HELP! New 383 SC is backfiring

I just got my new motor all in and ready to roll. it is a 383 Stroker all forged with 8.5:1 Compression. I have a Powerdyne 6 PSI SC on there. At idle the car idles good except it has a LOUD back fire I would say every 15-30 seconds. I tried to drive it to the gas station (1/2 mile away) and I didnt even make it out of the neighborhood. The car was backfiring so bad :mad: Then it would just shut off. The car hasnt been tuned yet it is running a a PCMFORLESS tune for my old 383 solid roller motor. Could it not being tuned cause this or is it something else? Someone PLEASE help me as I am totaly Stumped :confused: If it is the tune I saw here somewhere there is a list of basic tunes you can download to build a tune off of but cant remember the site. if anyone has a link to that I would also appericate that as well.

Thanks
Matt

Not being a smart a$$ or anything but have you checked your plug wires and made sure there not crossed up?. It has happend,just one of those small things you can miss while getting your motor togeather.

Not being a smart a$$ or anything but have you checked your plug wires and made sure there not crossed up?. It has happend,just one of those small things you can miss while getting your motor togeather.


Yes I have gone over the waires prob 10 times. The timing is DEAD on I have a double roller timing chain in there with a Electric H20 pump Everything has been checked I was wondering maybe the FMU is set wrong since it is ADJ?

Matt

I was wondering maybe the FMU is set wrong since it is ADJ?

Matt

What kind of fmu is it?, some are adjustable and some arent

What kind of fmu is it?, some are adjustable and some arent


It is the stock 1 from powerdyne but the guy I bought it from bought a fit to make it ADJ? I am not used to all the SC stuff I am just really getting into it. I have the fitting to take it back so it isnt adj.

Thanks
Matt

Who adjusted your valves? Are you still running the solid roller set-up?

yeah i went over my wires 10 ten times. problem is when you think you're right it's hard to convince yourself otherwise. have some else do it. i always grab someone who knows nothing about cars (like my wife).

Start the process of elimination.

Disconnect the blower, probably just the intake piping to the intake, and the fmu and try it from there.

Does this do it at idle or just while driving?

What was your old cam and new cam on this rebuild? Just to see how far the tune is off.

If it's back firing every 15-30 seconds I'd say that the wires are ok. Does it smell overly rich? Any detials no matter how odd would help.

check your fuel pressure. Make sure all your blower tubing is all in one loop or your maf will see problems.(no leaks) Also make sure your valves are adjusted correct.

Just out of curiosity did you change injectors since your last setup?

Peace,
Josh

Well Everyone I found the problem. The oil fill cap had white crap on it so I decided to drain the oil and a 7qt oil pan filled my 14 Qt bucket and then some of nothing but water! SO I have a BLOWN HEAD GASKET :Owned:

Matt

Thanks for all the help I bet no one saw this 1 comming :shock:

The question is.. why is it blown? :)

Peace,
Josh

The question is.. why is it blown? :)

Peace,
Josh

Id have to guess faulty torque down of heads, or just got a bad gasket. Its pretty hard to f$*k that up. Its not rocket science to follow a torque sequence. You didnt by any chance re-use stock head bolts or anything silly like that did you?

Id have to guess faulty torque down of heads, or just got a bad gasket. Its pretty hard to f$*k that up. Its not rocket science to follow a torque sequence. You didnt by any chance re-use stock head bolts or anything silly like that did you?


Nope when I did the gaskets I used ARP bolts and it hasnt blown yet (ehhe)

Matt