2F Large Cap Dizzy Governor Springs (1 Viewer)

[Slow Left]

Hey folks,

I posted this question a while back over in the 60 section (I've got a stock 1981 FJ60), but decided to post here, too, since I haven't made any progress and was hoping that some of you all might be familiar with the large cap dizzy...

Posts over in the 60 section:
https://forum.ih8mud.com/threads/1981-87-fj60-governor-springs.813846/
https://forum.ih8mud.com/threads/distributor-stop-pin-bushing-dimensions.784670/

Toyota lists the 2 Governor Springs for the 1981-87 FJ60 2F large cap distributor as NLA:

part# 19154-61102
part# 19153-61102

Does anyone know:
1) if the OEM parts are still available elsewhere?
2) what the spring constant for each of these OEM springs are?
3) if there are aftermarket springs with the same OEM spring constant that will work?
4) if there are aftermarket springs with similar spring constants that might be an improvement?

I'm trying to adjust the ignition advance curve because I'm seeing full 38* advance before 2000 rpms!! So if anyone has been working on DIY improvements such as changing springs or weights for adjusting advance rate as a function of rpm, I'd be interested in hearing any suggestions you might have...

Thx.

 

[1911]

Have you contacted Jim C. here on mud (fj40jim)? He rebuilds and re-curves these (he did mine as a matter of fact) and he would surely have the answers to all your questions.

 

[Slow Left]

Have you contacted Jim C. here on mud (fj40jim)? He rebuilds and re-curves these (he did mine as a matter of fact) and he would surely have the answers to all your questions.

Yeah, Jim has been really helpful here on MUD. I've read through his threads...so I've got a general idea of what a 'better' ignition advance curve should look like...

I'm constrained by both resources and working on a DD, so I'm moving forward step by step...

My research indicates that these stock large cap dizzys give:
23* of mechanical (centrifugal) advance
18* of vac advance
6* of HAC (High Altitude Compensation) advance
So total max advance according to Factory Specs should be ~41* at sea level...

My rudimentary ignition advance curve measurements (taken by reading timing tape on the fly wheel - fully smogged stock 60):

With the Stop Pin Pushing Installed & Vac Advance Lines connected
RPM Measured Advance (Total = Base + Mech + Vac)
Idle (650) 10*
1000 10*
1500 16*
2000 41*
2500 41*
3000 41*

With the Stop Pin Pushing Installed & Vac Advance Lines disconnected
RPM Measured Advance (Total = Base + Mech)
Idle (650) 10*
1000 11*
1500 16*
2000 21*
2500 21*
3000 21*

...so both my mechanical and vac advance are all in by 2000 rpms!

According to a post by Jim in the following thread (also from the 40 &55 section):
https://forum.ih8mud.com/threads/ignition-advance-curve.321573/

" Start w/ base timing of 10*.
Do not use timing for idle speed stabilization. It does not work well on a trail rig. Use an IAC for that.

Do not bring on too much timing too soon. The engine makes peak torque @2000, so cylinder pressure is highest, so flame speed is highest. Mild advance until past 2000, then a little more, but not too much because there is a second tork peak @2600, then bring on the advance after 3000.

Above 3000, piston speed is getting high, and the engine is starving for air, so cylinder pressure falls way off, so much more advance can be used all the way thru 4000."

I've been slow to take risks with trial and error because I don't want to damage the engine, but looking at the curve I currently have, I am beginning to think that adding any heavier springs can only help and that I'm doing more damage with my current weak springs because all the advance is coming in so early in the rpm band...but it would be nice to know if someone else has more specific recommendations to reduce the amount of trial and error I'm facing...

Thx.

 

[DougAustinTx]

I'm not familiar with the springs on the large cap dizzys, but trial and error has always worked for me back in my racing days. You can experiment by replacing just one of your weak springs with a stronger spring and see what happens. You need the type of spring that has a longer loop on one end that doesn't pull on the spring post until the weak spring is partially extended. That will get the early advance, but hold off max advance until you hit the sweet spot in the cam's power curve. It is not unusual at all to have two different spring rates in the dizzy to vary the initial, versus all-in timing. The bottom line is that timing errors won't hurt your engine unless you run it at max output for a long time, so I wouldn't invest too much time in trying to precisely fix the advance curve.

 

[Slow Left]

I'm not familiar with the springs on the large cap dizzys, but trial and error has always worked for me back in my racing days. You can experiment by replacing just one of your weak springs with a stronger spring and see what happens. You need the type of spring that has a longer loop on one end that doesn't pull on the spring post until the weak spring is partially extended. That will get the early advance, but hold off max advance until you hit the sweet spot in the cam's power curve. It is not unusual at all to have two different spring rates in the dizzy to vary the initial, versus all-in timing. The bottom line is that timing errors won't hurt your engine unless you run it at max output for a long time, so I wouldn't invest too much time in trying to precisely fix the advance curve.

Thanks for the reply, Doug.

Yeah, I'm really starting to think that I can only make things better than they currently are by trying out new springs.

Right now I'm leaning towards trying these MSD kit #8464 (available through AutoZone):

Not sure if it is possible to put them in backwards (does one end go on the weight?) or upside down (if the 'mass' of the coil faces up or down...but they have to fit under the breaker plate, at the very least), but I'll take a look at the originals that are currently installed to see if there are any clues...

And based on my current curve measurements and the recommendations that Jim provides, I'm wondering if the way to approach this is to try to use the vac advance for the lower rpms and have the mechanical kick in at higher rpms...because at higher rpms the "cylinder pressure falls way off", so I'm wondering if that means that the rate of vac generated/rpm decreases?
Or could I be misinterpreting that and if the "pressure falls way off" then the vac increases exponentially?

If vac decreases at higher rpms, then I will want heavier springs, say a medium and a heavy, so that the mechanical advance kicks in later.
If vac increases at higher rpms, then I will want the mechanical to kick in at low/medium rpms, so light and medium springs...

Another factor I might take into consideration is leaving/removing the blue VTV that is inline with the primary vac port on the dizzy. I think the VTV retards vac at lower rpms.

 

[FJ40Jim]

My research indicates that these stock large cap dizzys give:
23* of mechanical (centrifugal) advance
18* of vac advance
6* of HAC (High Altitude Compensation) advance
So total max advance according to Factory Specs should be ~41* at sea level...

My rudimentary ignition advance curve measurements (taken by reading timing tape on the fly wheel - fully smogged stock 60):
With the Stop Pin Pushing Installed & Vac Advance Lines disconnected
RPM Measured Advance
Idle (650) 10*
1000 11*
1500 16*
2000 21*
2500 21*
3000 21*

...so both my mechanical and vac advance are all in by 2000 rpms!
Thx.

The stock dissy will give 21-23* of mech advance at 4000RPM. Starting with idle timing of 10, the timing will be 31-33 when mech is all in. The above data does not show advance all in at 2000.

Vac advance will be all in when the throttle is lightly opened (free revving the engine in the driveway).

HTH

 

[Slow Left]

Oooohhhh...Thanks for catching that Jim!!! I failed to subtract out the Base timing...so here is the data again with this clarification...

So, I relabeled the above curves to show which curve has which component incorporated in the measurement (Base, Mech or Vac).

Here are those curves with the Base timing subtracted out (first two curves) and the last curve subtracts out both the Base and Mech components...

With the Stop Pin Pushing Installed & Vac Advance Lines connected
RPM Measured Advance (Total = Mech + Vac)
Idle (650) 0*
1000 0*
1500 6*
2000 31*
2500 31*
3000 31*

With the Stop Pin Pushing Installed & Vac Advance Lines disconnected
RPM Measured Advance (Total = Mech)
Idle (650) 0*
1000 1*
1500 6*
2000 11*
2500 11*
3000 11*

With the Stop Pin Pushing Installed & Vac Advance Lines connected
RPM Measured Advance (Total = Vac)
Idle (650) 0*
1000 0*
1500 0*
2000 20*
2500 20*
3000 20*

So, if I am expecting to see:

23* of mechanical (centrifugal) advance
18* of vac advance
6* of HAC (High Altitude Compensation) advance

then it looks like I am seeing:
11* of mech advance between 650 to 2000 rpms
20* (full) vac advance between 1500 and 2000 rpms

So, assuming that the measurements correctly reflect what is going on:
1) I'm not seeing any vac advance until 1500 rpms and then it is all in (this contradicts the principle that you mention above, that at low rpms I should see vac all in...so something's not right here)
2) I should expect to see another 10-12* mech advance up to 4000 rpms (something's not right here, but I don't have data above 3000 rpms)
3) I am seeing mech advance rise steadily between 650 and 2000 rpms... (this seems to be the only thing that jives)

 

[Slow Left]

If...vac advance is supposed to be all in just as the throttle opens as acceleration from idle begins...
...and my measurements show that I am not getting vac advance at the dizzy until 1500 rpms...

...then either:
1) vac is not pulling on the primary advance port at the dizzy, or
2) vac is pulling on the primary advance port at the dizzy...but isn't transduced into mechanical actuation of the arm or the breaker plate

If 1)...then:
a) primary throttle plate is not calibrated correctly (don't see how this is likely, since the throttle plate must open for the engine to accelerate)
b) hose to Advancer port is incorrectly routed (I checked this before by pulling vac from the hose connection at the primary vac port at the dizzy with the engine at operating temp (BVSV 1 open) and it pulled vac on the hose that connected to the Advancer port on the carb)
c) Advancer port on the carb is blocked and needs to be cleaned
d) there is a vac leak somewhere along the vac circuit outlined in red below...and the leak is small enough that it can be overcome as vac increases at higher rpms...

If 2)...then:
a) the diaphragm on the primary vac port at the dizzy is leaking (I put Mighty vac on the port and it held)
b) the diaphragm is not actuating the arm (I put Mighty vac on the port at idle and saw the timing advance)
c) the arm is actuating, but breaker plate isn't rotating (I put Mighty vac on the port at idle and saw the timing advance)
Note: it took ~5 inHg Mighty vac at the primary port on the dizzy until I began to see timing advance

 

[ducktapeguy]

I don't really have any useful advice since you're talking about a 60, but Im following this thread closely because I finally got my stop pin bushing installed and was going to take a baseline reading of my current advance curve before swapping over to the large cap dizzy. I know at least one other person has done it before, just can't find the numbers right now.

Just curious if you've hooked up a vacuum gauge to one of your ports and plotted vacuum vs. rpm? One of those things I've been meaning to do but never got around to doing. I just remember reading an article somewhere about using manifold vac vs. ported vac for the vacuum advance and the explanation was very interesting.

 

[Slow Left]

I don't really have any useful advice since you're talking about a 60, but Im following this thread closely because I finally got my stop pin bushing installed and was going to take a baseline reading of my current advance curve before swapping over to the large cap dizzy. I know at least one other person has done it before, just can't find the numbers right now.

Just curious if you've hooked up a vacuum gauge to one of your ports and plotted vacuum vs. rpm? One of those things I've been meaning to do but never got around to doing. I just remember reading an article somewhere about using manifold vac vs. ported vac for the vacuum advance and the explanation was very interesting.

Thanks for the reply, ducktapeguy.

Yeah, appears like what I had originally attributed to a dizzy spring/weight issue might very well have roots in the confusion that is the 60's vac switching...1980's emissions...uugh...but I'm still not ruling out a weak spring, they are 30 years old after all...it's just that the data is pointing me towards checking the vac advance again for something I might have missed.

I have a vac gauge installed in the cabin of the vehicle.
The vac gauge ports off the A/C idle up union (next to the brake booster port) on the rear of the intake manifold.
The manifold vac reads ~21 inHg at idle.
At WOT the vac drops to ~2 inHg.

So this could be an issue. My crude measurement at the primary vac advance port on the dizzy was that it took ~5 inHg (applied by hand held Mighty Vac tool) to advance at idle. So if the current condition of the vac pot/arm/breaker plate demands at least ~5 inHg of vac in order to advance...and under acceleration the engine is only generating 2 inHg of vac, then that is insufficient to get the vac advance when I need it.

But that is manifold vac. I think you're right...I will take some more measurements (at idle and different rpms) by t-ing in the Mighty Vac:
1) at the primary vac advance port on the dizzy
2) in line between the VTV and BVSV
3) at the Advancer Port on the carb

Also will check valves/switches and pipes for vac leaks...

I'll post up the info as soon as I get it.

Thx.

 

[FJ40Jim]

Vac advance is zero at idle and zero under heavy load. Vac advance applies extra advance when the engine will tolerate it: at light load.

 

[Slow Left]

Vac advance is zero at idle and zero under heavy load. Vac advance applies extra advance when the engine will tolerate it: at light load.

Alright, thanks for the clarification, Jim. It really is helpful to have confirmation on what to expect for measurements from a properly working system.

I'm thinking I'll go ahead and recheck these vac routes/components just to make sure I didn't miss anything last time I went through the emissions systems...the VCV on the EVAP checked out good last time I went through it, as did the VSV for the EGR.
EGR Valve and Modulator are both brand new...
I did bend the vac piping that sits on top of the manifolds when I installed a Saginaw PS bracket (mounted on the two front DS headbolts) so I've always wondered if I might have cracked or pinched pipe(s), but when I went through and tested for vac between the advancer port on the carb and the primary advance port at the dizzy, it was pulling vac...

Anyway, I'll double check to rule it out (and make sure all those lines on the carb are ported correctly...it could be something stupid like I've got the EGR ported incorrectly,...maybe...) and then step back and go back to the basics...

 

[Slow Left]

Vac advance is zero at idle and zero under heavy load. Vac advance applies extra advance when the engine will tolerate it: at light load.

Questions:

1) Is there any benefit to performance by rerouting the primary vac advance hose so that:
a) the VTV is eliminated... and
b) the primary vac advance diaphragm sees direct manifold vac at all times (instead of ported manifold vac)
...while keeping everything else (ie EGR) stock (ie installed)

2) If yes, then where would be the best place to t into to route that hose...above the PCV valve on the PS side?...off the small air filter on the manifold on the DS?

I'm wondering if the primary advance diaphragm sees direct manifold vac then that might improve transition and off-idle performance and increase MPGs...?

 

[76technician]

Nope. You want ported, not manifold vacuum. Ever watched a vacuum gauge as you open the throttle? Manifold vac Is highest at idle, and drops instantly when you apply throttle.

 

[Slow Left]

Manifold vac Is highest at idle, and drops instantly when you apply throttle.

Yes, I agree this is how the manifold vac behaves on a properly operating engine.

Nope. You want ported, not manifold vacuum.

This is my question. I'm not sure that I necessarily want ported vac for better performance. My understanding is that ported vac became a 'thing' when emissions standards kicked in to lower emissions at idle...at the cost of performance.

So, since manifold vac is highest at idle (~21 inHg) and falls off quickly (down to below ~5 inHg at WOT)...AND, for a ported vac advance system...vac advance is effectively shut off (ie ported) at idle when manifold vac is highest...and falls off towards 0 when the throttle opens (under load)...then what is the point of ported vac advance?

Shouldn't I want to have (for best performance) vac advance at idle that then falls off under load as the mechanical advance kicks in?...Wouldn't this give the best/smoothest transition?

My question is directed at the benefit of keeping ported vac if I can increase performance by routing the primary vac advance to see direct manifold vac.

 

[Slow Left]

Oh, I should add that the reason I'm thinking this way is that flame speed (the rate of explosion of the combustible gas/air mixture in the cylinder chamber) is not constant for all engine rpms...

So, at idle (lower rpms), the engine needs more advance to compensate for a slower flame speed...at least this is my understanding...

 

[76technician]

There's a problem - ported vacuum is low / 0 at idle, rises at low throttle, then drops at WOT. This gives a smooth transition of rising advance until the mechanical advance catches up (at least as I understand it). Paging Jim C!

 

[Slow Left]

ported vacuum is low / 0 at idle, rises at low throttle, then drops at WOT.

Yep, agreed...this is how ported vac advance works.

ported vacuum is low / 0 at idle, rises at low throttle, then drops at WOT. This gives a smooth transition of rising advance until the mechanical advance catches up (at least as I understand it).

This is what I'm questioning.

I'm wondering if switching from ported to direct vac advance, then instead of:
...having to go from 0 all the way up to full (or, if the VTV is in line, then the rate of vac delivery to the primary advancer port is retarded even further) then back down again as manifold vac in the cylinders falls off under load towards WOT...as seen in ported vac advance systems
...then just let the manifold vac regulate the vac advance as required from the get go...as I would expect to see rerouting directly to manifold vac

It seems to me that two things complicate efficient use of vac advance when using ported vac:
1) the fact that porting the vac advance (so, 0 vac advance at idle) adds a lag in timing/delivery during transition at low rpms...when vac advance is needed most...
2) the ported vac advance routing tries to coordinate with the EGR system...adding complexity to the system (see the red highlighted routing in post #8 above, at BVSV 1 on the dizzy side, it splits...one hose going to the primary advancer port on the dizzy (with the VTV in line) and the other leads to the EGR VSV and EGR Valve Modulator...

There are some very good explanations on vac (how it is generated and used) pasted in two posts (two different sources) in this thread:
http://board.moparts.org/ubbthreads/showflat.php?Number=6765885

Just trying to figure out if this simple switch from ported to direct manifold vac for the vac advance is beneficial to the requirements of the USA 2F (read smog here) keeping the stock EGR system installed.

 

[76technician]

Sorry, been a while since I read the whole thread, now I remember your whole dilemma. What were your numbers for ported vacuum at increasing rpm? I would suspect time for an overhaul of the carb or replacement of the distributor - rather than the extended tinkering.

 

[FJ40Jim]

No, manifold vac will cause the dissy to pull in all the vac advance as soon as the engine starts, then the timing will fall off the instant the throttle is cracked. That is bad.