Retimed 440 with dial back light

[AR67GTX]

Given how the distributor is set up, I suspect someone has already been through it and set it up for performance by limiting centrifugal advance, using light springs to speed up the curve, and limited the amount of vacuum advance. A vacuum advance canister that is only adding 10 crank degrees of advance to the idle is a good idea on a car set up with a lot of initial advance and a quick centrifugal advance curve. Otherwise at highway cruise rpm on light throttle the engine could see as much as 54 +/- degrees total advance and the cylinders firing off so early that the engine feels like it’s missing as the cylinder pressures are peaking before TDC.

 

[HawkRod]

i would think if your engine runs lean at idle you would want less timing advance not more ?

No, exactly the opposite. A lean mixture burns SLOWER, so you need to ignite it sooner, so you need more advance.

Now, mind you, when we talk lean we are talking 14.5-15 to 1. If an engine is too lean it can cause damage

 

[mvent]

Worked on it today to experiment a bit. 20* BTDC at 625 rpm in drive, place it in park idle jumps about 200 rpm. Best vacuum I could reach with this timing was 14hg in park dropping to 9hg in drive. I tried both ported and manifold vacuum, with manifold rpm drop from park to drive was more than I like. Connected to ported and went for 30 mile ride highway back roads etc. Ran smooth at 65mph, no bucking, no hesitation at tip in from stop or highway speeds and no pinging WOT or rolling up hills from 45mph. Advance does come in fast but pulls strong without pinging, no kickback at hot starts, IF gauge reads 170 at gooseneck. I’m pleased with how it’s running, time to enjoy. Thanks for all responses.

 

[icetech]

Worked on it today to experiment a bit. 20* BTDC at 625 rpm in drive, place it in park idle jumps about 200 rpm. Best vacuum I could reach with this timing was 14hg in park dropping to 9hg in drive. I tried both ported and manifold vacuum, with manifold rpm drop from park to drive was more than I like. Connected to ported and went for 30 mile ride highway back roads etc. Ran smooth at 65mph, no bucking, no hesitation at tip in from stop or highway speeds and no pinging WOT or rolling up hills from 45mph. Advance does come in fast but pulls strong without pinging, no kickback at hot starts, IF gauge reads 170 at gooseneck. I’m pleased with how it’s running, time to enjoy. Thanks for all responses.

Ported, the way god intended

 

[RJRENTON]

Received an Innova dial back timing light and went to work. Prior to having it I was just doing the bump until it pings and backed off a bit, ran pretty good but was curious what my timing numbers were. Disconnected vacuum, set total to 36* at 2800-2900 rpm, checked at 750 rpm and landed at 20*. Reconnected vacuum to ported for now. Starts fine hot, no pinging uphill under load seems to pull harder when getting on it. Will try manifold vacuum as well just to compare but my thought was 20* idle was more than enough didn’t think necessary to add more with manifold vacuum at idle. Know idea what cam is in it but surely nothing radical. It’s an auto with 3.23 rear gear.

Having a "dial back" timing light is fundamental.....sort of like having a socket wrench set....or a screw driver set......
BOB RENTON