The Dodge Challenger Message Board

I recently orderd a new distributer from a well know´n company that made a better curve built in a Mopar unit whit out vacume can and when i recived it i lookt at the rotor location on it and compared it whit my old unit by simply placing the reluctor tooth strait to the pick up on my old one and it whas almost dead on center of the brass in the cap but the new unit whas not.... This picture shows my Mopar Perfromance that i have been using for 4 year´s !

Here is the cap were you can see were the spark hits on the Mopar Performance unit i have used pretty centerd

And last here is the rotor location on the new unit that show´s that the rotor will throw out the spark before the rotor is in phase whit the brass in the cap so mabee you also should look at some of your distibuters guys im guesing this one will shoot the spark at the corner of the brass in the cap and that maybe isent so good

That's a good point Pat
FBO offer a phasing service.
Phasing of distributor caps and rotors is a basically a free way to make your ignition a consistent performer.
I seem to remember The Daveman doing something with the distributor shaft bush as an experiment, I like this type of modification, all based on ingenuity and enthusiasm

Ade i rephased it my self and made some adjustement to the axial end play of the reluctor unit as it whas to large due to a to thick washer under the screw that holds it in place on top of the shaft becas i dident whant to return it to Don !

I think Dave installed a locking collar at the end of the shaft,,then pushed it in place, remove,,tighten set screw with some lock-tight, the timing was much steadier after this mod. I'm doing the same to my FBO dizzy. Don is something else aint he!

Don't tell Don he gave you something that was not quite right! He thinks he is NEVER wrong and will jump down your throat for suggesting otherwise.

Yes I put a collar on the distributor shaft to limit the up/down play on the shaft as this seems to make the timing more (but not completely) stable. In particular at idle when you are trying to set initial timing and the timing mark seems to be jumping all over the place.

Forgot I had done that to be honest.

Hey Eddie and Dave ! I know of the collar trick Hughes sells them to and i got one from them but the hole in it whas to big..... I will do one my self if it isent stedy whit´this one. I told Don about it and sent him the pic i showed you guy´s and got a lame explenation so im not going to hassel him any more He stopt replying my email.

Pat,, I know you are VERY knowledgeable but I gotta ask. Did you check to make sure there is minimal 'slack' in the timing events by moving the crankshaft and checking the damper in degrees,(X2), in regards to actual rotor movement? With the timing chain, Intermediate gear drive to cam gear, and finally the rotor phasing? This is where I would start. If there is too much machining tolerance 'Stack up" then there is not much that can be done without replacing parts for new ones. Don and dave hughes are exceptionally Malcontents!

If my memory is correct, Rick Ehrenberg might still be selling special reluctors that are machiend with several slots, to allow some phasing.

Eddie wrote:Pat,, I know you are VERY knowledgeable but I gotta ask. Did you check to make sure there is minimal 'slack' in the timing events by moving the crankshaft and checking the damper in degrees,(X2), in regards to actual rotor movement? With the timing chain, Intermediate gear drive to cam gear, and finally the rotor phasing? This is where I would start. If there is too much machining tolerance 'Stack up" then there is not much that can be done without replacing parts for new ones. Don and dave hughes are exceptionally Malcontents!

Yes Eddie i did check that ! The pic im showing is whit the reluctor and pick up dead on there piont and where the rotor ends up in the cap and were my old one throw over the spark in the cap and you can see the the rotor in my old distributer on engine have a delay of about 1mm from center of the brass but thats in phase or good for me so to speak and i found the resone for why the new one was out of phase as they did a bad work when they lockt the pick up as it is a vacume can distributer that they rebuild so im al good now.

fbernard i have seen Rick´s special reluctor on ebay a coppel of times ! He is a great source to that i used several times

Sounds great Pat! Yeah,,I too have purchased Parts for my MoPars from Rick Ehrenberg. He always has great parts,,great price,,and has helpful advice! Pat,, BTW,,,I am seriously considering a new B (Low deck), FireCore Distributor ,,from what I have been researching,,there doesn't seem to be any issues regarding rotor phasing? I have a new MP dist. that Don set-up for me,,but doesn't have vacuum advance,,,which I am adamant about using on a true street/ road trip engine. I just might send it back to him for a vacuum adv. retro fit. Or a new Firecore!

I wouldn't go out of your way to retro fit a vacuum advance. I can live quite happily without one as long as you have a good mechanical timing curve with as much initial as you can get away with.

It always nag me to drive on the road without a vacuum distributor (even though I don't even have a vacuum nipple on my Indy intake). Especially on hot summer days, stuck in traffic jams.
Additional timing really helps with the cooling.

I agree with that entirely Fabien
Vac advance on a street car for me is essential. You can't possibly dial in enough initial to match the 50 or so degrees of advance a vac can will give on the overrun or light throttle.
I still don't entirely understand the use of a non vac dist in anything but a dedicated race car

I just never needed it.

It is low speed in traffic that makes cars overheat due to the lack of airflow through the radiator.

25 degrees advance at idle was enough to stop my car overheating no matter what the conditions.

I might use a vacuum advance on a milder car. But I would be limiting the amount of vacuum advance given to about 10-12 degrees. I did this when I had a milder street/strip cam and only 14 degrees initial in the 90s.

Adrian Worman wrote:I agree with that entirely Fabien
Vac advance on a street car for me is essential. You can't possibly dial in enough initial to match the 50 or so degrees of advance a vac can will give on the overrun or light throttle.
I still don't entirely understand the use of a non vac dist in anything but a dedicated race car

Ade when you are running an engine whit 11.5 of competion on the street whit a LOT of duration you wouldent mind loosing the vacume can ! The vacume can responde to slow so detonations will likely be more of if you just floor it from light throttle.

Eddie i havent seen the firecore distributer but i gues there nice if you say so Mopar Performance made a state of the art distributer whit a manual tach drive that use same cap/rotor as Prestolite that are true bearing on shaft if i understand it corekt whit a nice fast curve that suite auto trans bb whit snappy cam and i have one that is in the pic for you ! The resone im not useing this one right now is becas i dident whant to send it to Don fore re curve service so i orderd the parts i need to do it my self later.

Don just fits a thin slotted plate in over the weights. Easy to make.

If you measure the amount of mechanical advance in the distributor and the length of the slots the weights move in, you can work out how many degrees per mm movement the weights give you. Cut a plate to suit on the smaller side and then test. Open up the slots until perfect. Then all you have to do is change the springs to give you the rate of advance you want.

Yes it is a bit of a time consuming job if you have to do the testing on the car. But still really only a Sunday afternoons work.

So it's the slowness to respond then that makes vac not so popular on more extreme street engines

I used an FBO limiter plate on my 440 and set the initial at 20 deg, installed the plate at the 14 deg slot, total mech adv 34 deg and 18 deg of vac, 52 in total. Runs like a dream on the road and broke into late 12's last time out with everything hooked up on street tyres, 3.23 gears and appalling smoking 60 ft times of 2.3 seconds.
I know there's a half second to come of that on headers and sticky tyres.

Adrian Worman wrote:So it's the slowness to respond then that makes vac not so popular on more extreme street engines

I used an FBO limiter plate on my 440 and set the initial at 20 deg, installed the plate at the 14 deg slot, total mech adv 34 deg and 18 deg of vac, 52 in total. Runs like a dream on the road and broke into late 12's last time out with everything hooked up on street tyres, 3.23 gears and appalling smoking 60 ft times of 2.3 seconds.
I know there's a half second to come of that on headers and sticky tyres.

Yes Ade becas lets say your runing the engine at about 2200rpm and the vacume can is giving you around 50 deg BTDC and you just floor it the can will maybe need about a half second to fully let go youl have some pings in your engine whit like what i run whit 11,5 of compresion ! Im not trashing it and could run it if i just drive along on the road but as soone as i have to drive past a car fast i need to unhook the can i do not have any heating trubbel so far even if im standing still for a long time on idel.

Yes Dave i have seen the parts Don use do recurve and i did order that set he is selling to the race distributer maynly becas i whant to save some time making it my self becas i always have so mutch extra work in the macines at work and so littel free time so a vacation in April is welcome right now and i will just have to do what i like for 3 weeks !

I wonder if the delay is actually caused by the mechanical aspect of the distributor plate or the fact that it's using ported vacuum? I know that Don is an advocate of using manifold vacuum as am I. A distributor machine, (King or other setup), can show the delay in degrees. I like that Tach drive distributor Pat! When the engine is on light throttle or closed throttle,,the mix is too lean and needs as much timing as possible. New cars use as much as 60 degrees! This keeps the chamber much cleaner and the valves/rings last much longer! Either way,,thanks for showing that Pat! I will check this out when the time comes and post pics of whatever set-up I decide to use! ( Don's or a new Firecore)

I would've thought that the most modern performance distributors would be able to combat any advance delay, mechanical or vacuum.
I assumed that those MSD ignition in cap distributors were beyond all that?

The MSD digital (Small Block only),,might do that,,don't know for sure, Ive never had one apart to observe the advance mechanism whether it's activated by RPM and a sensor or strictly mechanical. But Pat is correct,,the advance rate combined with rotor to tip position is dependent upon both centrifugal force and vacuum and this can delay the advance rate enough to place the rotor tip in an incorrect position. Add in friction, bad design ectt and major detonation can result which is why I mentioned the FireCore dizzy. I will have to research this further when my time comes for ignition set-up. I don't want to invest a lot of cash,,because eventually I want to use a FAST-MAN XFI,,,of course I'll have to use a dual pickup dizzy,,but the spark advance is strictly PCM controlled and very accurate.

Eddie wrote:,,but the spark advance is strictly PCM controlled and very accurate.

That's the way to do it!

The design of our muscle car distributors is over 100 years old now. They didn't change much until the points were replaced by a transistor in the 70s. We had put a man on the moon and that was the best advance in automobile ignition since before the first world war?

Dave i get i kick out of making old parts work and make them even better thoe they are from the past always look back before you go forward to hi tech becas those are the routs thats tells you how it works !

From what i have learnd about the vacume cans they keep the engine cooler on idel becas you need to burn up the gas earlyer to avoid it burning in the exthaust manifold and then there might be some gas to save on the miledg driveing loong ways but my stroker so far uses just about the same amount as a 440 Six Pack engine driving like above discribed but lets see what the BG´s will end up whit.

Fired up the mule today and it seam to run propper Will start on the carbs change soone !

Nice work Pat keep at it mate