MOre opti spark help


Narrow A$$ Racing
Jun 18, 2001
This is a different car then my first post this car is a 383 with a t-trim vortech lt1 car runs about 14-15 psi the customer said it made around 500hp then brought it home one week later opti spark went out so they install a new opti spark once getting it to run again they bring it to the dyno and have a bad dip at 4500 and loss of power do anyone think this is the opti spark doing this dip

like i said boost is at 14-15 psi timing on about 20 with good gas

thanks for any help that can be given

here is the dyno sheet


From looking at the AFR chart, it looks like an A/F just under 13 to 1 at 15# of boost could be a problem. The engine is going lean?? I'd also wonder why the A/F is still at 14 to 1 at 3000+ rpm.
Given the blower is fairly linear w/ respect to air flow vs rpm, the A/F situation would give me reason to look at the fuel system..
What kind of ECM is on the car??

Also, I would be looking at why an engine as big as 383 at 15#, is only making 500+ HP??

2 atmospheres of air should produce power somewhere in the range of a 760" N/A engine....
At 1 HP per cube, that would be a BUNCH more than this engine is making..:confused:

Does the boost stay constant??
Does the fuel PSI stay up at base plus boost?
What size injectors are in the engine?
Could be the belt is slipping???
Could be the "Sloptispark" is going south.
What do the plugs look like?
chuck it makes 15 psi at 6k it is only making about 5 psi at 3500 which the a/f goes to 12.5 on the a/f on the fast system

it has 72lb injectors it also has a weldon pump on it
fuel pressure is fine

we think the opti spark is going out again but this will be the third one was wondering if people see this type of problem with the opti spark

the customer wants to make sure it is the opti spark before he goes to an edist and ls1 coils
IMO, it's very unlikely to be an optispark problem. There is no indication of misfire, just a drop in power.

As Chuck said, it is a bit lean (and WAY down on power).

Timing is 20deg? Any possibility of an exhaust restriction?

There has to be some major issues. A 6-speed 383/T-trim LT1 should be making alot more power.

How about listing the entire combination?
Got any....

Since this is a FAST equipped car, did you do any data logging??

If so, I'd like to see them and the GCT file too. I use the FAST on my BUICK, and have seen ALOT of different "situations" on it. I may be able to spot something there...:D :D
opisparks are very unpredictable.I recommend getting rid of that as your ignition source and just using it as your sensor. Bob Baliey has a nice conversion that I have been using with no problems. Its the LS1 coil setup, I making decent power with it and have not had any problems yet.
It could be belt slip, what do you guys think?
as soon as the dip happens you can see the torque starting to back up. There might be something else wrong though.

If you have a Fast System I would get rid of the opti-spark and drill the hole in the intake and put a distributor in it, its the cheapest way.

I put a distributor in mine LT1, I have a 396cu/in N/A it made 434rwhp.


I would check the spark plug wires, I had the same problem and changed out the opti three times. I have headers on the car and the plug wires were getting burned. Also make sure your crank angle is set to one not six.