School Me On Distributor Performance

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indirect_connection

indirect_connection

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I'm wrapping up the installation of a new engine into my '68 Dart. One of the last "while I'm at it" items is upgrading the distributor. I've seen countless threads where it was advised to recurve the distributor for a notable power increase. As engine tuning is new to me, I thought I would ask some question before I proceeded.

Application: What I have is overhauled Magnum 360, Edelbrock heads, Lunati Voodoo 263/271, Airgap, Quick Fuel VS 750, and 340/Magnum manifolds. It will start off with a stock stall converter and 2.96 or so gears. The next major project will be rebuilding an 8.8 with 3.31's.

This is not a race car, but a fun street cruiser. So my power goals are focused more on throttle response and midrange torque.

The distributor is (I assume), the stock 273 points distributor, with the points replaced with a Petronix electronic conversion.
IMG_1912.jpg


I purchased a Mr Gasket spring kit. Multiple times I have seen it referenced that you need to replace the heavier/slotted spring with one of the lighter springs from the kit. However, when I got down to the advance weights I found two identical springs, with about 10 loops each.
IMG_1913.jpg


So would replacing one spring still be the best starting point?

When I played with the timing on the 273, I found that about 34 degrees all in left me about 10 degrees at idle. I'm assuming that leaves me with enough idle advance that I don't need to fool with a limiter plate. Please correct me if I'm wrong.

Also, anything I should clean/lubricate while it's apart? I noticed there is a little trap door that looks like would allow me to lubricate the shaft, but not the advance mechanism. How often should I be adding lubricant, and what should I use? Engine oil?
 
indirect_connection said:
I'm wrapping up the installation of a new engine into my '68 Dart. One of the last "while I'm at it" items is upgrading the distributor. I've seen countless threads where it was advised to recurve the distributor for a notable power increase. As engine tuning is new to me, I thought I would ask some question before I proceeded.

Application: What I have is overhauled Magnum 360, Edelbrock heads, Lunati Voodoo 263/271, Airgap, Quick Fuel VS 750, and 340/Magnum manifolds. It will start off with a stock stall converter and 2.96 or so gears. The next major project will be rebuilding an 8.8 with 3.31's.

This is not a race car, but a fun street cruiser. So my power goals are focused more on throttle response and midrange torque.

The distributor is (I assume), the stock 273 points distributor, with the points replaced with a Petronix electronic conversion.
View attachment 1715691090

I purchased a Mr Gasket spring kit. Multiple times I have seen it referenced that you need to replace the heavier/slotted spring with one of the lighter springs from the kit. However, when I got down to the advance weights I found two identical springs, with about 10 loops each.
View attachment 1715691093

So would replacing one spring still be the best starting point?

When I played with the timing on the 273, I found that about 34 degrees all in left me about 10 degrees at idle. I'm assuming that leaves me with enough idle advance that I don't need to fool with a limiter plate. Please correct me if I'm wrong.

Also, anything I should clean/lubricate while it's apart? I noticed there is a little trap door that looks like would allow me to lubricate the shaft, but not the advance mechanism. How often should I be adding lubricant, and what should I use? Engine oil?
Click to expand...
What are the tag numbers on the distributor?

Jake
 
People have spent lifetimes learning how to tune distributors. You wanting "schooling" in one thread ain't gonna happen. The best thing you can do is get on youtube and look for some good how to videos regarding ignition curves. This thread could go on for 150 pages and you still not know how to do it. Not saying that as a reflection of you, rather the fact that the internet isn't the best place for this type thing. At least not in a typed style forum. Something like this needs to be viewed either in person or on a good quality video in order for you to get a full understanding. You'll be forever chasing your tail with dozens of opinions on a furum.
 
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Oh I understand that there are many variables and each engine combination responds differently. I'm not trying to tune to 1/10 of a horsepower. I'm only trying to move closer to a performance curve vs emission curve.

That's why I focused on just a few questions in my actual post. As for the title, I've found that not being a regular poster, unless the title grabs attention, no one bothers to read or respond.
 
initial and total timing are important as well. And messing with the curve, total, and initial will require you to tune the vacuum advance also. I don't run a vacuum advance, but that's just me
 
Actually so far as OEM advance, "you lucked out" way better'n most of us. That is an early dist and has a fairly short advance. The 8.5 stamped visible in the one photo means you (should) have 8.5 degrees advance in the distributor, which is 17 crank degrees (2x 8.5). What you SHOULD have, then, is (with 10 initial) only about 27 full advance

You are not including vacuum in your readings are you? It should be disconnected for this
 
indirect_connection said:
I've seen countless threads where it was advised to recurve the distributor for a notable power increase.
Click to expand...
Go back and see how many have actual results.

indirect_connection said:
I purchased a Mr Gasket spring kit. Multiple times I have seen it referenced that you need to replace the heavier/slotted spring with one of the lighter springs from the kit. However, when I got down to the advance weights I found two identical springs, with about 10 loops each.
Click to expand...
That was possibly good advice with certain engines, and for drag race only when running points distributors.
Not generally a good shape for a Chrysler smallblock. (see ref 2)

indirect_connection said:
When I played with the timing on the 273, I found that about 34 degrees all in left me about 10 degrees at idle. I'm assuming that leaves me with enough idle advance that I don't need to fool with a limiter plate.
Click to expand...
That would be about right for a factory 273. That's assuming the curve shape and rpms are close to factory
indirect_connection said:
Oh I understand that there are many variables and each engine combination responds differently. I'm not trying to tune to 1/10 of a horsepower. I'm only trying to move closer to a performance curve vs emission curve.
Click to expand...

The way to get anywhere with so much hype, so many sales pitches, and so many self proclaimed experts is to understand what the timing needs to do. Then take a look at known working examples. For example comparing the timing on the same engine from the pre-smog to smog (CAP).

ref 1. Here's a short overview with links back to the Chrysler Tech booklets.

ref. 2. Examples of pre-smog vs. CAP timing in this post

For a general guidelines on vacuum advance timing - see the How To section here.
How To Limit and Adjust Chrysler Vacuum Advance Cans

For the initial, this will put you in ballpark.
Distributor starting point for a curve
On the engine, move it around to get the lowest rpm it will idle with power. That means going back and forth between the mix screws and the idle speed screw so the transfer slots stay in their operating range. Then adjusting the initial timing a couple degrees to see if you can improve the power or idle speed as needed.
 
Many of us here have spent countless hours of "seat of the pants" testing. Your situation is rather simple. If you care about any gas mileage- go conservitive with a vacuum advance. A mild increase in advance rate will serve you well. How much total advance and how quickly it advances is best checked by someone with a distributer machine. How are the bushings? How is the vacuum advance?
 
indirect_connection said:
Oh I understand that there are many variables and each engine combination responds differently. I'm not trying to tune to 1/10 of a horsepower. I'm only trying to move closer to a performance curve vs emission curve.

That's why I focused on just a few questions in my actual post. As for the title, I've found that not being a regular poster, unless the title grabs attention, no one bothers to read or respond.
Click to expand...

I would recommend a video.......hang on, @yellow rose didn't you have a video with a distributor machine? Surprisingly, it actually wasn't very gay. LOL Maybe that would help. You gotta link to it, Tim?
 
Thanks for all the input. Lot to think about. I was thinking that proven combinations were a little more cut and dry. Guess I'll have to tinker.
 
toolmanmike said:
And so does @halifaxhops and he is a member here.
Click to expand...

My distributor was part of a MopPerf. points to electronic kit. I sent it to halifaxhops and he recurved the distributor after asking all the right questions about what I was doing with it and back it came freshly rebuilt and ready to go, with all the paperwork so that down the road I would know what I had, all for a reasonable price... can't ask for more than that.
 
Normally, I do not recommend dial back timing lights. They are usually not very accurate....that is unless you spend a lot of money on a digital one. BUT, you can get an old analog one cheap. Why? Because you can learn a lot from it. Play around with it and see how it works. That will tell you a lot about what's goin on right there. Then use a standard non dial back light to set timing.
 
My only other suggestion is to make sure you have a backup distributor in case your tinkering goes south... Get a newer distributor post 72 distributor. They are all electronic and cheap.
 
indirect_connection said:
Thanks for all the input. Lot to think about. I was thinking that proven combinations were a little more cut and dry. Guess I'll have to tinker.
Click to expand...
Each new build is different and needs a different curve. Watch the MP kits really a fast curve. Same with the MG springs.
 
indirect_connection said:
Thanks for all the input. Lot to think about. I was thinking that proven combinations were a little more cut and dry. Guess I'll have to tinker.
Click to expand...
The governer in there makes that a good distributor to work from.
Correct. The combinations are not as simple as two points or two springs. On the other hand, the combustion and piston position relationship for an engine family will have similar timing needs.
Set up a baseline using the guidelines linked above. Then make a change and retest.
If you're interested in doing it all yourself, I've posted about how to change the start of the advance, how to slow the rate, and other adjustments. I didn't post link to those 'cause figured you had enough to read through now.

Speaking of proven combinations, the gearing and torque converter you are starting with is going to put a high load on that engine at idle and coming off idle. The engine combo you posted is relatively weak at idle and low rpms. Getting the fueling and timing such that it will actually pull the load effectively will be very difficult. The quicker you want to load it (open the throttle) the more load it will see. That's why an engine with a cam like that is usually paired with a looser converter.
 
Mattax said:
Speaking of proven combinations, the gearing and torque converter you are starting with is going to put a high load on that engine at idle and coming off idle. The engine combo you posted is relatively weak at idle and low rpms. Getting the fueling and timing such that it will actually pull the load effectively will be very difficult. The quicker you want to load it (open the throttle) the more load it will see. That's why an engine with a cam like that is usually paired with a looser converter.
Click to expand...

Now those cam numbers are advertised duration not at .050. Lunati did recommend deeper gears, but said that a higher stall was not needed.
 
RustyRatRod said:
I would recommend a video.......hang on, @yellow rose didn't you have a video with a distributor machine? Surprisingly, it actually wasn't very gay. LOL Maybe that would help. You gotta link to it, Tim?
Click to expand...


Here you go...

That is a video of the timing retarding with RPM I think. Been a while since I did that one, but I think this is it.

And I forgot about this video. I made it because this is a cheap eBay distributor that is UNtuneable. In fact, I finally got pissed off spending time trying to locate some parts and called the dude that sells them. He says they were designed to be UNtuneable, which IMO is REtarded. One curve doesn’t fit all and their is no way to change the curve on that without spending more time and money than its worth. In fact, I had the distributor so far apart the guy wanted me to send him pictures. I thought he wasn’t going to take it back when he looked at the pictures, but he did. He said no one was supposed to take them that far apart. How else do you figure out how stuff works.

So I put it back together, made sure it worked and sent it back.
 
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