4 bolt main?

[73redblaze]

anyone know what engines are 4 bolt main stock engines? why is the 4 bolt so much better than the 2 bolt? please explain this to me. for a good race engine you want a 4 bolt main right? also what is a good set up for a good race engine? what heads what cam??? so on

 

[apache]

The main bearing caps have 4 bolts compared to the 2 bolt,simple as that. Its a stronger setup for a high HP mill,is it a must?? depends on what you call high HP and how you drive.

 

[4by4bygod]

Just get ARP main studs and you can have fun with a two bolt main block if that's all you have available. How much power do you plan on making?

 

[4X4HIGH]

There is no way to tell what came factory with a 4 bolt block, there are many cars that are both ways and there are a bunch of cars that you would have figured to be a 4 bolt but were in fact a 2 bolt.

Actually a 2 bolt block that is converted to a splayed 4 bolt is stronger than a factory 4 bolt block.

 

[GsxrMike]

What do you mean by race engine? There are several differant "races" you could be building for. For offroad you want to stick with torqueier options like dual plane intakes and smaller runners in your heads and a mild RV cam type set up. But that also depends on what type of "offroad" we are talking about. Be more specific...

 

[Wrench]

Like apache said, it depends on a lot of things, but the rule of thumb I think for Chevy smallblocks at least is that for a built engine (presuming a decent balance job) you don't really need the 4-bolt block unless you're spinning it over 6K a fair bit. A good balance job is the number one priority when it comes to value/return on cost.

That being said, if you have a wrecking yard you can go to, look for casting numbers ending in 010 and 207. I'm not sure they are all 4-bolt blocks, but every one I've checked has been. I have 4 or 5 in my basement right now.

 

[bot0611]

Ive seen 4 bolts gotten messed up on the outter studs due to big engine stress, i have a 2 bolt main in my truck

 

[73redblaze]

im looking to make about 500HP for a drag car.

 

[Wrench]

Ive seen 4 bolts gotten messed up on the outter studs due to big engine stress, i have a 2 bolt main in my truck

Are you trying to say that 2 bolt mains are stronger?

 

[Thunder]

If yur lookin at making 500+ Hp you should definatly get a splayed 4 bolt setup like 4x4 high said.

 

[73redblaze]

If yur lookin at making 500+ Hp you should definatly get a splayed 4 bolt setup like 4x4 high said.

thats what i was thinking. but theres no way of telling what block is a 4 bolt main with out gettin it apart? and if im hearing you guys right a 2 bolt main thats been tapped for 4 bolts is stronger than a stock 4 bolt main?

 

[4X4HIGH]

thats what i was thinking. but theres no way of telling what block is a 4 bolt main with out gettin it apart? and if im hearing you guys right a 2 bolt main thats been tapped for 4 bolts is stronger than a stock 4 bolt main?

Only if the 2 bolt block is converted to a SPLAYED 4 bolt. That means that the bolt arrangement would look like this... / I I \ rather than this... i I I i

 

[dyeager535]

I suspect you can tell 4 vs. 2 by the suffix code, but there are so many different suffix codes it's been (or was) difficult getting much in the way of data to support or disprove that theory.

It should hold true though, since 4 bolts were *typically* used in what GM considered HD applications...Corvette's, HD trucks, etc. Which the suffix code always denoted. Any suffix codes I've got data on (physically verified) that are duplicates, are the same number of main bolts. But there are so many engines that were turned out, it would likely be impossible to say for a fact that XYZ suffix code ALWAYS had 4 bolt mains.

 

[bot0611]

73redblaze nailed it!!!

the ones ive seen are in 1/8 mile drag cars you know you have lots of HP in thoose, so yeah if you convert a 2 bolt main into a 4 it will be stronger to my knowledge

 

[LVJimmy]

Trucks were a more common use for the 4bolt main. It seems torque more then RPM was the reason for the 4 bolt mains. On 350's the only way I have been able to tell the difference externally was by the oil plug on the block behind the water pump. I won't say it always works but it has for me.

 

[bot0611]

trucks id say specially 4wd trucks and heavy duty ones, vans

 

[odin]

Ive seen 4 bolts gotten messed up on the outter studs due to big engine stress, i have a 2 bolt main in my truck

I call BS

Ive built, raced, and destroyed more than a dozen SBCs and never seen any "messed up" outter bolts or studs.

 

[Slapperbar]

Ive seen 4 bolts gotten messed up on the outter studs due to big engine stress, i have a 2 bolt main in my truck

Only by over torquing or operator error on install.

4X4HIGH is absoutly correct on the SPLAYED over conventional 4 bolt. Besides, from a material standpoint, how strong is a conventional 4 bolt over a splayed one? The conventional has the bolt holes right next to each other in the same sized web. Not the greatest IMHO.

 

[dyeager535]

I was just researching this, I thought at one point I read that splayed put the bolts into a weak area of the web, but I can't find it. I probably got that mixed up with the stock 4 bolts.

The problem with the 2 bolts is that the caps walk at higher power/RPM levels. They will actually rub against the block where they mate. 4 bolts (vertical) will alleviate that problem to a degree, but even in looking at a picture of splayed caps, you can see that the splayed caps are much thicker than the stock caps across their entire surface. So splayed are both anchored better, and made thicker so they don't move (or crack).

 

[wayne]

500hp can be done on a 2 bolt block with no issues. Like mentioned ARP studs go a long way. If your going to go with 4 bolt do a splayed set up. If your planning to use a 350 block look on the back for 3970010. It can be either 2 or 4 bolt. I prefer the 2 bolt blocks to build.