IIRC, GP suggests a 6000 rpm top end for dependable performance from a Duraspark distributor.
Curious what other owners' experiences are.
Larry
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Ford used the same centrifugal advance in all of their distributors, but always removed or disabled the vacuum advance in their 7000 rpm distributors. I run the Duraspark distributor (with vacuum advance) to 7200 rpm with no worries. I'd say its OK to that rpm as long as the advance mechanisms are in good operating order.
That extra 1000 rpm (from 6200 to 7200 rpm) is one of the reasons I prefer the Duraspark I ... it charges the coil properly at all rpm. The Duraspark II module does not.
That extra 1000 rpm (from 6200 to 7200 rpm) is one of the reasons I prefer the Duraspark I ... it charges the coil properly at all rpm. The Duraspark II module does not.
First, I only ran (past tense) the Duraspark II.
At times with a vacuum advance, at times without it.
It was not a dependability issue, just a tinkering issue of making the engine run better across the rpm spectrum.
I don't recall ever having issues with it, just looking for a way to fire the spark plugs in a way to keep them clean at all rpm.
This was both with a Holley 4779 carb and the Weber IDA's.
The Holley was the problem child, not the Webers.
RPM consistency is much better with the Duraspark without a vacuum advance.
I will agree with George in that my rpm limit was about 7,200 rpm.
All the advance considerations of a dual point Ford distributor are going to be the same as with the Duraspark since they use the same internal mechanisms.
The "rap" on using the vacuum advance in virtually any distributor is that the vacuum mechanism tends to create a "advance plate" that starts to bounce at around 6,000 rpm thus causing "instantaneous" timing variations.
It is a fairly simple procedure to remove and lock out the vacuum advance from any Ford derived distributor and many race teams/cars do this as a matter of fact.
Two Ford dual point distributors had no provision for vacuum advance in the distributor castings that I can think of. The 427 and the 289hp. Even the Boss 302 and the Boss 351 dual points were made to use a vacuum advance as well.
The Duraspark is a very dependable system but in my view is intended solely to eliminate the points from the "equation".
With an engineering criteria of lowering emissions, consistency of the ignition system was a prerequisite which the Duraspark delivers.
An additional thought of mine in I vs. II, is justification that it is available generically anywhere in the country at virtually any auto parts store. I am pretty sure that is true of the II but not convinced that is true of the I considering that primarily the I was a "California only" item?
Another thought is that the Duraspark system is limited to using a "coil in a can" whereas something like the Pantera-Electronics "engine-controller" uses your choice of an electronic coil, so in that case the Ford is at a disadvantage.
However you are not going to get another P-E unit at any parts store so I suppose that is a consideration as well?
In ANY case all of the Panteras need a very serious ignition upgrade and the Duraspark is a great way to go.
Rocky. Don't rev this thing to 7,200 backing it out of the garage, ok?
At times with a vacuum advance, at times without it.
It was not a dependability issue, just a tinkering issue of making the engine run better across the rpm spectrum.
I don't recall ever having issues with it, just looking for a way to fire the spark plugs in a way to keep them clean at all rpm.
This was both with a Holley 4779 carb and the Weber IDA's.
The Holley was the problem child, not the Webers.
RPM consistency is much better with the Duraspark without a vacuum advance.
I will agree with George in that my rpm limit was about 7,200 rpm.
All the advance considerations of a dual point Ford distributor are going to be the same as with the Duraspark since they use the same internal mechanisms.
The "rap" on using the vacuum advance in virtually any distributor is that the vacuum mechanism tends to create a "advance plate" that starts to bounce at around 6,000 rpm thus causing "instantaneous" timing variations.
It is a fairly simple procedure to remove and lock out the vacuum advance from any Ford derived distributor and many race teams/cars do this as a matter of fact.
Two Ford dual point distributors had no provision for vacuum advance in the distributor castings that I can think of. The 427 and the 289hp. Even the Boss 302 and the Boss 351 dual points were made to use a vacuum advance as well.
The Duraspark is a very dependable system but in my view is intended solely to eliminate the points from the "equation".
With an engineering criteria of lowering emissions, consistency of the ignition system was a prerequisite which the Duraspark delivers.
An additional thought of mine in I vs. II, is justification that it is available generically anywhere in the country at virtually any auto parts store. I am pretty sure that is true of the II but not convinced that is true of the I considering that primarily the I was a "California only" item?
Another thought is that the Duraspark system is limited to using a "coil in a can" whereas something like the Pantera-Electronics "engine-controller" uses your choice of an electronic coil, so in that case the Ford is at a disadvantage.
However you are not going to get another P-E unit at any parts store so I suppose that is a consideration as well?
In ANY case all of the Panteras need a very serious ignition upgrade and the Duraspark is a great way to go.
Rocky. Don't rev this thing to 7,200 backing it out of the garage, ok?
quote:Rocky. Don't rev this thing to 7,200 backing it out of the garage, ok?
Doug - Good advice!
I will second Doug's comments on the availability of the Red (Duraspark I) modules. They are harder to find.
quote:Originally posted by Rocky:quote:Rocky. Don't rev this thing to 7,200 backing it out of the garage, ok?
Doug - Good advice!
I will second Doug's comments on the availability of the Red (Duraspark I) modules. They are harder to find.
I did check and SOME do show in "the parts books" here as "California only". They don't seem to be in the normal parts "distribution" networks here which means they need to be shipped in from a central warehouse somewhere?
One supplier I use often didn't even have a listing for them at all, at least the listing didn't show more than one type available.
West coast may have better availability as a result? You aren't going to find them on the shelf in Northern Michigan or Caribu, Maine.
I have a feeling that "California only" is kind of a black mark against them as "one of those EPA Emissions requirements that we don't want"?
So Doug -
Are you saying the advance plate mechanism that is connected to the vacuum canister in the Ford Distributor vibrates, or something, and affects the BASIC timing of the system at high RPM?
I can see that a person could remove the linkage to the canister easily, but isn't the pickup mounted to that plate?
How would one then fix the plate in place?
Thanks -
Rocky
Are you saying the advance plate mechanism that is connected to the vacuum canister in the Ford Distributor vibrates, or something, and affects the BASIC timing of the system at high RPM?
I can see that a person could remove the linkage to the canister easily, but isn't the pickup mounted to that plate?
How would one then fix the plate in place?
Thanks -
Rocky
Lance Nist a Pantera guy and inverter at Electra-Motive sells a crank trigger ignition that is good for 10,000 rpm, if you want perfection buy it.
quote:Originally posted by Rocky:
So Doug -
Are you saying the advance plate mechanism that is connected to the vacuum canister in the Ford Distributor vibrates, or something, and affects the BASIC timing of the system at high RPM?
I can see that a person could remove the linkage to the canister easily, but isn't the pickup mounted to that plate?
How would one then fix the plate in place?
Thanks -
Rocky
What happens is that first off, you are not getting any vacuum advance at WOT which essentially over 6,000 rpm operation is.
Centrifical force is pressing the plate to move and the diaphram in the vacuum canister tries to resist but the flexibility of the rubber diaphram in it isn't strong enough to hold the plate steady, so yes, it begins to essentially cavatate/vibrate.
Exactly at what rpm this happens I can't tell you.
I have run vacuum advance distributors up to about 6,800 rpm with seemingly no problems. That's probably because I am not using it under "race conditions", that being on and off the throttle.
For serious racing, you must pin the "advance plate" if the distributor is equipped with one
You just bolt the plates together using a piece of tubing as a spacer between the plates. Something like a #8-32 screw with a lock nut and a 1/8-3/16" long piece of tubing. A plastic "stand off" would work also as a spacer.
The vacuum advance situation is easy to understand.
Engines operated at part throttle NEED vacuum advance, because the "light" part throttle fuel/air charge requires more time to burn. BUT ... if the engine has a cam in it that has so much overlap, or the intake valve opens so early, that the intake manifold vacuum at idle or the ported vacuum just above idle are erratic, then vacuum advance would also be erratic and make the ignition timing erratic. This is why some pre-1968 Ford "street engines" with big cams only had centrifugal advance.
I purchase the Duraspark I modules on eBay ... as anyone in any state can ... so everyone has the same availability I do. There was a guy in Texas that seemed to have a bunch of them.
Engines operated at part throttle NEED vacuum advance, because the "light" part throttle fuel/air charge requires more time to burn. BUT ... if the engine has a cam in it that has so much overlap, or the intake valve opens so early, that the intake manifold vacuum at idle or the ported vacuum just above idle are erratic, then vacuum advance would also be erratic and make the ignition timing erratic. This is why some pre-1968 Ford "street engines" with big cams only had centrifugal advance.
I purchase the Duraspark I modules on eBay ... as anyone in any state can ... so everyone has the same availability I do. There was a guy in Texas that seemed to have a bunch of them.