2 bolt crab on a 21 stud question
 

Hi guys. I ordered a rebuilt 2 bolt crab distributor from Bubba. I have a 3 bolt cover and a 2 bolt cover. Can I just bolt the 2 bolt cover on and be good? My cam has a fiber pressed on gear. Just want to know what all I need to make the swap.

Re: 2 bolt crab on a 21 stud question
 

Nope, you can't just bolt it on. The distributor housing is "deeper" on the crab than on the authentic helmet style and as such the crab must be spaced outward to accommodate this.

Re: 2 bolt crab on a 21 stud question
 

speedway has the spacer. most, mine and others i have heard of, require a little trimming around the vacuum port. not a big deal, a few swipes with a file. i cant remember, but i think it hits a timing cover bolt or something. check the fit when you get it.

Re: 2 bolt crab on a 21 stud question
 

Here's the 2-bolt spacer at Speedway. Click the link below! DD


https://www.speedwaymotors.com/Flath...cer,25074.html


https://content.speedwaymotors.com/P...b4aafaefa1.jpg

Re: 2 bolt crab on a 21 stud question
 

Ok cool that is not a bad price at all to make it all work.

Re: 2 bolt crab on a 21 stud question
 

You also have the option to stay with the original, to that 21 stud engine, three bolt cam gear cover, and go with the spacer that bolts to the three bolt cover, and accepts a two bolt distributor. When going this way you could initially go with the two bolt crab style distributor, but quickly change back to a three bolt style distributor if you ever wanted to go back to your original distributor. This is the option I prefer to use on my '35, 21 stud engine so I can run my two bolt Harmon Collins distributor with the 3 to 2 bolt adapter, or quickly switch back to the stock 3 bolt distributor, if/when I ever care to do so, without the need to change the timing gear cover. Its mostly about flexibility for me on long distance touring.

Here's a picture of the late, great Dick Spadaro's reproduction offering of a three bolt to two bolt adapter for mounting a crab style two bolt distributor on an original three bolt timing gear cover used from '32 to '41.

Re: 2 bolt crab on a 21 stud question
 

I run a crab distributor on a 3 to 2 bolt adaptor on the 21 stud Pilot motor in my 33 coupe.

Re: 2 bolt crab on a 21 stud question
 

Re: 2 bolt crab on a 21 stud question
 

You can also run a late style 49/53 dist with a gear drive adapter and the late front cover. However your cam protrudes out from the cam and the adapter must be clearanced or the cam ground down.. Not an easy project. and the crab distributor is a good one.

Re: 2 bolt crab on a 21 stud question
 

Hey guys if I am going for optimal clearance, meaning distributor as close to the cover which one do I use? I have both a 3 and 2 bolt cover. I think the 2 bolt cover and spacer will get me closer to the engine. Reason I ask is because I am running a ‘46 crank gear, fan with hub and generator. I don’t want the crab pushed out to far to interfere with the fan belt.

Re: 2 bolt crab on a 21 stud question
 

Vanspeed: What cam do you have in it? If the 46 type cam then the 2 bolt cover and the crab dist. will bolt right on. No spacer required.

Re: 2 bolt crab on a 21 stud question
 

So you're running a '46 front crankshaft gear on....which year crank shaft?? So...which cam and camshaft timing gear are you actually using in your 21 stud engine?? There are what's known as long and short cams, and depending on which one you have, will determine if you need a distributor spacer or not. Your first post says... press on fibre timing gear, which usually/normally means you have the long style camshaft, but let's make sure before we attempt to answer your last posted question....

Re: 2 bolt crab on a 21 stud question
 

Just looked and it is the press on type fiber cam gear.

Re: 2 bolt crab on a 21 stud question
 

Yeah I know you are thinking why a ‘46 crank pulley and fan? I am fitting a 36 LB engine into my ‘29 A coupe and I needed a mechanical fan that was in the center of my radiator.

Re: 2 bolt crab on a 21 stud question
 

In that case the two bolt cover with the spacer or the three bolt cover with the three to two bolt adaptor will both give the same result. They are both designed to mate a crab distributor to a long nose (as in 21 stud with a pressed on fibre gear) cam.

Re: 2 bolt crab on a 21 stud question
 

So they both then must push the dizzy out 3/8 of an inch then correct? To me the 2 bolt to 2 bolt spacer is better looking than the 3 bolt to 2 bolt spacer. I didn’t know they both push the distributor out the same amount.

Re: 2 bolt crab on a 21 stud question
 

Vanspeed, you said '46 crank gear....so I'm guessing you really meant '46 crankshaft pulley?? Or am I confused??

"Correction, I thought you were looking for max fan to distributor space for using a crab vs. helmet type distributors.

I believe the crab style distributor with spacer would give you the most space between fan and distributor, with your present engine construction.

So, if you're only talking crab distributor and long cam, the best you can be is whatever space you have using the crab and one of the two spacers, with the appropriate timing gear cover.

To get the maximum space, you would need to go with the short cam, bolt on camshaft timing gear, and two bolt timing gear cover, as I believe Mart has already said.

Re: 2 bolt crab on a 21 stud question
 

The distributor will only correctly engage with the cam at one spacing. Both setups should give you this spacing.

The ideal scenario would be to swap the cam and go direct two bolt and no spacer.

Re: 2 bolt crab on a 21 stud question
 

The only advantage that I can think of at the moment, with the 2 to 3 bolt spacer, 3 bolt timing gear cover is...if your ever wanted to quickly go back to a 3 bolt helmet distributor. Which is the best way for me, since I carry both 2 and 3 bolt distributors when I'm on long distance, possibly cross-country, tours.

Re: 2 bolt crab on a 21 stud question
 

I don’t think I could ever get a stock helmet back on because of the ‘46 fan setup.