I've done some searches on bad-opti symptoms and not quite found my situation.

I've had this car for 4 years and done two heads/cam swaps in that time. I replaced the Opti with a brand new unit each time. So I've never actually had one go out on me, but I think this time it is.

I was on the dyno Friday, the car was missing a little bit at part throttle as I was getting up to speed to make my dyno pull. THen at WOT, it would cut out and break up as it pulled up through the RPM range. We thought at first it could be some pre-ignition, so I pulled timing, added some fuel (wideband was showing lean), and we eventually tried some 104 octane unleaded race gas. Nothing seemed to affect the breaking up.

Plug Wires are Taylor over the valve cover wires and are 6 mos. old. Plugs are 3 week old TR6's. Coil and module were original to the 68K mile car and the opti is only 3 mos. old put it on during my most recent heads/cam install.

So Saturday I'm at the track. THe car runs 4 12.32's at 109.49 mph in a row, all 4 with 89.46mph 1/8th speeds too. But I can hear it breaking up a little going down the track. I'm also getting P0300 Random Missfires code, and the idle is a bit rough. You can feel it bucking ever so slightly when cruising in 4th gear.

its not popping or backfiring, its just as if its missing randomly. I even went so far as to replace the coil and module yesterday with no change to the condition.

Opti? Sounds like the optical side is probably OK since there's no backfiring or popping, but that the cap/rotor are perhaps corroded or damaged.

I've also eliminated a bad ground as a cause. Opti is the only thing I can think of that would cause this. I am debating between Dynaspark and the LTCC coil pack setup. LTCC is superior IMO but the dynaspark is plug and play with no downtime of any significance.

 

Im having some of the same problems you just listed. Are you having any starting problems too??

 

Not really, it doesn't just come to life with a slight bump of the key but it doesn't crank and crank either. Generally I think starting is OK for a cammed engine with 11.15:1 compression.

The crazy thing was on the dyno or the track it didn't matter what changes I made to fuel or timing it didn't affect power output. I had 8 pulls of 357/358hp despite 4 degrees difference in timing and 10% added to the power enrichment.

The dyno graphs, if you turned smoothing off, showed big spikey drops of as much as 40hp..its as if for a split second there was no spark at all.

 

anybody else?

 

Do you have something to scan it with? Perhaps it has thrown a code.

 

I have a laptop and scanning software.

No codes except for P0300 Random Misfires. I know that's a common code with cammed OBDII cars but I was getting that same code even when I had the tiny 210/220 cam in.

 

Chris,

Your symptoms sound just like mine. Started as a little breaking up, replaced coil, which seemed to fix it. But then it came back, eventually getting to the point where it felt like it was hitting the rev limiter. Anyways as part of changing it I too went to a new cam and just finished this past weekend.

Fired it up after finding that I had a bad starter and it's running great. Idles correctly and revs like a banshee. Of course I now have a fairly bad oil pan gasket leak.. Oh well I guess it keeps me off of the streets.

BTW never threw any codes. I would also pay very close attention to the dowel pin length. I just put in an XE 227/233 Cam from Combination Motorsports and the dowel pin is WAY TOO LONG. I believe that this is probably killing a lot of opti's prematurely.

 

My 224/230 came from Cmotorsports also. I may very well have too much dowel length, I never thought to check it. Thanks for the input.

 

Out of the box mine was .863 inches. I believe GM specs say .618. I installled mine at about .540 and that was plenty long enough - I checked very carefully. It cuts pretty easily with a die cutter.

 

Wondering about plug gap. The spark has to jump two gaps, one inside the opti from rotor to cap terminal, then again at the plug. With the increase compression and increased cyl pressure caused by the cam, wonder if it has caused the plug gap to become harder to jump, thereby sucking voltage from the spark?

I am running TR6 plugs gapped at .050. Maybe I should try .040 or .035?

I know a lot of forced induction guys shrink their plug gap, wondering if just a heads/cam motor really needs it or not?

 

Chris I am having the same problem. Had it scanned and got the p0300 code. changed the cap and rotor on the opti and it work good for about a day.The cap and rotor were badly corroded.Let me know if gapping the plugs smalleer helps or fixs it. Thanks

Rob.