Need Help With Advance Curve Tuning on MP Electronic Distributor

[TxDon]

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!

What do you consider "God-Awful?"

 

[Cranky]

2 times I had the pleasure (displeasure?) of tuning low compression engines with cams that really should not have been in them. Total timing ended up being 50!! The first time I ran into that I grabbed another timing light and then another. It was a 440 in a 67 Coronet and it actually ran pretty good. The other engine was a teen with 360 heads and estimated compression ratio came out around 7.8-1 and was in a 72 Demon. The 440 produced a whopping 115 psi cranking pressure and I didn't even bother to check the teen. The net was pulling mid 12's spinning off the line and breaking loose going into 2nd. The Demon ran a best of 13.51 @ 102. There wasn't any bottom end and it was lame until 3000 rpm but the Coronet was balls to the wall from the very start. I've been around some strange combinations but those two took the cake. Both had initial around 25+....

 

[TxDon]

2 times I had the pleasure (displeasure?) of tuning low compression engines with cams that really should not have been in them. Total timing ended up being 50!! The first time I ran into that I grabbed another timing light and then another. It was a 440 in a 67 Coronet and it actually ran pretty good. The other engine was a teen with 360 heads and estimated compression ratio came out around 7.8-1 and was in a 72 Demon. The 440 produced a whopping 115 psi cranking pressure and I didn't even bother to check the teen. The net was pulling mid 12's spinning off the line and breaking loose going into 2nd. The Demon ran a best of 13.51 @ 102. There wasn't any bottom end and it was lame until 3000 rpm but the Coronet was balls to the wall from the very start. I've been around some strange combinations but those two took the cake. Both had initial around 25+....

Wow. I don't think I'll run into anything like that but who knows. Without any real history on my car I have no idea of compression ratio, cam specs, etc. I just don't think it runs as strong as it should - part of the problem may be that I am comparing it to memories of the GTX I had in the early 70s - 45 year old memories! And of course I'm processing those memories through a 68-year-old brain....We'll see where this all leads.

 

[TxDon]

OK here we go. I set the centrifugal advance at 16 degrees to start with and will do the rest with initial, I'm leaving the springs as is for now. Now that I've done it adjusting that distributor is a snap, good design.

 

[TxDon]

So it took a while but I finally finished all the ignition updating and got it buttoned back up. I hooked up my fancy new Innova timing light and checked her out this morning. Without adjusting anything the initial was at 20 degrees and the total was 34 degrees at 2250 rpm. 2 degrees less centrifugal than I set but I decided to leave it alone and do a test drive. Summer is already kicking our butt in Texas, its about 92 with a heat index of 104, so the A/C was on for my whole trip. I stopped and got some gas then drove for about 30-40 minutes mixing regular stop and go with some highway at 60 to 70 mph. So far I'm very pleased! It pulls harder and smoother in all gears and revs more willingly. It does not seem to be straining at higher speeds like it did before. I did not notice any pinging although with my lousy hearing and those damn loud mufflers who knows? - at least nothing obvious. I'm going to recheck total timing at 2500 rpm and maybe fiddle a bit but for now I'm glad this last project has paid off. Thanks to all who responded!

 

[Cranky]

If it's pinging enough, it should show up on a plug check. My hearing is like yours and usually got my wife to go on a ride along to let me know if she could hear anything. A quick pinging at the initial hit of the gas off of idle usually won't hurt parts but I like to try and get rid of it all. Now pinging that doesn't go away quickly and keeps on during a hard pull is the type of stuff that kills parts and it does it pretty fast.

 

[demonram]

Guys I have a firecore dist. I know the adjustment is just like the MP dist. The problems I have are my all in advance is about 44 with an initial 12. Of course I'm getting pinging with half throttle input at any speed. I don't have the adjustment set for it. I'm running a 451, 10.5 aluminum head, 500 lift cam. Before the firecore I had a MP dist, never had an issue. The reason for the change was for the male cap and larger wires. I was thinking it was gas. I can only get 91 here in Az. in Illinois it was 93. I now think it's too much advance. If I could get a drill bit size equivalent for advance increments I believe I could dial this thing in. Thanks in advance( pun intended ) Howard

 

[demonram]

Well I took a shot and pulled it apart. The plates were set full advance. I loosened the screws and back it down to about a 10 drill bit each side 2/3ds total and I think I've got it. Now just have to get some good gas, mix it in and see what happens.

 

[Cranky]

Guys I have a firecore dist. I know the adjustment is just like the MP dist. The problems I have are my all in advance is about 44 with an initial 12. Of course I'm getting pinging with half throttle input at any speed. I don't have the adjustment set for it. I'm running a 451, 10.5 aluminum head, 500 lift cam. Before the firecore I had a MP dist, never had an issue. The reason for the change was for the male cap and larger wires. I was thinking it was gas. I can only get 91 here in Az. in Illinois it was 93. I now think it's too much advance. If I could get a drill bit size equivalent for advance increments I believe I could dial this thing in. Thanks in advance( pun intended ) Howard

Could use a bit more info on the cam and where it's degreed in and what your cranking PSI is. A cam that's advanced will usually build more cylinder pressure down low and could be why it's pinging. 93 gas would be better but 10.5-1 usually isn't a deal breaker even with 91. Hot Rod rag just did a cam test with different LSA's and timing etc and it was a pretty interesting read. A lot of people (including me) thought that a tighter LSA would affect cranking PSI....it does but not as much as thought. Where the intake closes has more to do with that. An RV cam that opens the intake late and closes it relatively early will build a good deal of cranking PSI for instance.....

 

[demonram]

Thanks cranky, like I wrote I had no problems with the MP dist. I hadn't driven the car except to put it on the trailer prior to moving to Phoenix. The torque converter had an issue. I didn't get it going until about 2 weeks prior to loading it. I installed the dist and never thought it would be set full advance. That was the problem. I will get better gas, I know where to get it finally. Then I can dial it in. I can finally nail it and not worry about machine gun Kelly showing up. It'll again break the tires at 15-20 mph.