Well as always at the end of a project I have run into issues. Have recently done some mods to my car, and it is now backfiring very badly out of the exhuast.

Mods done were:

• Victor Reinz .026 Head Gaskets
• SA GMPP 1.6 RRs
• Comp 987 Springs
• Comp Ti Retainers
• Comp 10* Race Locks
• Comp Hi-Tech push Rods (7.050)
• OEM Valves
• Valve Stem Seals
• LS7 Lifters
• Battery Relocation
• MSD coil (used)

and several other things not related to the problem like coolant catch can, and wieght mods.

The car sat for 6-7 months with a full tank of gas and no stabul, it smells bad, but I've run some out, and put 10+ gallons of 93 Chevron in it. I looked at the plugs, and they were totally toasted with maybe 40 miles on them. So we've swapped in some new plugs, started it, and the backfire is still there. I have track day next Saturday, and really need to get this taken care of.

The wires are in good shape, plugs are new. The coil is new to me (perhaps the culprit?) and I followed Shoebox's instructions on rocker adjustments and they sound good no ticking other then the normal sewing machine sound. I measured my pushrods (rookie at it) and the 7.050s were closest to my measurement.

I had no head work done, but have good compression as far as I can tell by turning the crank.

Ideas? Suggestions?

 

Tune maybe ?

 

I doubt its the tune, as the tune was dead on and all Ive basically done is bump the compression and added 1.6rr. No cam, or headwork.

Im wondering if I measured the pushrods incorrectly and they are to short resulting if in complete combustion?

 

Check the routing of the plug wires VERY carefully.

 

LOL thanks, would your respose count as a double post :p

 

What kind of coil? Ive heard MSDs arch because they supply more power than the ign system can handle and jump the spark right from the coil.

 

Ive not ever heard that before. The coil is relocated off the head, and not really near anything it can arch onto. I will check it out 1st thing in the morning.

 

dude you just pull the plug off the opti and leave it on the coil and sit it by the manifold/header and watch it spark....did you even gap your plugs?

 

I agree with ac hotrod, the msd coils are teh Junk!

 

Junk or too good for our cars? I havent decided that one yet??LOL!

 

I heard they supply more in lower RPMs but less up top, compared to factory!

I would say mis-adjusted valves.

 

Sounds like junk!LOL!

 

Yep, either way you look at it, junk!

 

I would triple check your valve adjustment. If you can determine which bank the backfire is from you might know where to concentrate your efforts. I couldn't tell you how many times I had to go through mine before it was dead on.

 

well i had the problem with the MSD coil arcing and so MSD told me to replace the wires so i did with some 10.2MM and some NGK plugs and that took care of that!

The car never backfired when it was arcing though so i dont think thats your problem!

My car did do what you described when my OPTI was going it would backfire like a mother! I took the OPTI off and shook it and it sounded like a bunch of rocks where in it! I replaced it and that fixed it!

how old is your OPTI? you might want to check that!

 

I would say the opti has about 20K miles on it, and its been in there for 2 years. It worked fine before the project, and the backfire didnt start until we adjusted the rockers, and replaced the p/r's (sounds like a winner).

The plugs were gapped correctly.

Its backfiring from both banks. I will double check the rockers adjustment as mentioned above just to cover my bases. Perhaps the lifters collapsed before we got it right. (there is no odd valvetrain noice though.

I will also swap in a OEM coil and see if thats the problem.

 

LOL 10.2mm geeze, weee bit of overkill eh?

 

GO BIG OR GO HOME!!

YEAH THEY WERE FUN TO PUT IN! THEY LOOK GOOD AND THE CAR RUNS BETTER SO I CAN SAY IT WAS A GOOD INVESTMENT!

 

Im running the Taylor 8mm race fit wires. The 10mm's on the set up in his sig does seem a bit overkill, but hey if it works it works.

Can someone give me links to the so called MSD coil problemHere is the plan of attack today. I will check the spark wires, and makes sure they are hooked up right, If they are then I will borrow a coil from a friend and swap it with mine. If that doesn't fix it then I will readjust my rockers, and if that doesnt do it, Ill throw a fit, and probably replace the Optispark.

 

did you adjust the rockers running or not running. I usually do a dry adjustment and then once its close enough to run I go back through them. Once its running the lifters might "pump up" alittle and throw off the adjustment some.