Distributor question

[Tim7139]

I've been running an MSD 8594 on my FE built to about 500HP with a Quickfuel 780.
Now I must say that while Ive really experienced no issues to speak of and drive the car without thrashing it, Ive now read 2-3 very well done pieces by long term auto engineers that state in no uncertain terms, for anything other than straight race applications you really want a vacuum advance.
Even though I tend to not fix things that aint broke, Id be interested in opinion/experiences.

[tcabece427]

Hopefully I can answer your question. First off you need to understand that gasoline "burns", it does not explode (not nitromethane). That means it takes a few milliseconds for the gasoline to reach full burn. This is the reason most engines are set to fire a few degrees Before Top Dead Center (BTDC), typically 4 - 6 degress. When you set you initial timing the engine is turning over at idle RPM fairly slow (and warmed up). With mechanical advance what you set it at is what you set it at. However when you're using vacuum advance then you attach it, after initially setting your timing. It advances it a little more typically from 4 - 6 to something like 8 - 10.
Another thing about gasoline is the different grades. Higher octane gasoline not only has more power but burns faster. Requiring less timing advance. Now today's gasoline there isn't a lot of difference in octane, usually 85 - 92. Vacuum advance works better for lower octane gasoline. Vacuum advance also "buffers" the advance based on load. If you open the throttle wide open your vacuum drops to 0 therefore your advance drops to the initial 4 - 6 degress BTDC. But when your engine is turning over faster than idle you actually need more degrees BTDC because you piston is moving faster but gasoline still burns at the same rate. Mechanical advances more (up to a point based on springs and weights) based on RPM.
From a strictly street driving and this means typical commuter, running to the grocery store driving. Vacuum advance makes more sense from a fuel economy and warranty perspective. But Cobra's and specifically 427's are not about fuel economy or warranty. Their more about fun driving and occasionally getting your foot into it. Certainly for all out racing Mechanical advancers are a requirement. Additionally with high lift overlapping CAMs these typically affect vacuum. Using a Mechanical advance probably makes sense based on your CAM more than race driving vs. commuter driving.

[r67cat]

Recently discussed on the ignition forum. All the answers you are looking for. Rick
vac advance or not for FE Cobra

[RICK LAKE]

Tim 7139 Tim My timing for my fe is controlled by my FI system. The timing is locked out in the distributor. Timing controlled by ecu. Base is 10 degrees.
Heres the issues, Does the motor knock, ping, backfire out the intake or exhaust on coast down or hard hit to WOT? Do we have an A/F meter telling us A/F ratio out the tail pipe? What color are the spark plugs looking like? Are you adding a octane gas booster? When the motor is hot, does it start easy or a problem? If it doesn't have any drivibilities except for low mpg. Leave it alone.
If the camshaft is a 600" + lift monster in your motor and the motor only is pulling 10-13 hg you will need an adjustable vacuum advance with a soft setup. Yes a vacuum can will help stablize the signal. You may pickup 1-3 mpg. I don't have the size of your motor.
The other sensor I would have on the motor is a knock sensor and see where the motor is happy running and in a safe range, Reading of a knock sesnor would let you play with the timing without damage or pre ignition to the motor. Depending on where you live some placed change the fuel for different times of the year. We have 4 -5 different fuel changes in the NE area.
Here another thought, play in the timing chain. When new the chain is tight and no slack. With miles on them, they stretch and the timing starts to float. Gear to gear clearance between camshaft gear and distributor gear. this has effects on the timing.
If the motor is running a little soft and the MPG's are not bothering you, leave the motor alone. If you are looking for more power, better MPG, or little better drivability then switch. You can always swap back if this doesn't work out for you. Be careful with the ful timing at 36-38 total. More than this could be trouble. Rick L.

[Tim7139]

Well, as indicated, my setup is pretty solid, I have no issues to speak of. This engine was completely Dyno'd when switch was made from a Holley to the Quickfuel to have all properly jetted etc. So while I'm comfortable that I'm set pretty good, the previous thread was very good and I look at it as a learning oppurtunity as much as anything.
The milage thing is a non-starter for me, nobody, I assume, has one of these things for great milage IMHO.

[RICK LAKE]

Tim 7139 Gald you are happy. I don't know how weel your cap and rotor are holding up but this is a issue with msd. The carbon connact in the cap, breaks off, falls out, turns to power. Rotor, depending on which coil you are using burns a hole in the spring end or the plastic gets hot and one of the retainer bars to keep the rotor plate in the correct position melts and bents or breaks off. I run the "E" coil and have lost 1 cap and rotor over 15 years. This coils is more for racing than street. IF you travel in the car, a SMALL tool box with the basics of spare, cap, rotor, and distrubutor sensor are great to have if you break down on the side of the road. repair in 5-10 minutes or call AAA for towing. Wrecker guys with roll back do a good job but have yet too see them not rub or do small front spoiler damage to a cobra or vette. i also havw spare 6AL boxes (2).
SEcond note coils, this applies to oil filled coils mounted on a motor or horizontal. IN the old days yes they mounted them on the motor. Ign output for spark about 30-35,000 volts. Today 80,000 is not out of reach. There have been guys on the club have coils blow, or loss spark when car has been running for a while. IMO Oil coil is the same as 50 years ago except for double the output and this creates alot of heat. With coil up and down oil level raises and lowers to cool windings. Some coils used to have a vent. Vibration of the motor was also a oil killer from the vibrations and no hot days would cause a foaming inside and again kill the coil and give a hot spot and kill the winding in side. Coils laying on there side has 1/2 of the winding not being cooled and again you have hot spots. Mounting the coil vertical is still alot better than horizontal. Off the motor another plus.
If you look up some old threads you will find that some of the guys are using standard caps with solid center piles and heavy duty rotors. They paint the caps black to look better than red or blue. Have a good day. Rick

[Tim7139]

Rick, Thanks for the heads up, I have researched most of the stuff you listed. My distributor seems to be holding up well, no obvious heat/wear issues with the cap or pickup. About the only thing I have issue with is the electric pickup with mild corrosion issues, which I've cleaned up. Mine dates to when they were not clearcoated and I have a spare, but so far, so good.
Using a MSD blaster coil which is vertical off the front of engine, however, in my somewhat short time with this car, excessive heat does'nt seemto be an issue and I see no heat degradation.
About the only issue I have at the moment is playing with the Quickfuel electric choke settings and fast idle cam, but I think that It takes a bit to get everything humming from cold because I run a fuel/water seperator, filter, system and have been told it takes a few seconds to get everything fully primed. Makes sense and it's really not a major issue.
Thanks again for the input.

[Tim7139]

By the way, although this is off topic, since I mentioned it, how many of you guys run any type of fuel/water seperator/filter systems in your cars?

[RICK LAKE]

Tim7139 Tim some of the guys run the large fuel filters that looks like an oil filter. I don't allow my fuel to stay long in fuel tank. I run system dry for winter and leave 5 gallons in it with stablizer. Have not had to clean injectors in 15 years. Pressure 48 psi and fires up on 2nd rotation.
Mild corrision in distributor. GM sells die electric grease in a little 2.0 oz white container. Blow out inside distributor. NO cleaners. Want to add a very thin covering around module and plate.Works as a heat sink to help cool module too. The good stuff is non conductive. The last couple of years the quality of metal has dropped and connectors are failing at a high rate. They can't take the ampage like the old ones. The littlest bit of corrosion and a problem happens. I will get you the # if you want to get some from GM. There are different grades of this stuff. It's not the same as brake pad grease. That's a die silicone grease. Couple of wing nuts tryed this and had problems.. Any way later. Rick

[Tim7139]

Thats what I used, Wurth die-electric grease. I use the Mercury filter system which uses the large filter but is in an unobtrusive location.
Its not so much my practices but the fairly high rate of water contamination in lots of underground gas tanks and unintended contamination. Its a higher risk than most appreciate.
Anyway, thanks again.