B'klyn9C1

What is the horsepower and torque limit of a 2 bolt main LT1 shortblock??

Can the use of ARP bolts and fastners make it as strong as 4 bolt mains?

I want to use the motor for AutoX and roadracing, not so much drag racing and living life less than 13 seconds at a time.

dirtynorth

are all lt1s two bolt mains? if not how can you tell without taking it apart?

creepingdeath94

iTrader: (1)

Honestly, you can make just as reliable a 2 bolt motor as 4 bolt for what you are wanting to do. 4 bolt mains originally only came in trucks because of the loading from towing heavy loads and trailers. You can make plenty of power with a 2 bolt set-up with the right supporting parts...crank, rods, pistons, etc.

1badzee

iTrader: (12)

Most of the 4 bolt LT1's came in the special corvettes lol. Some came in a select few SS's (IIRC)

RamAir95TA

iTrader: (2)

There is no HP/TQ set limit to when/if they will break. Most failures come from extended high RPM usage when the rod bolts let go.

All factory LT1s are 2-bolt blocks with the exception of all Corvettes and OEM-replacement short-blocks (4-bolt). There is no way to tell what type of main you have without removing the oil pan.

See above for which cars have 4-bolt mains. A 2-bolt main motor will always be weaker than a 4-bolt equivalent once the RPMs begin to rise.

2 bolt main < 4 bolt vertical main < 2 bolt splayed main < 4 bolt splayed main.

All Corvettes had 4-bolt mains. Never seen an SS with a factory 4-bolt main, although I suppose it's possible for GM to sneak one in.

creepingdeath94

iTrader: (1)

Maybe so, but depending on what you are trying to accomplish, most of the time, it can be done with the 2 bolt set-up for what he is describing. But yes, definitely the splayed mains are superior to straight...do you need them...depends on what you are doing, what supporting parts you have internally in the engine, what revs you want to wind it to for how long, etc. Like you said.

As far as what had what mains, originally, before 4 bolts were as common, they started out in trucks is what I was trying to say. Corvettes have them now, and for a while, but they didn't always.

96lt1m6

iTrader: (31)

If money is tight you can always instal ARP main studs to your 2-bolt block have the mains align-bored and honed go have a blast...if you have some extra money get the steel main caps have the block splayed to 4-bolt align-bore and honed. that will be plenty strong! so 265.00- 850.00 will get you a reliable beyond stock block.....

97Z28SS

iTrader: (5)

There were 100 1997 SS Z28s that got the LT4 engines all of which had 4 bolt mains.

MattSapp95_T/A

iTrader: (35)

I made 559hp and 600tq to the wheels on a 2 bolt main block....

95ztrey

a 4bolt main block came out of my 95???????

AChotrod

iTrader: (17)

If you didnt buy it new it was a replacement block

robsquikz28

iTrader: (246)

2 bolts can and will hold up a lot of power, YOu will never really know when it goes.

ThreeHonks

iTrader: (10)

You guys are right on the money that the two bolt blocks are not as weak as people think. When put under the stress of heavy boost or nitrous, then yeah, they can be an issue. But if you build it right with quality machine work and fasteners the stock 2 bolt mains are fine!

What I have heard about the 4 bolt f bodies is that a few cars recieved them near the end of production in '97 because there were left over ones from GM. I have only heard of one confirmed case of this though

SS RRR

iTrader: (2)

It would have been in the LT4 SS models then. No Z28 models had 4-bolt mains.

That has been argued to death about as much as the difference between a 5.7 and 6" connecting rod... Most will debate the fact that a straight 4-bolt main is not as strong and actually weaker because the outside two bolts are tapped into the weaker part of the block webbing which then also takes away block material and the webbing is then subject to crack under high cylinder pressure and load compared to a 2-bolt main setup. I had a friend who had a MTI built 383 stroker on a 100 shot back in the mid 90's, was billed for a 4-bolt splayed block, found out much later he had a 2-bolt bock w/ stock caps and all had cracked in half except for the two outter caps.

95 TA - The Beast

iTrader: (2)

Wrong.

For LT1 blocks there is less material in the webbing thus a 4-bolt splayed is WEAKER than a 4-bolt straight.

Really tired of making this argument. Too many retard machinists trying to get as much cash as possible from customers have pushed this 4-bolt splayed agenda on LT1 blocks. Again the webbing is weaker on LT1 blocks, thus splaying them only puts the bolts into the weak webbing. The webbing is strongest where the caps register, thus 4-bolt straight conversions are stronger.

The end of it is that you take a seasoned 2-bolt block, convert it to 4-bolt STRAIGHT with billet caps and you have the strongest "normal" bottom end for an LT1. It will handle 800-1000hp. The next step is a stud girdle and then 4-bolt the end caps for the ultimate.

A good compromise is take a 2-bolt block, and add a stud girdle. Good compromise on price and not too difficult to accomplish. I did this myself on my latest 383 for my convertible.

Puck

iTrader: (17)

Not this mess again .

We've all been wrong for 17 years, straight mains are stronger, the machinists are overcharging us to be dicks, splayed mains are a waste, its all a conspiracy, the sky is falling, etc .

wht97ws6ta

If you are making enough power to break a 2 bolt main then you will break a STRAIT 4 bolt main just as quick. And splaying the outter bolts will most definely make a stronger block for a number of reasons. Have you actually taken the time to take a look at where the outter bolts go into a production 4 bolt main. Where the bolts are is right where the bottom corner of the cyl is in the main webbing. Barely a half inch of threads there for that outter bolt to go into. Its like driving to many nails in a board, eventually you will make it weaker. Splaying the outter bolts will put them into some solid material around the oil pan rails. Also the splayed outter bolts will use their tensil strenght to pull the block together while using shear strenght to help from stretching the 2 inner bolts. I mean how can strait 4 bolt main using tensil strenght alone be stronger than using splayed outter bolts???? And for the record how many motors have you seen that failed due to main caps alone. Not sayin it dont happen but its not very likely. Unless you are running lots of boost or hosing it down with tons of nitrous, then a studded 2 bolt main will take everything you throw at it.

Matt97Ta

iTrader: (30)

i made 580 /657 to the ground through and auto so if you are really going to spend the money to make big power splay the block.

engineermike

I'm not buying that...

I'm making around 940 fwhp for several years on a block converted to 4-bolt straight. I highly doubt a 2 bolt would hold this power level without failing main bearings or breaking the crank.

I am seeing some fretting between the cap and the block. Clamping force is what prevents that, and the 2 bolt has 1/2 the clamping force. Going to a splayed will not increase clamping force. The only remedy I've heard of for this fretting is doweling the mains because any other method still allows axial travel of the cap.

Also, the amount of threads is pretty much irrellevant as long as you have about 1 bolt diameter of threads.

Mike

wht97ws6ta

So all this time everyone has been puttin splayed caps on for nothing. Well dont dat just beat it all. I guess that just makes dart and all the other aftermarket block manufacturers retards for splayin their blocks.