OK, so I had a nasty knock, and I still drove the car for like 20 miles after the bearing spun. . . and come to find out my number 7 rod chewed a quarter inch into my crank and the shavings chewed out my main bearings. . oooops, so I need a new block. So my questions are, besides the obvious, that the 4 bolt has 4 bolt mains instead of 2. . what is the difference?? I can get a 350 4-Bolt for 150 plus 100K+ mile rotating assembly (which I DO NOT plan on using) for $150. My 2 bolt is garbage, yet at the same time I can get a 2-bolt from a friend of my brother's for $20. Is it worth it for the 4 bolt?? I am planning on either doing a 383 or a forged 355. . do I need to bother with the 4 bolt? one other thing, the 2 bolt that I can get has a peice rear seal, while the one currently in the car, and the 4-bolt have one peice rears. . . . do I need the one peice to match up to my 700r4? it is out of an 87 formula 350. and one last thing. . . am I going to need to do work to the block if it is pre-87 to keep the hydrolic roller cam?? or am I all set?

 

the only time you really need a 4 bolt is if your running deep into the 10's or faster other then that the 2 bolt will be more then fine./

 

It is generally acceoted that 2bolts will last up to 450hp. I'd splurge for the 4bolt.

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You have walked onto the biggest baddest dog porch and you will be dealt with accordingly.

I'd rather be historically accurate than politically correct!

 

I'd go 4 bolt, especially if you're going to stroke it. It's just extra protection.

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei distributer
'95 3.23 rearend
hotchkis rear suspension
PST front polygraphite suspension
"speed kills. buy a f@&d, live forever."

 

You can just a easily put a stud kit into a 2 bolt to make it as strong as a 4 bolt.

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block (times are for the current engine)

Best ET on a time slip: 11.447 altitude corrected to 10.99
Best MPH on a time slip: 119.42 altitude corrected to 124.86
Altitude corrected rear wheel HP: 493
Best 60 foot: 1.586

Racing at 3500 feet elevation with a typical race day over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

No offence, but I doubt you need a 4bolt. (I really dont need 4 bolts but thats what I have so)
4 bolts are only really nessasary when your pulling heavy loads in a truck, even then there not nessasary.
If you can get a 2bolt main cheap go for it.
SSC

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85 Camaro, 355/400 "drag car" current DD 13.1@ 101mph on its last season run.
Plans: Possibly add N20 for next season.
82 Firbird, rebuilt 355 for it and slaped a 700r4 in. The 700r4 crapped out so back to the tb350

 

Like Stephen says. You can even drill and tap a 2 bolt block for splayed 4 bolt caps and have it stronger than a factory 4 bolt if you really think you need it.

 

Four bolt mains will only help if you're putting more than 400 horse power out AT HIGH RPMS. No more, no less. If you're staying under 7000 rpms, you've got nothing to worry about.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...
http://www.spinfrenzy.com/stingerssx...easures.html#4

 

Go for the one piece rear seal. The fact that it is a 4 bolt is irrelevant (as per the reasons stated above).

I do believe that there may be an issue with the flexplate if you go 2 bolt. I will see if I can find the differences in one of my archives, but it is something that needs to be checked too if you plan to swap to a 2 piece rear seal.

Of course, if you do plan to stroke the engine to 383 you may wish to go with the 2 piece as most of the cranks for the 1 piece are more expensive, though I believe Scat now has a reasonably priced crank for 1 piece rear seals to stroke you to 383.

 

I think you'll have to buy aftermarket roller lifters for the 2 bolt main block. The GM lifter links don't clear the top of the lifter valley. The aftermarket lifters are linked higher so they work. I think you can use the same cam, but I think there is something different on the distributor gear. Help me out some here guys,
Craig

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84 Z28 305HO, 5spd, 222,000 miles, Edelbrock intake, Hedman headers, low restriction exh(w/cat), K&N air filter, 14.630 at 93.17mph
Del-A-lum front control arm bushings, Moog ball-joints, Energy suspension front sway bar end links, Moog rear sway bar end links, Eibach pro-kit springs, tokico shocks/struts, AU secondary rods
www.indycamaro.com

 

if you drill and tap the block, can you still use the "2-bolt" end caps, or will you have to buy "4 bolt" end caps