526 SS 96

Hi, I don't understand my problem. Last week the opti spark blew up and left me stranded, so I replaced it with a brand new GM opti, and in less than 6 hours of use it blew up again. The 1 st opti was in the car for 3 years, now it blew that one and a new one in 6 hours. What is going on? After I took it appart the rotor was melted down and smeared into the cover. Also (and this may be unrelated), My factory tach is not reading properly, above 4500 RPM it just pegs to the max 7000+ (full or part throttle) I have a sport comp tach and it's run of a MSD 6AL and it never fluctuates, but the stock one is all over the place.
Aleks

Injuneer

Something is forcing the rotor to move forward and impact the cover. Normally, this only seems to happen when someone swaps cams and forgets to check the dowel length. But it appears something has caused the cam to move forward and push on the back of the Opti. Possibility????

LT1Brutus

If Injuneer's theory is correct...it wouldn't be the first time that I've seen the factory bolts on the cam retaining plate work their way completly out and into the oil pan....just as Frank w/ the Black 96 SS. You need to investigate this immediately because the cam walk also destroyed several lifters and the cam itself.

Mtrhds94Z

Full manifold vacuum on a vented opti can also distort the cap.
You do have the appropriate restrictors, etc on the vacuum/vent harness?

526 SS 96

Thanks for the replies, I'll check the plate and make sure it's tight, and then I'll measure the end play and let you guys know what I found.

Don 97 SS

Ditto the advisce above regarding ensuring there is vacuum delay in the vent to the opti. Don't run a straight hose.

Also. according to DynaTech who make the Dynaspark opti, the cam dowel should be no longer than .605" (while GMPPs state .620") How long is your dowel?

526 SS 96

My Dowell pin is the same length as the one on the factory cam, so I don't think that is the issue, unless some how it may have walked out of the cam. Remember this problem just started, and I had my cam set up for almost 2 years now without any incident. It's frustrating, but I guess that's racing.

nateh

It sounds like your cam is walking. If a lifter has turned in the bore, higher RPM would create a thrust against the cam retainer plate (ask me how I know this). Pull your upper gear and look for evidence of scoring on the back of it and on the cam retainer plate. Any score marks will tell you the cam has been walking forward. If you have scoring, you will need to look at your lifters and your cam for damage as well.

526 SS 96

Ok, I tore it down and there is nothing wrong. The timing chain and gear are fine, and the cam retainer is tight, and the cam has (what feels like 0 end play). I will measure it and give an exact # later today, but for now I am lost. I took appart the optispark and sure enough the rotor was smashed into the cover and disintigrated.

shoebox

You didn't say anything about having checked the vacuum lines as suggested.

526 SS 96

Sorry dude, the vacume lines have the vacume delay's in all the factory locations.

Injuneer

Was the rotor securely screwed on? I've seen a couple cases where brand new GM Optis have had the rotor come loose.

526 SS 96

Hi, I took appart the new opti, and the rotor was securly fastened. This just blows my mind, there is no evidence of mechanical problem, not the cam, timing gear,opti, every thing checks out. Is it possible to have a voltage spike cause the rotor to break appart? The car has had a variety of electrical gremlins after a recent battery relocation to the trunk, for example the starter would engage and disengage like it had a weak battery, but it was an intermitant problem, so I threw an optima yellow top battery in it, checked and cleaned all the ground locations, and had the same problem. So the next idea was that the 4 guage wire was too small so I replaced it with a 0 (Zero) guage wire, no luck there either. Then I bought a new starter still the problem persisted. In the end we found it to be a bad relay behind the glove compartment . Also the clutch safty switch went bad, then the guage cluster started acting up with the tach and speedo' maxing out to the pins over 4500 rpm (for the tach at any throttle position) and anything over 80 mph for the speedo' all this crap happened in less than 1 month of use (30 of 90 days). I am bummed out because I just put in a killer sound system. I have a phionex (sp?) gold 500 x 4 amp w/ matching component speakers, and a 10" sub-woofer I still use the pioneer 8000 deck because I can't afford the Alpine in-dash DVD system. And the worst part is I don't know if I will make it to Smack Down @ Norwalk at the end of the month. There are alot of Mustangs out there that want to race me real bad. So I need all the help I can get , and I am open to suggestions.

526 SS 96

Ok, I think there may have been a problem with the vacume system after all, but I am not sure. First the vacume delay was filled with a very fine particulate matter (rotor debrit), so there is a possibility it was cloged, but that may only explain the new unit failure not the original one. Also there are 2 vacume lines one goes to the high voltage side and one goes to the low voltage side. The high voltage vacume line is bigger and has the delay & check valve. The low voltage side has a smaller line and is infront of the TB. What would happen if the high voltage side didn't have a working vent? What would happen if the low voltage side was attached BEHIND the TB instead of in front of it?

526 SS 96

Ok, it's back together and running. I bought a new like kit from Dal, and installed the system correctly. So far so good, I have a week of driving and one visit to the strip, so it looks like the problem was solved. Thanks for the ideas.
Aleks