Harmonic balancer bolt

[Mark E.]

Re: Harmonic balancer bolt

I believe that's correct, Dom. Cast cranks are generally a ductile iron, while forged cranks begin as a cast carbon steel ingot then go through the forging process.

[Mark E.]

Re: Harmonic balancer bolt

I didn't know some harmonic balancers do not have a retaining bolt.

How are they installed? It seems this might be difficult with a tight press fit.

[Richard G.]

[Steven B.]

Re: Harmonic balancer bolt

For what it's worth, I came across this article that does a reasonably good job at addressing cast vs. forged crankshafts. I thought that tuftriding and nitriding could both be used in surface hardening. Now I'm not so sure. I have a forged crank in a 350 that was out of a C-60 series mid 70's truck. It was the same crank that was used in high performance applications to the best of my knowledge. I was aware that grinding would remove the nitriding or tuftriding because of the shallow surface penetration of the hardening process.

Steve

http://www.hotrod.com/articles/crankshafts-how-to/

[Richard G.]

Re: Harmonic balancer bolt

In Tuftriding, the crank is immersed in hot cyanide compounds, creating a tough, resistant surface that improves fatigue resistance.
It is a good bet that this process is no longer used because of the environmental issues.

[E R.]

Re: Harmonic balancer bolt

Thanks everyone for the help it was a learning experience
EV

[Gerald C.]

Re: Harmonic balancer bolt

What would be the size of the bolt that I would use on my 63 300 hp harmonic balancer if I wanted to install the bolt for engine turning manually purposes?

Thanks

[Timothy B.]

Re: Harmonic balancer bolt

The factory bolt size for the drilled cranks is grade eight 7/16x20 (fine thread) and length approx 1.5". It's the same bolt that holds the steering damper to the relay rod on the C2 cars.

[Joe L.]

Re: Harmonic balancer bolt

What would be the size of the bolt that I would use on my 63 300 hp harmonic balancer if I wanted to install the bolt for engine turning manually purposes?

Thanks

Gerald-------

Drilling and tapping for a center bolt is, in my opinion, a machine shop operation. I would not attempt to do it with the crank installed in the engine or, even, with the crank out of the engine on a do-it-yourself basis.

[Richard G.]

Re: Harmonic balancer bolt

7/16 20 x 2 1/4 Grade 5 with Hole through head for what appears to be provisions for wiring to retain the bolt. (never used in this application)
1 3/4 OD x 17/32 ID x 1/4 Thick Washer

[Joe R.]

Re: Harmonic balancer bolt

Gerald-------

Drilling and tapping for a center bolt is, in my opinion, a machine shop operation. I would not attempt to do it with the crank installed in the engine or, even, with the crank out of the engine on a do-it-yourself basis.

I agree with Joe Lucia that drilling the crank with the engine in the car is not ideal. However, several years ago I wanted to drill and tap the 300 hp crank in my '67, but the engine was in the car and I had no other reason to remove the engine.

I made a simple drill guide out of a block of hardwood with a 1.25" hole in one end (cut using a Forstner bit) to fit over the crank snout, and a 1/8" hole in the other end to fit over a long 1/8" drill for making a pilot hole. After the pilot hole was drilled, I enlarged the 1/8" guide hole to the 25/64" size for a 7/16" tap, and then drilled the crank with the larger drill. After that I used a tapered tap to cut the threads.

Recently I learned from a friend that there are two available fixtures kits that use a similar approach:

https://www.12bolt.com/store/p164/Crankshaft-Drilling-Fixture-Balancer-bolt-283-327-250-235-261-230-215-194-Tool.html

https://mrhotrod6.myshopify.com/products/crank-shaft-drill-and-tap-fixture-tool-kit-sbc-283-and-327-cid?variant=1142530117

The only thing that I don't like about the first one is that it does not use a pilot hole, but an insert could easily be made to support the pilot hole drill. The forged crank material is fairly hard to drill, and I think the pilot hole helps with drilling the 25/64" hole.

The second one above uses a pilot hole but costs more.