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I'm fighting an overheating 289 in my '66 fastback. In order to eliminate the possibility, I want to check the mechanical and vaccuum advance in my distributor. It's stock, as is the engine. I've installed a timing tape, and can see that both mechanical and vaccuum advance seems to "work", but are there specs for each? The shop manual wasn't much help, just talked about putting the distributor in a test machine. Thanks.
 

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can you see the complete distributor part number (like c5af-n-12127)? if so, I have an old motors manual that has the specs for 8 different 1966 289's. If you casn find out, I'll post the right one
 
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Great. Here's what I could read off it. C50F-1213 A, then had a 4B I think down below, maybe a date code. Thanks for your help.
 

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Ron: the specs for dizzies are confusing, as they are written for the camshaft or crankshaft rotation, so the rate of increase has to be doubled with RPM. It's crazy, and I can't remember the specifics. Bob Mannel's Small Block V8 book explains how to read the specs and test your dizzy advance. He also gives complete specifications for all varieties of the dizzies.

What I did? Disconnected the vacuum advance and measured the advance via a timing light at various rpms. I did the same thing with the vacuum advance connected. Although I have a Motorcraft aftermarket dizzy, the advance was correct for my particular model.
 

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Ron, the closest that number comes to in my book is a 289 hipo, which isnt supposed to have vacuum advance.....if the car is a K code, it shouldnt be the original dizzy.

If you care to recheck the numbers under a bright light or know which engine code you have and auto or manual tranny, I'll try to help as much as I can!!
 
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You know, my book (the shop manual) showed the same thing. I had the same thought, why the vaccumm advance?? I checked again and that's what it reads. Makes no sense. My car is a C code car, but no clue if that's the original distributor. Any suggestions?? Do you even know how to use the figures given in the shop manual to test it in a running car?? Another poster (Midlife, I think) has pointed me to a book, but I don't own a copy. May need to go buy one. Thanks for your help.
 

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I may be stating the obvious......a "c" code car isnt a hipo, and a dizzy having vacuum advance would make sense

Our dizzy listings may not cover the one you have, but this isnt necessarily bad.....quite honestly each motor is a little different and responds to a little different mechanical advance curve...the vacuum advance can be tested with a vacuum tester and a timing light.

I know that doesnt seem like much help, but it's the truth.

BTW.....Honestly, ignition advance probably isnt your problem......though low quality points and condensor could wreak havok on a motor's performance...when I use points, it's MOTORCRAFT or nothing!
 
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Thanks for the info. I understand that a C code motor should have a distributor with a vaccuum advance, like mine. No clue why it's marked the way it is. Basically, I'm having overheating problems, and one thing recommended I check was the advance. It's "working", I checked it with a timing light, with and without the vacuum line hooked up. I just don't know how to tell if it's working appropriately. I wish there was a way to say if it's giving you X advance in degrees without the vacuum advance (therefore, from the mechanical) and Y advance in degrees with the vacuum advance, then it's in spec and working OK. That's what I'm trying to get to.

I've got a new 3-core radiator, aftermarket electric fan with a shroud (the one specifically made for the early mustang, Dallas Mustang Parts sells it, and still it runs hot. It's been 95 - 100 here in Dallas lately. Without the AC on, it's hitting 215 - 230 per my mechanical gauge. With the AC on, it got hotter, and even overheated once. Am I asking too much to be able to drive this thing in the heat with the AC on? It's my first summer to have the car regularly drivable, and I want to use it!! I used some chemical cooling system cleaner this weekend, and have run lots of fresh water through it to flush it out as well as I can, without pulling the motor. Haven't run it yet since, maybe I'll get lucky.
 
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