I am building a 94 based motor and it is time for me to buy my timing chain. About the only option for me is this Lunati Chain on a unvented opti setup. http://store.summitracing.com/egnsea...+115&y=17&x=25
My question is will it work with a 1997 stock crank and 1997 timing chain cover? Do I have to use the Crank position sensor in the timing chain? I am just trying to figure this all out before I drop off the motor to be built.
Thanks,
Steve

 

Probably better answered in the LT1 section, but my limited experience with LT1 engines is that the Opti drive is different. Somewhere around 94 they started driving the opti with a long dowel pin from the front of the cam (the same dowl pin that typically aligns the cam to the timing chain but longer). Prior to that they used a splined stub shaft that mounted in the end of the center of the cam or timing chain and drove the opti on the other end. That's probably the reason you can't mix-n-match optis, timing chain covers, timing chains, etc. between the two different styles.

I don't think LT1s ever had a crank sensor- I think they took all their data about engine postion from the Opti trigger wheel inside the distrutor.

 

For the F-Body LT1's, the 93/94 unvented Opti uses the splined drive shaft and timing cover version #1. And the splined shaft needs matching splines in the cam sprocket, which is hard to find in anything other than an LT1 timing set. The 95 vented Opti uses the cam dowel pin to drive the Opti, and uses timing cover version 2. The 96/97 cars use the vented Opti with the dowel drive, and added a crank sensor with a reluctor wheel on the crank and a sensor in the timing cover, hence version #3.

The crank sensor is used only for OBD-II misfire detection.

The version 2 and 3 timing covers won't work with the unvented Opti, because of the larger hole for the Opti drive system.

 

IMHO, I would use the 97 timing cover with a vented opti. You can cap off or leave an old crank sensor unused in the cover (or get a 1995 cover). Vented optis are cheaper and give you more selection for a timing set. This is assuming you are not going to use a stock 1994 cam with the small hole in the front.

I have said it before-I don't see any difference in the Lunati set and a stock GM set. Even the pic of the Lunati set clearly shows GM numbers stamped on the cam gear.
If you go with an electric water pump, you can get a strong double roller for half of what that Lunati set costs.

 

that half you save could go towards the pump...thats what I would do...those link type chains strech like crazy pretty quick

 

What about my pcm? It is a 94. I need this explained like you are talking to a 5th grader. Nothing makes any sence? How can I just swap opti's when they clearly have different electircal and vacume conections? If I had a smaller cal. gun than a 12 ga. I would have shot myself in the foot awhile ago.
Steve

 

Go here to see the parts needed to swap out a non-vented to a vented opti.
http://para.noid.org/~muttvette/opti.html

 

Thanks everyone!!!! This is a nice write up and I now understand what it takes. The only question I have now is there any way to go vented opti, E. duty LT4 chain, and still use the stock water pump? On my 96 Z the fuse went out on my elec. water pump causing my heads to warp. I DO NOT trust an electric water pump. If not I guess I can get that watch dog alarm for high temps.
Thanks agian,
Steve

 

The LT4 ED set will run the stock water pump.

 

Awesome... I feel like dancing now!

 

Exactly the reason my 94 runs:
-stock water pump
-95 timing cover
-95-97 vented Opti
-LT4 ED timing set

As far as the PCM is concerned, the PCM has no idea what the Opti vacuum system looks like, nor does it care. There is no interface between the Opti vacuum system and the PCM. As far as the harness wiring, the signals produced by a "vented" Opti are identical to the signals produced by an "unvented" Opti. The wiring from the Opti to the PCM is identical in both cases. Only the harness connector has a slightly different shape to it. The PCM works fine.

 

I finally made the switch to an electric pump and i have one of these kits on order. http://www.longacreracing.com/catalo...d=371&catid=11
Instead of using the warning light though i'm going to wire up a buzzer to make sure i know when the car is getting hot.