The Holley 502-3 is the replacement TBI for 2.8L engines, having 400cfm. I had it on my 2.8 for a long time. My original had a worn throttle shaft so I opted for the Holley. It never idled well but well enough, rich.
Then I built my 3.1 and used the same Holley TBI and bored the manifold out to the size of the gasket, a 4.3 gasket was the same size as the Holley throttle bore. It idled OK but again, not great.
So recently I put a set of Comp Cams 1.52 roller tip rockers on the 3.1. It now idles very badly. Part throttle has a surge. Pedal to the floor performance is excellent, no misses and it pulls strong. In my signature you can see my particulars.
I cleared the ECM memory and reset the IAC. Small improvement, but very small. Are the rockers causing it to run richer (more lift) or are the rockers out of adjustment? I have read that the Holley will run rich no matter what you do but I had no major troubles with it until I changed the rockers. I haven't readjusted the TPS yet but it, as the IAC were undisturbed.
Timing is right on. The rockers are adjusted "0" plus 3/4 turn.
I'm thinking of going back to a stock TBI to see if this helps. Should I go over my valve adjustment again? Could this be the problem?
Thanks
Then I built my 3.1 and used the same Holley TBI and bored the manifold out to the size of the gasket, a 4.3 gasket was the same size as the Holley throttle bore. It idled OK but again, not great.
So recently I put a set of Comp Cams 1.52 roller tip rockers on the 3.1. It now idles very badly. Part throttle has a surge. Pedal to the floor performance is excellent, no misses and it pulls strong. In my signature you can see my particulars.
I cleared the ECM memory and reset the IAC. Small improvement, but very small. Are the rockers causing it to run richer (more lift) or are the rockers out of adjustment? I have read that the Holley will run rich no matter what you do but I had no major troubles with it until I changed the rockers. I haven't readjusted the TPS yet but it, as the IAC were undisturbed.
Timing is right on. The rockers are adjusted "0" plus 3/4 turn.
I'm thinking of going back to a stock TBI to see if this helps. Should I go over my valve adjustment again? Could this be the problem?
Thanks
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