Back fire through intake when floored

[Connorpod]

Has anyone had an experience like this before?

 

[Hipster]

Has anyone had an experience like this before?

Wot throttle misfire is a classic, the distributor is a few teeth off symptom.Advance comes in and spark jumps the wrong cap terminal. Not an expert on scanners so not sure what if any assembly errors would show up through that method. A timing light won't tell you the distributor is out of phase either. If you're not 100% certain on the install might pay to revisit the dizz install. No amount of turning the the distributor back and forth in an effort to set timing is going to correct a phasing issue.

 

[Connorpod]

Thanks for the suggestion! I have a brand new distributor installed and it was acting the same way with the old one. I’ll definitely investigate the new dizzy. Would a deep clean of the tbi improve the situation?

 

[Connorpod]

Wot throttle misfire is a classic, the distributor is a few teeth off symptom.

My distributor was definitely rotated out a tooth. Just finished reinstalling in correct location and set timing to zero. Seems to be in a much better location (wires facing the back instead of aimed at driver side) However, the WOT misfire persists. Plugged in my timing light with the tan wire plugged in and my timing was jumping all over the place at idle. From 9-12 degrees. I just ordered a new pickup stator. I heard that can help.

Any other suggestions? Thanks everyone!

 

[Connorpod]

Update:
I advanced the distributor 4 degrees from factory yesterday and now it isn’t barking out the intake! However, now when I floor it, the RPM drops near to zero and stays there for a moment before RPM’s pick up. Sometimes a couple seconds. Am I on to something?

 

[Schurkey]

Verify spark power with a spark-tester calibrated for HEI.

Maybe the coil is weak, and when voltage demand increases with load, the coil shorts-out.

 

[Connorpod]

Good idea! Thank you!

Verify spark power with a spark-tester calibrated for HEI.

Maybe the coil is weak, and when voltage demand increases with load, the coil shorts-out.

 

[Connorpod]

@Erik the Awful do you have a picture of how you mounted the coil on your carb intake? Oem coil mount doesn’t line up with the bolt holes on my intake. Thanks!!

 

[L31MaxExpress]

Needs acceleration enrichment aka pump shot probably near double what the TBI system is calibrated for and also needs substantially more timing at low rpm and WOT aka high map. Also 14 psi will never be enough with stock 350 injectors. Needs more like 22-24 psi. I have fixed a bunch of them back in the day trying to run Brian Harris' tuning with issues on his "Vortec" chip and 18 psi spring which is still inadequate.

 

[Erik the Awful]

@Erik the Awful do you have a picture of how you mounted the coil on your carb intake? Oem coil mount doesn’t line up with the bolt holes on my intake. Thanks!!

Not a good pic. Also, it's probably on a custom bracket. It's been a while.

You must be registered for see images attach