Don Terrill’s Speed-Talk

It's been a eternity since I found myself having to install Heavy metal in a cast crank.
Got one now.
It's a scat cast BBC.
Just wondering how much press fit anyone has done?
I am skittish of more than .001.
Your thoughts.

Are you installing it radially? or through the counter weight? When I install radially I like .0015 to .0020 press.


If I go though the counterweight I am ok at .0010. but I always weld mine also.

Horizontal. CAST crank

I clamp it in the vice length wise,dimple it up with a punch and red locative them in.

I would use .001" to .0015" max depending on how close tou are to the edge of the counterweight and how smoothe the internal finish is. I also loctite insitu.

Dave I always figured you for Classic Rock...

GARY C wrote: ↑Fri Jan 10, 2020 8:53 pm Dave I always figured you for Classic Rock...

I missed the joke but yeah.

My reamer is one inch but cuts slightly over. Since the slugs measure 1.002, it works out to be around .0015 interference. They press in tight so don't drill close to the edge of counterweight to avoid cracking.

The reamer thing has always been a little hit and miss for me.
I got to the point somewhere along the line that I drill and then final bore it to size.

I've had issues with reamers cutting perfectly round holes on nitrated steel cranks but not so much with cast. If you are skeptical at .001 and are boring the hole, make it .0008?

Update:
I settled on .001 and green loctite.
It's amazing how much pressure it takes to press .001. I was seeing around 3500 lbs.
With the crank being cast iron I still held my breath.

Don't worry about that amount of press for a heavy metal slug in a cast crank, it's made of material nothing like the cast iron encountered in other engine components such as crankcases. It's a different class of material all together. Tensile strengths range from 65,000 to 80,000 psi for typical stock pieces to as high as 100,000 psi for high performance cast cranks. It's far stronger than many folks imagine.

Many, many millions of engines can verify how tough the stuff is if done right.