vacuum advance

docchevy · January 27, 2006, 10:55:23 PM

Does anyone know how to set the vacuum advance on the distributor? I put in a new Assel distributor and coil. I have no power. Initial advance is set at a normal 8 degrees. I tried to set up the vacuum avance with the allen wrench and things improved. But I have no idea what the "correct" setting is. Also, now it backfires through the mufflers on WOT.

enjenjo · January 27, 2006, 11:27:42 PM

First, how much centrifugal advance do you have? The way to find this, is to check the timing at idle, with the vacuum disconnected, then slowly rev it up until the timing stops advancing. the difference between idle timing and the higher rpm timing is the centrifugal advance.

Most Chevys like about 34 to 38 degrees total initial, and centrifugal advance, without vacuum.

When you get that dialed in, the vacuum advance can be set, somewhere between 8 and 14 degrees at idle, depending on what the initial advance is, and what makes the engine run good.

At WOT, the vacuum advance is inoperable, because for practical purposes there is not enough vacuum to make it work.

Most vacuum advance canisters adjust how much vacuum is needed to start advance, but do not adjust the amount that it moves. There are a couple ways to adjust that, depending on what you find when you check it.

docchevy · January 28, 2006, 09:34:31 AM

When you get that dialed in, the vacuum advance can be set, somewhere between 8 and 14 degrees at idle, depending on what the initial advance is, and what makes the engine run good.

Thanks for the advice. Is that 8 - 14 beyond the initial advance set at idle without the vacuum attached?

enjenjo · January 28, 2006, 09:56:47 AM

yes

HOTRODSRJ · January 28, 2006, 10:12:09 AM

Quote from: "docchevy"When you get that dialed in, the vacuum advance can be set, somewhere between 8 and 14 degrees at idle, depending on what the initial advance is, and what makes the engine run good.

Thanks for the advice. Is that 8 - 14 beyond the initial advance set at idle without the vacuum attached?

Depending on cam and engine specs.... 8 to 12 degrees intial "static" advance (without VA hooked up) is a good start. And again, 30+ total (static + mechanical) is a good start too.

Vacuum advance is a misunderstood subject. Most engines like to have at least 25+ degrees of advance at idle (again depending on idle speed specs etc) and more is sometimes okay too. I have seen some around 40 degrees with no problems. The faster the idle...the more advance they like to make the burn time correctly. I usually like around 25 to 30 degrees of static + vacuum advance for all my applications. It aids in cooling and leans the mixture out. It also takes some of the "cammy" attitude out of the exhaust note...but no big deal to me.

In case you want to know more about vacuum advance ...go here for a good discusion and my diatribe on Vacuum Advance 101 (I stole it tho!)

http://www.chevytalk.org/threads/showflat.php?Cat=0&Board=UBB64&Number=1105501&Searchpage=1&Main=1105264&Words=%26quot%3Bcamaros.net%26quot%3B&topic=&Search=true#Post1105501

docchevy · January 28, 2006, 11:04:24 AM

Thaks guys!
What do you think the backfire throught the mufflers is all about? I leaned out the primary jets 3%. Should I lean out the secondaries too? So where can I get jets from Edelbroch besides Edelbroch? That takes forever.

enjenjo · January 28, 2006, 01:11:25 PM

It sounds like it may be too lean. You can get a Carter Strip kit from Summit that has a selection of jets and metering rods. The price is reasonable. Carter jets will fit.

EMSjunkie · January 28, 2006, 10:54:20 PM

Hey Johnny, hope you get her figgered out. :?

take the time to read the article Steve posted the link to.
very informative.

even taught this old dog a few new tricks.

I read it over at SRS a while back, applied it to my ride, and
it made a world of difference.

good luck

Vance

docchevy · January 29, 2006, 07:54:52 PM

Right, Vance! That was worth the read. I had it set on the timed port. I'll quickly fix that. Over heating at idle was a big problem!

HOTRODSRJ · January 30, 2006, 07:10:14 AM

Quote from: "docchevy"Remember; physics explains everything!

Right on brother!

Well...er....ahh....how about women??

BFS57 · January 30, 2006, 10:43:16 AM

Hello;
Ok, I see you are in Kissimmee, Fl. I got a Edelbrock kit from a Auto Zone store! You must take a eye lope (magnifying glass) with you to make sure all the proper jets and springs are in the kit as I had to look through two kits to make one kit that was right. The other thing that helped me (no experience in carbs) was the Edelbrock "owner's manual" it shows what metering rods as well as jets you need to go where you want. Keep in mind that the kit only has a few of the rods and jets necessary to do all adjustments.
After a while, I finally got mine running great but I am still having trouble getting those two black spots off the white garage door!
Bruce

docchevy · January 30, 2006, 06:09:50 PM

I bought one too. The problem is that they don't have the secondary jets in the kit. I tried to find them in Kissimmee but no one even stocks Carter jets. According to the manual I need .093's.

BFS57 · January 31, 2006, 07:58:56 AM

Hello again:
If you need specific jets may I suggest A-1 Speed shop on Orange ave near Kaley. They have many things to choose from. I have found that speed shope in our local area are getting to become a rare sight!
Before you go, give them a call (407) 422-6168.
Hope this helps.
Bruce

chopped · January 31, 2006, 08:31:58 AM

Post hi-jack. Any chance you guys are going to the Rumblers show in Daytona this weekend?

BFS57 · January 31, 2006, 02:53:49 PM

Hello;
Didn't know about that show!.What with all the construction at my house and job this weekend is kind of out for me.
Bruce