Inliners International Forums General Discussion Engines Drilling crank for bolt

I was just wondering is y'all had any suggestions or comments on drilling the crank for a dampner bolt? The Power Manual says "Recommended option 1/2 - 20 UNF by 1" deep minimum thread" with a total bolt length of 2.5 inches.

This is for my 250, and this will be an "in the truck" project. Anything would be great. Thanks. John

Yes that is the same Bolt i use on my 250.It's a Big Block bolt. the one i use is a ARP bolt.
Hope this helps }[oooooo]

Drilling the hole in the crank snout by hand while in the vehicle is not too easy.The hole must be absolutely parallel to the crank,if it's cocked, even slightly,the bolt will be stressed and eventually fail.
If you're using RPM limits similar to the stock engine ,like 4000 max, the bolt is probably unecessary for street use.

An additional benefit of drilling the crank is it makes installing the balancer a heck of a lot easier. By using an installer, you eliminate some risk of damaging the motor when pounding the balancer on.

Bruce, that's the main reason I'm doing this. I saw the bolt listed in Summit (their brand) for $9.99. I think I'll be able to pick it up locally for cheaper (hopefully).

I should be able to unbolt the radiator and lift it up, so I'll have more room to drill. This will be my first time drilling and tapping anything though. That's why I asked. Thanks. John

i did this on my 250 while it was in car, in order to use a dampener installer tool instead of pounding in place and i did it using a regualat electric drill. it took me all of 10 mintes to drill and tap the hole. its easy to center because the groove on the crank pulley goes to a point in order to use a puller...you justcenter the drill bit on that and use pleanty of cutting oil.

One thing that will help is to start off with a smaller size drill, say like 1/4", and work up to larger sizes. I, too, did this in the driveway. Use some JB weld on the threads and torque the sucker down to whatever the bolt is rated at. You will still be able to break it loose with a zip gun, but it will never loosen up.

Thanks guys. That's the kind of info I was looking for. How far should I drill? The book says a minimum of 1".

theone61636-- I like the puller idea. Luckily I just bought another one to replace the one I lost.

Jack- Will it be alright to just use red Loctite? I just want to be able to get the bolt out incase I have to work on it. Right now I don't have a compressor. Also, what type of drill bits should I use, and will it be ok to get the bolt from ACE? I just don't want to screw this up. Thanks. John

Yes, the red loctite should be OK - I would use new carbide tip drill bits - Sears has good ones. Considering the trouble you're going to, don't use a harware store bolt! Get one from ARP and find out the torque rating, then install up to just below that reading.

Cool. Thanks, Jack. John.