Inliners International Forums General Discussion Engines tapping crank snout

I have a 66 chevy 250 and I would like to drill and tap the crank snout. I know what size I am going to tap but I would like to know how deep I can safely drill into the crankshaft before hitting any trouble. Thanks in advance.

Since you will likely be using a SBC balancer bolt and washer, you can look at the snout of SBC crank and measure how deep they are drilled and tapped. I've done it many times, and works out very well.

gtbrain,

Are you doing this in the vehicle?
If so, what's your plan for drilling it straight and centered?

regards,
Leon

the engine is actually out and on a stand.

I had the block and head machined and I rebuilt the engine. I had asked my machine shop if they could tap the snout for me. Nope. They said they couldn't do it. I was a little disappointed. Their other shop that inspected and polished my crank also said they were not equipped to tap it for me. I have the engine 90% assembled.

I know in the past the balancer was just installed using a hammer and drift. But the more i thought about it after I have it together, I was leaning towards tapping threads to make it a little easier on all the parts involved.

I was just going to use a hand drill and trust my bearings to keep it straight.

How much of a time frame are you up against to do this.

oh, not a big rush. And I'm thinking if i don't get any threads tapped, I will just apply a little hammer wrench like the oldtimers did it. I guess I was just curious as to the depth of hole I should be drilling. I sure don't want to go too deep.

I don't have a 250 to measure but I just checked my spare 292 and it is 1 3/8 " (one and three eights inch).

A drill press works pretty good for this, takes a little set up, but drills real easy. I did mine using a cheap-o Harbor Freight drill press with the crank setting on blocks of wood and the head swung of to the side.

Joe

Ia the 235 crank snout the same diameter as the late models?

regards,
Leon

Well, I got it done with no problems. I drew out a template giving me the center point and the locations of my balancer bolt holes. I then cut a piece of 1x wood and transfered the template to it and drilled 3/8th inch holes so I could mount it to the balancer.

I drilled the center hole on the wooden template 15/64ths. I then tapped the balancer on the crank, mounted the wood to the balancer and drilled my first hole with the 15/64th bit roughly an inch and a half deep. I removed the wood template, cleaned out the shavings. I drilled out the center hole on the template to the next size bit on my drill press to 9/32nd. Remounted and drilled the crank to the same depth with the 9/32 bit.

Repeated the above switching to a 21/64th inch bit.

I removed the wood template, cleaned out the shavings and repeated the previous steps with my final bit of 25/64ths.

The one inch thick wood template held my drill centered and the hole came out just fine. I tapped the freshly drilled hole with a 7/16- 20 tap.

Although I probably would have had no problem BFHing my balancer on, I feel a lot better being able to press it on with an install tool.

Good going and thanks for the info!