ignition timing

[Cpt.Fred]

i checked my timing again, this time with a strobe light and a good friend of mine who really knows about physics.

the timing was aproximately on tdc, he laughed at me and turned the distributor

till we reached 10 degrees advance. he told me with our 95 octane fuel this would be the minimum what the engine would be capable of.

now this is a just a different car i'm having! the motor is really much more agressive, acceleration has improved a 100% (feels like it anyway;))

no sparkping so far.

i'm really curious about the consumption, too. the last tank was bone dry after 146 miles... arrgh. how much does it contain, by the way, about 50 litres?

what timing do you have on your flatties and how much octane does the fuel have over there in the US?

Edited May 30, 2010 by Cpt.Fred
my poor english...

[David Strieb]

US '40s have a 17 gal tank, I run 87 octane (regular unleaded). Maybe your tank has caved in or the pickup tube is bent??. If it's caved in, sometimes air pressure will pop it back out.

[james curl]

Cpt. Fred, Ten initial is going to be too much if your centrifugal advance is working and the vacuum also. Suggest you install a vacuum Gage on your intake manifold, there is a threaded boss located below the carburetor. Check the vacuum you are pulling at the speed you plan on driving your car. You may find that you still have enough vacuum for partial vacuum advance at that speed. Next calculate the RPMs at that speed, to do so you will need to know the tire diameter and the rear end ratio. Probably 3.9:1. The formula is RPM=(mphx3.9x336)divided by the tire diameter. Now look in your manual under distributor and find the specs for both centrifugal and vacuum advance for that RPM to calculate the total advance you are running at your cruising speed. I can testify that 10 initial at 70mph with a 3.55:1 rear and 26.28 diameter tires will result in broken top rings and extruded piston pin bushings in the top of the rods. I took a 4600 mile trip and those were my results. But doesn't the old girl run good with 10 initial advance?

[greg g]

I run 6 degrees BTC. using 87 octane with about a 8.0 to 1 compression.

You can be doing preigition damage without actually hearing a spark knock even with 91 octane. I would back it off a bit. Also timing that far advanced initially will exascerbate a hot start problem if you ru into that situation.

[Cpt.Fred]

james, i'm suspecting the vaccum advance isn't working like it should on my car.

i went for a ride after posting here yesterday and really let the car have it,

just to see how the engine would react.

i came home running a little rough and making little fast paced puffing noises.

idle speed was higher than before as well.

i found an air leak, too. i sprayed brake cleaner on the intake and the carburator base and the car choked, so i guess i'll have to fix that first.

now what i'm going to do is take the distributor out of the car and disassemble and clean it.

i guess maybe the centrifugal advance doesn't go back all the way when dropping back to idle speed.

the strobe light didn't show differences between vaccum/ no vaccum operation,

so i guess the membrane might be gone.

a valve job can't hurt either...

afterwards i'll try going back to 6° and see what it does. does that sound like a good plan to you?

17gal equals 65 litres, that's more than i thought. the tank isn't caved in or anything, but i think the car's consumption is far avove normal.

if i calculated this right i'm having 10miles per gallon.

that's a little greedy for an asthmatic grey wale, don't you think?

thanks for the tips, guys!

i'm still having fun here:)

greetings from berlin,

frederic

Edited May 30, 2010 by Cpt.Fred

[james curl]

On short runs the gas milage is not all that good on the old flathead I/6, without OverDrive if you get 16 mpg on the highway in flat terrain you should be happy. Most with OD do good to get over 20 mpg on sustained runs of 100 miles or more. Your vacuum advance can be rebuilt, there should be some place in your area that provides that service for old cars. Check the springs on the weights to be sure they haven't stretched and taken a set. The weights should be free to move out and the plate should rotate freely on the center bearing. The grease in the bearing gets old and hard an slows the advance process way down. Pull the plate and wash out the bearing then add some assembly lube such as lubi-plate to the bearing. The bearing must rotate freely without any tight spots.