What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

distributor weights

COCHEV

COCHEV

1/2 ton status
Joined
Jul 9, 2002
Posts
4,054
Reaction score
5
Location
Washougal WA
so it was oil change and tune up time on my work truck- 82 pickup with newer 350 gm crate in it. i noticed that my distributor weights/ mechanical advance was all stuck and didn't spring back like it should. i also noticed that it had wimpy little springs and little weights on it. so pulled apart a spare dizzy i had off a 454 and it had bigger weights-stamped 60 and much heavier springs. i swapped these on and it worked better and gave me better throttle response than i was having. but what i'd like to know is what weights and springs should be in there for my 350? also, how do i grease/lube/service the mechanical advance?

thanks,

jason
 
You'll need a timing light with the advance feature and then you just play with how you want the vehicle to perform. The weights and springs determine how much advance and how fast the advance comes in. Keep in mind that you want no more than 36* total advance. You'll need a vacuum pump as well to determine how much advance the vacuum advance gives. Let say you have initial timing set at 10* BTDC and there is 15* advance coming from the vacuum advance then you only want to have a max of 11* mechanical advance to total the 36*.

There is one small teflon pad under each distributor weight and that should have a very small amount of grease on it for the weight to rub against. Make sure the weight pins aren't worn out and ready to break. If they are it's time for a new distributor as those aren't replaceable.
 
gm had a large variety of weights and springs that are engine and vehicle specific. i would recommend that you check you total advance of your timing and see what iit is at. anytime you change the weights and springs it affects the advance rate and also the total timing.
 
4X4HIGH said:
Keep in mind that you want no more than 36* total advance. You'll need a vacuum pump as well to determine how much advance the vacuum advance gives. Let say you have initial timing set at 10* BTDC and there is 15* advance coming from the vacuum advance then you only want to have a max of 11* mechanical advance to total the 36*
Click to expand...

You want to have 32 - 38 total WITHOUT the vacuum advance. Setting it up for 36 total with vacuum advance is a recipe for no power and crappy mileage. Vacuum advance is not operating at WOT and you want that timing at WOT or power will suffer. The vacuum advance helps throttle response and efficiency at low load. You want to have 48 - 54 with the vacuum advance, 54 is pushing it, 50-52 is better. To be conservative I would set it at at 34 @ 3-4k RPM with vacuum advance disconnected and then reconnect it and make sure it's not too high. You want the lightest springs that don't cause detonation. However, if they aren't functioning then that's a different problem. Obviously if you get detonation at any time then you need to retard timing.
 
how do i solve the stickiness in the mech advance itself. i sprayed some wd40 on there and worked it around but it only did a little. can it be greases some how or is it shot when it gets to this point? i guess i can just rob the other distrib, but i'd like to know if this is a servicable problem.

the difference in the weights and springs between the two is significant. isn't there a "stock" 350 setup? its my work rig. i want it to start up and drive down the road
 
GM probably had MANY weight/spring combinations. You can buy a kit from some company that has a couple of weights and springs, but I don't think they come with the teflon pads.

WD40 isn't a good long-term lubricant BTW (in a pinch use what you have of course), WD stands for Water Displacing and it is better at that.

Need to really inspect the posts the weights pivot on as Scott mentioned, any binding will screw up your timing, which may affect things like idle.
 
its actually sticky where the rotor attaches in relation to the distrib. shaft- with the weights off and just moving it through the range of motion the mech advance allows, if that makes any sense...

dyeager535 said:
GM probably had MANY weight/spring combinations. You can buy a kit from some company that has a couple of weights and springs, but I don't think they come with the teflon pads.

WD40 isn't a good long-term lubricant BTW (in a pinch use what you have of course), WD stands for Water Displacing and it is better at that.

Need to really inspect the posts the weights pivot on as Scott mentioned, any binding will screw up your timing, which may affect things like idle.
Click to expand...
 
folkenheath said:
You want to have 32 - 38 total WITHOUT the vacuum advance. Setting it up for 36 total with vacuum advance is a recipe for no power and crappy mileage. Vacuum advance is not operating at WOT and you want that timing at WOT or power will suffer. The vacuum advance helps throttle response and efficiency at low load. You want to have 48 - 54 with the vacuum advance, 54 is pushing it, 50-52 is better. To be conservative I would set it at at 34 @ 3-4k RPM with vacuum advance disconnected and then reconnect it and make sure it's not too high. You want the lightest springs that don't cause detonation. However, if they aren't functioning then that's a different problem. Obviously if you get detonation at any time then you need to retard timing.
Click to expand...

You better go back to the drawing board. 36* is the optimal advance for performance. I've been doing this for 31 years now so maybe i just don't know what i'm doing. :rolleyes:
 
Then that would be 36* mechanical advance, right? Which is what you are both saying....36* mech (acceleration), more with vacuum, which would be idle and cruise.

I'm going to be the third dissenting opinion here, and say that max advance is based on the engine combination, not a theoretical optimum. While it does seem to fall into a pretty narrow band, so does best AFR for power. But it's not exactly the same, again determined by engine combination.
 
dyeager535 said:
Then that would be 36* mechanical advance, right? Which is what you are both saying....36* mech (acceleration), more with vacuum, which would be idle and cruise.

I'm going to be the third dissenting opinion here, and say that max advance is based on the engine combination, not a theoretical optimum. While it does seem to fall into a pretty narrow band, so does best AFR for power. But it's not exactly the same, again determined by engine combination.
Click to expand...

No, 36* TOTAL being a combination of initial, vacuum, and mechanical advance. If you don't run a vacuum advance then it would still be 36* TOTAL between initial and mechanical.
 
4X4HIGH said:
No, 36* TOTAL being a combination of initial, vacuum, and mechanical advance. If you don't run a vacuum advance then it would still be 36* TOTAL between initial and mechanical.
Click to expand...

Well if you've been setting it up that way for years you've been doing it wrong for years. :rolleyes: I don't care if you do build engines for a living that's just the wrong way to set up vacuum advance. You do not include vacuum advance in your total of 36 degrees, vacuum advance does not operate at WOT. I've been doing it this way for only 15 years, but my father and uncles have been doing it for probably 40 years this way. If you don't agree with me then give this a read and see what you think....maybe you'll believe some of the people who helped design it.

http://www.maliburacing.com/forum/viewtopic.php?f=4&t=2484

And if you don't want to believe it thats fine, go ahead and keep giving up fuel economy and horsepower by limiting your timing at WOT and cruise conditions and pretty much the entire time the engine is running. :rolleyes:
 
COCHEV said:
its actually sticky where the rotor attaches in relation to the distrib. shaft- with the weights off and just moving it through the range of motion the mech advance allows, if that makes any sense...
Click to expand...

If you're careful you can remove the distributor and punch out the roll pin on the dist gear. Then take it all apart and clean it and lubricate it and put it all back together, it should free it up unless you find another problem when you take it apart. Just make sure you get the spacers and washers etc all back exactly where they came from between the drive gear and housing. And make sure the roll pin is not damaged or sticking past the OD of the gear.

Also, the last advance kit I bought for $9 or something at the parts store did come with the little bushings, but they all might not. If it's your work truck just use the medium or heavy springs and be done with it.
 
X2!

What I have always done is used the Mr Gasket weight and spring kit, with the lightest springs. Then bring the engine to 3500 RPM and set timing to the 34-36 degrees advanced. This worked very well for me, I also had the adjustable vacuum advance canister. Im sure there are about as many different ways to do this as there are members on here.
 
Last edited:
i would like to comment that total timing is not everything in performance. 36 degrees sounds like a good area to have the total at without the vacuum advance added in. what the advance curve actually does on an engine is different for every engine. i would concentrate my main efforts on getting the initial timing correct and then find a weight and a spring combination to get the desired total timing that i want. the intial timing makes the engine perform better at low rpms combined with the vacuum advance. crane cams makes an adjustable vacuum advance that you can select the amount of total vacuum advance by adjusting a simple cam inside the distributor with a screwdriver. the total timing is only really needed for 3500 rpm and up. i would try to get the initial timing around 13-16 degress and then get the total timing around 35 degs. basically the total timing should be maxed out by 35-3800 rpm. i dont know about you but most of my driving is done below 3500 rpm. if you take some time and have some patience the timing work will pay off big. the fuel today is not designed for carbs, it is designed for fuel injection. when the engine gets bad fuel the efi can make changes to the timing and the fuel rates and the carb and the distributor cant they are a set amount of parameters that they function in. and remember that it is only a machine it only knows how to run as good as you can tune it. for the sticky weights and the mechanical advance plate try using some tri-flow or try some super slick slick stuff. the later of the two works awesome and also has a great smell and has no residue left over after it has dried. hope this helps you
 
I never found a lubricant that kept the weights moving long term. (I tried silicone, lithium, ATF and dry. You don't want to use graphite for obvious reasons.) Teflon is your best bet there. As for the mechanism itself, you'll just have to clean out the distributor every so often. The problem is that the dizzy is open to the heated engine oil below. You don't always notice that it's sticking until you clean it and see how much better it runs.

I don't want to get involved in the argument about how to set timing, but keep in mind that "total" timing has different meanings for mechanical/vacuum timing and electronic timing. The "total" for electronic is a number that is actually achieved, whereas for mech/vac it's a theoretical number. You really never get that high, since they are active in different ranges of operation. How can you run at 5000rpm with the throttle closed?
 
You must log in or register to reply here.

Latest Posts

Top Bottom