Differences Between Small and Big Block Distributors
Apart from the differences that exist with distributor shafts (plates and weights), as well as the vacuum advance components, is there any dimensional difference between a Chevrolet small block and big block distributor? Specifically, can one interchange the same distributor between small and big block engines (understanding the calibration might not be correct for the specific engine application).Thanks In Advance,Rob Vanderhoeven
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Rob
SPEAK YOUR MIND, but ride a fast horse. -- Anonymous -
Re: Differences Between Small and Big Block Distributors
Rob------
Completely interchangeable with one slight caveat. 1965-66 big block distributors have a "half round" annular oil groove on the bottom. I would not use one of these in a small block. However, distributors with a "full round" annular oil groove (which includes the vast majority of 62-74 Corvette distributors) can be used in either small block or big block.In Appreciation of John Hinckley -
Re: Differences Between Small and Big Block Distributors
Joe--THANK YOU! As always, I truly appreciate your assistance/comments, and always hope for your knowledgeable response(s). Anyway, the reason I asked the question originally, was because I do not know what distributor is currently in my car, other than it is a Corvette tach drive distributor; and did not know if I needed to get a different distributor when I perform the "big block swap". I will look for the oil groove on the bottom as you describe. Thank again. RobRob
SPEAK YOUR MIND, but ride a fast horse. -- AnonymousComment
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Re: Differences Between Small and Big Block Distributors
Rob -- Here's what you should look for when you remove yours. The one on the left has the partially filled oil groove; on the right is for all small blocks and later big blocks (according to current majority thinking).
Ignore the white plugs -- because both of these are transistor ignition. Also ignore the gear teeth direction 'up to the left', as this is a reverse-rotation distrib.
P.S. actually, it's driven off a reverse-rotation (gear driven) cam; the with this gear the distrib. will then rotate in the conventional direction (clockwise when viewed from above).
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Re: Differences Between Small and Big Block Distributors
Wayne--You're awesome! Thank you! A picture is worth a thousand words! As an aside, the quality of some of the photographs shared on this website is truly amazing; and this example of the two distributors is such an example. It will be very easy now for me to identify what is in my car. Thanks again!RobRob
SPEAK YOUR MIND, but ride a fast horse. -- AnonymousComment
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Re: Differences Between Small and Big Block Distributors
Michael -
Because the left hand didn't know what the right hand was doing between two different engine design groups. The small-block guys bungled the design of the rear cam journal and bearing and distributor annulus oiling in '55-'56, and fixed it in '57. In that grand tradition, the Mark IV design group also bungled the design of the rear cam journal and bearing and distributor annulus oiling in '65-'66 and fixed it in '67.
A full-annulus distributor will work just fine in any big-block; a partial-annulus distributor will result in no oil to the lifter galleries if it isn't oriented within the range of motion permitted by the partial annulus. I'll quote from the Chevrolet Engineering instructions on how to assemble the Mark IV Can-Am engines:
"Install distributor (1111263 - transistor with downward thrust bearing) in block so that the dwell angle window faces forward towards the front of the engine and the rotor points toward contact in cap for the #1 cylinder. If the distributor is not installed reasonably close to this position (25 degrees either side of engine's centerline), the cast partial oil annulus in the lower distributor housing will adversely affect the oil flow in the engine."
None of the above monkey-motion and cautions are required when using a full-annulus distributor - you can install it oriented any way you like without affecting engine oiling.Comment
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Re: Differences Between Small and Big Block Distributors
For future reference of SB/BB oiling see photos in this post...
https://www.forums.ncrs.org/showthrea...230#post778230Comment
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