Thoughts on Straight 8 Spark Advance

[Aaron65]

When I take my '53 for long highway runs, the temp gauge always creeps up as I drive. Before it was rebuilt and after. It never overheats, probably never gets above 220 (at idle after a freeway run), but it's gotten me to thinking. **It does have a recored radiator***

I've tried jetting up to no avail (other than ruining my mileage).

Looking at my 1954 Motor manual, I notice that the centrifugal advance curve on this engine is 24 degrees at the crank, all in by 4000 engine RPM. Factory initial is 4 degrees, leading to a total (not including vacuum advance) of 28 degrees, pretty weak for a 7.6:1 (maybe) compression engine. I have mine running maybe 6 degrees initial for a total of 30. So at freeway speeds, we're maybe looking at 20-25 degrees of timing, plus vacuum advance (which has a quite heavy spring). I can't advance initial anymore because of the 6 volt starter (drags it down).

My 60s cars all seem to like much more initial timing on today's gas, but their compression ratios preclude advancing the curve too much, so I end up limiting the total by messing with the weights. But the '53, with much higher octane available now than then, seems to have an opposite issue.

I've been thinking of using lighter advance springs in the distributor to get the total 24 degrees in by highway speed. With 87 octane in the tank, I would think the car should easily handle this much advance without potential damage. It should run cooler and have a bit more power too. It might even be easier on that long exhaust manifold by running cooler. Any thoughts, for or against?

UPDATE!!!

Well, I spent a couple hours doing this today...

You have to pull the distributor to do this, because you have to pull the breaker plate to do this...it could PROBABLY be done in the car, but pulling it is a lot easier. It gave me an opportunity to clean stuff up in the distributor too.

I used the heaviest springs in a Mr. Gasket spring kit for GM top advance distributors...they worked great. My guess is that full centrifugal now comes in at 3000 RPM rather than 4000 RPM. It runs the same as it did before, but it makes an odd, loud moan when I floor it at 60 MPH...it may have done that before; I don't often floor that car. No audible pinging, even when flooring it from a dead stop. It's hotter than heck today, too...at least 90 degrees. With the 180 thermostat, it got up to around 200 or so after a 15-20 minute drive, but cooled back down to 185 or so idling in the driveway (using an infrared thermometer on the thermostat housing)...We'll see how it works this summer on my longer drives on hotter days.

[Buick Guy]

Aaron,
The heavier spring that you used will delay the centrifugal advance, not make it come in earlier as you stated. If it came in by 3000 before, it will come in at 4000 now, or were the stock springs even heavier than those?
Doug

[Aaron65]

Aaron,
The heavier spring that you used will delay the centrifugal advance, not make it come in earlier as you stated. If it came in by 3000 before, it will come in at 4000 now, or were the stock springs even heavier than those?
Doug

It was the heaviest spring in my kit, but much lighter than what was in there...

[telriv]

As you bring in the mechanical advance sooner you need to limit the vacuum advance. I don't know excatly what the straight 8 likes, but I usually have FULL advance (32-34*) in by 2400-2500 RPM's & limit the vacuum to 8*-12*. With mechanical & vacuum added in for a total how much is it suppossed to have stock??? By the book??? Use a dial back timing light & you can play till you feel it's best & right.
JMHO

[Aaron65]

Looking at my 1954 Motor manual, I notice that the centrifugal advance curve on this engine is 24 degrees at the crank, all in by 4000 engine RPM. Factory initial is 4 degrees, leading to a total (not including vacuum advance) of 28 degrees, pretty weak for a 7.6:1 (maybe) compression engine. I have mine running maybe 6 degrees initial for a total of 30. So at freeway speeds, we're maybe looking at 20-25 degrees of timing, plus vacuum advance (which has a quite heavy spring). I can't advance initial anymore because of the 6 volt starter (drags it down).

Hey Tom...

According to the same manual, the '53s total mechanical advance came in at 4000 RPM compared to 3400 in '52, but had an 11 degree vacuum canister compared to 6-8 in previous years. So, I'm running the same total as before, just bringing it in earlier. So, at cruising speed, I'm running about 41-42 degrees (with vacuum advance). I'll check it with my dial back, but I'll have to hook it to a 12 volt battery, as the '53 is 6-volt and won't operate that light. Considering that gas was something like 75 octane in '53, I feel like a little extra timing at cruise will be good, but we'll see.