I am going to adjust my mechanical advance from the factory setting of 24* @ 3000RPM down to about 16*.

JPG of instructions for adjustment

I'm hoping its as simple as taking the thing apart and turning the plates to limit the advance.

However I'm wondering, if that when I adjust the plates to stop the weights from giving as much advance that my curve won't change.

Meaning....lets ASSUME that the factory springs give 16* @ 1500RPM. I know that full advance of 24* right now comes in at 3000RPM.

If I adjust the advance total from 24* down to 16*, will the 16* STILL come in at 1500RPM? Meaning, my total mechanical will be lowered, by my curve will be all screwed up, and I will have full mechanical advance before 3000RPM.

Blah....anyone understand what I'm asking? Am I going to need to get a spring kit?

Dave

 

Are you going to set the F*&^&ng thing up or analyze it for 3 years. Stop worrying about the small stuff and get to it.
As long as it advances smoothly from just off idle to about 3000-3200 and maxes out there and returns to initial at idle don't worry about what advance it has at what rpm in between. take the thing for a ride and see how the motor likes it. (Unplug the vacuum advance for now.)
You'll end up with two medium tension springs or one light and one medium.

 

I'm wondering if I should buy a spring kit. If 24* comes @ 3000RPM....won't 16* come earlier? I'm not worried about middle RPM advance, I'm wondering if when I set it to 16* that the 16* won't come in at 3000RPM.

 

If your limiter is a "top stop" then it will max out sooner at 16* advance than with 24*. You're basically just cutting the last 8* off the top of the timing curve. Everything up to that point is the same.

How much sooner will it max out? Consult the instructions or do some testing with a timing light and a friend hokding the engine at known RPM levels as you take measurements.

 

JPG - Adjustment

That is how it works....so I am correct to be concerned that the adjustment is just limiting the weights and that my curve will need to have new springs to get full deployment delayed until 3000RPM?

Thnx

 

From idle to 1500 you will get full advance by 1500 and it will stay fully advanced the rest of the way of the rpm range. That is too soon for full advance, if you want the 16* to come in later as in right at 2800-3000 then you will have to switch to a stronger spring to slow it down so it doesn't just come in so quick.

 

Okay, I'll go try and pick up a spring kit for my distributor. Will ANY spring kit work? I have a 71000 series accel distributor....are all the distributors the same when it comes to spring locations and such? So could I use any springs I want?

F-Bird: Isn't it pointless for me to try and tune the vacuum advance if my mechanical timing curve is all out of wack, if I'm crusing down the road at 1500RPM and my mechanical is putting out all 16* too early since my springs are wrong wouldn't it ruin my attempts to get the advance set?

The car is going into the exhaust shop bright and early to get my hooker catback installed tomorrow (Friday). I'll have it back by night, and I'm going to pick up everything I need (long vacuum line and hopefully pep boys will have a spring kit though I doubt it, I think I'm going to have to order online to get the right one unless any spring kit will work) So all saturday is set aside for getting it all worked out.

 

I adjusted the mechanical advance today. Right now I have about 12* mechanical at 2000RPM. Thats where it maxes out. Now...I'm going to have to pull the distributor again and give it a few more degrees but should I put in different springs? Does it matter if the maximum mechancail advance is coming in that early?

 

Ok, fine tune the total mechanical travel.

The common generic springs from most distributor advance curve kits. Accel, Mr. Gasket, Moroso, etc will work as long as the springs in the kit are the same
length as the ones in your distributor when closed.

A smooth curve starting as just above idle speed
and ending about 3000-3200 rpm is the most practical
for the street.
Get this sorted out before you start to tune in the vacuum advance.

 

...

 

Can I use MSD springs?

http://store.summitracing.com/partde...art=MSD%2D8464

Accel keeps telling me to buy the Mallory 29014 kit for my distributor.

http://store.summitracing.com/partde...rt=MAA%2D29014

But it's 30$ and comes with a bunch of worthless crap, I don't want weights, timing tabs and other useless stuff, just springs. Seems like accel just wants me to buy the mallory kit to charge me 30$ for a bunch of useless stuff I don't need, instead of offering me a spring kit for 10$.

 

Refer to my picture. The MSD springs are the bottom type. Stock GM springs are the top type.
Which type are used in your distributor?
Are they approx the same length when closed ?
As long as they provide some tension when the weights are closed.

If they are you'll be fine. Mr. Gasket makes a spring kit that most local speed shops carry. Many local auto parts stores have them too. Might even rob the stock springs out of a old stock HEI distributor. Give it a try.

Mr. Gasket Advance Springs

 

The springs in mine look like the bottom type you drew. Where the spring is centered on the hangers at each side. From looking at the picture of the MSD kit the springs look like the ones that were in my Accel unit. I can't imagine that there are any huge differences. I'll just go pick up some springs from my local store....worst case scenario I have to return them. Thnx

 

-Fbird88

I just went out and did 65MPH on the highway....I was reading 17" almost the entire time off my ported vacuum @ 2200RPM, my cruise doesn't work, so it fluctuated slightly down to 15" up to 18"....but for the most part it was 17".

Now that is with stock mechanical.

 

Ok and what did you set the mechanical timing at?
initial,,,,, and total?
should have been 16 and advance to 34 at about 3000rpm right?.

How did it run? Did it ping at WOT?

if its ok then you can now dial in the vacuum advance.

hook up the vacuum guage to ported vacuum and rev the motor in neutral until the guage says 17".
Hold the motor steady and then plug in and adjust the vacuum canister to add *10 additional degrees of timing* when the guage says 17". Hook up a vacuum "T" so you
can run both at once. If you can't get 17" at high idle
just pinch the vacuum line till you do get 17".
the rpm (in neutral) that this happens is not relevant.
When you get that set up, plug it in and go for another ride and see how it runs. (smoothness, throttle pedal, temp, throttle response etc. And vacuum guage reading (more, less or the same.) Does it ping or rattle now when you roll into the throttle from cruise speed?
If every thing is ok you can experiment with a little more than 10degrees at 17" at cruise but it will be real close to this. between 10 and 15degrees vacuum advance.

 

....

 

I checked, when I rev my motor in neutral and get 17" and I plug my vacuum advance in, I get 10* more.

Right now my initial is 18*, with 12* mechanical. I'm going to add 2* back to mechanical next weekend when I can get back out there. The engine doesn't ping anywhere, WOT or under load.

I don't think anything has really changed, since my vacuum advance was already putting out 10*, the only thing that changed is that my mechanical was reduced. Should I run more initial? There is still a slight bog when I hit the gas quickly from no load to load.

 

"There is still a slight bog when I hit the gas quickly from no load to load." Are you winging the throttle in neutral
to check the response or driving the car. (Launching it from a dead stop at idle to WOT)?

Overall is the bog problem the same as before, or much improved but still there a bit? You should be able to slow the idle speed down now. Should idle rock steady at 700 rpm when warmed up. You may have to readjust the accelerator pump linkage to get an instant shot of fuel right as the throttle moves.

Try 2 degrees more timing at a time to a max of 36.
that would be 24 initial the way you have the distributor set up now. If you get any ping or rattling at all get off the gas. See how it reacts. yes go back after and readjust the advance travel to get more than 12degrees out of it. 18 should be about right.
Are the plugs old and fouled? can't get sharp throttle response with fouled plugs.
if changing the timing does not cure the rest of the throttle responce problem then you then want to tweek the accelerator pump shooter size and cam shape.
be sure the accelerator pump linkage is adjusted properly. A lot of novice tuners like to crank down the little spring till its tight. All this does is bend the linkage arm and mess up the fuel delivery shot. The spring should never compress to a tight coil bind condition as you wing the throttle open (or the linkage will bend out of adjustment) (liquid fuel in the accelerator pump will not compress) If the arm has become bent out of adjustment no amount of pump cam or shooter changes will get the response right until the arm geometry is corrected.

 

Well before it was a full on bog before, whereas now it's a slight hesitation, much better then before. I've been told that Vortec heads like less total timing then most, around 30*-32*. I have a .31 pumpshot, I can't imagine needing a 50cc pumpshot or a bigger nozzle.

Is it bad to run like 20* initial timing? I'm thinking 20* initial + 12* mechanical I have right now. That would put me right on 32* for total at WOT. (i'm running 18* intial right now)

I floored it on the way to school today on a nice long road. I was doing 25MPH, dropped it into 2nd and floored it, took it to about 90MPH before I ran out of road, I shifted when it hit 5000 and carried third till I hit 90MPH and saw traffic ahead.

No pinging, the engine sounded really good. When I downshifted from 3rd to 2nd and the engine reved to around 3000RPM and I mashed the gas, it pulled really nice and strong. I like how it felt. I don't think I'm going to need to add much more TOTAL timing. My only question now is if I want to trade initial timing for mechanical timing. Meaning run more mechanical and less initial. Someone told me that the mechanical timing curve isn't a big deal, as long as it's all in BEFORE 3000, that I don't neccesarily need it to come at 3000RPM. Is this BS?

I have the car idling 750-800m in park and 600-650 in gear, it's nice and smooth once she warms up, no problems at all. At this point I'm happy with WOT timing and I'm mainly concerned with fuel economy and anything that will help me in that area. I put fresh R42LTS plugs in before I adjusted the mechanical advance. The old plugs all looked perfectly normal, no black buildup, all just tan with no signs of deterioation. Only abnormal thing I saw was that my #8 plug looked like it had just come out of the box when I changed it. I can take a picture tomorrow if you want, but all other 7 plugs looked slightly tannish brown like they should, but #8 the plug was still completely white, with no wear whatsoever, it looked like the thing had never fired.

 

# 8 cylinder is much leaner than the rest.
This will definatly cause a pesky lil bog.

This strongly indicates a manifold vacuum leak on that cylinder. You need to correct this before tweeking other parts.

My 350 vortec motor ran the best MPH with 36 degrees timing at the track(the difference was small). its not that vortec motors typically only need 30-32degrees it that typically they run the same at 30-32 as they do at 36. the more conservative timing often gives the same performance and is much less likely to detonate. The difference won't be that much really.
You'll have to track tune it to be sure. (but you definatley don't want to over advance it)
As a note on my vortec motor the motor didn't care wether you used a fast timing curve or a stock slow curve that didn't max out till a higher rpm ( stock GM springs) the distributor had 20 degrees of advance built in. It also didn't change much with different carb jetting or different secondary vacuum springs.
Actually ran the best with the stock silver vacuum spring.

Is the motor hard to crank over when hot? Does the starter labour?

 

I've noticed the starter "lugs" a couple times then the engine fires right up sometimes, other times if will fire right up w/o lugging.

A manifold leak on that cylinder...hmm...retighten the intake? This would make it the 2nd time the intake has been removed and resealed to fix a "supposed" vacuum leak.

My thought was if #8 was lean or not firing well, that would also hurt my MPG correct?So I could probably get away with running the current springs for my mechanical advance w/o problems? The fact that my total WOT timing is coming in slightly earlier shouldn't affect me?

 

I'd fine tune the advance curve to be 16 initial 34 total and 10-12 vaccuum at hi cruise.

mechanical should be all in by around 3000-3200 or so.

Your present setup is a little to radical right now. I'd slow it down a bit.

What do you have plugged into the vacuum fitting hole
on #8 intake runner? Could be leaking (Air conditioning control, power brakes, The PCV does not belong there.

The carb spacer has to go. can't you trim/ modify the carb linkage so it doesn;t hit the intake manifold?
Where does it hit. Or get a proper divided spacer.

 

Here is an easy way to set it up. With the initial timing set,Run only ONE spring and put the weakest one on. Reassemble your distributor, start the car and then rev the motor while watching the timing mark with the light. Rev it until it stops then mark the number. Say your initial is at 16 and this test produces another 16 then you have 32 total. Next mess with different spring strengths to get your total in at about 3000. The mark should move quickly to the total up to 3000 rpm then stop, it should not go more if you rev the motor higher and it shuld not come in sooner than 2800. PM me if you need specific help.