318/360 flywheel

[tlockwood]

I know this has at least been touched upon on these forums because I found it in the search. Unfortunately, I did not find the answer. I have seen before a procedure to effect the balance of a standard 318/340 flywheel to make it compatible with the standard 360 cast crank setup. There is a very specific location that I believe you need to drill to make this work. From what I understand it is in the older editions of the chassis manual, but has been omitted from future editions such as those available now.

I need either the very specific instructions on how to do this, or the name of an engine/machine shop in the Chicagoland area that has this information and can make this change for me. I am hoping to get this car together in the next week or so, and I would really appreciate any information that anyone can supply me.

Thanks in advance.

Tom Lockwood

[72Challenger]

According to my 1984 Direct Connection chassis book, you need three holes to convert a symmetrically balanced flywheel for use with a cast crank 360. The picture shows it pretty clearly, I'll try to describe it.

Lay the flywheel engine side up, and orient it so that the four symmetric flange bolts form a rectangle with the long sides running from left to right. Extend a line through the exact center of the flywheel, parallel to the lines formed by the short sides of the rectangle. This line should extend just across the edge of one of the offset bolt holes, and miss the other offset hole by about the diameter of the hole.

Now move along an arc 3.88 inches from the center of the flywheel, 41 degrees 26 minutes from the line which touches the offset bolt hole. This will be exact center of the first hole. The other two holes are centered along the same arc, 2.5 inches on either side of the first hole.

Now drill each hole with a 1 13/64 inch drill bit, .66 inches deep to the point of the drill, and you're done! The actual balance amount is 19.79 in.-oz.

Simple, right?

[tlockwood]

Hey 72 challenger,

A friend of mine supplied me with a newer version of that book, but it does not seem to have the same information. It has instructions for converting a normal flywheel to a 340 externally balanced flywheel, but not 360. The 340 only appears to need 1 hole. I think, anyway. I wouldn't call the instructions I can see very clear though.

After reading your description and seeing this drawing I think I understand what you are saying. Do you have the 340 drawing I am talking about in your book? If so, do you only see instructions for one hole, and that one is 5.625 inches from the center. It is also a smaller hole, only 33/64 in, and is .84 inches deep.

I don't suppose you have the ability to scan that page you have and e-mail it to me, do you? I know it would be a pain, but I would be forever grateful. If you can't do it, I would also understand. If you can do it, my e-mail address is tklockwood@charter.net

Thanks again,

Tom

[72Challenger]

Yes, that one's there too. The orientation of the flywheel bolts are exactly the same for the 360 mods, just that instead of one small hole there are three larger ones. It makes sense that the 360 would have different balance than the 340. One thing bothers me though. I've also got the newer book as well, and in the text it says that the 360 has three holes, but that they are 1/2 inch in diameter. The older book says 1-13/64 inch. That's a big difference!

Anyway I scanned it and emailed it to you. If anyone else wants it, now's the time to ask!