1970 LT1 rotor part number

[Kenneth H.]

I have an original Delco distributor cap, and I'd like to get an original rotor. A friend has a D409R rotor that I can get, but I don't know if it's correct. Any help would be appreciated.

Thanks,

Ken

[William C.]

Re: 1970 LT1 rotor part number

Technically it's "correct" but I'd read my article in the "Restorer" Vol 36 #1 before going out and buying a D 409R.

[Kenneth H.]

Re: 1970 LT1 rotor part number

Bill, thanks. I'll take a look at it tonight.

[Kenneth H.]

Re: 1970 LT1 rotor part number

Bill, great article. I don't know how I missed it. I took another look at the rotor and when comparing it to the pictures in your article, the bakelite base looks more like a D-409 than a D409R, however, it also appears that the rotor tip was replaced sometime in the past (if that's possible). I'm going to pass on buying the rotor.

Thanks for your help.

[William C.]

Re: 1970 LT1 rotor part number

As best I can tell, there was no difference in the plastic part between D-409 and D-409R, just the "E" stamp and the shortened tip.

[Kenneth H.]

Re: 1970 LT1 rotor part number

Bill, I don't know if it matters, but if you'll look closely at the two pictures at the bottom of page 16 in your article, there's a difference in the placement of the circles on the bakelite base on the two rotors. On the D-409, there are circles at about 1 o'clock, 5 o'clock and 9 o'clock and also a number that looks like either "A19" or "419" at about 10 o'clock. On the D-409R, there is only one circle at about 7 o'clock, and no number. Also, the end of the rotor tip nearest the center (where it connects to the spring) appears to be round on the D-409 and square on the D-409R. Again, I don't know if these differences mean anything, it's just that I noticed them.

The one that my friend has (D-409R according to the handwritten number on the box) has the same bakelite configuration (i.e. circles, number) as the D409, but the center part of rotor tip is square. I don't have it in hand, so I can't measure the length of the tip, which I assume would be the true test of what I need.

Thanks, again for your help.

[William C.]

Re: 1970 LT1 rotor part number

Typically those marks were from "knockout pins, built into a mold to extract the part from the mold cavity, and for the rotor, there would have been dozens of molds each one having built at a different time, many by different vendors, with subsequent minor differences related to the tool design. Location of the pins could vary from one mold designer to another. Remember Remy was making around 20,000 of that part each day, and I believe the base material is Phenolic, which has a fairly lengthy cure time in the mold. Same with Dist caps, you will see minor variations in the knockout areas due to multiple tools.

[Kenneth H.]

Re: 1970 LT1 rotor part number

Bill, thanks for the information on the manufacturing process. Not being in the industry, and knowing what lengths we go to in our judging process to insure that the part is "correct" in every detail, I guess I sometimes tend to over analyze aspects of the parts that I'm thinking about purchasing for my LT1, without truly knowing what I should be looking for. In this case, I want the part to be correct but, more importantly, I want the 'vette to perform as intended. Hence, the D-409 is what I'll be looking for.

Thanks for your help, Bill. I wouldn't even be having this discussion if you hadn't spent your valuable time to write your article and respond to my question. I've learned something this weekend and I think that's what our discussion board is all about.