prestolite dist springs

[makomark]

I'm as skeptical as you are Rick...just stumbled across that post, saw it was current, and figured I'd share.

Now, based on lack of OEM spec's, I figured a trusted aftermarket would be the best place to start. Our good friends at Mallory, yes the Unilite builders, said their replacement distributors for the 318's are provided with 24 degrees, at 3200 rpm...and say they have had no issues using this curve. May not be Factory values but their performance kind speaks for itself...my two cents

[fastjeff]

That's fine unless you cruise at 2,500 rpms, which I do!

Jeff

[RicardoMarine]

I'm as skeptical as you are Rick...just stumbled across that post, saw it was current, and figured I'd share.

Now, based on lack of OEM spec's, I figured a trusted aftermarket would be the best place to start. Our good friends at Mallory, yes the Unilite builders, said their replacement distributors for the 318's are provided with 24 degrees, at 3200 rpm...and say they have had no issues using this curve. May not be Factory values but their performance kind speaks for itself...my two cents

Yes, I believe that is correct. Add BASE of 5* and that's 29* TA @ 3,200 RPM.

I had called Mallory a few weeks ago and posted what I was told (same numbers, BTW), but I can't remember which thread that was in.

If you also recall, I plotted out those silly OEM Chrysler numbers in post #32 in this thread a while back.
When plotted out, the curve really looks goofy.
http://www.marineengine.com/boat-for...x-timing/page2

Yes, I caught the Unilite comment!

That's fine unless you cruise at 2,500 rpms, which I do!

Jeff

If this is a planing hull, and if 2.5K rpm gets you fully up on step, that would work if the progressive advance is correct for that RPM.
However, if 2.5K rpm does not get you fully up on step, that could be a rather dangerous rpm to be cruising at, IMO.
Perhaps not only dangerous, but you're certainly waisting fuel as well.

If we're going to detonate an engine, it will be more likely to detonate at/near 2,500 rpm while pushing lots of water, than if operating at a higher rpm with less hull friction.


.

[fastjeff]

Boat holds plane down to 2,000 rpms, even in a full lock turn, so it's not laboring in the least at 2,500 rpms. I'm tempted to bump the timing curve to give full advance at that rpm, but I'm chicken! Better to leave well enough alone.

Jeff

[captain_ed]

I do not have the service manuals. Someone sent that info to me via email pdf.

If someone has a 80s Chrysler Marine Engine manual, please look up this info for all of us.

I have the manuals and I directly quoted the numbers given in the last chrysler 440 timing curve thread. They are similar to the numbers above. They seem very vague as the above numbers are.

I am about to replace my carbs with Edelbroch 1410's next weekend. I will try to map out the curve on each engine. If they match, we should be good.

[tundrarules]

I have the manuals and I directly quoted the numbers given in the last chrysler 440 timing curve thread. They are similar to the numbers above. They seem very vague as the above numbers are.

I am about to replace my carbs with Edelbroch 1410's next weekend. I will try to map out the curve on each engine. If they match, we should be good.

Can't wait to see what you chart Thanks for helping us with the info on this mystery !!!!!

I will chart my Pertronix Marine distributors as well...they came with copper springs installed with a curve in the chart here http://www.pertronix.com/support/manuals/pdf/billet.pdf . I replaced one copper spring with a silver spring.... so I need to chart the curve......if I can ever get back to my boat ..... season postponed this year due to sick family.


Glad Richard posted the question on ask....can't wait to see results.

[RicardoMarine]

Again, that data is for automotive. Not saying that you can't make it work, just take note.

Also, while we are able to change the curve via spring values, this company also offer advance limitters.
I.E., 12*, 16* and 20*.... (add BASE, and you have the total value).

Between the spring value and the limitters, you should be able to make multiple curves/limits... but just what those correct numbers are...., is still a mystery.


.

[tundrarules]

PerTronix answered my question they don't know either ...http://www.pertronix.com/prod/ig/fla...et_marine.aspx

Greg,

I'm sorry we don't know exact the advance curve for the Chrysler marine
engine. Normally my customers are using the springs already installed on the
distributor. That would be my suggestion.

If, you wanted to try another combo. I would remove one of the silver
springs and replace it with one cooper. If, you get any pinging then you
would need to go back to both silver springs.

Marvin Grebow Jr.
PerTronix Inc.
Technical Department
909-273-6006
marving@pertronix.com

[tundrarules]

Checked my numbers this past weekend.

My factory new Pertronix distributors I installed have the following curve....

5 deg base + advance = Total advance

5 degrees at 800 RPM 5 degrees at 1000 RPM
5 degrees at 1500 RPM
8 degrees at 2000 RPM
22 degrees at 2500 RPM
22 degrees at 3000 RPM
22 degrees at 3500 RPM

Now what

[RicardoMarine]

Checked my numbers this past weekend.

My factory new Pertronix distributors I installed have the following curve....

5 deg base + advance = Total advance
If this includes the total advance at the "full in" rpm, that would be correct!
IOW, what you see at the crankshaft in degrees, and at the full-in RPM = TA (total advance).

5 degrees at 800 RPM
5 degrees at 1000 RPM
That sounds correct, since we don't require any mechanical advance any sooner than 900-1,000 rpm.
We have to remember that most Marine Ignition curve graphs do not include BASE advance. They show distributor advance only!

We also must remember that BASE is always part of what we see when we strobe the timing marks dynamically. It can't help but be included!


5 degrees at 1500 RPM
Does this mean 10* actual advance (base of 5 + 5 = 10) @ 1,500 rpm?

8 degrees at 2000 RPM
Does this mean 13* actual advance (base of 5 + 8 = 13) @ 2,000 rpm?

22 degrees at 2500 RPM
Now I'm a bit confused!
Why the large jump in just 500 rpm...., and does this include BASE?
Looks like you did not include BASE in the previous numbers... so if we add BASE of 5*, this would be 27* @ 2,500 rpm.... correct?

22 degrees at 3000 RPM
Why no increase in spark lead from 2,500 to 3,000?
If this is full-in, it would have been full-in @ 2,500 rpm!

22 degrees at 3500 RPM
Again, why no increase in spark lead from 2,500 to now 3,500??
Again, if this is full-in, it would have been full-in @ 2,500 rpm!

IMO, 2,500 rpm is a tad bit too early to be full-in.... but I"m by no means a Chrysler Marine expert!


Now what

I'm not arguing with you.... I'm just observing what you saw and what you posted here.

I'd say; "back to the drawing board!"

Plus, it would really be helpful to see this plotted out in graph form. This way you can look at the graph and see if it's linear, or if there is an odd curve to it.
Automotive curves are often not linear, whereas the Marine curves tend to be more linear.

You can find on-line inter-active graphs that allow you to enter both values.... RPM and Advance in degrees.
I think I made on a while back.... it was pretty cheeze-ball, but it got the point across.

.

[tundrarules]

This was my port engine.

All numbers listed are total advance. I have a mechanical limit of 22*

I can't put in graph form as I am not as computer savvy as I should be.

The fast jump between 2000 and 2500 seems a bit much. Could have been because that was the first high rpm run of the season and it could have been a little sticky. I will double check it soon.

Also will check my stb engine soon.

[RicardoMarine]

1.... All numbers listed are total advance. I have a mechanical limit of 22*

2.... The fast jump between 2000 and 2500 seems a bit much. Could have been because that was the first high rpm run of the season and it could have been a little sticky. I will double check it soon.

1.... Just so that we're speaking the same language, here's what we actually have:

• BASE is BASE.... and is a result of where the distributor housing is positioned, and with no distributor advance inlcuded.
• Progressive advance is what the distributor offers throughout the RPM range. When strobed with a timing light, it will include BASE.
• TA (total advance) is what the distributor offers at the limit and limit RPM. When strobed with a timing light, it will also include BASE. In your case, if the mechanical limit is 22*, we would add the BASE of 5* to it, which makes a TA of 27*. If I read your numbers correctly, your TA of 27* is full-in @ 2,500 rpm. Like said; "IMO, 2,500 rpm is a tad bit too early to be full-in.... but I"m by no means a Chrysler Marine expert!"

2... That is odd. It should not make that jump. The flyweights should offer a nice smooth increase as it passes through the progressive.



I think that we still have a mistery on our hands here regarding the correct 360 Marine curve.

[tundrarules]

Got a few emails out today to Prestolite and a few marine engine rebuilders asking about the big mystery!! Crossing my fingers.......is that crickets I hear?

[fastjeff]

That's about all you'll hear.

Jeff

[RicardoMarine]

Tundrarules, I did the same thing a while back, and all I got were the crickets!
I even did several extensive Internet searches, I tried the "Chrysler Marine ignition timing curve site:xyz.com" seach............ same thing, base advance only specs, or crickets!

I'll keep my fingers crossed that you have better luck.

.

[jp253]

any idea where ican get springs for the counter weight in my prestolite dist. should the be different or both the same??

[fastjeff]

Try Jeggs or Summit Racing on-line. Get a springs kit for GM distributors and make 'em work. Springs are springs: If too stiff, go with a softer one (in thekit); or vica versa.

Jeff

[RicardoMarine]

any idea where ican get springs for the counter weight in my prestolite dist. should the be different or both the same??

First, we need to see the OEM advance curve, which appears to be non-existant.
Secondly, the flyweights may or may not be the same.
Thirdly, the two springs will definitely be of different value.

Lastly, if you do find the OEM curve, I'd recommend that you take the distributor to a shop who owns/operates an old school Sun or Allen distributor machine, and have them set this up for you. They will be able to tweak things, and bring the curve into specs.

Then when you re-install, you'll set BASE, and if they've done their job, the progressive and TA will be correct..... but I'd certainly verify this by strobing at the various RPM.

.

[fastjeff]

Criminy! Its not that hard to do; just add what springs look good and try it out. If the advance comes all the way in below the rpm you want (say, 2,600 to 2,800) then the springs are too soft. Try a stiffer one. If the opposite happens, go with a softer one.

Hell, I did all this 50 years ago without a problem!

Jeff

[RicardoMarine]

Jeff, you are correct, it is fairly easy for someone with yours or my skill level. You or I would fit the springs, run it up, look at progressive, check TA, and would make any necessary changes!
However, people who typically seek forum information, pertaining to this, very likely don't have the same skill level nor confidence that you and I may have!
The likelihood of a costly error is greater, IMO.

This is the reason that I tend to default to suggesting that it be done by someone with experience, and preferably with the aid of a distributor machine, AND with the OEM curve in hand!

.

[fastjeff]

It's not rocket science. Unlike a car engine, the advance in a boat engine (due to the service) is either IN or OUT, Period. All you need is springs that will allow the advance to come all the way in by 2,600 to 2,800. Period. It takes only a simple timing light and a tach to acomplish this.

I did this--easily--as a kid 50 years ago with just that equipment.

Jeff (the former rocket scientist)

[tundrarules]

So Jeff, you're saying if my total timing is "all in", 25* at 1500 rpms, that's OK?

If the advance goes from base 5* to 25* between 1000 and 1500 rpms, that's OK?