How much power are you making and how many bolts are your main caps? Or how fast are you running and how many bolts in the main caps? I have a 400 SBC that I was considering making 4-bolt splayed but the machine shop wants too much to do it. So I am considering just keeping the 2-bolt.

 

It really depends on how much power you are going to pull out of the 400. The 2-bolt should be ok up towards the 350-400 HP range. If you are going higher, then it might be a good idea to splay it.

I have a 2-bolt that is going to have over 450 HP. It has already been converted to 4-bolt splayed mains.

 

regardless of 2 or 4bolt, splayed or not.

about 3 years ago.. there was a guy named cam406@aol.com. He had built several hundred 400s in the 500-600 range and for the most part used stock cranks and studded 2bolt mains. Even running nos he did not see problems for mains. The factory crank will run into trouble in the 600 range.

Actually I like factory main caps better. They are made of the same material as the block and grow at a rate much more consistent than steel caps.

Its not the physical failure of a cap that causes a problem. Its the distortion of the mainbearing saddle (and cap) causing some type of oil loss. The distortion can be because of strength being insufficent or because of vibration. So.. just make sure you have a good aftermarket crank, good oiling, well balanced and I don't think you will have problems.

PS, my 400 is a 2bolt with studs and it has over 500hp. It could live with spray noprob.

 

jcb999 thank you!

 

The real question to ask here is "What RPM will the engine be seeing and where is the powerband going to be?"

You can have a 500HP 406 that makes its power at 5500 rpm and still use 2 bolt mains with a stock crank. In fact, when Chevy Hi Performance used the Trick Flow 23 degree heads and Comp Cams 274 extreme cam, they made 450 HP.

If I was going to make over 500 HP, I would do it at a lower RPM and stud the main caps, just to make sure. The stock block, if properly tested for strength (sonic testing) can be used to 600 HP. Also, it depends on if you are getting to 550-600 HP N.A. or using nitrous too. If you are N/A and constantly at the 600 HP level it is different than using a 150 HP shot of juice to get your there.

In short, the 400 block will be ok to 500 HP, over that make sure you figure out what you want. Also, if you only want 450HP and want to rev to 6500 RPM, then I would be more concerned.

 

A friend and I built a 2 bolt 350 that makes over 500 hp and spins 6800 and never had a problem. Stock rods and crank.

 

ok, unless your running in the 6500+ rpm range you dont need a 4 bolt block. even then a stud girdle is better. cast cranks are good to about the 500-600 hp range. actually the only cranks i have ever seen break are forged units. the 4 bolt caps and forged cranks are usually to keep the vibrations at high rpm's from getting out of hand, wiping out the main bearings crank and sometimes block in the process. 400 2 bolt blocks are stronger than the 4 bolt blocks , there's simply more meat left in the block to hold things together (remember 400 have siamesed bores, and heat up faster than other SBC's so distortion is more of a factor) . if your going to spend money , use it where it will do the most good. rods and good bearings are top prioriety. A#1 motor failure is a broken, bent, or exploded rod, 99% of the time due to a spun bearing. get good pistons, and pay close attention to the heads, since thats where you make all your power. i dont mean to say not to have quality machine work done, but only get what you need. sure true blueprinting on a motor is great and can be worth 50-hp to??? but do you need to spend $3500 at the machine shop only to have a cheap rod bolt go and waste the motor because you didnt have any money left for arp's? dont believe the hype, you dont need 3/4 of the crap you hear about to go fast. knowledge is the key. and dont be afraid to experiment.

 

That is pretty interesting...as the "experts" would say it should blow up that way...

You bring up an interesting point comparing the 350 to the 400...the stock rod ratio on a 350 is much more conducive to higher RPM use. When you do build a 400, buy 5.7" rods for sure (6" if you can afford it). The 400 isn't really the best engine to rev for power. A 377 (destroked 400 with a 350 crank) would be a better choice.

I though that the key is parts selection. Sounds like the 350 wasn't just slapped together to stay together, and also, it may last for a while, but I like the idea of engine longevity. I don't see any reason that a higher HP engine shouldn't stay together for 50,000 miles or more, if built right.

 

well the reason I am building the 400 is not for high RPM power but for more low end grunt. I have a superram for it. So at the most I will pull to 6000 but that is it! 6000 is where I will set my rev limiter. I don't want to go any higher. Thanks for all the imput guys.

 

Oh and I am using eagle 5.7 rods and a scat crank. TRW pistons. SO I did go for somewhat strong stuff but will not kill the wallet. except for the fuel injection!