shoebox

Sorry, I did not go back and read it already had an MSD opti. They are no more immune to failure than any other (actually maybe a little more failure prone than OEM). If it is still under warranty, they will repair it for free. If not under warranty, they will repair it for a reasonable cost (cheaper than getting another opti).

Injuneer

I'll try and take a look at the data log in a day or two.

DTC 36 would appear to explain the delayed start. The description of the code in the factory manual indicates that the engine will run with DTC 36, but may lose some timing accuracy. There's got to be some method built into the PCM program to allow it to decipher the low res pulses and run on that signal only. I've read through the V6 system description, and as I recall, that can run without the cam position signal, and it describes how that works. I'll have to go back to the V6 writeup, and see if I can draw a parallel to the way the Opti signals are used.

cmaddox03

Thanks for the help.


Injuneer, I'm anxious to see what you think of the data. I believe it's running rich.


Do I want Optispark I or Optispark II? I found both on Summit. The Optispark I is $452.97 and Optispark II is $378.97.

shoebox

You want an opti with the spline drive (if you have a stock 94). You'd save yourself a bunch of money by sending the MSD in for repair.

Injuneer

Let's take care of this first:

https://www.camaroz28.com/forums/lt1...nature-879835/

cmaddox03

I heard back from MSD about rebuilding the Optispark. They will charge $112 and take 5-8 working days.


So, while I have the optispark removed, what items should I replace? What seals are good to replace while accessible? Should I replace the water pump?


Thanks!

GaryDoug

I can't really answer that question, but you may want to look into modifying the water pump (new or used) to add a fitting to the weep hole with a small hose to redirect any pump leaks to a location away from the distributor. I have seen many online photos of this mod.
http://www.corvetteforum.com/forums/...-hole-mod.html

Fred, In case you haven't already seen this, I have some of the ASE auto course sections in the Mediafire F-body manual site. Number 8 has info describing the various ignition timing methods.

But there really isn't a parallel between the V6 engines' timing and the V8 Opti timing signals. The Opti uses the high res pulses as a simple angle/time base (since the cranking rpm can't be accurately relied upon), while the V6 systems use the cam sensor for identifying the engine stroke in progress.

I suspect the the V8 pcm, once confronted with the missing high res pulse problem, has to rely on it's own internal clock to compare the length of the different slots in the low res section of the disc. Apparently it takes many revolutions of the disc to be reasonably sure it has identified the timing correctly before allowing the engine to start.

Fatdog2

Didn't folks in the olden days just drill out the v-shape of the weep hole and install a grease fitting( drilled out)and run a hose away down past the opti?Maybe it didn't work I'm not sure.Guess I'm going back to the 90's.Hope this helps.

Injuneer

I would agree. The single degree slot between each of the variable degree slots would give the base velocity of the cam (hence crank) and provide a reference for measuring the width of the next variable degree slot. Since cranking velocity at startup is fairly low and fairly stable, it would seem to work very easily. I just wanted to re-read the V6 section, because losing the cam position in that configuration, while being limited to a crank signal would seem to provide a more hit-or-miss-startup. That configuration is not as big an issue, since the ignition is firing 2 cylinders at once 180* out of phase, and even sequential injection will run without the injectors in phase with the cam. If the valve is closed when the injector fires, the fuel just sits there until the valve opens.

I've run my LT1 engine with an early Electromotive "Opti-Eliminator" ignition, using just a 60-tooth/missing tooth crank wheel, which could sync the PCM to the wrong crank rotation, and the only effect of being 1 crank revolution out of phase was..... increased cranking time to start.... and a slight hesitation on increasing throttle when the engine was still cold and the sequential injectors were firing against cold valves and the fuel was puddling and not vaporizing. The Electromotive did include a 4-coil "waste spark" ignition.

cmaddox03

I got to work on the Camaro last night. I got the Opti extracted. There was oil on the optical sensor so that cannot be good. I'm going to send the Opti off to MSD. In the meantime, I'm going to rectify some oil leaks. The timing cover needs new gaskets but I'm thinking the intake manifold needs re-sealed. There is oil above the timing cover which would indicate either valve covers or intake manifold. The pass side valve cover is dirty/oily so I'll replace both valve cover gaskets. The intake manifold has been removed previously because the china rail RTV is definitely not factory. It also has fresh oil on the oil filter and rear of the oil pan so it might be the rear of the intake manifold. I haven't searched into the source of those oil drips.


Side note, how do I identify which intake manifold the engine has? The more I research LT1 info, I realized this isn't the stock manifold. I want to find out if its a stock manifold that has been powdercoated or a LT4 intake manifold. What additional information do I need to provide / look for?


Thanks!

Injuneer

LT4 intake manifold PN is 12550630. Part number should be on the flat surface, near the manifold bolt, right in front of injector #6.

Will not fit on LT1 heads without machine work. The taller runners on the LT4 interfere with the valve cover rails on the LT1 heads.

If the manifold appears to have an "air gap" under the plenum, could be the Edelbrock aftermarket intake. Their "sort of" LT4 intakes were red.

GaryDoug

That distributor cap is definitely history and maybe the rotor also. Lots of black dust on top of the rotor. Wonder what happened to lose the carbon slug? Looks like the rotor was rubbing on the cap.

cmaddox03

The casting number is 12552138. This is a 96-97 LT1 manifold, correct?

Injuneer

There are a number of different part numbers for the intake manifold. The "LT1 vs LT4" website shows the LT1 as 12552137 or 12552138. The LT4 is shown as 12550630 or 12550631.

For your future reference on anything LT4:

LT1 vs LT4

Specific to the intakes:

LT1 vs LT4 Intake Manifold Differences

cmaddox03

While I've got the Optispark off to MSD for repair, I'm addressing all the oil leaks of this engine. I'm at the point of re-installing new parts with gaskets.

The PO had lifted the car by the oil pan (It was dented horribly!). Since the oil pan gasket was leaking, I pulled both. I also pulled & cleaned the TC cover. What order should I install? TC then oil pan or vice versa?

I don't have the tool for the water pump drive seal. I've cleaned up the water pump coupler so I can use it as the tool. Do I leave the drive coupler in place while installing the TC cover with seal installed?

I don't see stamped # or letters on rod caps but did see a "B" stamped on the oil pan rail. I'm trying to figure of the engine is original or rebuilt. I'll try to get a picture of the cylinders. They have decent cross-hatching which makes me think it doesn't have the 130k that the odometer shows.

Thanks!