Timing a Howell TBI

[iapexl8r]

Hey y’all

I have a Cheif with the 401 and a California Howell tbi efi installed by previous owner. Some time ago i installed a new Davis HEI , I had timed it to 12 degrees with the vac advance disconnected it has idled high since. Did the idle adjustment per Howell’s instructions. Anyways I am revisiting the heigh idle issue. And just went to Howell’s website and went through the instructions and did not see the procedure for timing the dist. I also noticed the vac line to the advance is full vac at idle. I was wondering if anyone knows if 12 Deg advance is ok and if not What should it be set at?

[Dave Jeeper]

I have the 360 with the California Howell. Timing at sea level is 8 to 10 degrees BTDC with the vacuum disconnected and plugged.


Add 2 degrees for each thousand feet of elevation above sea level. At 2000 feet, 12 to 14 degrees BTDC. At 5300 feet (Denver), I run 18 degrees BTDC with an HEI distributor and .040 spark plug gap.


A change in timing when installing the HEI from the previous timing of the old distributor could account for the increase in idle speed.



Make sure that the vacuum for the distributor is being pulled off the correct port on the throttle body (Port J). The vacuum diagram is in the Howell manual. Here is the manual link:

https://howellefi.com/wp-content/uploads/2017/04/AMC_V8_TBI_install_instructions-5-19-05update.pdf

Page 4 shows the distributor vacuum is Port J, the left of the three ports on the lower, front of the throttle body. Pulling vacuum off the wrong port is a common error and will cause incorrect timing which will affect idle speed.



Page 11 has the idle air adjustment.


If the throttle plate is not closing all the way, then the idle will be high. Check for obstructions to the throttle cable and throttle link on the throttle body and the also the position of the mount for the throttle cable behind the throttle body on top of the intake manifold. A lack of free return of the accelerator pedal to it's proper rest position would also increase idle speed and could be caused by a mat on the floor or carpet interference with the pedal. Vacuum leaks could provide excess air to the engine which would increase idle speed.



Dave

[babywag]

12* should be fine...
timing should not alter idle speed as it(idle speed) is computer controlled.
whatever howell uses in .bin should be the idle speed.
maybe there is a problem with iac or their tach filter?

imho best to alter the system to utilize gm timing control.
I modified my 90 and it passed CA smog easily even with stealth timing control.
I hid the GM module inside an old gutted duraspark box.

[iapexl8r]

The jeep is in Idaho no smog naziss here I like the sound of gm timing control but first I want to get the idle right the IAC is the first part I will load into the cannon

[rang-a-stang]

Scribing!