I have two 350 blocks here and im debating which one to use... Im going to be building a 383 that im looking for around 400 HP and maybe a shot of N2o... One is a 10066086 ... its a 4 bolt mexican block that came from a target master... there is no year range for this block or any info on it so i dont even know where a person would go about getting gaskets and such for it... it is a 4 bolt though... The other is a 3970010... its a 2 bolt, but much higher in nickel, and what alot of people have used.... Which block should I use and which one should i hand to my friend for just a mild 355 build up... both blocks are virgin and havent been run that hard... both will get the full machine treatment... decking, boring, etc... Any advice would be greatly appreciated Thanks! :hail:

i'd use the 2 bolt and splayed caps

I agree with ede.

Me too.

how is it that a 350 2 bolt is stronger than a 4 bolt?, and how much does it coast to have caps splayed? what ever that is.

Ok, the two bolt block here has a high nickel content which makes it stronger in general. What we're weighing here is the weight to strength ratio. The 4 bolt blocks generally had a taller deck height and thicker cylinder walls and main webs. This all made them stronger, but added about 60 lbs to the block. Splaying mains is a procedure where the main webs in a 2 bolt block are drilled at a an angle outside of the stock main holes to make it a splayed 4 bolt. Steel caps are generally used here as well. Since the outer two holes are at an angle the stresses are distributed more into the block than into the webs. You get a block that is for most purposes just as strong as a 4 bolt and weighs 60 lbs less.

Uhhmm.... when did sbc blocks have different deck heights? The reason why you don't want to use that particular 4 bolt block is because it's a crappy mexican block [questionable casting/material] not suitable for performance use.

If a 4 bolt block actually does weight 60 lbs more than a 2 bolt, thats not a bad thing. The additional weight is where it's needed, thicker walls, beefier main webs=stronger, more rigid, dimensionally stable block.

Uhhmmm... since they started making them. We're not talking a couple of inches here.

True, but if you consider that the car is extremely front heavy already and that a late model thin wall 2 bolt block will handle 600 hp then how do you justify it?

2 bolt splayed or just regular

EVERY Generation-1 small-block Chevy, as delivered from the factory, in a production vehicle, had the SAME deck height.

ALL of them.

9.025" was the factory deck height specification.

There are non-street production small-block Chevy based blocks with a taller deck height but they are very expensive (tall-deck Rocket block, for example).

jms

Another thing, I doubt if there is even 5 pounds difference between a two-bolt small-block and four-bolt small-block of the same year production and cubic inch.

If the nitrous is kept to a reasonable amount, I would just use good main bolts (or studs) and keep the 010 two-bolt main version as a two-bolt.

Sell the "hencho en Mexico" block to someone that thinks its something special.

jms

I'm not going to argue with you, because you're convinced you're right. I'm just speaking from what I've learned from machinists who've been in the business over 20 years.

well just for the hell of it why not post the "other" SBC deck height. seems funny all the pistons in any catalog work for both of them. i could damn near believe one block might have a THICKER deck surface but not taller and thicker would add to a weight increase.

Yeah, i'd love to see the 'other' sbc deck heights

Twenty years of machining experience?

Well, I've got underwear older than that.

I've probably built more engines in my 30-plus years of racing than your 'machine shop' friends have seen.

My proof is easy---go measure ANY factory first generation small block Chevy's deck height.

More proof I can generate---over 3,000 magazines and books from the 1960s to date. With a little effort I could list 100s of issues that back up my claim.

I'm not going to argue with you. I'm convinced the REAL experts are right. Like GM, Smoky Yunick (RIP), Grumpy Jenkins, etc.

9.025"

jms

Another question. How did GM know which block was gonna be a 4 bolt, and which was gonna be a 2 bolt, when both used the same casting?

Example: I have a 638 block (I don't remember all the numbers before that) and EVERY book and website ( www.mortec.com for instance) shows that casting # to be EITHER a 2 or 4 bolt main. So IF they increased the deck thickness, etc., then it would be on both the 2 and 4 bolt blocks, right?

I think maybe 5 lbs. is more accurate and only due to the increase size of the main caps, and adding 6 more bolts.

AJ

thanks for the replies guys... i can tell ya by carrying them down the stairs myself there is no weight difference... i dont know how heavy they are but i can only curl them a couple times

there are also no real visual differences... the two bolt doesnt have splayed caps though, just the standard ones.. or are you meaning to get aftermarket ones from like summit and get the block tapped?

ive got a guy that will take the 4-bolt so ill probably be working on the other one shortly

:lala:

OK I'm a moron. I don't know what the hell I was thinking. I know better than that. I was just super retarded that day for some reason. I apologize.

thats ok i'm still retarded, i really don't under stand the whole two bolt is stronger thing, cause i found plenty of two bolts around here but i never bought because i thought they where crap! is it exspensive to have caps splayed? and do they work for 383's?

the caps cost around 200 dollars plus another 50 to 100 for the machine work to install them, then you need the mains honed, but you'd be doing that anyway.

I dont think anyone said two bolts were stronger... just in this case this two bolt block is better then the other one..

Im not sure how much it costs to get the machining... i can usually find people to do stuff for free or for cheap... the caps are 199$ though... and the caps have no effect on which crank you can use is all in the journal size.

a 383 requires some clearancing for the block in regards to the rods hitting in several spots... its time consuming.. put a rod in, check for clearancing, dremel the block until its good, pop the rod out and then check the next one i guess its not that bad..

now i just have to figure out what third gen im gonna put this in... theres no way im ripping out the motor in my 92 GTA

:hail:

thanks ede. well ace i guess i miss spoke my self i did not mean to say a splayed two bolt would be stronger than a four, and i do relize what a 383 is! i ment would a splayed two bolt hold up, in other words is it as storng as a factory four bolt, but thanks for the advice anyway, also i have some caps off an old 350 four bolt could i use those? not that i would just curious.

yeah you could use 4 bolt factory caps and have the 2 bolt block machined to accept them. the cost for machining would be about the same either way and for the strength gain i'd still go with splayed caps if i were spending the money on machine work anyway.

mexican block, they have much thicker walls. If your rotating assembly and heads can take it, then you could spray a hefty shot.