Which is a better block? four bolt main or two bolt main. i know its a total noob question but im a noob to chevys lol

 

i would think 4 bolts are better then 2 bolts.
you can always make a 2bolt main into a 4bolt. i heard that they are stronger if you do that. im not to sure tho.. i never done it before.

 

four bolts are stronger than 2 bolts from the factory, 2 bolts can have splayed main caps (offset rather then linear) installed which make them stronger. 2 bolt blocks are just fine unless you're making some serious power.

 

thanks guys

 

And to add to that....

If you are making serious HIGH RPM power, you can break a 4 bolt block! It may crack BETWEEN the two adjacent bolts that hold the main cap down. 4 bolt blocks are great for low rpm, stump pulling torque. Like in a dump truck when you drop the clutch and try to get going out of the sand pit. High rpm engines do much better with the splayed caps mentioned above (which is made from any good two bolt block) or cross bolted mains like the old Chrysler Hemi blocks used.

 

The Hemi isnt the only big block Chrysler to use that. As fas as 2 bolt blocks, my 360 spins 7800rpm with KB hypereutectics, 12.8:1, Eagle h-beam rods, stock .10-.10 cast crank, externally balanced, and a stock 2 bolt block. Been running that way for 6 years now and its never come apart. That just proves one thing about Mopars, theyre tough.

 

to start with you have to decide what you are going to do with the motor, with an automatic trans 2 bolt blocks will take 8500r's been there with 4 motors one was even a 400ci talk about music. For manual trans you probably should go 4 bolt they will take the end thrust abuse better. most people read H/R mag' and get all wraped up in the hype. A good streetable strong motor will almost never see 7000rpm so a 2 bolt will work for this application, just do your home work. I built a 327 with 305 "601" castings, 268h comp cam. installed it in a 1989 chevy short stepside under the TBI got 22 to 26 mpg and could out run a vortec truck. the truth is for dependable streetable motors go the other direction. smaller intake valves and larger exaust valves, torque is your friend, HP is your enemy

 

I've been running a 2 bolt main block for 4 years with regular trips up to 7,000 rpm. Only mechanical failures have been 2 pushrods breaking about a year apart.

 

now thats what I'm talkin about

 

i heard 2 bolts are good unless ur throwing 600hp+ and see RPMS above 6000. it really depends on how u drive the thing. but all this info is great

wat about my situation. im looking for a rotating assembly and block for my 383

i got this all just staring at me in my room
HSR... Ported and about to port match to felpro 1206 intake gaskets to head
58mm TB
comp cams XFI280 cam. 230/236 .567/.571 113lobe
patriot 195cc aluminum heads, CNC bowl blended, ported, 64cc straight plug, dual spring upgrade good for .670 roller cam lift
ford SVO 30lb injectors
1.6 extruded aluminum roller rockers
comp cams .100 longer extreme energy pushrods
amoung other goodies.

im expecting 480-500hp. more like 500 after the porting im doing
car is a 87 formula 350 with a built 700r4 and stock 3.27 9bolt.... for now.

im stuck on what i should do as far as the assembly, i want the motor in so i gotta start pricing wat i need, and on a budget (full time student), im not sure if im ever gona throw boost at it... god knows i prob will in a couple years but i was thinking 9.5 comp ratio, i was looking into some stroker kits from Cnc-motorsports.com but im not sure what to get. i kno i would need forged pistons if i were to ever throw boost at it. but would i be ok with my stock 87 2 bolt roller cam block? i kno played caps are better but that is $$ to do and the motor wont see more than 6000 bc peak power will be 5500-5800. car will be a daily driver as well

http://www.cnc-motorsports.com/produ...43&CtgID=20134
budget hyper piston kit 705$

http://www.cnc-motorsports.com/produ...24&CtgID=20450
forged piston kit 8.8 comp 905$

 

Two-bolt blocks are stronger.

Four-bolt engines are used by the factory for trucks, Vettes, and most performance crate engines.

The 2-bolt block is stronger because the holes for the outer bolts on 4-bolt main blocks reduces the material thickness in the block main bearing web. The 4-bolt caps will reduce cap "walk", which is what the factory intended with the design.

The superior design is to take a 2-bolt block and have splayed 4-bolt main caps installed. The outer bolt holes in that design maintain the web cross-section, because the bolt holes go into the meat of the web and not in the smallest cross-section like the factory 4-bolt design. The splayed configuration also clamps the caps in such as way as to prevent cap walk better than the factory design.

For most street applications, a 2-bolt block is just fine. 2-bolt main was the only thing available in SBC's until 1968, and main cap failure was hardly ever heard of even back then when they spun those poor 283's & 327's to the moon in an attempt to get power out of them.

 

Hey confusion, As to your question about 2 bolt main vs 4 bolt main small block Chevy blocks - LOTS of 2 bolt main blocks see 600hp - just ask IMCA
champ Lane Whittington ( if you can catch him that is ).


" The secret of life is honesty and fair dealing...
if you can fake that,you've got it made. "
Groucho Marx

 

I may be overly cautious sometimes, but I dont think you will get the 500 you are looking for from that combo. Patriots are great heads, but Im not sure thta with those heads and that cam, you will make it 500. 500 is an awful lot of go.

 

thanks for all the info guys. i guess i'll be going with my stock 2bolt block.
since i shouldnt be making over 650hp with my supercharged combo.

ljnowell... what do u think i'll be making with my combo? ive gotten many responses sayin i should be in the 480hp range with peak power in the 5500-5850 rpm range. but im always open to opinions. so im curious to see wat u think. i'll prob get it dynoed. how much is dyno'n now? and how bout a dyno tune? is it just the heads that are keepin me from the 500hp goal?

 

My personal guess is closer to 450HP with your aforementioned specs.

If you're seriously considering a blower later on, build it for a blower now. Don't turn a NA spec'ed engine into a half-a**'ed blower motor. Build it for one purpose or the other. That way it'll work a lot better.

 

Hey customblackbird, in my neck of the woods dyno "time" is about $100 per
hour with parts or extra labor - well - extra. Also,like Sonix said about yer
huffer there you'll need to watch your CR.

" The secret of life is honesty and fair dealing...
if you can fake that,you've got it made. "
Groucho Marx

 

damn only 450hp.... boo! hell vortec headed 383's with a carb make 430hp. i'll have to dyno it and see but thanks. yea i kno about hald @ss'd part.... i dont think i can afford a completely forged rotating assembly as a student. my stocker has 132,000 on it and my sterwart warner performance electric 100psi oil pressure gauge says i got about 10-15psi oil at idle 20-25 at cruzing. fully warmed

shes gettin old.

how long do u think it would take to dyno tune a car? and hour? lol
b

 

Rent the dyno for about 3hrs. Bring every part you can possibly need to it (plugs, etc). By the time you're done it'll be worth the $350 or so.