Blown SBC crank question

I am changing from SBC snout to a BBC snout

the RCD crank hub has 2 1/4" keyways per Paco at RCD
the Crank has 1/4 and a woodruff key way

how is this handled?

do you mill out crank to 1/4" or Paco mentioned a step key

help please

it's a Lunati blower series crank BB snout

 

A (blower) crank with only one 1/4 keyway?

Probably so you can run a damper "or" a crank hub.

What size is the woodruff and is it 180* from the 1/4?

 

3/16 standard

yes 180


that is standard on a SBC with SBC snout
but we broke two hubs and ruin a crank and was told we need to change to BB snout

 

I can remember at least one crank we had that the second 1/4" straight keyway was milled right over the top of the existing 3/16" woodruff.

 

Crank

Oddly enough I was looking at my crank key ways last night and, yes you can see the bottom of the old woodruff keyway in the new 1/4" square keyway. They just machined the new 1/4" one right over top of the old woodruff.

Corey

 

Find a machine shop.

A good machine shop shouldnt have any problems with putting a 1/4 key right over the woodruff like SoDak said, I would think that would be better than a stepped/woodruff/square adapter key and easier to machine.

 

do you remember how far back it was cut?
the crank gear is still woodruff key right?

 

Keys

To tell you the truth I was only looking at the hub keys, didn't look that closely at the inboard key for the geardrive gear. Im going to be pulling the crank out of my engine tommorow, I can look a little closer if nobody else chimes in on this.

Corey

 

ATI makes a special 3/16 to 1/4 key if your interested.

Blessings........Ron.

 

yes I looked at a step keyway today, problem with them is they don't fit the woodruff slot.
I looked at making a woodruff key with a 1/4 inch top but was afraid it would not be that strong

thanks for the input

 

I do a few of these keyway mods each year. The 3/16" crank gear key is left alone. The 1/4 keyway is done right over the front original keyway. Then another 1/4" keyway @ 180 degrees.

You will also want to get a front crank support on this piece. The BB snout is a good thing but sooner or later...........

 

thanks Dave, I do plan to have the second KEYWAY cut over the woodruff key plus
I do have a RCD crank support

 

If you're going with the BBC snout on your SBC crank, you should expect another area of problem, as you've now moved the "weakest link" to the crank gear (for the gear drive). I know multiple people who have broken about every brand of SBC gear drive out there. The problem is that when you increase the diameter of the crank snout, you have to decrease the thickness of the crank gear in order for the gear drive to still fit. The only solution I've heard is to toss the gear drive and run a Jesel belt drive instead.

Chris

 

Machine shop

You would be surprised how machine shops around here (Lakeland, Fl) shy away from work like this. I had a blown sbc with a single keyway and not one of the shops around here would touch adding another keyway because they were afraid of the liability of messing up my crank and having to pay for it. I finally found a guy who had his own small shop and did it for me. It was aggravating to say the least!

 

I had my local engine builder send my SBC snout crank off the have the keyway cut and it was not perfect 180 out, had to drive hub on with sledge hammer, guess that's why it broke

anyway thanks to all that has helped.
I am shipping it back to Lunati and they are going to fix it for me

 

I now have the BBC crank hubs in stock with the 3/16-1/4 keyways. These hubs take the RCD style degree wheel.

Call 626 815-8815 9 to 5 M-F PST for more info.

 

dang, just shipped it back to Lunati to have it cut so my RCD hub will fit

thanks for letting us all know tho

 

So if I'm understanding properly You take the pos woodroffe key out and cut a lenthways keyway over the old one? and a 1/4 keyway on the other side so You can run key stock instead of woodroffe keys? I damaged the crank and the hub last year when the bolt worked loose and bent the old keys and welded to the crank.
Steve

 

Steve3410
Yup, you got it.

 

Wow, I wish I would have seen this thread when it started, I JUST went thru all this exact same stuff. I had to do a lot of homework, a lot of machine work, and in the end everything came out BAD-ASS

So starting from scratch.

I have a Cola 4340 crank with SBC snout that I found out could have a BB snout installed onto my crank by Marine Crankshaft (dave at marine is a wizard) Since my snout was good, he turned it down, machined a new BB snout to my specs (overall length) and shrunk fit, and welded to my crank, said they do it ALL the time, even on top fuel cars when they do crank repairs so I will not have any problems.

Needless to say, I get my crank back and there are a few challenges to overcome. #1 is I need a new gear for my Summers brother front dist drive geardrive. No problem, call them up and they have them in stock and ship. I get the gear, install it, dry fit everything and the idler gear is riding on the seal area (if you ran a belt drive) behind the timing gear, and the timing gear sticks too far forward and doesn't get full engagement on the idler gear because unlike a SBC the BBC gear butts up to the seal area, where the SBC gear is counterbored to go over the seal area.

No problem, talked to Rick at S&S, and they had that issue before, said you have to turn that down, grind some radiuses and it will clear. So I get together with my neighbor Steve Woods who has a machine shop in his garage (A-Gas corvette owner/driver) and he turns down the seal area, machines the timing gear like a SBC gear with a counter bore so the gear will move back 1/4" or so, now the problems with the timing gear are resolved.


Now on to the crank hub w/support. RCD's BBC hub is .65" shorter in overall length than the SBC hub, which means the hub/pulley and everything will be .65 closer to the front of the block and nothing will line up. No problem, we machine a .65" spacer, cut keyways into it, and weld it to the end of the hub, machine it all smooth on the OD and make sure the ID is smooth, welded it together on a turned down stock of steel for a mandrel with a 1/4" key cut into it so everything was straight and lined up.

It sounds easy enough while typing this but it was a lot of work, measuring, figuring out, calling people, ect but in the end I'm left with a BBC snout that has atleast 2" deapth of contact area into the hub, cut the front cover to accept a BBC Seal but there wasn't enough meat, so we had to machine an adapter for the seal that bolted to the cover. If anybody is interesd I could take some pics in case anybody is trying to do this also.

But things to think about, you CAN have a BBC snout put on your crank, no need to spend 2k for a new crank like I almost did. Cost 400 bucks from Marine Crank www.marinecrankshaft.com

Your timing gear will not sit back far enough, so you need to make sure you specify that the seal area is turned down, counterbore your timing gear to move it back, extend the crank hub or run a spacer, make sure you have your snout built with 3" overall length from seal area to end for maximum contact area inside of hub.

As for Keyways and woodruff's they are all standard, size/location, ect. 1/4" double keyways for the hub, with a woodruff key behind them for the timing gear.