Since main cap distortion is the main reason for getting 4-bolt billet caps.. can you stay with the stock LT1 2 bolt mains, but upgrade to some good billet steel caps w/ ARP main studs? I suspect a set of pro-gram 2-bolt caps would hold almost as good as the 4 bolt ones... right?

 

I think a signifigant part of why people do 4 bolt is to stop the cap from moving.

 

Thats exactly right. You don't want the main bearing caps dancing around.

 

As an old timer (old fart?) it's interesting to see how what used to be considered exotica only used by high-budget sponsored pros now is considered a necessity by hobbyists. Things like solid roller cams and splayed 4-bolts main caps are the two that come quickest to mind.

No one has ever really defined when it becomes necessary to upgrade main caps. So, even if you specified your application it would just be a WAG. And you haven't speciified your application. So, I didn't vote in the poll.

Rich

 

I've seen significant instances of cap-walk on two-bolt (w/ARP studs) LT1 main caps even at horsepower levels well below 500. My Corvette four-bolt block is much better even at about 600 horsepower. It's just too time-consuming to track down stock four-bolt blocks when billet steel caps are so easily come by.

 

Yea, I don't think cap flex is the issue here. All steels have the same modulus of elasticity, so mild steel and 4340 will have the same amount of flex. It's just that 4340 will flex alot further before breaking. Anyway, the issue is cap walk. I can tell you that my Pro-gram 4-bolt steel caps with studs still walk and fret the block at the 900 hp level. I believe the danger is actually a broken crank since the mains aren't staying inline with each other. The steel 2-bolt studed caps don't help in this area at all. Besides, it takes 90% the machine work to install new steel 2-bolt caps as opposed to 4-bolt, since they still have to be register-fit and line-bored. The cost difference will be minimal, so you might as well go with 4.

 

I've called two local machine shops that are supposed to be good shops. One quoted me ~600$ with me supplying the caps and studs. Another quoted me 1,000$ without caps, 800$ with..

Apparently all the shops around here are trying to rape me blind

 

The last set of caps I bought cost about $260 (including tax) and the installation was about $360.

 

Plenty of postings on the subject. Here is one on another forum.
http://www.speedtalk.com/forum/viewt...ight=bolt+main

 

At what rwhp level (roughly, of course) would an LT1 block converted to splayed 4-bolt mains become a weak link?

 

More than you are going to make Unless you are going to run it at WOT for hours on end anyway.

Rich

 

Once the bottom end is stabilized the weak link in the chain will relocate but by definition the weak link will still be present. Keep an eye on the cylinder wall thickness. Sonic testing the cylinder walls before overboring is a good idea if you intend to abuse the combination severely.

 

I ran into a similar problem. I called a dozen shops before I even found one capable of doing the conversion. Most said they're not setup for that sort of thing. The place I decided on quoted me $500-$600 with me supplying the caps.

After dropping my stuff off yesterday and talking to the guy, he said that was a "worst case scenario" quote. And it all depends on how much work he has to do to get the caps to fit properly.

Good luck, finding a place.

I had slim pickin's.

 

Guess I got a killer deal (for a change).