LUVTruck.com

whats the difference in a 2 and 4 bolt main on a chevy 350? im doin a V-8 sawp soon and have no idea what that is...do you have to use a certain one for the swap?

the two and four bolt refers to the main bearing caps. The 4 bolt blocks are a bit stronger but if you are just building a mild street motor a 2 bolt woul dhold up fine for you. it makes no difference in your swap, just makes a difference in the bottom end strenght of the engine.

Yep... But you can get into a big debate over the virtues of either 2 or 4 bolt blocks. But in a motor build, it really doesn't matter. Basicly all the major components are the same.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

I agree with Blue Meanie, everybody has a different opinion. If you go with a 2-bolt I would atleast use studs for the added strength.

_________________
Money can't buy happiness, but it can buy horsepower...and that's kind of the same thing...

although its good insurance, I personally dont see a need to use a 4 bolt main unless you plan on spinning 6500+ RPM a lot OR your motor is a dedicated or heavy nitrous user. no matter what you should always use good (ARP) bolts though.

400 blocks are another story... some will argue that the stock 4 bolt mains are weaker because the holes that the outside bolts thread into compromise the block webbing. If running a 400 block for street strip use I'd recommend leaving it as a 2 bolt main with of course good cap bolts or studs.

Full race 400 blocks should be machined for splayed cap 4 bolt main

_________________
1978 LUV Truck 2WD
450 "Small Block" Chevy
3.70 Ford 9
28x10 Goodyears

Yeah, I agree with luvsadrag on this. A 2 bolt block is fine unless you are making a lot of power. A lot of circle track guys buy only 2 bolt blocks and have them converted to splayed main caps. They say that the cap strength is more of an issue than the number of bolts. The engine in my truck will run in the eights in the quarter and it is a two bolt main block.

My last 2 motors have been 2 bolt mains . It does not matter , when you get above 6500 your killing bearings . Add nitrous and it gets bad quick (not that I'm against nitrous) , As a minimum I would put aftermarket bolts on the mains and rods . It is all about you . if you crank it up in 1st gear , say 6000 burn outs , then it will break . If you bring it to say 4000 and shift 2 second and take it to say 4500 just out of the water box until you feel it pulling on the motor , then rollout and shift at say 6 with a delay to 6250 , then it will probably last 2 seasons. Just my .02

It is also steel forged steel crank vs cast crank....Cast can be good for quite a few RPM's . A bigger thing is to have the engine internals balanced.

I do know that a stock SBC forged steel crank will break at the 7-8 rod journal right past the last main cap almost every time. Why you say old dog.. it is how they twist the crankshaft to get the basic shape, by holding the flywheel side still and twisting the rest of the crankshaft.

You should see the cross section of a steel crank. you dye the split crank, and use the biggest maginifer you can get. Look at the grain of the metal. A cast crank is all random. A steel follows the basic shape of the crank with a differnt differance the farther to the rear. Also cryo treating things makes the grain more dense. Don't ask how. It is like good beer. you can really tell the differance

_________________
75 Luv, 350 V8, TH350, Camaro rearend. New 1975 Luv Step side. Stock for now.
Grandmaster of the "Shade Tree" way.. I can't see the yard for all the cars. Come on down and we will sit on the porch and watch the grass grow.

I crew chief several sprint cars here and we only run a 010 GM block that is a 4 bolt. But then again we run 9000 RPM's every Saturday night. We can get about 3 seasons out of a engine at about 600 HP.

We also have a 410 car, but that is a alum. rodack block, that one is about 800 HP. 4 bolt as well.

Bottom line is I run 4 bolt blocks, I like the extra insurance. I also only want the 010 block due to the extra nickle content.

_________________
Certified pilots, looking down on people since 1903.

I use the 010 blocks as well they seem to hold up a little better. But mine is also a 2-bolt. Three years 250 passes about half of them on the bottle, and he motor looked brand new when I went to freshen. I think that unless you are really going hardcore, doesnt matter 2 or 4 bolt. Just do your homework and use good internals and a good machine shop for the balancing and always check your bearing clearences you will be good. If you are really hardcore and want to protect your investment use an aftermarket block.

_________________
Money can't buy happiness, but it can buy horsepower...and that's kind of the same thing...

I can feel the flame on this one , but i have moved away from the 010 block . I have 2 of them in the garage greased down . I have been running the newer 638 and 880 1-peice blocks hydraulic roler cam blocks . Good hardware , good parts , good machine work and proper assembly are key .