holley 4di

int77345

int77345

Active member
Does any one have any experience tuning a Holley 4di system?
My brother has this system on his Chevy truck, 350ci. It always runs Rich, epically when the motors is cold. The oxygen sensor voltage hovers around .8 I don’t know much about fuel injection but shouldn’t that o2 voltage be around .4 ? At idle the map sensor dosent seem to be holding a constant reading. Does the map bounce around at idle, or should it stay constant. ? any idea to give us a little knowledge of these things will be much appreciated.
 
What is the vacuum reading at idle!

Cam spcs @.050?

The Holley system is easy to tune once you get some baselines set up for your engine. But you can't have vacuum leaks to start...
 
Thanks eagle,
ill get a vac reading at idle.
Also after a few days of messing with this, I am beginning to think the motor is in bad condition. We put a exhaust scanner on it and idling it puts out 2.8co and the hc are 1324. That seems like a lot of hc to me? Low compression? Trashed plug? Driving it, it doesn’t feel like a cylinder is missing.
 
The older style Holley injectors are known to be junk, leak etc... But the newer ones are pretty reliable.

If your motor has issues like burning oil or something causing a vacuum leak or vacuum flucuation like a bad intake valve. Well then your not going to get any efi to run correctly because it's getting bad information. :hand:
 
Thanks eagle,
I dont know for sure what year his Holley is, I think it is the first generation 4di. I have been at work all day so I havent talked to him or mesed with it. This weekend we will get the vac reading and give it a good inspection for leaks.
 
Good morning,
the vac is 30 lbs.
We checked for leaks using propain and it didnt seem to have any leaks.
 
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