is a two bolt main worth beefin up?

[gabet40]

my old engine is on a stand in the backyard and i wanna rebuild it for my dads 71 blazer just in case the motor in it takes a crap. problem is its a two bolt main, is it safe to bore out, and throw in some performance parts (intake, cam, etc.)? or should i just rebuild it stock and have it as a back up motor sittin around?

[JD72]

Two bolt mains have no problem to the stanard bolt on tricks. They can handle towards 500 or so hp, if you were going to shoot gobs of nitrous or put a blower on it that would be different. But just normal street stuff it will be fine and I think Milodon sells a kit to convert 2 bolts to 4 if you are still worried. Hope this helps some.

[RED72blazer]

I've been told by a few engine builders that a two bolt block that is converted to four bolt is stronger than a stock four bolt block. I think it's because the two new bolts on the caps are installed at an angle instead of straight up and down like the original.

[junkyardjohn]

I WOULDN'T WORRY ABOUT A 2 BOLT BLOCK NOT BEING STRONG ENOUGH. I'VE BUILT ALOT OF (OVER A DOZEN) 2 BOLT BLOCKS UP TO 450 HP (REAL DYNO, NOT AN ESTIMATE OR A DESK TOP DYNO) & HAVE NEVER HAD ONE FAIL FROM BEING TOO WEEK ON THE BOTTOM END. OF COARSE I PREFER A 4 BOLT, & USE THEM ALOT BECAUSE THEY ARE PLENTIFUL, & COST ABOUT THE SAME FOR CORES. IF IN DOUBT, PICK UP A CORE FROM A BONEYARD FOR $50 - $75.

(MILODINE AFTERMARKET CAPS ARE ABOUT $210 & REQUIRE ABOUT ANOTHER $150 - $200 IN DRILLING,TAPPING & ALIGHN BORING & HONING)

[Longhorn Man]

Somethign that is forgotten, is it is RPM that rips an engine apart..not H.P. (coincidently, it takes RPM to make H.P. though)
You can spin one to 5500 on a reg basis, ans even to 6500 once in a while.
I have no reason to believe my 350 is a 4 bolt, and she's seen 7000 a couple times, and 6500 more than I can count.
The splayed conversion caps are much stronger (if done right) then a stock 4 bolt.

[chevy2racr]

2bolts are fine, for race motors guys want the 2 bolts and put billet splayed caps on, there i more meterail in a 2bolt compared to a 4 bolt.

[Crank]

Four bolt main blocks are desirable in high performance applications because the extra strength of the additional bolts keeps the bottom end rigid and less prone to failure. However, a properly prepared 2 bolt main engine will work just fine (often times you'll lose a rod bolt before you break a crank because it's "only" a 2 bolt main. Compliments of NastyZ28.com.
Brandon.

[Longhorn Man]

now...for a 400, it is bass ackwaerds, and you WANT a 2 bolt. The 4 bolt is not as strong as the 2 bolt...but this is only on the 400 small block.

[Blue_71]

like longhonrmail said, in 400 SBCs, the outside two bolts on the block are to close to the edge, and make it more likely to crack.. ive got a 2 bolt 355 in my 4x4, and will have a 2 bolt 400 in the 2wd.. my 355 isnt anythign special really, but decent little motor.. 350 bored 30, flat tops, 487s heads, Weiand 8004 intake, Holley 4175 650 CFM carb, hei, headers.. dont really know the real numbers but its estimated at 330 HP/370 torque.. so in short, i think your 2 bolt will be fine

[bigjimzlll]

install main studs(arp) and have lined honed...good rods and bolts and your good to go....

[gabet40]

ok well now i know not to worry about my 350 2 bolt. matter of fact i think i might just convert to 4 bolt since you guys are saying that its stronger than 4 bolt stock. any answers on how much the Milodon conversion kit is?

well what ever engine that ends up in it, it will be driven a couple times a week, but the real action will be in the Pismo dunes on the Cali coast. well give it a little lift, probly a 700r4 between this engine and the 3.73 rear, and a darn clean restoration. any reccomendations on how to get most out of it (cam, rocker, intake, etc. -wise)?

by the way- my engine in my 69 tops out at about 5050 rpms. brand new crate with the additions listed below, why cant i hit 6-7K rpms? (obviously, im new to all this engine building crap)

[bigjimzlll]

whats limiting your rpm 's.....cam...heads....intake... those are the big three. your engine has to be able to breathe at hi-rpms. thats when the flow numbers from your heads come in handy. the cam manufactors put a usable rpm range on the cam, so you can see what rpm range your in...but you must have all three set up for the rpm range you want

[gabet40]

well ive got a darn tall intake. very comparable to the edelbrock airgap, but accel makes it. then a spacer, then the throttole, then another spacer, then the K&N. my cam float is 6500. but i do have stock heads.
so a reccommenation might be to throw some roller rockers on?