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Backfiring under heavy acceleration

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jmbrown96
Posts: 2
Joined: June 28th, 2020, 12:45 pm
Stroker Displacement: 4.6
Vehicle Year: 1988
Vehicle Make: jeep
Vehicle Model: comqnche

Backfiring under heavy acceleration

Post by jmbrown96 » June 28th, 2020, 1:19 pm

hello! I've been using this forum to build my stroker and now am a part of it!
I built a 4.6 stroker block is machined .030 over, using comp cams 68-235-4 cam (210int/218exh), icon forged pistons (IC945-030 10.8cc), stock intake for now, 24lb [email protected], 50 psi regulator, im sure im missing a detail or two but hopefully that narrows it down enough to help with my problem.

Sitting on my driveway the engine runs great, once I upgraded to the 50psi regulator it runs like it should, revs fine and doesn't make any noises. Under load however (typically quick acceleration) It sounds to me like its backfiring out the exhaust. I can feel it in my gas pedal foot sometimes. I did have some check engine lights (obd1) but they were all sensors that I didn't have or weren't plugged in. I have since corrected that and there is no longer any codes

I posted a video in all things comanche on Facebook and they said it sounds like a cracked flexplate but in my opinion after watching other videos specifically nickintimes video about it and checking the flexplate with a pry bar and it seemed to be solid.

Im wondering if I should be worried about this being detonation or if I choose maybe the wrong size cam, wrong size injectors, o or something else that isn't good or maybe its just my intake is too small and its not getting enough air?. Just hoping to get some other perspectives and hopefully a solution

Its really only confusing me because it only happens under load.

Pic of my longblock right after paint.
Screenshot_20200628-151852_Snapchat.jpg
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Cheromaniac
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Posts: 2858
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
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Re: Backfiring under heavy acceleration

Post by Cheromaniac » June 30th, 2020, 12:50 am

Did you try indexing the distributor?
1992 XJ 4.6 Stroker - 5MT - Sold :cry: Stroker build-up, Stroker "recipes"
2006 Mustang GT - 5MT - Midlife crisis car :D with Mods

jmbrown96
Posts: 2
Joined: June 28th, 2020, 12:45 pm
Stroker Displacement: 4.6
Vehicle Year: 1988
Vehicle Make: jeep
Vehicle Model: comqnche

Re: Backfiring under heavy acceleration

Post by jmbrown96 » July 1st, 2020, 2:36 pm

Yes ive tried indexing it with no luck, also just put new plugs /wires in today and it didn't help im running out of things to try that aren't related to the internals of the engine. What confuses me the most is its only under load in the driveway it runs amazing, should I try swaping in a different ecm? Ive got a parts cherokee I can use

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Cheromaniac
Senior Member
Senior Member
Posts: 2858
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Backfiring under heavy acceleration

Post by Cheromaniac » July 1st, 2020, 11:36 pm

It could be something as simple as a header leak.

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