Looking for experiences. I have rebuilt my engine, .080 over, insert rods and mains, using B police head. I timed per standards, can only add about 12-15 degrees advance, then it pings. I checked with a timing light on the setting. Runs strong, just thought I could go a little more than I can. Any input using Brumfield 5.5 head-does it act similarly? Thanks, Dave
spark advance
- Thread starter Dave Dta
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nkaminar
Well-known member
The timing advance is predicated on how fast the air/fuel mixture burns. Several things cause it to burn faster: more turbulence, the correct air/fuel ratio, the combustion chamber design, the load on the engine, and the compression ratio. Less advance is needed with higher compression ratio.
Advance the spark until you hit the knee in the advance curve. This is the point where further advancing the spark will not cause any increase in rpm or power but retarding the spark will cause a drop in rpm or power. You can find the knee at a fast idle (1,000 rpm). Then do the test again when driving the car. The correct spark advance will change with load and driving conditions. Each car is different and will have different optimum ignition advance settings.
Running the engine will too much advance will ruin the rod bearings in short order. It's better to have the ignition one notch retarded from the knee.
Advance the spark until you hit the knee in the advance curve. This is the point where further advancing the spark will not cause any increase in rpm or power but retarding the spark will cause a drop in rpm or power. You can find the knee at a fast idle (1,000 rpm). Then do the test again when driving the car. The correct spark advance will change with load and driving conditions. Each car is different and will have different optimum ignition advance settings.
Running the engine will too much advance will ruin the rod bearings in short order. It's better to have the ignition one notch retarded from the knee.
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Ditto to post 3. Higher compression heads don't use as much advance on the quadrant /spark rod. Some h.c heads run fine at approx. 3/8 to 1/2 down the quadrant at speed.Someone may remind us how much degree advance each quadrant notch is. Listening to engine and frequent adjustment may be needed depending on roadway inclines, load, etc.
Bruce of MN
Well-known member
Here is the stop I made to limit the advance to suit my 6:1 head.
https://www.fordbarn.com/forum/showthread.php?p=1872563&highlight=stop#post1872563
https://www.fordbarn.com/forum/showthread.php?p=1872563&highlight=stop#post1872563
Big hammer
Well-known member
What octane fuel are you using! My local pure gas station went from 91 to 87 octane and now I to can’t advance the timing lever as much! You can read your spark plugs for timing! The closer the color change on the ground strap to the side the less timing needed, google reading spark plugs!
Answering some questions. Crankshaft degrees on NuRex timing tab. Regular gas 87. Sidebowl Zenith no air cleaner. Plugs currently W 18 Y Champions. They are tan in color, running properly. I can change to 3X for testing. Using premium gas would be a waste of money. When new it was around 65 octane. Forgot to mention I'm using a 160 deg thermostat. Car runs at 160 unless stuck in traffic
Synchro909
Well-known member
I decided to put a stop on the timing advance when I fitted a 6:1 head but I didn't like that arrangement. I made a bracket that I screwed to the side of the distributor which has a screw in it that acts like the idle setting screw but acts on the top plate. I set the maximum advance using a timing light and a degree scale on the front pulley. It is a dead stop to the advance - no sloppy spring loaded linkages between the stop and the distributor.
Jim/GA
Well-known member
Switch to a cooler spark plug. I am running the Autolite 3076 plug. This is the plug Larry Brumfield recommended for his 5.9 CR head. A 3X would be cooler than your W16Y.
Try opening the GAV a bit more. Your carb may be jetted a bit lean and that can cause knock under load.
Big hammer
Well-known member
I was at my daughter’s waiting for grandson, the grass needed mowing started their rider and it was low on gas and running bad. Looked around grandson area in the garage and found some gas put in a couple of gallons,After 1/2 hour of mowing the mower ran much better had more power wasn’t bogging down and a nice smell. When the grandson got home he asked how the 110 octane racing gas worked! Ops sorry for using the 12 dollar a gallon gas, but it did make the mower run much much better!
burner31
Well-known member
Way way back in the early 70's when I was in the Military we had a guy that thought it would be a good idea to run some JP-4 (jet fuel) in his car.
Can you guess what happened?
If your guess contains anything that resembles the word "catastrophic" you would correct.
And I'm not even going to go into what another knucklehead was doing with a 30mm A-10 round and a hammer and vise. And yes it did go Boom and blow out the wall of the alert shack.
shew01
Well-known member
nkaminar
Well-known member
The Model A will run just fine on model airplane fuel, which is methanol with about 10% nitro methane and some oil. You have to open up the GAV a little. Expensive. Got me home from the flying field one day in the 1980's when I ran out of gasoline. No change in the spark setting that I can remember.
shew01
Well-known member
The Model A will run fine on 5 year old, 2-stroke line trimmer fuel with oil in it too. I needed to dispose of some very stale line trimmer fuel a year or so ago, and the Model A didn’t complain a bit when I poured it into the car’s tank. It’s an amazing car.
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Sent from my iPhone using Tapatalk
Synchro909
Well-known member
I don't know how many times I have had fuel go stale in the tank, especially during the covid lockdowns. By doing no more than topping up with fresh fuel, the car was none the wiser. Drive on!
Jim/GA
Well-known member
Try the Autolite 3076's. They don't cost much. My HC head likes them.
BillCNC
Well-known member
Does it have an odd popping sound every now and then? Mine has since switching to 3x plugs.
Regards
Bill