Travis01gt

I have a 96 impala with a custom comp 248/254@.050" duration and 112 lobe sep. 383CI 10:1 compression, Ported Trick Flow LT-1 Heads, hooker headers, Burnt Pcm By Fastchip, stock MAF(also tested Granatelli with worse results), 1.6 rockers, comp tie bar hyd. roller lifters, MSD opti, wires and coil. 255 in tank pump, 42lb injectors, new Fuel filter,

Car is Breaking up like a misfire from 4200 up. Timing is staying at 35 deg. at wot. New o2 sensors, checked everything I can think of, Everyone around here is saying that the camshaft is too large for the computer.

Any ideas!???

94'BLKBRD

iTrader: (76)

You need a tune! you can send out your stock computer to get tuned.........im sending mine to pcmforless

Travis01gt

It has the PCM Tuned by Ed at Fastchip. They had all of the info when they burnt it. They are saying that the cam is too large?

Ray@Nitrous Outlet

I am running a 246/254 .613/.590 112 on a stock PCM with no issues.....sounds like an ignition problem, not a cam problem.

fergymoto

iTrader: (129)

What kind of plug gap are you running? I had this problem and it was because I was running the stock .050" gap. I went down to .035 and it has improved a lot.

Tony Shepherd

iTrader: (4)

That cam is not too large for stock PCM. With Ed tuning it I would say the tune will be right on. Sounds like an ignition issue to me as well.

jester1

iTrader: (1)

I would say ignition too, but I had a similar problem. Everything pointed to ingnition turned out to be valve float.

95 Formula

iTrader: (2)

do you have a box on that thing? Mine did the same thing untill I put a msd box on it. And no that cam isnt too big. Ran one a good bit bigger and it worked just fine.

Speedy

What kind of valve springs are you running?

Rick Speed

iTrader: (55)

I had the same problem and wound up with a bad opti... I know you have the msd but those are a waste of money and may be bad anyway

96capricemgr

iTrader: (1)

I would say the cam is too big to be right but should run better than it is and that you have other problem as well.
Why is the compression so low?
Did you fab up a timing pointer to go with the MSD opti so you can 100% verify timing.

Sounds to me like a case of throwing money at a car without research and getting typical results from such. I know some of you will think I am an *** for saying it but sometimes people just need a wakeup call.

ZEX-Z

iTrader: (4)

I had a similar problem with the car breaking up really bad at 3000+ and up with a brand new opti. it turned out that a wiringharness ground came loose by the starter and the righthand O2 passenger side header. good luck man and tell me how it goes. That cam is not to big. You need to go see a tuner though. he can find your problem.

Ed Wright

iTrader: (1)

I have never told anybody that cam is too big, and I just asked John, who you probably talked to, he says he hasn't told anybody that cam is too big. I have SEVERAL guys with bigger cams than that. One guy has that same cam, and just put his times in the "Fastest LT1" section, 11.02 @ 122 mph, all motor LT1 head & cam 355" '95 Camaro. That cam is on the large side for a big heavy Impala if you don't have a LOT of gear and converter under it. That has nothing to do with it breaking up. That will be fuel or ignition related, probably ignition. If you drove it before it was tuned with NGK plugs, you will have to change them. Once they get dirty, they don't clean back up like Autolite, etc. I use 104 Autolite plugs in mine gapped at .032".

Btw, you don't have NEAR enough compression for that cam. Never run less than 11.5 with that much cam, it will just be a turd unless you spray it, which covers up a lot of poor combinations. It would still be even faster on the bottle with the correct parts. I wouldn't use less than 12-1/12.2-1 compression with that cam if it were mine.

Good luck, Ed

ggk

iTrader: (1)

ed u probably told him his cam is too big for his combo.
that would make sense

redneck01

iTrader: (3)

may be valve float..check spring install heights. after you're safe on that..check the wiring to the ignition, if they are too close or out of wack they may act up. just little things that may have 10% chance of being a problem..and have been issues on mine.

moehorsepower

iTrader: (3)

Tuned many LT's with bigger cams than that, No Problem