390ci engine timing questions

Pscarlato

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What vehicle(s) do you drive?
1959 coupe deville
Hi, new to this forum and happy to be here. Can anyone give some guidance on timing for my 59 coupe with a 390 engine. I switched from ported vacuum to manifold vacuum. I set initial timing to 5 BTC as per the book. Mechanical timing adds 20 crank degrees and it hovers around 25 degrees BTC. Seems to run fine. With vacuum advance canister hooked up it adds about 12 crank shaft degrees so it ends up at total timing of 36 degrees at about 2500 or 2800 rpm - somewhere around there. Given it’s a high compression engine (10.5:1) and it’s a big heavy car, does this sound right? I see posts all the time saying it can go up to 40 or more degrees total advance. I want to avoid detonation. Running 93 octane. Any guidance on this timing would be helpful. Thank you.
 

Caddylackn

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I dug out my Cadillac factory shop manual. Forgot I had it.
The mechanical adds only up to 8 distributor degrees and the vacuum advance is up to 11 distributor degrees. I will try to add some photos. My shop manual is a '61 but it should be the same as a '59 as there really are no mechanical differences between the two years except yours has the old style oil filter, mine has the spin on type. I have the factory mechanical advance and vacuum advance curves. I will try to upload them.
 

Caddylackn

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Here are the factree specs and curves on the 390 distributor

As you can see, that total timing advance could be over 43 degrees total timing at 4,000 rpms with 16 inches of mercury vacuum if initial timing is set at 5 deg BTDC.

IMG_1117.JPGIMG_1118.JPGIMG_1119.JPG
 

Pscarlato

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What vehicle(s) do you drive?
1959 coupe deville

Darius

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Bro. Caddylackn,

You just gotta love old Service Manuals! They have details found no place else!

d
 

Caddylackn

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This is a big help. Thank you for taking the time to find, post and answer my question. Very much appreciated.
Let me know if you need any other pages or sections scanned.
I bought this manual on Ebay like 20 years ago. It is almost 60 years old but the pages are all like brand new.
 
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