My buddies 383 seems to be acting up. It runs like PURE ***! At idle it runs very rough, has this exhaust leak sound coming from the #7 area, we put new header gaskets on a few days ago, still there. When you give it some gas it stumbles, pops, and somtimes stalls. It's running kind of rich we know, so we need to tune it but it's something else. We checked the rockers, they are fine, I checked the pushrods on the #7 cylinder, they are fine, no broken springs, etc. When you drive it, it runs bad under 3k rpms, stumbles, surges, etc. When you get on it and it goes up around 4k rpm+ it runs like a bat out of hell, but when you let off the gas and decel, it backfires, pops, etc.

The plugs are brand new, wires aren't burnt, etc. On the scanner it's misfiring and getting 13 degrees of knock. We have narrowed it down to an optispark gone bad, but not 100% sure, so we are replacing that tomorrow to see if it fixes it.

What do you all think it sounds like? Here's a brief list of the parts....

383ci
Comp Cams 306 cam
AFR 190 heads
Hydra Rev kit
Crane 1.6 rockers
Chromoly Pushrods
Hooker long tubes
3" True Duals with Magnaflows
Canton oil pan
Manley rods
J&E Pistons
10.5:1 compression
Street Twin
Meizere electric water pump
MSD 6A
and many more.

Any help would be greatly appreciated!

 

Was it tuned corectly? And when my opti went bad it would miss consistantly in high rpms, so I wouldnt think its the opti if its clean up top, but dont count it out. It is after all an opti. I would get a scanner on it to see the a/f more than likly it is running lean in the lower rpms causing it to detonate. just my thoughts, you didnt mention injectors, I assume and hope there not stock.

 

It seems that the majority of posts that start out this way, end up being a burnt wire in the end. If you haven't already, it certainly wouldn't hurt or cost anything to try the "pop the hood in the dark test" before replacing the opti.

 

The tune was good, we added a Walbro fuel pump, MSD and true duals since the last time it was tuned. It ran great, then progressivley got worse and worse, now it's undrivable. The injectors are 30lbers, they are working fine.

I have checked the wires, they aren't burnt, they look brand new, none lay on the headers, etc. We just can't seem to pin point the problem, it's frustrating as hell! I did run it at night and looked for arcing, nothing was arcing, all normal.

 

I have heard that MSD will kill optis but I have had mine for a month now with no problems, but my was a brand new opti at the time and I have full MSD, wires, 6al, and coil. Another thing you may want to check is the opti harness. The one that plugs into the opti and ties into the main harness around the valve cover. i had a problem where mine would always get coroded up and the car would run like ***. Its a long shot but its worth a look.

 

I never knew the MSD could kill the opti, bummer We have the MSD coil too, I took the MSD out of the equation, and ran the stock plug to the coil, the car ran the same way, so I assume it's not the issue. I will look around when I do the opti tomorrow to see if I can find anything out of whack

 

They don't.

 

Good to know, I was under the impression they helped ease the stress on the opti by making it more efficient, but I'm an LS1 guy, what do I know

 

You know nothing

 

You suck!