Can't account for all of my timing advance, please help.

[Gregski]

so with the new PCV grommet and things air tight, the truck properly warmed up to 180° F (got a 180 thermostat) and it's what it likes etc.

I still can't get it to idle below 1100 RPM now

I did not budge, nudge the distributor, I did not mock with the idle speed screw, I did not mess with the two idle mixture screws, all I did was unhook the vacuum advance hose off the carb and plug the nipple to get my base timing without the vacuum advance, then I put the hose back on

now my timing at idle aka 1100 RPM is 34° truck seems to run OK, but I don't want it idling that high

to lower the timing I tried backing out the idle speed screw and I can completely unscrew it and it won't drop under 1100, before it was super happy at 780, remember?

this reminds me of a car show I was watching, Hot Rod Garage or something where two very competent technicians changed the carpet in the car and afterwords it would not start or run properly, LOL

[Gregski]

Originally Posted by geezer#99

Lubricate the grommet with wd40 and it should be easier to install.

no need the dragon spews oil all over the valve covers so it is [ahem] pre lubricated, but I appreciate the tip and will do it on other dry elements, thank you as always

[Gregski]

what is going on, just went out there to check my idle RPMs and after I warmed the truck up in the driveway to 180° and I put the timing light back on it (vacuum canister connected) it now idles at 850, all I can say is that can it be Humidity, as it is "only" 87% right now and it was 100% the other day

[Gregski]

So my mechanical only timing looks like this (no vacuum advance)

RPM - - - - - - - ADVANCE DEGREES

700 - - - - - - - - - - 15° (base timing)

1000 - - - - - - - - - -17° (includes 2° mechanical)

1500 - - - - - - - - - -30° (includes 15° mechanical)

2000 - - - - - - - - - -31° (includes 16° mechanical)

3000 - - - - - - - - - -33° (includes 18° mechanical)

4500 - - - - - - - - - -34° (includes 19° mechanical)

5000 - - - - - - - - - -35° (includes 20° mechanical)

Proform claims this distributor adds 24° of mechanical advance, well this is why we test, and this is why we don't "trust" mechanical advance and seek justification to go electronic. I am not ranting, I am simply stating facts based on my data, not only in this experiment but of the last 5 years, it's always been accurate(ish) ha ha

[rpmerf]

That's an interesting timing curve. 15* by 1500, but it takes another 2500 to get the next 5. A different spring kit would allow you to get all in faster. I thought it was normal to have it all in around 2500-3000 RPM.

[Gregski]

Originally Posted by rpmerf

That's an interesting timing curve. 15* by 1500, but it takes another 2500 to get the next 5.

indeed

Originally Posted by rpmerf

A different spring kit would allow you to get all in faster. I thought it was normal to have it all in around 2500-3000 RPM.

I did buy a weight and spring kit from Proform as well and tried playing with it, but my days of mechanical timing advance adventures are over, I am about to install my brand new MSD 6AL-2 Programmable ignition box and never look back, I just wanted to plot my current advance curve so I could have a baseline.

[burnin oil]

You will really like that ignition box. A word to the wise. Carry a spare high quality distributor cap and rotor. With a hot coil you can eat the contacts up faster and that little black brush under an HEI coil can overheat and melt the cap. Never had a problem in town but when I went on a road trip I lost 3 caps and coils about 150 miles from the house. Of course it was after midnight on a back highway. Luckily I had a couple of old spares in the tool box. The key is that black bushing has to be quality, the lesser parts store caps have to much resistance. Also be preparred to clean the contacts more often. You can normally clean them up with a dremel tool several times before replacing.

[Gregski]

Originally Posted by burnin oil

You will really like that ignition box. A word to the wise. Carry a spare high quality distributor cap and rotor. With a hot coil you can eat the contacts up faster and that little black brush under an HEI coil can overheat and melt the cap. Never had a problem in town but when I went on a road trip I lost 3 caps and coils about 150 miles from the house. Of course it was after midnight on a back highway. Luckily I had a couple of old spares in the tool box. The key is that black bushing has to be quality, the lesser parts store caps have to much resistance. Also be preparred to clean the contacts more often. You can normally clean them up with a dremel tool several times before replacing.

thanks for the tip, did you phase your HEI distributor, I hear its a must for these electronic MSD ignition boxes if you expect any type of precission out of them, but then I hear MSD doesn't make an adjustable HEI rotor so I'm a bit perplexed

[burnin oil]

Honestly I dont remember. I gave up on the factory HEI unit a couple of years ago and went to a MSD small cap dizzy. The HEI was still good but worn a little to much for the RPMs that I was turning. Those proform weights are junk. I went as far as making my own and actual screw down advance stops. I was almost to the point of just locking the timing out.

Being that the box can only pull timing you should be able to get the cap lined up and hitting in a decent place. From memory I was getting a little burn and scale towards the tail end of the terminal and the most wear was in the middle to 2/3rd mark.

One thing thats real nice about the box is that you can ramp the timing in quickly so that you can run a ton of advance without ripping the starter off. I would have to check the graph points to be 100% but I am adding around 10 degrees of timing at 600RPM. Starter is alot happier. You just need to ramp it in slowly so it is a smooth transition as the motor catches or the starter will not like you! At this point I havent played with the timing in about 2 years but I am ideling at around 22-24 degrees at 900isg RPM. Loping away. This finally got it where I was not fouling plugs nearly as often. No more reving the motor to fast idle at a stop light.

My motor never really cared for vacuum advance so I have not tried tying in the MAP sensor. I am sure that it works well though.