My flywheel has these special bolts that go in thru the front and how do you get the nuts on? Or does everybody tap the crank and machine the flywheel for 12pt bolts? All hemi's the same? It almost like you need to bolt the flywheel on before you put the oilpan on it to access the bolts, but then you can't have it on an engine stand. makes no sense to me, like I'm missing something. thanks, Oj
The holes are correct size for ½-20 BUT, you must have near-perfect alignment with the tap or else you end up with bolts on some bastard angle and zero clamping force. You can make a tap fixture from some bar stock; ½ x 2 x 4. Using a milling machine, D&T a hole in one end for the ½-20 tap and then drill a couple additional holes at the other end, one at about 1.4" and one at 1.2". These numbers will vary depending on the size of the hole itself, but they are used with a 3/8" bolt to secure the bar to the face of the flange and hold the tap in alignment. If you pay for the ride both ways I'll loan one to you. As to the oem bolts/nuts, they work very well but are a PITA. You need a long 5/8 box end wrench and skinny fingers. .
If you are going to use the stock bolts weld a flat washer to the back side of a long box end wrench.
The holes should measure somewhere close to .450, means a 29/64" drill is the correct size. Good to double check it. Tap drill = NOM-(1/PITCH) which is .5 - (1/20) -> .5-.05 = .450, gets you close to 29/64 which is .453, out to 5 places it is .453125.. show off... I just make up tapping blocks most of the time, have some drill bushings around the shop too. The big thing is getting the tap square to the flywheel face. Make sure the chamfers for the holes are pretty generous too. Cast iron taps dry (by the book) but I use water soluble coolant anyway.
Make sure you use cap screws with a shoulder or add 3 dowels if your planning on hammering it... PS: I wouldn't bolt it "up" .. It's too heavy to hold it on with engine in a vertical position.
I left the stock 7/16's bolts in my 392 flywheel... My flywheel came from WilCap drilled for 7/16s bolts..... Just turn the motor and tighten one at a time... Just put a piece of tape on the open end wrench to hold the nut...Never had any issues at all...Running blown 392 with a duel disk clutch...
I've these Big Gator Tools tap and drill guides (Metric, UNF and UNC) to maintain surface squareness however it'd be ideal to have a machinist do it to ensure accuracy and squareness. However if crank is still in engine that's another issue that could be resolved with these guides. It still needs to be clamped into the correct location and secure before you even contemplate breaking out the drill and tap. I always use tapping compound and take my time, don't rush into it.
This worked for me. I cut a piece of thin plastic from a quart oil bottle and taped it to one side of my wrench. IT holds the nut while you fish it up behind the crank flange yet is flexible to allow you to tighten the bolt to torque.
Here is a pic of the fixture that I use. The only real downside to using the oem bolts and nuts is getting them started. Torquing the nuts is a bit of guesswork so you need to practice with the box end wrench to get a 'feel' for the amount of force. Be sure to use an internal tooth washer as did the oem. .
I bought a Wilcap set up for a hemi. They included a plastic machined tap guide as well as the tap in the group of pieces for the adaptation. Worked well, just need to be cautious and deliberate when tapping. I can see where a bolt down guide would be an excellent method to insure proper tap alignment.
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