Hi all - hope everyone is having a great holiday season. My car is away for the winter, but i'm still working on it. I bought a spare distributor and I'm looking for some info.
1) I understand that my '51 Hornet should take an Auto-Lite 1AT-4009A, but the one I bought is a 4009B. Does anyone know if there's a significant difference between the two (i.e., can i use a 4009B in my 51 Hornet)?
2) Does anyone know of a competent distributor re-builder - someone who will check the run-out on the shaft and vacuum and centrifugal advance curves, etc?
3) I'm thinking of doing this myself anyway. How does one drive out the pin in the shaft...or better yet, how does one put a new one in?
4) How does one tell the difference between any of the various vacuum advance chambers? My car is supposed to use an 1AT-2023RD. Also, what does the little number stamped on the link mean? Mine says 3.5 on it. Does that mean anything?
5) Check out the set-up I used to measure how many degrees the vacuum advance imparts. I set up a dial indicator to measure the liner displacement of the link at various vacuum settings. The max displacement was only 0.040". Then, using a radius of 1.25" from the center of the distributor to the link x 2 x 3.14159, I was able top calculate a maximum advance of 1.83 decrees (measured at the distributor). This is only half the spec, so that's why I'm wondering how one knows how to identify the right vacuum advance canister.
Thanks all you Hudson nuts out there.
Mike
In reference to getting the slop out of the centrifugal weights, and rebuilding dizzies, I hear Mr Maas offers this service. I did my own.
If you are referring to the gear pin it is driven out, and peened back on. But removing the main shaft from the dizzy housing requires removal of a c clip- don't go hammering til it is removed.
Both IAT-4009A and IAT-4009B are shown in the 1948-1952 Hudson Service Manual in the online library @ hetclub.org/burr/lithomepage.htm
Open the manual and type in IAT4009 in the search box. Click on 1948-1949 Manuals file.
There's a 1951 shop manual in there as well - but that lists only IAT-4009.
Hudsonly,
Alex Burr
Hi Alex - thanks for the heads up. I checked the 48 - 52 shop manual and found the reference to the IAT-4009B distributor. It seems identical to the IAT-4009A except that the vacuum advance come on at lower vacuum. That certainly answers one of my questions. Mike
The number stamped on the vacuum advance is for the degrees that advance carries. From 48 to 54, the engines all take very little advance. Don't try to advance it past Hudson's numbers, a good way to burn a hole in the pistons. Walt.
Hi Walt. Thanks for the reply. According to the shop manual, I should get a maximum vacuum advance of 3.75 deg, so this sounds like the right unit for my car. The manual indicates 3.75 deg of DISTRIBUTOR advance though, and I measure only 1.83 (by my dial indicator plus a little geometry). Does the shop manual mean a max of 3.75 deg as measured on the flywheel? It might be a coincidence that my 1.83 x 2 = 3.66 deg, which is close to the spec of 3.75.
The advance is the degrees of crankshaft rotation, NOT the distributor, which turns half the number of crankshaft revolutions. So yes, the distributor breaker plate will rotate about 1.8 degrees at max vacuum advance.
Thanks for the confirmation of this question. So, that leaves only my last question regarding the pin in the distributor shaft. Once I knock that out and clean up everything, are there any tricks to installing a new one? I see the one in there now looks like it was peened over with some csort of square pattern. Thanks again. Mike
I just reinstalled pin and peened it in place with a punch
Works for me...thanks.
Hi all - OK so now that Winter is over and i had a chance to work on my car, here's the outcome. I took out my distributor and removed the vacuum advance chamber. The number 7.5 is stamped on underside of the link (that goes to the breaker plate). From what i'm reading, this indicates that this provides a maximum of 7.5 deg of vacuum advance. Since the shop manual calls for 3.75 deg maximum vacuum advance, it told me that I had had the wrong vacuum advance chamber on my distributor for years. I swapped it out for an Auto-lite IAT-2023RD (stamped with 3.5 on the link) and re-installed the distributor in the car. The engine runs nice and smooth now, no "fighting itself" sounds at high vacuum conditions (e.g., 50 mph on the flats).
That's awsome, Michael! Glad you got it sorted out.
Hi Russ, et al. - do you or anyone out there know what the suffixes to the Autolite part numbers of the vacuum chambers mean? Specifically, my IAT-4009A distributor is supposed to take an IAT-2023 RN vacuum chamber. I'm doing a rebuild on a space distributor and i see other vacuum chambers on eBay, e.g., IAT-2023 LL or -RM. Any guesses what the two letter suffixes mean? I assume they indicate different vacuum advance curves, such as the maximum advance and perhaps at what vacuum the advance begins to kick in. I'm wondering if anyone has a reference chart that indicates that e.g., "LL" means this and "RN" means that for the advance curve. Thanks, Mike.
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