Got a free '75 245. Have fixed a lot of problems just to get it to run, one of which is that the timing is way off.

But what to time it to? I believe this distributor is one of those with vacuum *retard* at idle. If so, should I be checking idle timing with the vacuum disconnected and plugged? And what is the proper spec? All I have is the owner's manual, which calls for 10BTDC, but there's an official-looking sticker placed over that line that says 5BTDC. What's right?

TIA,

Evan

I agree wholeheartedly with the other posts so far - run as much advance as you can without pinging (within reason, of course!).

On my B21F, I can run 16BTDC initial. With the 19 mechanical, I get 35 max, which sounds pretty dern good to me. This is with 87 Octane CA swill.

Up to a point, higher advance will give better idle, more power, better mileage, and lower temps. Strange but true!

Kyle
--
1980 242GT 197K, 1990 744Ti 113K

Unless the greenies are hot on your trail with emissions tests, etc,
I would set it to where it runs the best, and I would do it with everything
hooked up so you don't have to go back and readjust everything after you
hook the hoses back up. I run mine at about 20° btdc and if they kick back
against the starter or show undue pinking, I back them off till it quits.
Volvos are so sensitive to insufficient advance that I avoid it like the plague.
(Problems related to retarded ignition include overheating of the engine and
even worse overheating of the exhaust manifold and pipe, also poor performance.)
On a number of occasions I have just turned the distributor to where it idles
the fastest and then checked, and found it to be very close to what I wanted.

I realize that the above is not congruent with the manual citations but I think
the engine design and manuals were generated under the watchful eye of heavy-
handed but not exceptionally experienced EPA folks. I like to do what is
quickest, easiest and gives best performance without sacrificing durability.
It works for me.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma

For performance, I'd go with Walrus3's suggestion of fastest idle without pinging/pre-ignition/detonation while going uphill.

The official 5 degree sticker is probably for better emissions. Retarding lowers NOx (and maybe CO and HC).
--
1980 245 Canadian B21A with SU carb and M46 trans

Timing should be checked with vac hose disconnected. Given the age you might want to check everthing is operating as it should in the distributer. Pull vac on the hose with the cap off an see if it moves the timing, also check for leaks in the membrane.

Timing differs per engine type/size etc, find the correct figure for your car from manuals etc.

I assume it has mechanical speed advance/retard as well. The shaft can seize preventing the swing weights from moving. The distribution arm should rotate 10-20 deg when and then jump back. Also with the timinglight connected you should see a change in timing when you rev the engine (vac hose disconnected!).

If you are technically confident, you best of removing the whole thing, take it apart, clean and lub it and put it back. Be carefull not to bend and twist things, it is a little delicate.