Mark71

So about a year ago () I got a Moroso Advance Kit 72300. Here's the kit at Amazon:
I bought it way back in this thread: https://classicoldsmobile.com/forums...-hei-help.html

Anyhow, I finally got around to installing it. I pulled the "stock-style" weight and center bar setup and added the new Moroso setup using one heavy and one medium spring. I pulled the vac canister line and started it up and I knew the timing was waaay out (like less than 2* at idle). So I set the idle to 1100 RPM and then set the timing to 12*.

The question I have here is that the advance now has a lot less span in it. Setting it to 12* only gets me around 26* at 3K RPM. I know that's not right.

If I set it to 20* or so initial, I'll end up around the 34* that I am looking for, but that doesn't seem right either, especially since the vac advance will be way high when it is all in (50*+).

Can anyone give me some pointers on this? Should the mechanical advance "span" be so much smaller now that I added the recurve kit? I don't want to damage the engine by giving it too much advance but I think 26* is a little low, so advice would be appreciated!

Thanks,
Mark

Mark71

Oh yeah, I remember a post -- I think it was from SVNT442 -- that explained the difference between old-style advance curves and newer style ones with HEI's and advance kits. I've searched around a lot for that post, but I haven't found it.

If anyone knows where that post is, I'd really lilke to re-read it (probably a few more times). Thanks!

RetroRanger

hey Mark

On mine I used the same kit w 1 mid spring and 1 light spring, that allowed me about 16-17° of mech advance at a little over 3k rpms

Joe P advised a adj vac advance to limit the overall timing advance

oldcutlass

Mark, setting your timing to 34 btdc at around 3500 rpm is the general rule of thumb for all V8 engines. You can go higher but watch out for ping or detonation. The net result of that is usually around 16-20 initial timing, with vac advance disconnected.

With it connected it will wind up somewhere in the 50 plus or minus range. An adjustable vac can will allow you to fine tune your light throttle cruise advance based on the engines needs. If you get some surge or pinging at light throttle then you can cut down on your vacuum advance.

I hope this helps you.

Intragration

Using lighter springs allows centrifugal advance to come in more quickly, but will also tend to allow more. I used the Moroso kit and the two lightest springs, and with 14 degrees initial at idle, I get 34 degrees at 3,500 RPM. You would want to limit your vacuum advance to 10-12 degrees, I made an aluminum plate with a small tab to limit my factory-style unit. There are all kinds of vacuum advance units available, you might want to check yours at idle, vacuum disconnected and then vacuum connected, to see how much it's providing.

Mark71

Ok, had a bit of an "oh crap" moment... I went out to try the stuff suggested above. I still have one heavy and one mid-weight spring on there.

Anyhow, I set everything up, started up the engine and let it warm up. After it was warm, I realized I needed my distributor wrench that I had inside the house. So I shut down the engine with the ignition key so I could go inside. The engine stopped normally but right as it stopped - there was a loud hissing noise. It lasted less than a second, but was pretty darn loud.

The first thing I noticed was that the line up from the fuel pump to the carb was completely empty. The glass filter I have in there was totally empty. I cranked the engine over for like 20 seconds and there was still no gas in the glass filter. I had to prime the carb from a squeeze bottle and got it running again and slowly the mechanical pump filled the glass filter again.

Anyone have any idea what happened here? The timing was pretty far off at the time, but very low, not advanced.


Anyhow, I did change the timing around and get things setup as described here. I have an adjustable advance can, but it is the kind that takes an allen wrench down the throat of it... Dumb question: will that work or do I need the "tabbed" adjuster deal?
Like this:

I need to make some adjustments there, I guess. Right now, I have it at 20* initial and around 33* with the vac advance completely disconnected.

Oh yeah, how do you hold your engine up at a steady 3500 RPM to check that top timing? It seems like setting it up that high for a long period would be bad for your engine (and not great for your relationship with your neighbors, either ).

Thanks,
Mark

MDchanic

Just hold the throttle open with your fingers.

- Eric

oldcutlass

x2

The plate pictured is a way to limit the amount of advance from the can. The adjustable screw in the can sets the amount of vacuum required to bring in the advance. Sometimes you can accomplish both with the adjustment screw.