So last night on the way home I stopped at Harbor Freight and picked up a dial timing light. I have been having a timing issue for quite a while. it turns out that the vacuum advance pod on my distributer is always advancing the timing. I set it to 0* reved it to 2000rpm and I was getting 50* , disconnected I was getting 25* so I guess I have 2 options
1. I can just set it to 4* initial and disconnect the vac advance for racing and get another distributer later OR
2. see if anyone has an idea of how to get the distributer to give me less mechanical advance so I can give myself more inital advance.
I am going to be racing one week from today.
I also spent a couple hours inside my Holley last night. it was surprizingly clean. I wasnt really looking to rebuild I just wanted to replace the gaskets, bowl gaskets and the gaskets around the secondary metering block. I found out I have 57 jets. I had a small leak somewhere that is now gone. I also got the secondary spring quick change kit. I have a lot of pump cams I have to figure out which one I need.
Now today I am going to replace the idler arm and all 4 tie rods. Wednesday it goes in for an alignment.

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Well, that's a real problem. Here is my 2 cent.

For the moment, I'd set the timing to 4 and look into getting a working vacuum pod or reworking the vacuum plumbing if the carb is not providing the type of signal your distributor was designed for.

I've been driving my truck around with vacuum lines temporarily plummed into the passenger compartment and a gauge sitting on the seat next to me. I've got the lines connected with a T to the ported vacuum between the carb and the vacuum advance pod. I don't have any other accessories attached to that line due to custom plumbing.

At idle, there is nothing,
At very light throttle, I get 15" from the motor
The more I push the pedal, the lower the vacuum goes (while driving)
And at full throttle, I get around 3"

The next test is done with the engine off using a vacuum pump connected directly to the vacuum advance pod and watching the action of the vacuum advance pod with the distributor cap off.
With a little adjustment and experimentationaround the vacuum pod begins to pull at 6" and looks to be all in at around 10".

My motor doesn't ping unless it is at full throttle on a hill, and well after the vacuum advance has dropped off based on my experiment. That tells me that I need a heavier light spring in my distributor.

My numbers are not hard and fast to all carbs or vacuum pods, but rather some working figures so you can have an idea what to expect. If your carb put out a signal that is beyond the control of your vacuum pod then check out some of the information about different vacuum pods that was listed a few months ago to see if you can buy one that will solve the problem. I think slantsixdan posted a comprehensive list, but I'm not sure, it might have been someone else

Hope that helps,
Paul

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1980 Aspen 225 super six

Good stuff Paul,,,,,Ill add ....I had similar problems with the Valaint. I ended up using a very light vacuum pod(source unknown) and a set of springs from a stock 65 prestolite cast iron distributor...the springs are very heavy and limit advance to half of the slot. My suggestion would be to look for pre -emmisions point dist for springs,,,,,then use Pauls method.
Good luck racing!

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Thanks for your replies fellas.
I just got done replacing the steering parts, got it close enough to aligned to take it for a spin. I called Dan and told him it wasnt pulling as hard last night after backing the timing from 10* to 4*(duh). He came over and brought his jet kit. we swapped the 57's out for a pair of 64's (the smallest he had in his kit). I disconnected the vacuum advance and plugged the carb port and took it for a ride. there is a slight bog under 1200rpm but it still would give a slight chirp from the tires from a dead stop w/ the 3.23's. I hope the 3.91's dont give me serious traction problems. I used to shift at 4300rpm today I was shifting at 5000rpm and it pulls much harder over 3500rpm now. I am quite pleased with it right now. if I get any time to tinker this week I'll mess with the timing a bit but this week is going to be busy. I have 2 softball games and my wife has play rehersal every night.
I was wondering if anyone knows what each pump cam does. my Holley kit came with a bunch of different ones (Blue, orange, pink, white, yellow). I know they give different volumes and rates of shot but which would I use to cure a slight off idle bog?

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Not to ask , but what is your current distributor curve ? (mech adv @ rpm, vacc. adv @ inches Hg, and initial?)

What stamp do you have on your governor for mech advance?

Currently I have a 1976 Distrbutor installed that I set to 12-14 initial (depends on mileage vs. speed....speed would be 12 initial + 18 mech adv. with a 9R governor for a total of 30 mech). Plumb in a valve to shut off the vacc. adv for draggin' so you get your 30 deg with no rattle, but can go back to 50 for highway useage/ mileage.

2000rpm is an OK number for "all in" on the mech adv. I run all in at 2300-2700 since I drive on the street and shift out of gear at about 2000-2400. Changing this you'll need some springs and some plug and read time like Paul said( a couple spare distributors helps cut down time on getting it "right")


For the Holley, what cam do you have in there now? If it's orange , go to screw #2 on the cam, if that doesn't fix it, you can go "green", you may have to swap up your shooter to the next size up to get the correct shot size to fill the vaccuum gap when you tromp on it. (THe Hpak needs a #35 and a pink in the #1 position).

-D.Idiot

The problem DI is that I don't know what the degree advance the governor is. Last night I set the timing to 0* and reved it up to 2000rpm (it stopped advancig at that rpm, I took it to 2400) and it was giving me 24* of mechanical advance. Did they make 12R goveners?
The Holley kit came with 3-218's they are yellow(which is what was also on the carb using hole "1"), 2-427's blue, 2-466's orange 2-643's tan, and 1-44R330 pink. What would you suggest?

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If your vacuum advance is advancing the timing all the time (even at idle) you have connected the canister to the wrong port on the carburetor.

I have never bothered to find the right advance limiting plate for my distributors so I weld up the outside of the slots and file them to get the proper advance. I also have a little box full of distributor springs for tuning.

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Joshua

Is this something you have just accumulated over time, or are such box fulls available for sale somewhere?

Only the lightest springs are available (for dragggin') over the counter...If you're a good junkyard guy, you learn to pull every distributor you get for "spares"...I got my combo of springs by stripping the springs out of ll the old small block and big block distributors I had...
It's possible, I have a 13R unit (Canadian emmisssions timing curve....yucchhhhh) for later experimentation. You can do like Josh does and weld the slots file, test, and file more if needed, there is a post tht will give you the proper measurements to make the MP 10R governor slot out of a stock one. You can pull your distributor, pull the plate and see if it's stamped on the top, if not, you'll need some needle nose pliers to take out the snap ring to check it/replace the governor...

Dan has pointed out some OEM 'late' distributors on ebay, these have the curve you want, just re-spring to the rpm you need, and you're done.


What color is currently giving you an off idle bog? (You might need to adjust the throttle plate position, check the gap between the acc. pump arm at WOT, and the acc. pump lever-.015-.020 is acceptable).
If your leverage and plate adjustments are correct, then you'll need a bit more 'shot' to cover the "bog hole".

Holley's order of priority smallest to largest: white,black,blue,red,orange,green,pink,brown

Things to note: the cam determines "how much gas is pumped", and the "shooter" size restricts it "for how long"... so a small cam and big shooter will give a small quick "shot", and a big cam with a small nozzle will give you a small shot that will last for a while...


-D.Idiot

It's an assortment meant for working on distributors. I can't remember who gave it to me, but it's ancient. I also have a distributor machine.

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Joshua

the vacuum advance dosent come on until you hit it. there is no vacuum advance at idle. I do have another distributer I could try. it is a reman unit that I believe the vacuum advance pot is bad. I would have to cut the connector off of it and make up some wires if I wanted to try it. I'm going to wait until I can get another used one to try and make one up just for racing.
I swapped to the orange cam but havent gone for a ride yet. I'll let you know how it works later today.
Thanks DI for all you assistance.

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So what's wrong with leaving the vacuum advance the way it is? Is the engine pinging with it connected? You race at full throttle so you won't see any vacuum advance then. Am I missing something?

When I had a Holley 390 on a Clifford intake I needed no accelerator pump tuning at all. Then again I did have a 4 speed.

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Joshua

I get full vacuum advance at anything but idle so I have to disconnect it for racing. yes it pings under WOT w/ the vacuum advance connected.

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Are you 100% sure you get full vacuum advance at anything above idle? I'd hook a vacuum gauge to the port you're using and go for a quick drive if you haven't already done so. The vacuum at that port should drop under higher load. A lot of the original vacuum canisters are adjustable. I don't remember the size of the allen wrench that fits, but if you're you can dial out some of the advance.

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Joshua

I think it's 3/32"... One thing to note, on the cans that I've recently gotten if you "dial" them it changes when they come in but also it modifies how much advance you get out of it...the last one I "adjusted" came in a bit too late, after dialing it in, it came in just right, but instead of getting the 20 degrees of adv. I wanted, I only get 17.... (not sure if the extra 2-4 degrees would make any more mpg on I-5...)


Good luck,

-D.Idiot