I was torquing the mains in my just assembled engine and the #1 main bolt snaped! What the hell do i do now?

First of all, you had better check your torque wrench ! Then get the broken bolt out and put a new one in.

I thought you had to use the same mains that came out of the engine to put it back together (bolts that is) in the same hole they came out of.

Torque wrench is brand new, its replaceing the crappy one that was used to assemble the engine. I was untorquing and retorquing all the bolts to be shure they were torqued right. I had one other bolt that took an extra turn or 2 before it clicked, im afraid this bolt is stretched a little to much also, or somthing else is the problem. First engine build here (automobile) Ive rebuilt small engines and boat moters, this is my first car engine.

You dont have to use the same bolts. What were you torquing them to ? Were you using the torque wrench to loosen them too ... if so it is probably junk now.

I didnt use the torque wrench to loosten em, i had a different (crap) torque wrench that is only used as a breaker bar. 70 ftpds. In chat atm if you dont mind stoping in.

In order to get the old bolt out you need to drill it and use and "easy out" to pull the broken bolt. Then I would purchase a set of ARP main bolts. You could have a main bolt that was over torqued at one point before you broke it.

Whats the torque rating of arp mains? I guess i have to buy new mains. What torque rating would you go on the arp rod bolts. I was just going to use stock (according to haynes) torque values

Thats all you need to do, Torque them to recommended torque according to the manual. When I rebuild my 454, I will purchase all new bolts. I personally dont like reusing old Head bolts, main bolts, rod bolts etc. It is not that much more expense to replace all the old bolts with new.

Anyone have any part numbers? Have to go to autozone/advanced (their open) to fix this dam thing tonight

Like someone mentioned before i would personally never re-use old main, rod or head bolts, because of the fact they may strech. If you buy ARP bolts or studs, they tell you exactly how to install them. Its simple. I would go with ARP not some stock ones if you have spent the money to build this motor, and it has quite a bit of power i would go with ARP. Good luck

It sounds like you may not have a lot of experience,and if that is the case,I suggest you load the motor up and take it to the machine shop to have the bolt removed. First try taking a sharp ***** punch and try tapping the broken bolt at it's outside edge to see if it will back out.If this doesn't work I suggest you take it to a shop for removal. I have seen too many people break "Easy-outs" off in the drilled bolt, and then you have a real mess to deal with. I believe it will be well worth the trouble,and the cost will be reasonable to avoid the potential trouble and aggravation.

Charlie,
A Chevy main cap bolt is a pretty decent 7/16" bolt. For it to break, I still say something is wrong. I have seen guys pull the threads out of the block before breaking a bolt. I still say you need to get your torque wrench checked ... I dont care if it's new or not. If you dont have the experience putting engines together, you may not know when you are going too far with a bolt. I have done enough that I would know if something was wrong with the torque wrench before the bolt would snap.
Just my opinion,

I think Charlie may have run into a situation that I found myself in a few years ago. I was rebuilding a Olds 455 for my 442,when I began to torque the heads I managed to break two head bolts. I checked my wrench against another as near as I could tell they were within 5lb's. I tossed all the bolts and installed ARP's. I suspect the bolts had been over torqued and stretched at some time and then failed when I tried to reuse them.

I am not new with cars, this is the second classic i have restored. I have done all the work to every vehicle ive ever owned. I worked in a marine/small engine repair shop for a nice stretch and have rebuilt 5 hp to 150 hp engines (lawnmower to outboard) and have snaped bolts before. I have never built a automobile engine before but i have done many head gaskets, timing chains, gasket overhauls...exc. I got tired of blowing junkyard engines so i purchased a video (Rebuilding Your Engine) to be shure i dont forget any steps. Ive been using it and a haynes chevelle manual (for the torque specs). Ive done everything mechanically ive ever tried, so i know i can do this.

Thanks for all the help, picked up the tools at advanced tonight, so ill try to kill the bolt tomarow. Ill have to order the parts, or go to napa/carquest.. both closed on sunday.

All fixed, drilled the bolt out and used a flute to get it out. Just disasembled it for a quick cleaning before puting it back together.

You might consider Milodon, (or is it HPX?), main studs from Northern Auto Part's...

pdq67

Can i just swap the studs for the bolts or will i need a line bore?

Charlie,
Stop trying to make it into rocket science. The bolts will be fine, I raced a 355 in a 67 Camaro for over 15 years with stock main bolts. Shifted at 7500 and went through the traps at 7800. I have a log book with over 3800 runs on the same bottom end ... approximately 450 hp ... the bolts will be fine. Get some new, or good used main bolts and put it together. By the way, I still think you need to check the torque wrench.

I agree with Bill K., and will just add 2 more recommendations:
Run a tap through the threads to clean them, blow out all "crud".
Thread the bolt in the hole by hand (without the cap in place). It should easily run all the way to the bottom with finger pressure.