timing/vacuum advance

Without a doubt rotor phasing. Another possibility is the other system the can alters which is pickup gap tho usually that change ain't enough to effect a misfire. It's handy to have a hand held vac pump available for dist work as you can see (& measure) the pickup gap change with more vac applied to the can on your bench. To check phasing cut a 1/2" hole in the top flat of a dist cap 2/3 of the way between the center cap terminal and the #1 cap terminal then shine a timing light straight down in the hole while idling & it will freeze the rotor like a strobe light will do to bodies on a dance floor & see how far around the circumference the tip clocking is from dead center on the cap #1 terminal. You can also make a mark on the top metal perimeter of the dist rim at the center of a cap bulge then take off the cap & see how far the rotor is from pointing dead on to it (rotor retracted & not into the springs & they likely will be retracted if free) & the can will shift rotor phasing CCW from that position on a SB and CW on a Big block. You have that circumferential distance and the radial distance from a too short of rotor blade. If you like math you can get the degrees of the can from the number on its arm and the diameter of the dist housing & C=Pi x dia & divide 360 into the circumference to figure the distance around the arc 1 degree is then multiply that number times the # of degrees the can will shift the rotor around the arc. EDIT the X factor is at what distance does the required voltage exceed the available voltage (that's when it startts to miss) & each ign system is different & required voltage is the greatest at WOT & that's when you want the pickup gap to be close to .008 and rotor phasing to be in the good range

It may sound crazy but I've seen this more than once so here goes. Make sure the wires from the distributor pick-up are connected correctly to the ignition box. If they are reversed (there is a pos and negative) the car will run when you adjust the distributor position but throws the rotor phasing way off. In your case the extra vac can timing will push it too far.

This is all really good info. I'm gonna dig into it this weekend. Thanks guys

So I tried using a different port (manifold) and still the same results. There is something that is weird. When I press on the brakes my idle goes up. I tried it all over from 5 to 30 degrees. Is the mechanical advance enough? Do I really need the vacuum advance connected?

Just leave the can unplugged. Too much b.s. for little gain, imo. Never ran one in any hot rod I've owned.

Not yet. I did a little reading on the mopar performance instructions. I'm gonna start with the set screw all the way in on the vacuum pod (disconnected for now) starting at 5 degrees. Crank it up to 2000 rpm and see whats goin on with my mechanical advance first. It feels good otherwise. Pulls really hard. I'm definitely sold on the whiplash cam. Made my little 318 come alive.

I'd take off the cap & see what cap terminal the rotor blade is closest to then put the cap on & make a mark on the dist metal top rim in line with that particular cap bulge then take off the cap & with a 1&1/4" socket/breaker bar turn the crank slightly till the reluctor tooth is dead even with the magnet & at that point see how far the rotor blade is off from being dead on with the mark you made. The bold text is what I neglected to add to check phasing in my prior post. This ain't quite as accurate as the timing light method but it is very close & will tell you something significant regarding phasing in 5 minutes. Holler how it turns out for you

What's the reluctor tooth?

You might bump the crank CW till the tooth Boogie showed JUST moves past dead center on the magnet (& I'm talking a c hair past dead center) as it fires when the tooth just moves past being lined up dead on centered with the magnet. Im also thinking the NAPA 8 dollar Echlin MO3000 rotor may fix this WO you havein to mess with phasing but first see where it is. EDIT check the gap also (.008" with brass feeler gauge)

Im gonna get that rotor. This is becoming an issue. What causes rotor phasing?

318 whiplash cam open headers: http://youtu.be/7RW-M3mHr7Q

Don't mind the mess

I would check the tooth/magnet gap first. Speaking of the gap not RP you set it at .008" at rest (eng off/no vac) & the can increases it but not to the point where it will misfire but if the gap is too much greater than .008 to start with at rest then when the can kicks in it will increase it past it's "limit" where it will then miss with the can activated. The can changes reluctor gap and RP. A stackup of tolerances in the wrong direction from poor machining can shift it (RP) past it's (functioning) limit.

Ahh..... I'm learning a lot. Thanks for all your help

Yea but it's not just surging. It won't go much over 2500 with the va hooked up. No matter where the timing is set. I can't just let it go without knowing why it's doing it. Maybe it won't help much but at least I'll know

Thanks for all your help rapidrobert. Probably won't be able to get to it till the weekend but I'll be sure to let you know. I'm gonna set the gap and get the new rotor. Hopefully that cures it.

Just out of curiousity what do the plugs look like ? I remember many years ago I had a 6 cylinder Maverick that did the same thing and everything I checked looked good. Then I pulled the plugs and they all had a good bit of carbon buildup on them. It would idle fine and run fine without the vacum advance hooked up and run bad when stepping on the gas with the vacum advance hooked up just like yours. I cleaned the plugs and it ran great Yea it seemed with all the carbon on them they would not handle the extra advance and would breakdown and miss. I know it sounds wierd as I really scratched my head on it but it is the truth. The plugs would not fire with all the advance when the vacum advance was hooked up and with all the carbon build up on the plugs. But like I said I cleaned or replaced the plugs (was a long time ago) and it ran good. Ron

The #1 and 3 plugs were slightly darker than the rest, but nothing out of the ordinary. It's all still fresh and new. Not even 100 miles on the motor.

How many degrees is the vacuum advance adding to the mechanic advance? To check at idle, see how many degrees are at initial without vacuum advance connected. Then connect vacuum advance to manifold vacuum (full vacuum) and recheck degrees. The difference is your vacuum advance degrees. Most vacuum advance cans have plenty of advance built into them since they are focused on economy. For the most part, you will not need it, especially since you no longer have a stock setup. If it runs strong, and power is smooth when accelerating moderately, leave it unplugged.

Focus on the mechanical advance seetings. First find the total advance the engine likes. Then determine what initial degree setting that the engine /cam runs best at idle or idle in gear if auto. Then play with mechanical advance limits and advance curve springs until you get then best acceleration. Stick a fork in it a call it done!
Ron

If you can get the engine to tolerate the additional advance at idle it will help with cooling (as long as it isn't too far advanced of course). At cruise it typically helps with mileage and also cooling (although at cruise this is less of an issue).

Have you hooked up a vacuum gauge? Do that so you can see what your vacuum can is seeing in terms of vacuum and behavior. Having unstable vacuum is not going to do you any favors at idle if attached to manifold vacuum.

Just wondering if you might not have multiple things fighting against one another, or the build is just such that vacuum advance cannot be integrated.

Well here is what I do know. It's a 318 with j heads. I had 120lbs in each cyl before the build. I know this cam is gonna bump that up but how much? It also has an air gap manifold with a 2" spacer. Headers and 2.5" exaust. I just have to mess with it some more. I didn't check to see how much it advanced it plugged into manifold vacuum. I checked for leaks with a can of carb cleaner but it's sealed tight. How do I check if it's leaking on the bottom of the intake? If my vacuum readings are low will that be an indication? I'm at 18 deg now with no va. It's running fine. Still gotta get that rotor and check my settings with the can plugged in.

Ok when it's at 10 deg initial it's at 30 when I plug in the can. Way too much. That's at idle

What you're describing aftar all is said and done is PHASING. For some stupid reason when the ignition fires, the rotor isn't pointing directly at a pole. This isn't too bad, until the vacuum advance kicks in. Now, as the vac advance increases, the rotor moves farther and farther away from the correct pole until it is closer to the next pole and the spark jumps there.

Look at this Ebay link:
http://www.ebay.com/itm/Mopar-Modified-D...tr#ht_777wt_916 to see what the fix is.

I don't know if your particular distributor uses this kind of reluctor, but you need to move the reluctor with respect to the distributor shaft so the rotor is in a better place when it fires, and the vacuum advance doesn't move the rotor too far away from the correct pole.

Setting the gap is fine, making sure the wires are hooked up correctly is fine, but in the end it's phasing that's my interpretation of your problem.

R.

Yep gonna have to get that. Thanks for the link. I have it set up plugged off at 15deg for now.

Well the gap at the reluctor was way off. So I fixed that and bought the rotor from napa. Same results. Funny thing is it's backfiring out the exaust. I'm gonna try my old distributor tomorrow. There was a lot of slop at the rotor when it's bolted in. I'm gonna nail it tomorrow.

Bill have you made a mark on the dist rim or drilled a hole in the cap to see where you're phasing is at? On the rotor/shaft rotational slop is that lower shaft/intergear slot slop or very light springs (you're stretching the light springs when you twist the rotor) and with real light springs you cannot (easily) tell if you're into the springs or if it's the lower tang slop but lets see where you are at with RP first

I just put the old distributor back in and it works. The plate on the new distributor that moves the little transformer deal had a lot of slop. The new one didn't. I could move it up and down. Mostly up. The old one was solid as a rock. Still have some tuning to do but it really makes a difference.