Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics> Vacuum advance problem
User Name
Password
lost password?   |   register now

Thread: Vacuum advance problem Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
10-04-2012 12:26 PM
My 39 Buick Outstanding, I now know i am on the right track! My new Crane can arrived and has been installed. All of the help is greatly appreciated. I now have to tackle the carb and see if i can get it in line with this motor! Thanks again for all the help!
10-03-2012 12:17 PM
cobalt327
Quote:
Originally Posted by My 39 Buick View Post
While reading here about the ruptured diaphram it dawned on me that my vac can really has no function. I have set and reset the timing on my bare bones 350 and ported and manifold vac does the same thing. Dosent really change my timing. That being said, i removed the vac can and applied or tried to apply vaccume presure using a mighty vac tool and i can not get any presure to hold in the can. Translating to no movement of the adjusting rod. Is this a good method for checking these cans?
That's a good way to test it and it is telling you the can's no good if it won't hold vacuum.

Crane has an adjustable vacuum advance can kit- p/n 99600-1 that has the limiter plate, springs and an adjustable vacuum advance can including tool.

Quote:
Question 2 is, I have read that these cans can be adjusted with an allen wrench. Is this true for stock factory made cans? The one i just removed does not appear to be adjustable in any way.
This is all new to me and i have been head scrathing since i started tinkering with this car! So needless to say any and all help will be greatly appreciated.

Mike
Most adjustable vacuum cans will have a hex-shaped end where the vacuum port is located. Non adjustable cans are round.



More on timing can be seen here.

Until you get a timing light on it, put the line back the way it was. The link above has info on making a timing tape if you don't have a dial back timing light along w/other links at the bottom of the page.

Good luck.
10-03-2012 09:28 AM
AZDoug Read this.

Doug

http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf
10-03-2012 04:24 AM
454C10 holleys typically come jetted rich. Check the size of the front jets and get some jets 2 and 3 sizes smaller for testing.

I would also recommend that you buy an adjustable vacuum advance canister. summit racing sales them for 25.00.

Set the the idle timing to 20 degrees, this should give you about 38 to 40 total revving at 4000 rpm. Verify this!

Then use the adjustable vacuum advance on the manifold source with 10 more degrees of timing. When you plug it in, it should be at 30 degree at idle and around 50 when you rev it in park.

Then, adjust the idle speed to 800 rpms, and then adjust the idle air mixture screws for highest rpm.

You should be getting 10-11 mpg in town and 15-17 on the highway (depending on speed).
10-02-2012 03:10 PM
My 39 Buick
a little more info here please!

"When you connected the vac advance to the manifold source did the engine idle up? If not then it's likely the vac canister is ruptured internally causing a vacuum leak that is noticeable when connected to a manifold source. When it's connected to a ported source it's not so noticeable. So first things first, get a timing light, then test the vacuum advance unit, if it's ruptured get a replacement."



While reading here about the ruptured diaphram it dawned on me that my vac can really has no function. I have set and reset the timing on my bare bones 350 and ported and manifold vac does the same thing. Dosent really change my timing. That being said, i removed the vac can and applied or tried to apply vaccume presure using a mighty vac tool and i can not get any presure to hold in the can. Translating to no movement of the adjusting rod. Is this a good method for checking these cans?

Question 2 is, I have read that these cans can be adjusted with an allen wrench. Is this true for stock factory made cans? The one i just removed does not appear to be adjustable in any way.
This is all new to me and i have been head scrathing since i started tinkering with this car! So needless to say any and all help will be greatly appreciated.

Mike
02-29-2012 08:48 PM
DoubleVision First off, you should never make changes to the timing via vacuum or mechanical if you don't have a timing light to check the spark timing. Whoever timed it before you could have the timing set where it needed to be and when you connected the vacuum advance to a manifold source now the timing is over advanced which can cause the issue your having.
When you connected the vac advance to the manifold source did the engine idle up? If not then it's likely the vac canister is ruptured internally causing a vacuum leak that is noticeable when connected to a manifold source. When it's connected to a ported source it's not so noticeable. So first things first, get a timing light, then test the vacuum advance unit, if it's ruptured get a replacement. Afterwards, you'll want to disconnect the vac advance and plug it. Set the base timing to 12 degrees before top dead center. Lock distributor. Reconnect vac advance, recheck timing, it should be 18 to 24 degrees before top dead center. My next question is you said the engine was stock besides having a holley carb on it. So I'm taking a guess the intake is stock and there's a adapter plate on it? If so that's likely causing the rest of the issue such as horrible mileage and drivability problems. If it does have a adapter plate you have two options, get a aftermarket intake such as a Edelbrock performer or the like, or get a Rochester Quadrajet to go on it which is what I would do. The Quadrajets small primaries make for excellant low end torque development, throttle response and fuel economy. Another area to why it's using alot of fuel could also be partially due to the ignition system. What shape is the ignition system in? Are you still running points or has it been converted over to HEI? If it has points I would get a points to solid state conversion kit from pertronix. Are the plug wires cheapy parts store wires? If so I would replace them with spiral core wires which last twice as long and have far lower resistance plus better sparking power than the cheap parts store solid core wires. There are other areas you can also improve to get better mileage. If you should want to know just ask.
02-29-2012 08:17 PM
jmac1970
Vacuum advance problem

Hello everyone, i have a problem i was hoping someone could help me out with. I just purchased a 1970 chevy c10 with a 350. Only mod done to the engine is a holley 600 carb. I just purchased the truck so i dont know many of the specs on it. But here is my problem, the truck was running great however i am getting horrible gas milage, i know its not a prius but im getting around 5-7 MPG. So a friend said he just had the same problem and his was that the vacuum advance was connected to a ported vacuum rather than a manifold vacuum. Well mine is the same way so i moved my vacuum advance to a manifold vacuum port and now the truck stutters real bad like it doesnt want to run at all. It will idle but doesnt want to drive very well. If anybody has an idea please let me know. Thanks in advance.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 08:37 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.