Stock distributor advance springs. What RPM?

[AZMoparJoe]

What RPM do the stock distributor springs provide full centrifugal advance? I’m currently running two stock light springs in my 451, 18 degrees base and 35 all in, and it’s a little too much too soon (about 2200). I have another distributor I was going to pull the springs out of. It has one heavy, and one light spring. Anybody know how late the stock springs come in?

 

[dvw]

There are many different calibrations of distributors depending on the year and application. Better off buying aftermarket spring kit. If the advance plate hasn't been modified total will be to high as well. Your numbers don't look that aggressive. Unless the compression/head design/cam duration exceeds the octane of your fuel.
Doug

 

[AZMoparJoe]

There are many different calibrations of distributors depending on the year and application. Better off buying aftermarket spring kit. If the advance plate hasn't been modified total will be to high as well. Your numbers don't look that aggressive. Unless the compression/head design/cam duration exceeds the octane of your fuel.
Doug

I did modify my advance plate. I’m at 35 total, which is where I want it.

 

[lewtot184]

Some years ago i aquired a lot of factory springs and some extra parts to play with. The combination of all these is almost limitless. Factory combos were numerous. It's all about the engine combo and what you want to do or accomplish. Apparently you're too aggressive. Trying to stick with the factory light/heavy spring combo has been the best for me and street engines.

 

[AZMoparJoe]

Some years ago i aquired a lot of factory springs and some extra parts to play with. The combination of all these is almost limitless. Factory combos were numerous. It's all about the engine combo and what you want to do or accomplish. Apparently you're too aggressive. Trying to stick with the factory light/heavy spring combo has been the best for me and street engines.

Yeah I figured I’d try the stock heavy/light combo, and tune the vacuum advance accordingly. It’s a mild 451; actual 10.6 to 1, 284/528 solid. The base and total timing is right where it needs to be, evidenced by the annealing on the spark plug ground strap. It’s just too much too soon right now.

 

[JooCis]

What RPM do the stock distributor springs provide full centrifugal advance? I’m currently running two stock light springs in my 451, 18 degrees base and 35 all in, and it’s a little too much too soon (about 2200). I have another distributor I was going to pull the springs out of. It has one heavy, and one light spring. Anybody know how late the stock springs come in?

Stock springs (one heavy, one light) are usually very conservative and typically don't reach full advance until 4000–4800 RPM.


That heavy spring is exactly what you need to fix your 'all in by 2200' issue. It typically has a slotted loop, so it does nothing at idle (letting the light spring work) but kicks in at higher RPM to slow down the final part of the curve.

 

[lewtot184]

The mopar performance electronic distrubutor for an RB engine had a 13 degree plate, a green/ white primary spring, a bluish/pink secondary spring. Primary advance was all in around 1800rpm and secondary advance completed the centrifugal advance curve around 3000rpm.

 

[lewtot184]

some years back i worked on a friend's 440 with a 284/.528 cam; 4spd gtx. i put together two distributors and one had the out of the box curve mentioned post #7. i was amazed at how well the car drove and performed with that cam and moderate ignition curve. i had already gotten away from full centrifugal curves for my cars, but experiencing this with something cammed up was interesting.
i've learned in the past several years that good ignition curves are dictated by the engines ability to make vacuum. basically a higher vacuum more efficient engine doesn't need or want an aggressive curve. solid lifter cams will make a little more vacuum than hydraulics. a lot of initial timing is always recommended but i don't believe it's a blanket solution for all combos; in fact it can make matters worse. i always use a vacuum advance for my cars.

 

[AZMoparJoe]

some years back i worked on a friend's 440 with a 284/.528 cam; 4spd gtx. i put together two distributors and one had the out of the box curve mentioned post #7. i was amazed at how well the car drove and performed with that cam and moderate ignition curve. i had already gotten away from full centrifugal curves for my cars, but experiencing this with something cammed up was interesting.
i've learned in the past several years that good ignition curves are dictated by the engines ability to make vacuum. basically a higher vacuum more efficient engine doesn't need or want an aggressive curve. solid lifter cams will make a little more vacuum than hydraulics. a lot of initial timing is always recommended but i don't believe it's a blanket solution for all combos; in fact it can make matters worse. i always use a vacuum advance for my cars.

I wish I could find a set of the old MP springs. That stuff was EVERYWHERE until a few years ago. My 451 pulls 10in/hg at 900rpm. I found an old set of Mr Gasket springs that were buried in the garage. I removed the two stock light springs, and replaced them with two silver springs (medium) from the Mr Gasket kit and it’s much better. I just need to tune my vacuum advance for the change in the advance curve now.

 

[lewtot184]

I wish I could find a set of the old MP springs. That stuff was EVERYWHERE until a few years ago. My 451 pulls 10in/hg at 900rpm. I found an old set of Mr Gasket springs that were buried in the garage. I removed the two stock light springs, and replaced them with two silver springs (medium) from the Mr Gasket kit and it’s much better. I just need to tune my vacuum advance for the change in the advance curve now.

I would thimk that cam would do better than 10". I use a cam with more overlap than yours and i can get 13+" at 850-900rpm.

 

[AZMoparJoe]

I would thimk that cam would do better than 10". I use a cam with more overlap than yours and i can get 13+" at 850-900rpm.

Yep, that’s all she pulls.

 

[lewtot184]

Yep, that’s all she pulls.

I think you may have a total tune up issue. What degree advance plate are you using?

 

[AZMoparJoe]

I think you may have a total tune up issue. What degree advance plate are you using?

No tuneup issue. Running 18 degrees base, and 18 centrifugal for a total of 36 degrees.

 

[lewtot184]

No tuneup issue. Running 18 degrees base, and 18 centrifugal for a total of 36 degrees.

I use a 9 degree plate, staged centrifugal advance, vacuum advance, 36 degrees total. 9 degree plate makes finding a short heavy spring more difficult. This combo drives very nicely. Cruises close to 18" of vacuum with pump gas.

 

[hunt2elk]

I wish I could find a set of the old MP springs. That stuff was EVERYWHERE until a few years ago. My 451 pulls 10in/hg at 900rpm. I found an old set of Mr Gasket springs that were buried in the garage. I removed the two stock light springs, and replaced them with two silver springs (medium) from the Mr Gasket kit and it’s much better. I just need to tune my vacuum advance for the change in the advance curve now.

You could try @HALIFAXHOPS for some MP springs, I bet he could set you up.

 

[HALIFAXHOPS]

I will not touch them way to fast advance for the street. Thats why I had other ones made up.