I bought an 1987 350 this weekend for my 88 K30. I only needed the crankshaft because mine was bad, so I got the rest of the motor for free:D. Anyway the block has a hole in one cylinder becuase its piston split in half and did some major damage to the wall, however its a 4 bolt main block. I have another 350 in my toyota that I wanna covert to 4 bolts but its a 2 bolt, would it be better to run stock main caps or aftermarket? The motor will have about 450HP.

Why convert? A 2 bolt main is good to about 600 horsepower.

4bolt 350 are dime a dozen.


2 posts in row that the same responce applies, "pissing in the wind"

I agree, with "only" 450hp why convert to 4 bolt and add the extra cost of an align bore with the new caps?

If you're worried about it being just a 2 bolt main setup, replace the bolts with studs and rest easy

If you still want to spend the money then aftermarket splayed 4 bolt mains will be stronger.

If you still want to spend the money then aftermarket splayed 4 bolt mains will be stronger.

x2 "if ya gotta do it"

Ya I like the idea of using studs instead of bolts. Ya 4 Bolts would be overkill in my case, maybe if I had 600+ HP then I would go 4 bolt. I guess I'm overlooking this worth thing, thanks for the input.

i wanna see the ingredient list for 450 hp.

2 bolt main block with a stud kit. you wont hurt it.

Well my list included fresh rebuild with .030 over pistons, vortec heads w/beehive springs, roller rockers, etc. Also a 270/280 Blue Racer cam, Edelbrock RPM intake, 1 5/8 shorty headers, 600 Holley. The compression would be about 9.5:1, I hope to be around 400-450. I guess 2 Bolt should live with these parts.

i would put them on the self. not worth the money for any thing under 600hp.

Well my list included fresh rebuild with .030 over pistons, vortec heads w/beehive springs, roller rockers, etc. Also a 270/280 Blue Racer cam, Edelbrock RPM intake, 1 5/8 shorty headers, 600 Holley. The compression would be about 9.5:1, I hope to be around 400-450. I guess 2 Bolt should live with these parts.

Do you have better cam specs? 400-450 horsepower isn't out of the realm of possibility for that combination I suppose, but it is starting to get on the upper end of believable. Don't get me wrong. That engine will go...but most people would shit their pants if they ever felt an HONEST 350 horsepower.

FWIW I'm shooting for 300-325 hp using a very similar combination. The different might be in the cam, but every time I ran a different cam it really gave something up (had to rev to the moon, gave up torque, gave up the ability to idle, etc). My cam only has 196/206 duration@.050 and will have .461/.480 lift with my rocker set up and runs a tight 107* LSA.

If you still want to spend the money then aftermarket splayed 4 bolt mains will be stronger.

Not that much though, since the outer bolts will be tapping into unreinforced areas of the block. :D

so the crank you want to use is outa an engine that had a catastophoc failure?
I wouldnt use anything outa it
a new crank is cheap

Well my list included fresh rebuild with .030 over pistons, vortec heads w/beehive springs, roller rockers, etc. Also a 270/280 Blue Racer cam, Edelbrock RPM intake, 1 5/8 shorty headers, 600 Holley. The compression would be about 9.5:1, I hope to be around 400-450. I guess 2 Bolt should live with these parts.



That combo might come close to approaching 400 with a solid cam but even then i dont think its going to be the 400-450hp range you are hoping for.(i always assume when someone quotes a range they are hoping for the upper part of it).

All the dirt track guys i know use converted 2 bolt blocks with splayed caps, not stock 4 bolts. But you arent going to be making enough power or spinning it fast enough to worry about that.

I would go with a four bolt main if your not gonna splay the caps, the extra material on the caps helps keep them from deforming under load

I would go with a four bolt main if your not gonna splay the caps, the extra material on the caps helps keep them from deforming under load

um... yeah. no.

A 4 bolt block will fetch more money, true. a 4 bolt block will hold more power, maybe.
a factory 2 bolt block with studs will handle EVERYTHING he will be putting on it even if he adds a 200 hp nitrous shot.

keep it simple. if you want a 4 bolt block, then buy a freakin dart block with billet caps, and put twin turbos on it. is it overkill? yes, way overkill.

a 2 bolt block is FAWKIN FINE for this application.

grey cast iron wont really deform. it will fail before deforming. the cap bolts will stretch before failure, and that will cause the caps to show fret marks where they chatter and vibrate. then the caps will deform by failing.

kinda makes you wonder why chevy bothered to make 4 bolt main blocks at all.
they never had a motor make over 400hp from the factory yet the low powered trucks seemed to get 4 bolt mains an awful lot.
hmm wonder why

hmm wonder why

-Larger factor-of-safety with minimal extra cost. Racers are happy with 600HP but the factory probably only wanted to run 300hp in a 2 bolt block.
-Hardware wasn't as good back then (and good hardware was $$$).
-They (Ford and Dodge too) were doing similar things on their high HP motors so why not on their cheep motors too since you are drilling and tapping in that area anyway.
-Plus back then we didn't have guys being paid 75$ per hour to put on lug nuts (think American auto industry). Back then actually parts were worth more then time/labor.

kinda makes you wonder why chevy bothered to make 4 bolt main blocks at all.
they never had a motor make over 400hp from the factory yet the low powered trucks seemed to get 4 bolt mains an awful lot.
hmm wonder why



Because its really torque that kills your bottom end. A truck at full load or tow capicity will load up the engine way more then a much lighter unloaded car.

kinda makes you wonder why chevy bothered to make 4 bolt main blocks at all.
they never had a motor make over 400hp from the factory yet the low powered trucks seemed to get 4 bolt mains an awful lot.
hmm wonder why

Because its really torque that kills your bottom end. A truck at full load or tow capicity will load up the engine way more then a much lighter unloaded car.

Rustyrunner hit it, It's the torque and loading that kills your bottem end.

MJ, Dont forget about crankshaft flex. When the piston fires down all that force is put on the crank shaft lobe and while that's happening the truck is resisting movement. So... imagine your CS flexing about an 1/8th inch from when the piston pushes down before the truck starts moving. Now think about the difference between moving a crew-cab dually and a camaro. The GM engineers probably had that in mind when they added the 4 bolt main caps to the blocks.

Do the splayed caps.

i have a big block with 2 bolt mains and a stud kit.. it has been dyno'd and puts 333 hp to the ground at the tire, with a th400 and an np205. These are very power robbing units.

I have never had one iota of issue with the studs. you will not have any issue with your 2 bolt block and a stud kit in this application. it is a waste of money to go and blow it on something you dont need.

as far as loading the crank, imagine humming the engine up to 6300 rpm and dumping the clutch with a 5200 lb truck in 4hi on pavement. sure, the clutch slips a little. Ive done it more than once. when it starts to bounce and lurch, you just stay in it. I have never had any problem with the crank. its a stock piece, forged, yes, but stock, nonetheless. I run cast pistons, 3/8 rods, and it holds together. the engine has been running since 1993 with the only required repair being a new intake valve and guide when i bent an intake valve, and new retainers and locks to fix the problem.

attached is a link to a video that shows you how rough on it I have been.. while it isnt me driving (one of the boys borrowed my truck while i was out of town), this is a nice day for this engine....

http://i69.photobucket.com/albums/i53/d_waller1/th_broncohill021.jpg (http://s69.photobucket.com/albums/i53/d_waller1/?action=view&current=broncohill021.flv)

YOU DONT NEED THE 4 BOLT BLOCK.

I did a little searching on this and as it is here it is a pissin match as to what a two bolt will handle! Seen cases were were a 420 hp 350 was vibrating the caps with no sign of detonation of a balancing issue(with studs), other guy that that said that they had put 800 to a 2 bolt. But in my opinion if your gonna put the money rebuilding why not use a stock four bolt splayed caps are overkill.

http://speedtalk.com/forum/viewtopic.php?t=3798&highlight=400

so the crank you want to use is outa an engine that had a catastophoc failure?
I wouldnt use anything outa it
a new crank is cheap

Wow im falling behind in my post lol. It was just the one piston that failed the crank was perfect. If it wasnt for the piston the block would be been saved.

Ok as of the cam specs its a Wolverine Blue Racer P/N WG-1103 i believe, sorry i dont have cam box with me at the moment. Intake lift was .426 and Exhaust was .443, again I'm not certain I'll get specs up soon. I thinking of running studs cuz its cheaper and beefs up the bottom end. Vid was very cool :smokin:

Ok as of the cam specs its a Wolverine Blue Racer P/N WG-1103 i believe, sorry i dont have cam box with me at the moment. Intake lift was .426 and Exhaust was .443, again I'm not certain I'll get specs up soon. I thinking of running studs cuz its cheaper and beefs up the bottom end. Vid was very cool :smokin:

the cam in my big block is a 230* duration at .050 lift, total lift is .544, 290* duration from .006 lift. a tad bigger than yours.

LOL
thanks for listing all that guys.
small block chevys have horrible mains
every spun bearing I have seen is in a small block chevy

when a wall gets punched out by a failed piston the crank takes a hit
after all it was ramming the rod that pushed out the wall
at the very least you have to check it for straightness

exactly wtf was that stupid video clip supposed to prove?
that a rolling wreck cant cross a puddle??

Why on earth would you even bother with splayed caps or studs if you are running a stock cast crank and stock rods? Its a little bit like putting lipstick on a pig. Save the money and put it towards better heads if you want to make real power.

How many people do you know that have actually broken main bolts? Its not that trick stuff like this doesnt have its place, its just out of place on the kind of build you are talking about. Better management of funds will yeild a stronger motor then wasting money on stuff thats there just so you can say you have it.

Oh yeah i would check your cam for trueness. I bought one of those cams for a SBF in the late eighties and the runout was way excessive. Could have just got banged around in shipping but still worth checking.

Just to show the variation in cam specs, the cams in my two SBCs are rated 230*@.050" lift on one side(both split pattern cams) and one is a 268*@.006 and the other 280*.
COMP Cams 12-769-8
COMP Cams 12-268-4

Do you have better cam specs? 400-450 horsepower isn't out of the realm of possibility for that combination I suppose, but it is starting to get on the upper end of believable. Don't get me wrong. That engine will go...but most people would shit their pants if they ever felt an HONEST 350 horsepower.

FWIW I'm shooting for 300-325 hp using a very similar combination. The different might be in the cam, but every time I ran a different cam it really gave something up (had to rev to the moon, gave up torque, gave up the ability to idle, etc). My cam only has 196/206 duration@.050 and will have .461/.480 lift with my rocker set up and runs a tight 107* LSA.
When one of you computer 4 wheelers shows me a dyno sheet [and no chassie dynos ] whith numbers from idle all the way to redline and the HP and TQ curves, BSFC and all the proper info on the motor being run we will get into a good discution untill then its your lies, make em as big as you want!In 21 yrs. Ive built about any kind of motor you can name whith out getting stupid and have seen all kinds of power and all kinds of failures.The first thing you learn in a GOOD engine building school is failure annalisis.Then you move to building yhings to prevent those failures, tha is alot of why manufacturers use parps tha sometimes dont make sence in the motor they are in!IE 4 bolt mains in a low rev low power chevy. by the way I went to Eliete enginering in portland OR. A top notch school and still take refreshers from time to time.Check my post on the 4.3 vovtec Im doing for a customers 4 runner and you may understand!