The Stovebolt Site Forums The Parking Lot Big Bolts 1969 C60

I could use some vacuum advance tuning help, I'll start with the back round.

It's a 427TD, new plugs, wires, edelbrock AVS2 650, ss headers, full 2-1/2" dual exhaust with an H-pipe going all the way back, HEI, motor was pulled and completely gone through by me. I'm in the process of making it usable. Not completely restoring because it's in good usable shape, a lot better than most I've seen.

Last year after taking it for a ride and pulling back into my driveway it went up in flames. The fire cooked all rubber/plastic/wiring from the valve covers up. I've replaced just about all the wiring (70% done waiting on back order). It starts/runs/drives/stops and is street able.

When it comes to the tuning I've read to set it at 8 degrees which it is, mechanical advance comes in early with the lightest springs. My vacuum advance is hooked up but not currently doing anything. I need to adjust it and am not sure what how far it should be adjusted to. I never messed with my original HEI distributor advance, wherever it was it was great. Without the vacuum advance she's not near as happy as she was with it. I can't seem to find a number on the internet (not a rough one either) specific to my 427td. Anyone know what it should be at? Even a rough number to get me started or a total timing number.

Thanks for reading my long winded post.

Hy Pvmt-Pndr, when you say your vacuum advance isn't working, are you hooking it up to manifold vacuum or ported vacuum? Have you tested the vacuum advance diaphragm to make sure it will hold vacuum?

I currently have it hooked to timed vacuum according to edelbrocks picture. This is where I had it hooked prior to the fire with the old distributor still in place. My carb is the same carb just rebuilt, the only thing that changed has been my distributor. At idle with the old distributor in the same vacuum port as it is in now it would take my timing beyond where I was able to see and it ran great. I do not have a dial back timing light. With the new distributor I get no difference in timing at an idle with the vacuum hooked up and it just doesn't have the power it did with the old HEI.

I did verify with older engine pictures that I have that I was hooked to ported/timed vacuum. Everything I'm reading says I must have changed it to manifold/full vacuum at some point between when I changed it and it caught fire. I know for a fact that at idle timing would go beyond my capabilities of reading with my timing light.

If the idle doesn't change when you hook up the vacuum tube then you have it on ported vacuum or the vacuum advance chamber is defective. Ported vacuum does not have vacuum at idle. Actually the engines in 60 series trucks did not use vacuum advance. If you like the way it runs with full vacuum advance you can use it that way.
George

Hy Pvmt-Pndr, if you were getting a timing change with the old distributor, you must have had your vacuum line going to manifold vacuum, as Wrenchbender Ret. said there is no vacuum at the ported vacuum port at idle. You haven't told us if you have verified that the vacuum advance on your new distributor will hold vacuum?

I've been going off of old pictures I have in my phone and memory trying to get the truck back to how it ran before the fire last year.

You're both correct in that at one point I changed where the line was when I took the picture I have vs where it was after that. It ran very well with the advance.

I have yet to verify anything due to being at work. I looked at the link to the distributor that I have installed also and turns out it has medium weight springs in it.

I have purchased a new spring set and will be trouble shooting as soon as I get home. I have some other things going on with it also that I haven't had time to address so hopefully today is the day.

Thanks for all your help so far.

Everything seemed to have played in my favor yesterday. The truck idles good, I swapped to the lightest set of springs for a bbc in the distributor, moved the vacuum hose to the other side of the distributor, reset my timing around 9 degrees, put in a mechanical water temp gauge to rule out an "over heating issue" and let it idle for 20 minutes. All was well until I tried to drive it. It has good power now like it did before the fire but it dies when I let off the gas after driving. I think the only thing it could be is my idle mix screws are off (correct me if I'm wrong). It fires right back up with a quick bump of the gas pedal. I'll be adjusting those when I get home today.