mopowers
Well-Known Member
It seems to be very sporadic. I'm thinking it's timing related. I'll know more this weekend.
RPM Drop From Nuetral to Gear
- Thread starter mopowers
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It seems to be very sporadic. I'm thinking it's timing related. I'll know more this weekend.
straightlinespeed
Sometimes I pretend to be normal
I subscribed to this, because Im currently going thru the exact same thing. I messed with the timing and nothing made any difference. Like you it just keeps liking more and more timing. I had 24* in it for initial before I quit for the winter and put the car away. I had my dizzy curved, carb checked out and all was good, checked for vacuum leaks, then it was suggested that my cam was not degreed in. Checked with the builder and they degree every cam they install. Only 1 thing left that I could think of... new converter so ordered a converter built to my car. I didnt know the history of the one I installed even though it was new. It was sitting in someones garage for years and who knows if they dropped it.
I have yet to install the converter but it will be in by the time its warm enough to drive it. Its the only thing left to try since I tried everything else. I wish you luck with this problem and hope you get it figured out. Wish I could tell you that my problem is fixed by changing it but I cant, yet anyways.
I have yet to install the converter but it will be in by the time its warm enough to drive it. Its the only thing left to try since I tried everything else. I wish you luck with this problem and hope you get it figured out. Wish I could tell you that my problem is fixed by changing it but I cant, yet anyways.
pauly d
Member
Yes, its is sad that he's gone. I'm very glad most of his posts have been saved and his son seems to be pretty smart about this stuff too.
I think he would have liked us to think of it not as knowledge lost, but the other way around. That he was able to share his insights and knowledge. Maybe more than that, that he got us thinking about solving problems by looking at what is happening in the combustion process.
OK here's my thoughts
You need to decide what popping noise you have. fuel being suck thru the throttle blades or a bad valve causing a popping sound though the intake.
Here is how you figure that out.
Get a small glass of water(i know its weird but keep fallowing!) slowly dribble droplet of water in to the primary throttle...........does this sound like the popping noise you are hearing? if yes then carb and timing is the route.........If this is not the sound you are hearing, then i would say that you have either 5 and 7 spark plug wires mix up, or you have a leaking/bent or burnt valve. Bent pushrod or flat cam.
You need to figure out which "popping" you have.
You need to decide what popping noise you have. fuel being suck thru the throttle blades or a bad valve causing a popping sound though the intake.
Here is how you figure that out.
Get a small glass of water(i know its weird but keep fallowing!) slowly dribble droplet of water in to the primary throttle...........does this sound like the popping noise you are hearing? if yes then carb and timing is the route.........If this is not the sound you are hearing, then i would say that you have either 5 and 7 spark plug wires mix up, or you have a leaking/bent or burnt valve. Bent pushrod or flat cam.
You need to figure out which "popping" you have.
mopowers
Well-Known Member
Well, being out of town this weekend, I didn't get as much done as I would have liked. I did pull the distributor and noticed a few things...
1st- the reluctor was in an incorrect position. It was clocked slightly off where the roll pin goes (about 20* or so) and the roll pin was driven into the brass step to keep it from moving. I corrected the location of the reluctor making sure to use the correct roll pin slot to line it up.
2nd- The reluctor/pick-up gap was crazy wide! The quality of the pick-up seems horrible. Are all new MP magnetic pick-ups like this?? I noticed with vacuum fully applied, the gap was about .010", but without vacuum, it was close to .030". I didn't realize the gap changed that much with vacuum applied. Do they all do this???? I also noticed the magnetic pick-up was neither perfectly plumb (up and down) or straight (back to front) I actually replaced the pick-up assembly with a spare I had which was a lot straighter and plumb to the reluctor. The advance doesn't change nearly as much with vacuum either.
3rd- I replaced the heavy advance spring with the lightest one I had and shortened the advance slots to .155", which should give me about 16* advance. I'll adjust more as needed.
I didn't get a chance to fire it up, but will tonight.
Thanks again for the input guys. Once I get the timing nailed down, I'll post results and start trouble shooting the carb.
1st- the reluctor was in an incorrect position. It was clocked slightly off where the roll pin goes (about 20* or so) and the roll pin was driven into the brass step to keep it from moving. I corrected the location of the reluctor making sure to use the correct roll pin slot to line it up.
2nd- The reluctor/pick-up gap was crazy wide! The quality of the pick-up seems horrible. Are all new MP magnetic pick-ups like this?? I noticed with vacuum fully applied, the gap was about .010", but without vacuum, it was close to .030". I didn't realize the gap changed that much with vacuum applied. Do they all do this???? I also noticed the magnetic pick-up was neither perfectly plumb (up and down) or straight (back to front) I actually replaced the pick-up assembly with a spare I had which was a lot straighter and plumb to the reluctor. The advance doesn't change nearly as much with vacuum either.
3rd- I replaced the heavy advance spring with the lightest one I had and shortened the advance slots to .155", which should give me about 16* advance. I'll adjust more as needed.
I didn't get a chance to fire it up, but will tonight.
Thanks again for the input guys. Once I get the timing nailed down, I'll post results and start trouble shooting the carb.
67Dart273
Well-Known Member
Having the reluctor "off" is not a good thing, Google "rotor phasing"
All Mopars change either points gap (dwell) or reluctor gap with vacuum. That much, however is a "big" change. Make darn sure the thing reluctor does not strike the pickup.
Frankly, when I have issues "that could be" ignition related, I immediately pull the vacuum line AND LEAVE IT OFF until you get things sorted out, and of course if the symptoms change dramatically, you also know you are "in the area" of the problem.
All Mopars change either points gap (dwell) or reluctor gap with vacuum. That much, however is a "big" change. Make darn sure the thing reluctor does not strike the pickup.
Frankly, when I have issues "that could be" ignition related, I immediately pull the vacuum line AND LEAVE IT OFF until you get things sorted out, and of course if the symptoms change dramatically, you also know you are "in the area" of the problem.
mopowers
Well-Known Member
I've had the vacuum advance disconnected the whole time. Just thought it was interesting how much things changed on the bench with vacuum.
When setting the reluctor gap, are you supposed to set it at .008" with vacuum applied, or not?
67Dart273
Well-Known Member
I would set it to "average out" with change in vacuum so that let's say, no less than .005 or so at absolute closest point. Take shaft wobble / wear into account. I assume you have a handy "hand" vacuum pump?
That looks like a Mallory made MP distributor. It seemed like a great idea because of the adjustability, but its not as good as Chrysler built ones in some ways. I'll have to check mine for the gap movement. I didn't notice it, but I wasn't looking for it.
Replacing the heavy spring with a second light spring as you did was the best place to start. Because with the Mallory style slot adjustment, shortening the advance slots reduces the amount the weights move out. In other words it does not increase the preload on the springs. The heavy spring has a long loop in it, so it only slows the advance once the rpms get up to 2000-3000 rpm. It does nothing at idle rpm, and with the total slot distance reduced it may do little to nothing at the top.
The old tach drive distributors use the long looped spring to great advantage. But on vac advance dizzys they are only potentially useful if the slots are shortened on the inside. That way they can slow a reasonable portion of the advance curve.
Some pictures of the distributors here:
http://www.heritech.org/cuda/Dist.html
Replacing the heavy spring with a second light spring as you did was the best place to start. Because with the Mallory style slot adjustment, shortening the advance slots reduces the amount the weights move out. In other words it does not increase the preload on the springs. The heavy spring has a long loop in it, so it only slows the advance once the rpms get up to 2000-3000 rpm. It does nothing at idle rpm, and with the total slot distance reduced it may do little to nothing at the top.
The old tach drive distributors use the long looped spring to great advantage. But on vac advance dizzys they are only potentially useful if the slots are shortened on the inside. That way they can slow a reasonable portion of the advance curve.
Some pictures of the distributors here:
http://www.heritech.org/cuda/Dist.html
mopowers
Well-Known Member
Just got done adjusting it one last time. I replaced the pick-up with a better one from another distributor I had and adjusted the gap to .010" with no vacuum and .005" w/ vacuum applied. I used a mity-vac hand pump for vacuum.
Between fixing the huge reluctor gap and reluctor wheel phasing issue, we'll see what happens...
One last question... Do you guys drive the reluctor wheel roll pin all the down until it seats against the bottom of the groove on the shaft? Or half-way? All the way down doesn't seem to leave much left to 'grab' the reluctor wheel.
mopowers
Well-Known Member
Yeah, after taking this one apart several times, I'm certainly not impressed with the craftsmanship.
That's exactly why I took the heavy spring off. It wasn't doing anything once I shortened the slots. I also thought maybe because only one light spring was doing something at the lower rpms, maybe mech advance was being inroduced when the car was in neutral at idle vs. in gear at idle, exacerbating my issue.
Thanks for the link and the help. I appreciate it!
67Dart273
Well-Known Member
I've always seated them. To remove, I just put the dist. in some soft vise jaws, and use a couple of screwdrivers, across from each other to CAREFULLY pry the wheel up
And yes, I've chipped them in years past I guess you know.......the pin goes into the slot pertaining to CW. Those wheels are also used on B/ RB which rotate CCW
And yes, I've chipped them in years past I guess you know.......the pin goes into the slot pertaining to CW. Those wheels are also used on B/ RB which rotate CCW
mopowers
Well-Known Member
Thanks for the input. I actually stole the wheel and pick-up off a BB distributor I had. That's when I noticed the two different roll pin locations.
Stupid question... What does it matter which slot you use for the roll pin in the reluctor wheel? I realize it changes when the pick-up is triggered. But doesn't that change anyway when you rotate the distributor housing to set the timing???
67Dart273
Well-Known Member
I said it earlier. It changes rotor phasing. "When the spark fires" is triggered by the reluctor wheel. If the rotor is NOT aligned with a cap contact, the rotor is "out of phase." This causes a number of problems
1...The extra gap the spark has to jump causes a slight time delay which changes effective timing
2...Because the contacts are not aligned, "think further apart" the spark has to jump further, and the voltage goes up. At some point it can cross-fire to adjacent cylinders
3...This hot spark constantly jumping the gaps around the cap will eventually cause "tracking" in the cap, heat and ruin the cap material and turn it to carbon. Also, "more ozone" in there can't be good for things either
That's all I can think of for now, as if it ain't enough, LOL. As I said earlier, Google "rotor phasing"
1...The extra gap the spark has to jump causes a slight time delay which changes effective timing
2...Because the contacts are not aligned, "think further apart" the spark has to jump further, and the voltage goes up. At some point it can cross-fire to adjacent cylinders
3...This hot spark constantly jumping the gaps around the cap will eventually cause "tracking" in the cap, heat and ruin the cap material and turn it to carbon. Also, "more ozone" in there can't be good for things either
That's all I can think of for now, as if it ain't enough, LOL. As I said earlier, Google "rotor phasing"
straightlinespeed
Sometimes I pretend to be normal
Del, thanks for putting this in layman terms for us. I was unaware of what rotor phasing was although I have heard it many times. Of course I didnt even think to google it and find out more but I will now.
Thank You for alerting us to the quality issues I hadn't looked for.
A performance characteristic I don't like is that the advance curve increases quicker and quicker with rpm (exponentially, or concave slope). I'm pretty sure it has to do with the way the Mallory weights and rotor are shaped. Chrysler built advance is much more linear, and if the heavy spring is used, it slows down the advance even more.
With two short loop springs you should be OK.
Lightest to Strongest Spring Rates:
Pink
Gray
Blue
Brown
Orange
Black
But that's not the end of the story. Measuring the length of the loops, I found they are not all the same. As a result, the force applied may not be in the same order. My best estimate.
Lightest to Strongest Spring Force when stretched 0.72"
Gray
Black
Pink, Blue
Orange
Brown
Lightest to Strongest Spring Force when stretched 0.79"
Gray
Pink
Blue
Black
Orange
Brown
A little confusing, but what this means is that Black is fairly light initially but then slows the curve more. While Orange and Brown will start advancing later and also do so slowly. Pink and Blue will start advance later than Gray or Black, but once started, Pink will have a quick advance curve.
mopowers
Well-Known Member
Well, got the distributor back in. I verified that the reluctor wheel lines up with the pick-up at TDC, which it does. Tried setting the initial timing at everything from 15-30. It picks up RPMs the more I give it, even up to 30*!!! I backed it down to 20* in Park and left it at that. I still can't get it to idle in gear without opening the throttle blades past the transition slots in the carb, so setting the timing in gear is difficult.
It still has the popping issue out of the carb as well. I'll be addressing that next. It almost seems like there's a vacuum leak or maybe it's just running extremely lean. This is strange though because I have the car backed in my garage and it seems like it's pig rich to me. Almost even makes my eyes water after it's been running for a while. How can I fix this popping issue??? It seems to start doing it above 2200 rpm. I've noticed that when it starts popping, the dome light dims.
I still need to try Cudafever's water trick. Any other ideas??
Thanks again guys. I've never had this many issues trying to get a small block to run right.
It still has the popping issue out of the carb as well. I'll be addressing that next. It almost seems like there's a vacuum leak or maybe it's just running extremely lean. This is strange though because I have the car backed in my garage and it seems like it's pig rich to me. Almost even makes my eyes water after it's been running for a while. How can I fix this popping issue??? It seems to start doing it above 2200 rpm. I've noticed that when it starts popping, the dome light dims.
I still need to try Cudafever's water trick. Any other ideas??
Thanks again guys. I've never had this many issues trying to get a small block to run right.
moparlover
Well-Known Member
for the popping, you are getting a voltage drop at that rpm at the same time... pretty weird. make sure you have good ground between the block & frame & negative battery terminal. if needed pull off each of them and wirebrush the connection points. also make sure your electronic ign box and voltage regulator have good grounds.
the popping itself could be a lot of things. you actually may need a stethascope to track it down. could be valvetrain, could be intake crack, or 999 other things.
on the timing, i always used the redneck way to get it approximate, i'd advance it until it was top speed, then back it off slightly. (not 10 degrees!) just slightly. i know you are having trouble getting it to idle to adjust but advance as much as possible but not so much that the engine wont start, then back it off just a hair.
you can get fancy with the timing light later.
you could also ask around there may be a mechanic local to you who is good at rebuilding carbs.
the idle problem persists. if it was me... if i had the cash i'd get a good carb. if i didnt have the cash i'd get one of the hp version thermoquads somewhere, buy a rebuild kit and do it.
it's not that hard, i've done a few of them. rustyratrod Rob can give you pointers.
basically you can get a carb soak kit at auto stores. soak it over night; blow it out with compressed air then spray smaller orifices out with carb cleaner (watch your eyes that **** burns real bad... wear goggles for this part)
then assemble everything together. it's been so long, i dont remember. Rob can tell you where to start with the adjuster screws. all i know is when i put mine on after rebuilding she purred like a kitten. i didnt have a lot of money then and the carb rebuild kit was cheap, and the can of spray.
if you have a holley and want to stick with that you can also rebuild it. there is a book about rebuilding / tuning holley carbs. actually probably 999 books someone else may know the best one to get.
the popping itself could be a lot of things. you actually may need a stethascope to track it down. could be valvetrain, could be intake crack, or 999 other things.
on the timing, i always used the redneck way to get it approximate, i'd advance it until it was top speed, then back it off slightly. (not 10 degrees!) just slightly. i know you are having trouble getting it to idle to adjust but advance as much as possible but not so much that the engine wont start, then back it off just a hair.
you can get fancy with the timing light later.
you could also ask around there may be a mechanic local to you who is good at rebuilding carbs.
the idle problem persists. if it was me... if i had the cash i'd get a good carb. if i didnt have the cash i'd get one of the hp version thermoquads somewhere, buy a rebuild kit and do it.
it's not that hard, i've done a few of them. rustyratrod Rob can give you pointers.
basically you can get a carb soak kit at auto stores. soak it over night; blow it out with compressed air then spray smaller orifices out with carb cleaner (watch your eyes that **** burns real bad... wear goggles for this part)
then assemble everything together. it's been so long, i dont remember. Rob can tell you where to start with the adjuster screws. all i know is when i put mine on after rebuilding she purred like a kitten. i didnt have a lot of money then and the carb rebuild kit was cheap, and the can of spray.
if you have a holley and want to stick with that you can also rebuild it. there is a book about rebuilding / tuning holley carbs. actually probably 999 books someone else may know the best one to get.
mopowers
Well-Known Member
The carb that's on it (750dp holley) has been completely rebuilt.
Maybe I should toss the 600 edelbrock 1406 I have on it just to see if it does the same thing. That carb is near new and works well.
Maybe I should toss the 600 edelbrock 1406 I have on it just to see if it does the same thing. That carb is near new and works well.
Inertia
Well-Known Member
Depending on the year of Holley carb you have,, some Holleys have a problem caused by a back-fire ,, that blows the power valve,, -
the symptoms are as you describe,, power valve pukes fuel at idle,, won't idle down,, mixture screws in-effective,, - eyes watering, - had me wondering when you mentioned it wayy back..
Have you tried a fresh power valve,,
Pull the plugs,, they'll likely be sooty black..
Some-one mentioned a less than open exhaust valve causing a pop,, that's valid, and something to look into..
Check plug wires 6 & 8,, it will run amazingly well with them crossed..
Sure, try the Eddy,, lt'll help the process of elimination..
hope it helps
the symptoms are as you describe,, power valve pukes fuel at idle,, won't idle down,, mixture screws in-effective,, - eyes watering, - had me wondering when you mentioned it wayy back..
Have you tried a fresh power valve,,
Pull the plugs,, they'll likely be sooty black..
Some-one mentioned a less than open exhaust valve causing a pop,, that's valid, and something to look into..
Check plug wires 6 & 8,, it will run amazingly well with them crossed..
Sure, try the Eddy,, lt'll help the process of elimination..
hope it helps
mopowers
Well-Known Member
I'll try a 4.5 PV in the front tonight. The front currently has a 6.5 and the back is blocked off. The base plate is brand new from Holley so I believe it has the back fire protection check ball. Who knows how old the PV is though. Maybe it's bad... That'll be the next thing I check.
Put a PV plug in it when tuning your idle. That will tell you if the PV has an influence at all.
mopowers
Well-Known Member
I do have a PV plug in my carb tuning box. I'll put it in tonight and see what happens. Would in improperly sized or blown PV cause a 'popping' off idle?? Seems like it would just make for a super rich condition at idle.
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