C2 Distributor for 340 HP car

[Richard S.]

I would appreciate if someone would provide me distributor part information for my 63 340 HP car. In the not so recent past I had my distributor rebuilt. After a recent discussion with a friend who had similar work done some years back and found he did not get the same distributor back that was provided I decided to have a look at what I have (recent look). I did not give this any thought when I received my distributor back after the service.
What I see on the distributor case is part stamped 351. The cam has part number 530. The breaker plate stamping includes:
Patent 2769047
Delco
Not sure if there is something stamped under Delco

Made in USA
Remy

Thanks
Rich

[Timothy B.]

Re: C2 Distributorfor 340 HP car

Richard, I don't know about the 351 on the housing but I can tell you the weight base cam is stamped 724, the weights are stamped 37 and the vacuum advance control is #201. I think the auto cam on the top of the mainshaft is stamped 54. The distributor tag is the same part # as the 300hp engine and ends in 024, I can't remember the first few #'s.

[Bob R.]

Re: C2 Distributorfor 340 HP car

The distributor originally had a metal band around the base with the part number on it (1111024) and a date you can check the band to see if it is correct. However it is easy to swap out the band.

[Richard S.]

Re: C2 Distributorfor 340 HP car

Thanks Tim for the correct part numbers. Not sure what I have. Not sure where to look for the correct components. To bad I did not look into this some years back. One other bit of information I was looking for is the correct clearance between the distributor drive gear and the distributor housing. I have shims and would like to confirm that this clearance is correct. Appreciate any information on this number.
Thanks again
Rich

[Richard S.]

Re: C2 Distributorfor 340 HP car

Hi Bob. Yes this is the one item I have that is correct. Thanks for the confirmation.
Rich

[Timothy B.]

Re: C2 Distributorfor 340 HP car

Richard,

If you are referring to the lower gear that runs off the camshaft the factory production clearance is something like .060, (one hardened shim). If you desire to tighten that clearance I would shoot for approx .010-.015. The thrust is up when the engine runs so the gear runs on the hardened washer but on and off throttle and the gear can move down/up and change timing slightly.

GM didn't seem to think it was a problem, I can't remember ever seeing a factory distributor without the +- .060 clearance but it say's somewhere in the 1963 shop manual .002-.008 but that seems to tight to me.

[Richard S.]

Re: C2 Distributorfor 340 HP car

OK, quite a range of possibilities. Thanks for providing me the component part numbers it is appreciated I have no reference material for finding these numbers.
Rich

[John D.]

Re: C2 Distributorfor 340 HP car

Richard, Tim gave us some very good info.
Basically the parts mentioned are identical to the '63 fuel injection distributor. They share the same cam, weights and springs like Tim said.
Hopefully your distributor was not sold over the counter as a service replacement one.The 530 cam is a SR part.
Contact Don Baker, distributor guru to help you. I am not sure if I am permitted to put his phone number up here.
Bottom gear is as the manual says. .002-.007. clearance
John D.

[Duke W.]

Re: C2 Distributorfor 340 HP car

The last two digits of the cam assembly stamp are the max centrifugal advance in crankshaft degrees. All '63 distributors used the 524 cam assembly, which was good for the 340/360 HP engines, but a 530 would have been better for the base cam engines and that's what GM installed in the '66-'67 300 HP distributors. Live and learn!

High overlap cam engines need lots of idle and low rev advance (see my tuning seminar for all the reasons), so 24 centrifugal with 12 to 16 initial was good back in the day, but if the engine has the OE type domed pistons it might be too aggressive for today's fuel octane in at least some parts of the country, and in this case the 530 cam assembly might be a better choice to prevent detonation if the engine still has the OE CR, but most don't because they were rebuilt over the decades with "low compression" pistons.

The other problem with the OE distributor is that the centrifugal was very lazy and the VAC did not pass the Two-Inch Rule. 1963 was the first year that GM installed VACs on Duntov cam engines, and they just didn't get it right.

The best spark advance map for your engine is the 365/375 HP setup, which is just a matter of light springs and a 8" VAC.

All these Delco single point distributors are assembled from a family of interchangeable parts, and the OE setups were usually conservative and sometimes just outright ill-conceived, like the '63 340/360 HP engines.

So set it up with what works best or your actual compression ratio and available fuel octane, and get a repro tag with the proper distributor number embossed.

Duke

[Richard S.]

Re: C2 Distributorfor 340 HP car

Thanks John. Glad you and others have all the data on parts as related to application. Yesterday a friend provided information on a period correct distributor which I now own. In looking at this distributor I see a cam with a part number of 726. Since this is an old unit with unknown history I will keep it for parts. Fine on the 530 cam. My car seems to run ok with its present configuration I may just try to gather enough parts to build a correct unit. And, thank you for the contact information.
Rich

[Richard S.]

Re: C2 Distributorfor 340 HP car

Duke

Thank you very much for the history and detail for choices based on engine build and gas availability. You have a great memory for detail. Yesterday I picked up what I will call a parts distributor. I noticed that the distributor cam in this unit was marked 726. Now at last I see what the last two digits of the cam number mean. My engine does have the 097 cam. I have tried both aviation and pump gas but not sure if I saw any real difference. No dyno testing. The VAC I have is the B26.
After looking over information in your response perhaps my best choice for my distributor setup might be to just try some variations in my distributor setup and see what performance changes I find. Having some insight on what some of the part numbers mean to performance is a great start.
I could use a smoother idle from this engine.
Many thanks for all the information/help you have provided.
Rich