The Stovebolt Site Forums The Shop Area Engine Shop Crankshaft Snout Drill & Tap Guide

Most of us who build stovebolt engines have experienced situations where the harmonic balancer has gotten loose and worn out the crankshaft snout, the Woodruff key, or both. In some extreme situations, the balancer comes off entirely and does a lot of sheet metal and/or radiator damage. While it's possible to recondition a damper with new rubber parts, once one is worn or damaged where it fits the crankshaft, there's not much it's good for but an anchor for a canoe! The 235 splash engine I'm rebuilding has this type of problem, with the crank snout worn about .002" under normal diameter. This will make the press fit of even a good-condition balancer pretty marginal.

Fortunately, there's a fix available- - - - -drill a hole in the crank snout and tap it for the same bolt & washer small-block V-8's used from the mid-1970's on, and keep the damper from loosening up and doing any damage. The trick is getting that hole drilled straight and true, and tapping it correctly. There's only one chance to do it right! The simplest, safest way is to set the crankshaft up in a drill press or Bridgeport mill during a rebuild, and be absolutely sure the hole is straight and true. How about the guy who wants to do the job in the frame, without dismantling the engine? The drill/tap operation is difficult at best, and disastrous in a worst-case scenario.

I am in the process of building a set of two guide bushings to slip over the crankshaft snout, one for the tap drill, the other for the tap, which will assure the hole, and the thread, will be centered and straight on the first attempt, even with the crankshaft in the engine, and if there's enough clearance for a 1/2" drill motor, with the engine in the frame. I've also got a balancer press that can bolt onto the crank snout once it's threaded, to install the balancer without hammering on it. Once I've case-hardened the guide bushings, I'll make the whole setup available for loan to forum members, with maybe a small deposit required just to assure they find their way home in a timely manner! Anybody interested?
Jerry

Jerry,

This is a very generous and helpful offer. When I did my last one, the engine was on the frame and the radiator was removed. I held my breath and hoped for the best, drilling by hand. Luckily, it turned out OK. I'd prefer not to take any chances.

A substantial deposit and a modest "rental fee" would be quite appropriate.

Thanks,

or you can put a long gmc motor in there that has already been drilled. just messing. That is a very nice offer. that job would make my b-hole pucker every time without it.

I had already drilled mine too. I would have been glad to pay a rental fee for the peace of mind. It made me a little nervous to do it freehand but it worked fine and drilled much easier than I expected. I think anyone who has used a proper tool (balancer press) to install dampers will agree that this sure beats pounding them on. I would be very hesitant to try to pull one on with just a bolt.

Chuck

I've re-tapped several race car crankshafts to a bigger thread after someone stripped the original thread trying to pull a balancer on. The balancer press bolts on tight, and uses a 1" diameter fine thread to do the pressing. Much safer, especially if there's room for an impact wrench to zip it on quickly! Fortunately, a stripped 7/16-20 thread makes a hole almost big enough to accept the next larger size tap, a 1/2"-20! All it takes is a slight enlargement of the hole before re-tapping. BTW, the same drill-tap guide I'm building for the stovebolt engines will fit the early V-8 cranks, 265, 283, and early 327, that came without the center bolt.
Jerry

When I rebuild my 235 this winter I'd rent it from you,or send in a deposit, Thanks.

Pete

Last time I dealt with this problem it was on an early 327. I did it free hand and don't believe I got it straight.

However it worked a couple years afterward before spinning a rod bearing while a friend was driving the car well over 100 mph for some miles on the freeway. Until today I've never wondered if my drill work had anything to do with that failure.

Well, the Stovebolt "help your buddy out" spirit is alive and well. That's a very generous offer Jerry, thank you. Don't need it now but ya never know. I too think a rental fee would be in order to recoup some of your time and effort.

This posting is very timely as I've just posted the question concerning the lack of a threaded bolt for the damper. I have my crank out of the block and want to get it polished, I'm considering having it drilled and tapped while in a lathe. What would be an appropriate size bolt 1/2 NF? Nice offer with the tool idea to be lent out.

The standard bolt that's used with the V-8's is a 7/16 X 20, with a heavy flat washer. That's the simplest option, and it uses readily-available OEM parts. I have rethreaded a few to 1/2", but it's not my first choice. The lathe idea is a good one, IF you've got a big enough lathe, and you do something to protect the front main bearing journal when you set up the steady rest on it. A piece of oil-soaked leather wrapped around the journal might be a good option.
Jerry

Almost all parts stores have a kit like this hanging somewhere in the store.

Plenty to choose from (most with the diameter and threads posted by Jerry).

While you are in a generous mood Jerry....

...any chance of posting the design of our guide.... either in picture form or drawing so we can build our own.

Having to drill for a water pump adapter plate on a good fully rebuilt 261, we made our own guide using a 1/4 plate and a 3 inch section of tubing that held the drill bit exactly perpendicular to the block.... and we loaned it out..... and someone else borrowed it... now I can't remember who has it.

I have wondered if one bolted a home made guide onto the damper, using the puller bolt holes, if it would be accurate enough or more accurate than free hand drilling.

Thanks for your help.

Bob C

I suspect the guide pilots off the snout of the crankshaft, and has a concentric hole drilled in it the size of the tap drill for the chosen bolt.
Then if you want a tap guide as well a second one is made with a hole to fit the major diameter of the tap.

Were I to make one for repeated use I'd use drill bushings. If planned right the two bushings would be interchangeable in the same body.
In fact the same body would work for multiple bushings to suit different drill sizes.

Look at www.McMaster.com for these part numbers:
8493A263 bushing for 7/16-20 tap drill, 25/64"
8493A329 bushing for 1/2-20 tap drill, 29/64" As well as a bushing for 7/16" tap (~0.010" clearance),
8493A049 bushing for 1/2" tap, (~0.008" clearance)
Also need one of number 8496A13, a lock screw for the bushings.

The above parts would cost about $42, or half that if you only wanted two bushings (one tap size only) not sure what tap size is normal for this procedure?

I can also make some of these if there is interest, send me a PM.

Grigg

Grigg, you nailed it! I made two guide pieces, one with the diameter of the tap drill (Letter drill "W" for 7/16X20) and another one to guide the tap, with a 29/64" hole in it. I made mine with a few thousandths' clearance over an unworn crank snout, 1.152" diameter. On a worn crank, wrap a layer or two of masking tape around the crank to take up any slop. You'll need to remove the Woodruff key from the crankshaft, or broach a slot in the guide to accomodate the key. It's easier to remove it, unless you're trying to do it with the timing cover in place. My drill guide also aligns itself in the front oil seal, but I really don't plan to attempt a drill/tap job with the timing cover on!

I use Kasenit case-hardening compound, same stuff I use in my gunsmithing, to harden the fixtures. Coming soon- - - - -a harmonic balancer pusher that works with the old style balancer with the hand-crank lugs!
Jerry

Jerry,
Do you have any pictures yet?

When you caseharden it will the bore still be true and on size, or will you need to grind it after hardening?

Grigg

Kasenit leaves a little scale during the hardening process, but it's easily removed with a cartridge roll on a mandrel, either spun in a die grinder or a drill press. I've got some very small-diameter ones I use while doing finish-up work on cylinder head porting jobs.

No pics yet- - - - -I forgot to bring the pieces home from the school shop, so I'll take the casehardening powder back there from the gunshop Monday morning.
Jerry

I'd be very interested in using this tool once you finish it.
I've got my new balancer from Buffalo, and haven't had time to work on the truck yet, so this is quite timely.

regards,
Leon

Jerry,
Any pictures or progress reports, so we can all express our admiration, or are you flooded out?

Leon

We're not flooded, but school has been out all week. Lots of disruptions of bus routes, and a lot of students have been displaced to other schools in the district because of flooded homes, etc. The next 3 weeks to the end of the school year is going to be interesting! I'm almost finished with an extended-thread pusher for my balancer installer, and a special adapter for the older balancers with the hand-crank lugs on them. as soon as everything is done, I'll set up an album on my photo host site, Hunt 101. Thanks for your concern!
Jerry

Denny Graham made one shown here:

http://www.pbase.com/dennygraham/tools_of_the_trade&page=1

Here's a good bushing source:

http://carrlane.com/Catalog/index.c...09090C0015480013180B041D1E173C1B08535246

Hi Jerry. This is a wonderful tool. Thank you. I also hope all is well there in Nashville. I spoke with my sister (lives just east of the city) and she said they were OK but there is a lot of water flowing.

Take care

Jerry,
Just checking in
Is the drill guide ready for the public yet?

regards,
Leon

Hi, Leon!
I've done one drill & tap job at my home shop, and the first road trip has begun. I sent the tooling out to a bolter in New York yesterday. The kit includes guide bushings for the drill bit ("W" letter drill), and a taper tap and plug tap for 7/16-20, plus a guide for the tap. I've also got two pusher tools, one for 6-cylinder balancers, and another one for V-8's. The 6 cylinder tool is a couple of inches longer. We decided on a $50.00 deposit (postal money order) with $30.00 refundable when the tools come back in good condition. I'll post a notice when the tooling is available again.
Jerry

Sounds great.
My new balancer and I are standing by.

regards,
Leon

Is this ready for sign out/rental yet?

I finished with it and returned it. Here's an article on my website showing its use.

regards,
Leon

Yep, it's been out and back several times. If you need it, drop me a PM or an email. I take a small deposit, and return most of it when the tooling comes back in good shape. No problems so far!
Jerry

Hello , I really could use it!
I have an old 1965 chevelle with a 327 and sheered the HB pulley bolt , I need to drill and re-tap.
Can I rent your guide to drill it????

I can't reply by PM until you make a few more posts- - - -forum rules to discourage spammers. Drop me an email at [email protected] with "drill guide" in the subject line.

Jerry

You might also try a left handed drill bit. Sometimes they will grab the bolt and back it out.

Thanks for email Jerry I sent you email about special Drill guide and greatly appreciate any help. I am new here so I understand about PM. I am not spammer.
Thanks. Brad

I am so happy to read this post and find you guys. I live in Hawaii and just recently bought my 1950 chevy panel. I need to drill and tap my crankshaft to accept my new 2 groove HB..I am a newbie to this forum and not really sure how to get in touch with Hotrod Lincoln? I believe he is the guy that has the tool needed to do this install. Thank you for your help.

Aloha, Tim

If you have a drill and a tap you can do it by hand... its not a super critical operation. But the guides he has are a good deal for the rental.

Hey Jerry would you please PM me with the information on how to borrow your crankshaft drill an tap guide.

Thanks

can this be done without taking the radiator out?
i'm doing the 54 car engine in a 53 truck.

thanks
rolf

rolf,

If you have the clearance shown in a picture at this link, that person drilled/tapped with the radiator in place.

I do not think I could do in a 1954 truck, but a 1953 truck might be different.

tim
i'll have to look. i know i don't have that much clearance but i believe i have some.
shes only got the fender skirts and the lower radiator baffle on the front end.
push comes to shove i can take out the radiator.
i'd like to save that antifreeze though.

thanks
rolf

Remind me NOT to loan a tool set to somebody with only four posts! It never came back! At least I got to keep the C-note deposit!

Jerry

Jerry, did the C-note cover the price of the tool plus shipping? If not , maybe you need to increase the "deposit". We don't want to see you get mad and quit offering to help.

Yes, that's why I raised the deposit after two sets of tooling stayed gone for several months. It used to be $50.00, which was not quite a break-even situation on parts, and didn't cover lathe time to make all the parts work right. I refund $75.00 when the tooling is returned in good shape, and I still have 3 sets on hand.

I've got a couple of other projects in the pipeline, one of which is a machining jig for getting a set of Babbit rods ready for insert bearings. I'll leave the big end of the rod about .002" undersize, and let my friendly local machinist finish the job with his Sunnen hone. I'm not quite ready to spend over $5K for a rod hone and tooling for the occasional rod converting job. The boring jig will also serve as a rough-out tool for changing the bore size of a Babbit rod prior to scrape-fitting it and shimming for clearance. I just bought two Ebay rods for 99 cents plus shipping, but they're .040" undersize. With the boring jig, I can make 'em standard, 10, 20, or 30 under to fit whatever crankshaft I'm working with.

Later on, I'm considering getting set up to pour Babbit, such as the main bearings on the 1929 Model A Ford engine I'm rebuilding. At least Stovebolts don't have poured main bearings!
Jerry