OK today I went to the yard and got the distributer out of the 76 Volare I pulled the rear out of a couple months ago. I took it appart and found the govenor looks to say R7 on it and the vac advance pot says R7.5. So if I were to run it like it is I should set the timing to 0* right? that would give me 29* total?
when the vac advance come on is it an all or nothing situation? like no vac advance or the full 15*?
It had 2 springs a light weight one thet is red and yellow, and a heavy black one. I took the heavy black one out and replaced it with a light weight black spring that came from the distributer i returned for a core charge.
I am thinking I should set inital at around 10* and not use any vac advance at all. Do you guys think this is a good idea or do you have better suggestions?
Remember to factor in all the mods I have done and that I have determined that my running hot problem was mainly due to a timing issue(to much davance at cruising speeds).
any advise would really be apreciated.
thanks
Phil

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Take the govenor rating of 7*. Multiple by 2 for 14. Subtract the 14 from 30 and you get 16. Your initial settting can be at most 16* BTDC.

The springs affect the rate of mechanical advance. The lighter the springs the faster the advance. How fast this needs to be is dependent on your engine. The old rule of thumb is 30* total mechanical advance at about 2500 rpms.

The vaccum pod only affects timing when you are at a steady speed above idle and is granulated. More advance at a steady speed leads to better gas mileage.

How much total advance your engine can tolerate is determined by the compression ration, gas quality, cam profile and to a certain extent the rear gear ratio.

So If I were to set it at 10*+14mech+maybe3turnsvacwould=around 30*?
I'll let you know if I feel any difference when I get around to putting this thing in.
thanks for your help

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You want for performance 30 degrees total @ 2500 (I set for 2300 since that is my street shift/65mph highwaqy cruise speed)...

So you have 14 degrees mech + need 16 degrees initial to equal 30 degrees total....

The vacuum pod is a bit light, 50-52 degrees at cruise is needed to light the mix at highway speeds, so you need to scrounge a vacuum pod that's going to be a 9.5-11x....otherwise you're set for 30+15 =45 at 55-65 mph which may be ok on regular, but may cost some gas mileage too...

The vac. pod comes on during a certain vacuum range (I use a vacuum pump and timing light to see when it enters and when it 'leaves')...you want it 'out' during your heavy acceleration phase...so if you throttle it and your vacc. gauge during a highway fast lane pass goes from 15" at cruise to 0" at WOT then you need to find one or dial it in with the 3/32" allen key to dial out at 14"-12".... my cruise is at 17-19 at stop light driving, and at about 15-17 at highway speeds, so I dialed it in to come in full around around 17"+ (I idle at 23"hg...but mechanical advance at idle is only about intial + 2 degrees of advance at 850 rpm)...and have it taper out until it's gone totally at 13"....


that's probably clear as mud, but once you recurve one and see what it does then you'll say "jeez, DUH...."

hang in there, this is one of the coolest topics, but hardest to get a grip on until you find your car's 'sweet spot', I'm still waiting for a batch of experimental R-7's to come back for use by others on the board, since my car really liked being at 14-16 BTDC, but needed a shorter governor to make it work.

more soon,

-D.Idiot

Based on your description, your distributor should have 14 degrees of mechanical advance. This is good because you can set your initial timing at around 14 degrees which will give you good low speed performance. For your initial setup, you should use an allen key that D. Idiot mentioned to turn the vacuum adjusting screw fully clockwise. This will bring your vac advance in early. If, at 14 degrees initial, you encounter part throttle detonation, turn the vac screw counterclockwise two turns at a time until it goes away. You will lose very little performance/gas mileage with this vac unit. Use the distributor the way it is.

Mitch

thanks for all the advise. I'm going to do as mitch suggested and turn the vac advance all the way out then move in like he mentioned. I doubt I can set my inital that high though, due to my very high compression. I can not run anything less than 92 octane. I hope to install this thing sunday, tomorrow is very busy, and tinker with it in the afternoon.
P.S. the heavy spring I took out is VERY stiff I bet that thing would never stretch.

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I am running 14 initial on a 0.75 shaved head (~9.75:1 compression) with 14 mechanical (28 total) and 16 degrees of vacuum set to come in as early as possible.

Mitch

with the 9.2:1compression and currently set at 10 initial, 22 mech, and 17 vacuum for a total of 49 it runs good on plus and super (I can even run 1 tank of super, 2 tanks regular, then 1 tank of super to keep things from pinging...), but the best 'performance' and mileage was at 14-16 initial, but my governor was too long and 36 total initial and mech = ping at WOT with no vacc. advance, and then add 22 deg. of vac. adv. on top of it was adding insult to injury, but if you stay in the 30-mech adv=initial, and do not overshoot 52 degrees-initial-mech.adv=max vac. advance you'll turn out ok...

The one thing I did notice with the advance though is my temp gauge reads a smidge lower, and I had to readjust my jetting slightly on the hyperpak as it started to run a bit richer than it did...FYI....

-D.Idiot

I set it 10* inital and without any vacuum advance it pings slightly when i try to accelerate from highway speeds. So I have to pull it one more time and adjust the hold down. It does have a little more grunt than before .
I really have to get this thing to the track before the season ends. since Pittsburgh I have changed rears from an 8 1/4 W/3.21s to a 8 3/4 w/3.23SG(the 8 1/4 had some kind of vibration but wasn't in long enough to find and the 8 3/4 just feels better), I switched from 225/75R14's to 235/60R14's(1 1/2"shorter tires), and now the distributer.

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At what RPM does this occur? What is your timing at this RPM? To me it sounds like either your mechanical advance is coming in too fast, your A/F is lean or some combination of the two.

Mitch

Right now I have the timing set to around 7.5-8* btdc. when crusing at 60mph turning 2500rpm, if I floor it it will ping. Not badly but I can hear it. I'm going to go out and set it back to abound 6* and try again this morning. the vac advance is turned way down.
I don't think it is lean I really feel it is just due to my compression being really high. I borrowed my brother-in-laws compression gage last night. I should be able to check the compression tomorrow evening, I'll post the findings then. I took him for a ride last night and he said the car is running much better than it was at Pittsburgh, he is wishing he had a slant to play with now.

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So you floored it for a moment, then cut the ignition, put it in neutral, parked on the side of the expressway and pulled your plugs and found them all to be 'tan' or slightly sooty?

-D.Idiot

Well, what I would do at this point is pull the vacuum line to the distributor and with a timing light, map out how fast the mechanical advance is coming in. What spark timimg do you have at 2500? Are you sure your balancer timing mark is accurate?

Mitch

DI, no I havent done that(check the plugs on the highway) but it is an excellent suggestion. I do have some jets that I had drilled out slightly. With them installed it misses at WOT like it is getting flooded with fuel.
Mitch I was thinking I need to figure out how to read the advance at higher rpm's. my timing tab only goes to 10* before and after. Before doing my head work I used to run at what looked like 12-13*. Now it could have slipped since then I dont know.
as of right now I have it timed at 6* before top dead center and it has stopped pinging.
I really need a vac gage to adjust my vac advance. it is running much cooler now with the inital back at 6* and the vac advance turned down. I did need to add about 1/2 gallon of water this morning cruising at around 70mph(3000 rpm) for 5-6miles used to get it way up near the top of the normal range, this morning it stayed below the middle of the normal range.

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Time to ditch the BBD, you have reached the limits on what you can do with it. A Holley 2300 should be in the works.