anderson pms on windsor

[mike94stang]

i've got a 351 roller w/ z303 cam, 68 302 4 barrell heads(called closed chamber, 53.5cc before milling,)should be 10.? cr, was running great untuned w/ 14degrees base, no audible detonation, i put a series 4 pms on it, zero'd out all tables, set base to 10degrees, drove the car, it was running like 9.5 to one af, at wot, so i pulled fuel until it was pretty steady 12.8 to 13.0 from 2 to 5 k, ran great, but was pinging, so i switched from an autolite 45(heat range 5) to an autolite ar33 (heat range 1) plug, no change. drained antifreeze and added some purple ice, not only did the coolant temps not drop at all, it didn't help w/ the pinging, i had to pull 2-3 degrees at wot all through the rpms to stop it. forgot to mention running 93 octane, added +6 octane booster, didn't help, i cant understand why w/ less overall timing, it started detonating unless it was because i leaned it out, any experienced help would be appreciated

[05yellowgt]

I'll see if I can get Mike Bell to chime in. I know he's run a PMS on this Real Street Car.

[mike94stang]

forgot to mention, its around 23 degrees total advance, also may help to add that coolant temp is usually around 200. thanks...

[NXcoupe]

Wow, that's a lot of temp for one. For the other, a cast iron head with such a small combustion chamber is not going to take much timing at all. Keep it towards the 12.5 range of a/f and see if it will take a little more timing. Best thing to do is get it on a dyno and load it, see what the spark is doing. Do you still have your egr and O2's hooked up and functional?

[mike94stang]

yes on the egr and o2s, thats with a 180 thermostat, i'm going to put a better radiator and hi vol water pump soon, i'll richen it up and see what it does, and hopefully get it on the rollers soon.

[mike94stang]

that 23 degrees is at wot under load, on the pms data screen.

[NXcoupe]

wow, that's no timing at all. I wonder what is causing that internally on your engine? Any sharp edges in the combustion chamber? Your wideband could be off too, doubt it, but it's a possibility, are you running unleaded fuel?

[mike94stang]

yeah on the unleaded, I had hardened exhaust seats put in, its a brand new innovate wideband and I did the heater calibration and the open air calibration as the instructions said along with grounding it the way they said. I had to notch the pistons for ptv clearance, but I dont think the edges are any sharper than the edges of the factory combustion chamber, but how do sharp edges cause detonation?(not trying to turn this thread into science class, just trying to figure out how much smoothing I may need to do) thanks for the help Mike.

[facemelter71]

Sharp edge's will heat up and act like a spark plug and cause detonation.

[mike94stang]

wouldnt that be pre-ignition? with 2-3 degrees pulled from the factory wot tune, the detonation goes away, wouldnt it heat up and ignite regardless of ign. timing if it was due to the sharp edge?

[05yellowgt]

pre-ignition=detonation

Just for grins, have you double checked the base timing to be sure it is at 10*?

[facemelter71]

wouldnt that be pre-ignition? with 2-3 degrees pulled from the factory wot tune, the detonation goes away, wouldnt it heat up and ignite regardless of ign. timing if it was due to the sharp edge?

Pretty much the same thing.Your causing the fuel to ignite before you want it to.Mostly due to timing being off.I know that they currently have two different timing pointers.If you have the wrong one,you could be off by a few degrees.The two they have,one points at 11 o-clock and one points at 10 o-clock.I have not had any one definitive answer as to which one came on which motor.

[mike94stang]

http://www.enginelogics.com/detonation.html just something i read the other day, but still confused on the sharp edges, neat write up though.

[mike94stang]

you know, when i backed the base timing off, the pms was already on, it may have been screwing w/ the timing, when i get home later, i'll pull the spout, and zero the timing on the pms, and see what it is, i did make sure i was using the right set of marks on the p.p. balancer.

[facemelter71]

you know, when i backed the base timing off, the pms was already on, it may have been screwing w/ the timing, when i get home later, i'll pull the spout, and zero the timing on the pms, and see what it is, i did make sure i was using the right set of marks on the p.p. balancer.

Yea I have one of those also.I looked at all those marks and got kinda confused at first.Had to re-read the destruction manual.
I bet the PMS has some thing to do with it.

[mike94stang]

i fattened up the a/f to 12.4, added 2 degrees of wot timing all the way through the rpms, w/ the same curve(max timing at 2000, starts backing down from 3500 to 4500, flat till 5500) then added some more, and then some more, ended up at 33 total backing down to about 28, w/ no detonation. Whenever it does, it always seems to be between 3500 and 4500 rpms. seemed pretty good but i definitley need to get it on the dyno to get it perfect. i wouldn't have thought half a point of air fuel would've let it take that much more timing, thanks for all the help, and it was 2 degrees off on the base timing, oops.

[NXcoupe]

Yes, I usually go up and down on a/f ratio to see what a particular combo likes. You would be surprised at how much more power the engine will make at the a/f it really craves. That's a bit rich but if it's liking it, leave it alone. Dyno is your friend on these kind of things.