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Need Help With Advance Curve Tuning on MP Electronic Distributor

TxDon

TxDon

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I posted this on my project thread without response so I hope to do better here. I am in the process of tuning the centrifugal advance curve on my 440 but have never attempted this before so I'm not real sure how to proceed. The distributor is a newer style MP electronic, very clean inside and out and looks like it has not had much use. I still have to open it up but can see it has the Mallory style adjustable centrifugal advance with the slotted plate and screws. I have searched here and other online sources and learned that this is adjusted using red plastic keys which I am in the process of getting. My first question is what is best way to expose the adjustable plate? Online I have seen to just pry off the reluctor with two screwdrivers, remove the screws around the outside of the housing and lift off the pickup plate - is there any more I need to know?

Once I expose the plate I understand that the adjustment process may be trial and error.
My engine has a mild cam, high rise intake and 750cfm Edelbrock and its a 4-speed car used exclusively on the street with 93 octane ethanol pump gas. Based on my research it appears that the 440 with a few mods likes less distributor advance and more initial with a total of 36 to 38 degrees. The distributor key settings range from 14 to 28 degrees in 2 degree increments. What would be the best setting to allow fine tuning with initial timing?

The other question has to do with the advance weight springs. I don't yet know what's on there but assuming I have the "factory" performance springs is changing them something I need to do? A number of sources have said a common mistake is using too light a spring and having the advance come in too early. What has your experience been with this distributor? Thanks for your help.
 
It is all a bunch of trial and error. Too light of springs and you will get pinging. The red keys are nice, but the new sets only give you one of each. I have one motor that runs best at 21 initial and 33 total. With this setup, the smallest key doesn't work and I just kept experimenting with small drill bits till I got the gap I wanted.
 
TxDon said:
I posted this on my project thread without response so I hope to do better here. I am in the process of tuning the centrifugal advance curve on my 440 but have never attempted this before so I'm not real sure how to proceed. The distributor is a newer style MP electronic, very clean inside and out and looks like it has not had much use. I still have to open it up but can see it has the Mallory style adjustable centrifugal advance with the slotted plate and screws. I have searched here and other online sources and learned that this is adjusted using red plastic keys which I am in the process of getting. My first question is what is best way to expose the adjustable plate? Online I have seen to just pry off the reluctor with two screwdrivers, remove the screws around the outside of the housing and lift off the pickup plate - is there any more I need to know?

Once I expose the plate I understand that the adjustment process may be trial and error.
My engine has a mild cam, high rise intake and 750cfm Edelbrock and its a 4-speed car used exclusively on the street with 93 octane ethanol pump gas. Based on my research it appears that the 440 with a few mods likes less distributor advance and more initial with a total of 36 to 38 degrees. The distributor key settings range from 14 to 28 degrees in 2 degree increments. What would be the best setting to allow fine tuning with initial timing?

The other question has to do with the advance weight springs. I don't yet know what's on there but assuming I have the "factory" performance springs is changing them something I need to do? A number of sources have said a common mistake is using too light a spring and having the advance come in too early. What has your experience been with this distributor? Thanks for your help.
Click to expand...
This is the way to go. 14 to 16 degrees initial, 34 to 36 all in at 3000 to 3200.
http://www.4secondsflat.com/Mopar Mechanical timing limiter plate.htm
 
Thanks. Just to make it clear I have the later style MP distributor with the small advance weights and adjustable limit plate, the FBO plate doesn't work with that. Today I pulled off the reluctor and pickup plate, here is a pic of what I have. As I suspected it looks like I have the wide open limit setting, one lighter direct acting spring and one heavier spring that has clearance so it kicks in later. This is supposed be a "performance" curve, does anyone know what the stock specs were for these conversion distributors?

DSCF9420.JPG
 
Don for ur edification I installed a Summit replacement last fall and never changed a thing. Looked for total mech. about 3000 at 36* and ended up with 12* initial. This in a stock 440 that was originally supposed to be 5btdc. Runs great & no pinging.
 
TxDon said:
I don't yet know what's on there but assuming I have the "factory" performance springs is changing them something I need to do?
Click to expand...
I'd suggest keeping the springs, until you get farther along, until shown you want a change in the advance 'rate'. That's exactly what the springs control...the rate, or timing of the advance.
It's been a long time, though I've used about the same light/heavy combo, but on a Mallory dual point, mechanical advance. Just a pairing, or mixing, of the springs to set the advance rate you want.
 
hunt2elk said:
It is all a bunch of trial and error. Too light of springs and you will get pinging. The red keys are nice, but the new sets only give you one of each. I have one motor that runs best at 21 initial and 33 total. With this setup, the smallest key doesn't work and I just kept experimenting with small drill bits till I got the gap I wanted.
Click to expand...

Do you have any hot starting issues with that much initial?
 
oldbee said:
Don for ur edification I installed a Summit replacement last fall and never changed a thing. Looked for total mech. about 3000 at 36* and ended up with 12* initial. This in a stock 440 that was originally supposed to be 5btdc. Runs great & no pinging.
Click to expand...

OK that helps, mine is currently about the same, that would mean the "stock" setting is around 24 degrees in the distributor. Is a total mechanical setting of 36 degrees considered the max?
 
Mine has given me no problems. The really cool part is if I drive it often enuf before gas evaps from carb that thing starts faster cold than a new injected car does.
 
Different engine combinations like different timing setups. Generally, higher compression engines like less and low compression likes more total. Carb setup, cam, exhaust....it all plays a part. Like mentioned, try what you have out of the box and go from there. The engine and you just might like the way it runs.
 
Cranky said:
Different engine combinations like different timing setups. Generally, higher compression engines like less and low compression likes more total. Carb setup, cam, exhaust....it all plays a part. Like mentioned, try what you have out of the box and go from there. The engine and you just might like the way it runs.
Click to expand...

This is the distributor my car came with so apparently I have been running it the way it originally came. I think the engine can run better than it does so let the trial and error begin. I'll keep it at 36 degrees total but want to try the heavier initial setting. I'm waiting for the adjuster keys and a dial back timing light to show up then I'll let you know what happens.
 
TxDon said:
This is the distributor my car came with so apparently I have been running it the way it originally came. I think the engine can run better than it does so let the trial and error begin. I'll keep it at 36 degrees total but want to try the heavier initial setting. I'm waiting for the adjuster keys and a dial back timing light to show up then I'll let you know what happens.
Click to expand...
Another thing to think about is gasoline isn't nearly like it was back when our cars were new but on the other hand, the factory timing imo was somewhat conservative to say the least. When I first started learning how to do tuneups, an older guy at a dealership gave me several pointers (when you could actually still go into the shop and watch and learn) and I went from there. It wasn't until a several years ago that I found out just how much timing some engines can actually run good with but they were nearly always running low compression and cams designed for a good deal more. One of the things I've learned to do is check cranking PSI and keep that in mind when tuning. To do a good tune, you should know everything you are dealing with.....
 
No Don it would be pretty darn good, you only need another 8* initial at idle and you've got 36*. Then it's only how quick that 26-28 comes in. For the street it seems pretty good the way it comes.
 
You don't really need an advance type timing light. Clean off the harmonic balancer really good & put on a timing tape on it and then a regular light will work. My timing tape has been on for probably 20k miles.
 
I like a lot of initial advance in my street cars just because I like the crispness off the line so long as it's not pinging when it gets floored. Of course experimentation is what you need to do with the combination.....your combination. You would freak out (or call me a lair) with what I've done with total timing on a couple of low compression engines but that's what they liked. It's all about the combo.....
 
Cranky no " hot-start" problems?with I'm assuming "god awful" initial timing?
 
oldbee said:
Cranky no " hot-start" problems?with I'm assuming "god awful" initial timing?
Click to expand...
Not with low compression engines lol. If there were any issues, I'd back them down a degree at a time until it went away. God awful initial....it they don't back against the starter and don't ping, they get it! :D
 
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