440 swap into a 72 charger - crankshaft issue
 

Hi all,

longtime lurker, first time poster, hoping to get ya'lls opinion on a tough problem.

I'm working on a 318 to 400 swap into a 72 charger (the engine is a '69). I bought the engine built, and just had to put on a new harmonic balancer before I dropped it. Long story short, I dont know how it happened but the first 2-3 threads in the nose of the crankshaft have been bent inward, so the crank bolt wont thread. Is there anything I can do without having to replace the crank? Some buddies suggested using a dremmel to get rid of the first few threads, others said to use a tap. what do you guys think? If using a tap is the best thing, is there any specific/custom size I should use?

I spent all summer prepping the engine bay, sandblasting, priming, painting, and was hoping to get the dang thing in before it gets cold (just putting in time here and there after work)...is this a huge issue? should I just take it to a shop? just frusterated with the whole process right now.

Thanks for your input!

Joe

If the threads were bent, it stands to reason, the shaft could be bent too. I would a tap to try and repair the threads, then once everything is woking, carefully observe how the motor runs. You may be lucky, and the crank itself may not be bent. If it is bent, you may be stuck removing the motor to replace the crank anyway. Is there any way you can set it up on an engine test stand to make sure it is not bent?

j

once you use the tap to clean the threads and mount the balancer, remove the plugs and turn the engine by the crank bolt. it should not bind when turning. it's not a guarantee, but a start. it could be that the threads were damaged when the balancer was taken off.

How did you remove the old harmonic balancer? If you didn't remove it perhaps someone pried it off and in turn bent the end of the shaft.

Just a heads up to a problem for others that could occur if you do not use a steering wheel puller, or harmonic balancer puller.

I took the old balancer off myself with a proper puller tool, so I dont get how it got messed up. Maybe the center screw of the puller was pushing against the threads? arent those tools designed to prevent that kind of thing from happening? oh well...

This leads to another question. I got the new balancer on about half way via the mallet and big socket method. I couldn't get it any on further and was planning on just threading the bolt and having the bolt pull it onto the crank the rest of the way. Someone told me there is a danger of shearing the head off the screw doing that. Is that true?

So it looks like the tap is the way to go, eh? can I just use one from somewhere like sears? or do I need a custom one?

sounds like you removed the balancer with a pulley but without the bolt there in order to protect the threads id get a tap for those threads and re tap them you can do a dremel and fix the 1st couple of threads but much easier to retap alot less hassle ( meaning finding a starter thread)
goodluck

Hey rammen99 just find a mac or snap on guy and ask him for the right size thread chasser tap or a thread file and clean them up and you will be good to go but do not use a regular tap as you could start new threads and that would just be as bad as the bent over threads ..... me i would just find the right size chasser tap , i dont have the size in front of me but if you need it let me no and ill do some searching for you or maybe doc might know what the size it is off hand ok :D remember DO NOT use a regular tap

Is the front of the crankshaft bent in any way, when I put mine on my 440, it slid all the way on, except for the last little bit without using a mallet or the bolt. I am not saying that should be the case for every application, but it just makes me wonder if that got bent. You still may be able to get it on, but if it is bent perhaps it won't be able to turn, and cause other issues.

Wow ..... this is a bummer ..... OTHER than finding the PROPER TAP( I have have never seen on that big) ... the best way to handle this would be to (as suggested before) ... go in there with a die-grinder and knock those buggered-up threads off.

if you are going the dremel route when you get the cuttin wheel disc wear it down a bit before going in there so it will be easier to clean them up without really removing them then you can try your bolt to see if it starts or get another bolt and cut 4 grooves on it this will kinda be like a make shift tap after you clean the messed up threads with dremel