Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - searching for an idle problem fix
View Single Post
  #2 (permalink)  
Old 01-10-2013, 01:51 PM
techinspector1's Avatar
techinspector1 techinspector1 is offline
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 75
Posts: 15,460
Wiki Edits: 326

Thanks: 1,548
Thanked 2,082 Times in 1,611 Posts
Originally Posted by jdaviscgaz View Post
any ideas?
First thing I thought when I read your post was excessive fuel pressure. Quads won't tolerate much more than 5 psi at the needle and seat. More pressure than that will overpower the needle and blow raw fuel into the intake manifold, creating the nightmare you describe.

Tee off at the carb inlet and run a small pressure line (copper/nylon) back to the firewall, up past the hood lip and onto the cowl in front of the windshield. On the cowl, mount a mechanical 0-15 psi fuel pressure gauge so that you can monitor it through the windshield as you drive. Never-Never-Never run a live fuel pressure line into the driver's compartment. If you want to mount the gauge and leave it there, figure up a nice mount and some way to cover it against rain (I might be thinkin' a modified clear Tupperware bowl). If you just want to get your problem under control and then remove the gauge, mount it to the cowl with tie-wraps, duct tape or whatever.

If you're using an electric fuel pump, then you may need to mount and plumb an adjustable fuel pressure regulator into the system. If you are using a mechanical fuel pump, regulators don't work really well with them, so use a different pump that produces less pressure, maybe something like this....
Carter Muscle Car Mechanical Fuel Pumps GM4685 -

The other thing that will help if the motor is cammed-up, is dialing in more initial spark advance at the crank. You will need ~36 degrees total timing, which is the sum of initial and centrifugal. Depending on the cam, the motor will want more at the crank and less at the weights, again, for a total max of ~36. You might get a kit and try different combinations of advance at the weights and at the crank. In other words, you might try 16 at the crank and 20 in the weights, for a total of 36. Again, since you don't know the cam specs, you will have to experiment. 12 and 24 might work best. You just have to play with it and find the best results for your combination.

Actually, I'd begin the experimentation with an HEI. They're cheap to buy new or you could buy one out of a boneyard and clean it up. Run a new, dedicated electrical wire from the starter switch to the + on the HEI. Do not use any wires that are already on the truck to supply current to the dizzy. USE A NEW LINE, 10 gauge. Bulletproof. Let me say this again with emphasis....DO NOT USE ANY WIRES THAT ARE ALREADY ON THE TRUCK TO SUPPLY CURRENT TO THE DIZZY!!!!!!
Here's a simple, cheap kit to begin with....
Summit Racing® HEI Advance Curve Kits SUM-G5212 -
Use this kit from Crane to dial in your vacuum advance.....
Crane Vacuum Advance Kits 99600-1 -

Oftentimes, we find that the inertia ring on the damper has rotated circumferentially in relation the the hub of the damper. When this happens, you can no longer time the motor with a timing light because the ring does not coincide with the piston being at top dead center. Read through this turorial and fix the problem if you suspect that the ring has slipped on your damper.

Last edited by techinspector1; 01-10-2013 at 02:00 PM.
Reply With Quote
The Following User Says Thank You to techinspector1 For This Useful Post:
jdaviscgaz (01-13-2013)