Jump to content

IGNORED

Compatible vacuum advance pot


TomoHawk

Recommended Posts

I need a vacuum advance unit for my 78 L28 dizzy. It's got anautomatic trans. What would work? I'm not looking for an exact match, just need to get the spark a little closer than what the mechanical advance gives.

I was thinking of one from an L28 from 79-81 with any trans?

thx

Link to comment
Share on other sites


Do you mean a used one? Can you get them in certain advance rates (curves?) what would be about right?

My contact at NAPA tells metere is nada for that engine (75-78, or even 79-83) from any source.

What, and how much, difference is there between the MT and AT versions? just total degrees, or what?

thx

Link to comment
Share on other sites

So what is the purpose of the "vacuum advance" unit? If I put a large amount of vacuum on mine, I could see it moving, and rotating, the sensor plate inside the distributor, so it has to be changing the spark timing. Mine must be leaking or worn out, because t barely moves, and won't hold its position without a large & constant amount of vacuum; more than I think is available normally.

thx

Link to comment
Share on other sites

Tomohawk

Black Dragon list one for the 78 manual trans for $59. Total degrees is probably the difference between the MT and AT but either one would probably make a big improvement over not using any.

I do know that the 240 advance unit and the 280 advance unit are not interchangable. They will not physicaly mount up to the wrong distributor and the 240 unit has a spring loaded mechanism that is adjustable with washers.

Whether there is a mounting difference between the 280 MT and AT distributor I dont know.

Anyone else know?

Link to comment
Share on other sites

They are available at the parts store, little pricey, $42 at rockauto.com
That unit is for a MT engine, 75-78, so you think that would work, right? Just making sure. I'd still like to know how much more (or less) advance the MT unit gives versus the AT one. Either way, I hope it will get me back into the power on my L28. :)

thx

Link to comment
Share on other sites

Tomohawk, I'm not certain but, IIRC the difference between the advance curves on a MT and AT distributors are in the mechanical advance mechanisms...not in the vacuum advance pot.
The vacuum advance pot must be adding additional advance to what the mechanical part does. I'm still wondering, in that case, why there are different ones for manual and automatic transmissions, and CA or federal emmissions spec engines. Like Stephen said, there are 6 in all.
Link to comment
Share on other sites

Thanks Lance, for the tip about Rock Auto.

I bought a vacuum pod for a 79 AT dizzy, and it hooked up correctly. The engine works fine, but I want to do a tune up (plugs & timing) before I can tell for sure. It seems to be running smoother at WOT off the line; used to run a little rough at WOT from a stop.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.