Hi
Do any one knew what type of bolt it is to lock the harmonic balancer on a 312 from -56.
The length, thickness and type of thread, and also tightening torque and where to find one, i have searched all over the internet without result......

9/16"-18.  I don't have the length handy.  I've use grade 8 bolts, from a hardware store or industrial supply.  You may have to trim to length depending on that requirement and what is available.


Lawrenceville, GA

9/16" x 18 x 1.920" overall length, 1.500" thread length, with .230" thick hardened washer.  Joe-JDC

JDC

Hill's Thunderbird Part # 6A340 Bolt, Harmonic Balancer, $3.00. Order online at www.hillsresto.com

My catalog is not current; the price might have gone up. 

85-95 ft.lbs. per Ford manual.

Hi.
Do you know the diameter of the washer?

I’m not sure so I won’t comment on an original but I’m a firm believer in using Belleville washers on cranks bolts or studs. The are slightly larger in diameter than a stock size flat washer for the diameter of the bolt. I use 2 and buy them thru Mc Master-Carr. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

The damper washer is a snug fit to the inside of the damper, you cannot go larger like the BBC washer.  It will not fit.  I will check my 312 damper washer for size if no one else measures theirs first.   Joe-JDC

JDC

Damper washer is 1.750" diameter, ~.230-.235" thick.  Joe-JDC

JDC

Thanks a lot Joe and all others!!