258 hei vacume advance issues - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > General Technical Discussions > Engines & Drivetrain > 258 hei vacume advance issues

Rockridge 4WD IS Taking Zone Offroad Suspension Lift Kits BLACK FRIDAY SPECIALS!! You asked, we deliver!Rough Country Lift Kits and Parts!

Reply
Unread 06-30-2013, 06:13 PM   #1
Cj5toybox
Registered User
 
Join Date: Jun 2013
Location: Brunswick, Maine
Posts: 1
258 hei vacume advance issues

I have a 258 with offy intake holly 390 and mild cam. Runs great with vacume unplugged. Plug it in and it skips and pops. Base timing is 8 btdc and i have moved it both ways with no change. Please help im stumped. This is all brand new fresh rebuild on engine,new carb and new hei.

Cj5toybox is offline   Reply With Quote Quick reply to this message
Unread 06-30-2013, 08:45 PM   #2
james04si
Senior Member
 
james04si's Avatar
1977 CJ5 
 
Join Date: Apr 2009
Location: Arlington TX
Posts: 851
You could have stabbed the distributor wrong, don't just trust the balancer to be accurate as many have slipped throughout the years. Turn the engine over by hand with the spark plug out of the #1 cylinder until you are close to tdc on the compression stroke by having a second person plug the sparkplug hole with their finger. They will feel the compression as the piston moves up on the compression stroke. Once close to tdc put a wooden dowel rod or chopstick in the sparkplug hole and turn over slowly until it goes up as far as its going to before falling further back in and check your harmonical balancer and see if it matches with tdc on the timing cover. If not mark it as it is true tdc and the outer ring has slipped. Also pull off the distributor cap. The rotor should now be pointing directly at where the #1 spark plug wire would be. If it is not then you have 2 options. 1 move the spark plug wires around the cap to match where it is pointed to or 2 pull and restab the distributor so the rotor matches the cap.

Also make sure you are setting your timing with the vacuum advance disconnected. Most HEIs for the 258 are curved to use manifold vacuum not ported vacuum. And lastly you may need to tune the distributor using different springs which will change the rate that the mechanical advance comes in and most of the HEIs come with an adjustable vacuum advance where you put an Allen head wrench in the vacuum hole and turn to increase or decrease the amount of vacuum required for the vacuum advance to come in. You can even go a step further and get a vacuum advance limiter to decrease the total amount of vacuum advance.
james04si is offline   Reply With Quote Quick reply to this message
Unread 06-30-2013, 11:20 PM   #3
rjbruzan
Moderator
2004 TJ Wrangler 
 
Join Date: May 2008
Location: Lake in the Hills, illinois
Posts: 2,122
If you have a mighty vac.( a small hand held vacuum pump) hook it to the HEI and apply vacuum. If it sputters then the advance if internally shorting. I have seen this problem on older cars years ago. Does the tach work and is it smooth or does it flucuate when the advance is hooked up?

Ron
__________________
Of all the things Ive lost
The one I miss most is my mind

Its like a fart in a windstorm
It smells good but thats about it

Registered Six Offender
Home of the Buzzin Half Dozen
rjbruzan is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
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.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.