2 Bolt vs 4 Bolt

[typicalmarine]

So I've been searching but cant find the answer. Whats the difference between a 2 bolt and 4 bolt engine? I assume it's the number of bolts that attach to the tranny but hell I have no idea.

I have an 89 k5 350 4wd. Am I a two or four bolter?

Thanks

 

[JACKBURTON55]

I'm not sure what your blazer came with as I'm new to blazers but basically a 4 bolt main has a stronger bottom end as it has 4 studs holding the main bearing caps to the block, 2 bolt has 2. thought unless your redlining the motor and making some higher hp, it shouldn't be a huge deal

 

[86chevyk10]

2 bolts on main caps vs 4 bolts on main caps. Someone else should chime on whether your motor is 2 or 4. Try google next time, it works wonders on questions. Id think youd have to pull the oil pan to see.
Heres a 4 bolt big block

 

[typicalmarine]

Oh okay, so it doesnt really matter for me when looking to replacement my motor. I was thinking it could be a compatibility issue.

 

[doonjumper]

Hard to say because what if P/O changed engine. Then its not the original. Look at the casting numbers on the back of the block and go to your local engine rebuild shop and have them run the numbers. Or Im sure you can google and find a site that can tell you what you have. Not a big deal unless you plan on runnin' HP.

 

[doonjumper]

Oh okay, so it doesnt really matter for me when looking to replacement my motor. I was thinking it could be a compatibility issue.

If you are gonna replace it then I would get a 4 bolt just so you have one and they are stronger in the respect that the Main caps wont distort under high HP application.

 

[4X4HIGH]

People have you covered on what a 2 bolt versus 4 bolt means. There is NO WAY other than dropping the oil pan and looking to determine which it is. For most people have a 4 bolt main engine is nothing more than bragging rights.

Unless you plan to run a high compression ratio, turbo or blower or run at extended high RPM's there is no need for a 4 bolt block.

 

[76zimmer]

you can put main studs on the bottom end for some more strength, but that will require at least a check of the mains with the studs in it, probably a linehone also.
Its a happy medium between 2, and 4 bolt mains though.

 

[ryoken]

it's all about the splayed caps....

 

[76zimmer]

I'm digging that....

 

[TerryD]

it's all about the splayed caps....

ding ding ding! I'm turning a two bolt main almost 7000 rpm. I've got ARP rodbolts in it though. A four bolt main is just as likely to walk around as a two bolt main is. Splayed caps are the only way to truly prevent it.