small block, it probably would be best to start with a 2 bolt main block, and have it machined and fitted with 4 bolt splayed billet main caps. A stock 4 bolt main block will surffice for most race applications below 600 hp, however a block with a high nickel content would be best. As far as cost, I find that buying a 4 bolt main block is just as inexpensive as a 2 bolt if you get one from a boneyard...look for a 350 (5.7) out of 3/4 or 1 ton pickup or Surburban, I believe, 70-87 and it should be a 4 bolt. I missed out on a running 454 out of a rustbucket Surburban that just came into a boneyard while I was there getting doors off an Elky. The owner of the boneyard wanted $450 for it, I didn't have enough cash in my pocket, I'm still crying over it.