mercury advance curves

[Lawrie]

Would anyone have the advance curve info for the 4in stroke mercury.
Thanks Lawrie

[Ol' Ron]

I think this was run by a load a matic dist. which doesn't do well. I use 16* at 2000, with 8* vac adv in a gm dist. I vary the initial between 3-5 *. All this depends on compression and cam, but it's very close. Nice WOT and very good gas mileage,

[Lawrie]

Ron ,are you saying that at 2000rpm you have 16 Deg,
then 8 with the vacuum,is that 8 less with the NO vacuum? ending up with 8 degs?
Lawrie

[Ol' Ron]

I have 16 degrees mechanical advance in at 2000 rpm, in the distributor. I then have a vacuum canister with 8 degs at hi vacuum. The tuning process goes like this. Bring engine up to 2000 rpm and set timing at 20 degrees. Do not connect the vacuum yet. Go for a ride. Engine will be alittle suggest at low rpm, however when you go WOT from 2000 rpm you should be developing maximum torque. Different cams will have an affect on this. Now connect the vac. you will notice that the low speed operation of the engine is now vasley improved, and when travling down the road, you'll have 28 total degrees of advance, thus giving exelent fuel milage. This works very well with a 4bl carb where the orimarys are jetted for econmy and the secondarys for power. It took Richard several years to come up with this and it works. You may have to tweek it a bit, but what the heck. Take care Ron

[Lawrie]

Ron, how do I replicate these settings using a helmet dist on my 99a engine.
I think I have it fairly close,using a 40b advance unit,but at full throtle on accelerating from 50 mph its seems a bit too far advanced,but at light throttle at 30 mph seems a little retarded.this is only minor as it goes very good .
I also too .0150 from the heads above the pistons as this had only.025 clearance.
Lawrie

[Ol' Ron]

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I was asuming you had a SBC dist in the Merc. Can't do much with the crab or Helmit.

[Lawrie]

I will have to get my brain into gear and work on it.
eng has 97 carb 4in crank and .040 bore,

Lawrie

[Ol' Ron]

The stock 11A in good working condition usually works very well with this setup. I'd convert it to an 8BA style ignition so you could run a modified GM dist. But that's just Me.

[BUBBAS IGNITION]

Originally Posted by Lawrie

Would anyone have the advance curve info for the 4in stroke mercury.
Thanks Lawrie

Lawrie,

The Ford - Mercury service bulletin shows the curve to be 22 degrees at 3500 rpm. ( engine degrees) 15 degrees at 2500 rpm...pretty standard thru out the flathead years. I will scan that page when i get the time for the board...


Jim

[Lawrie]

Bubba, How close is that to an 11a curve.
Lawrie

[BUBBAS IGNITION]

Originally Posted by Lawrie

Bubba, How close is that to an 11a curve.
Lawrie

Typically the 11A curve is perfect , however it is pretty quick without the vacuum piston hooked up. Thats the cool thing with the helmet vac pistons it will allow some retard when the engine is reved up slowing down the curve a bit......

[Lawrie]

OK ,thanks ,I will be away for about 5000klms in the 33 in the next few weeks ,so I will make up a dist with the 11a advance and try that.
Lawrie

[Kahuna]

Lawrie
I use the 11A distributor in my 32. I have the Potvin 425 cam, but know nothing of the compression ratio. The engine runs real well with 26-28 degrees total. I have done what Jim (Bubba) suggests: turn the retard piston spring inwards to reduce/stop any ping.
I have just a light pressure on the spinning disc.

[Lawrie]

Have you got a 4 in crank fitted
Lawrie

[flathead4rd]

Kahuna; I've got a Potvin cam in my 8-BA 3-3/8 X 4. It is marked 415 and I can find no information on this cam. Any chance you might have some? It has a pretty radical lope (sounds good) and is a strong runner. Thanks.

[Kahuna]

Lawrie:
My crank is 4.125 stroke
Flathead4rd:
My cam was ground by Pete here on the forum.
He or Bored & Stroked may have some info. for you.