IROC & Vette 2

With $2+ gas, I parked my 454 pickup and pulled "old faithfull," my '85 IROC TPI out of the barn to cut my fuel bill in half. It's seen little use over the last five years, so its time for a tune up. I have done the basics, filters & fluids and am ready to do the ignition. I've already bought Bosch plugs and have a good set of plug wires.

I would like to upgrade to a MSD coil, module, cap & rotor.
Here's my questions:
1) What module does the '85 TPI use? 7-pin? If so, then the MSD won't work correct?
2) Who makes a performance 7-pin module? Is it necessary?
3) If I decide to go with a 6A box (totally overkill for my application), will I use the 8861(?) adapter and not use the module?

Thanks for any input.

Damon

Pretty sure it's a 7-pin. Regardless, don't mess with the module unless yours has stopped working. There's not much to be gained by replacing it, even if somebody does make a performance-oriented replacement.

Cap, rotor, plugs and wires are all fair game, though. I usually put a fresh coil on the list as well- they can get weak and/or fail in ways that aren't immediately apparent. I like the MSD HEI coil, but just about any performance replacement unit is better than stock.

BTW- MSD upgrade..... on a distributor like yours that relies on the ECM to supply it with it's timing advance (no springs, weights, vacuum can) you need to leave the stock module in place in the distributor to maintain communications with the ECM- so you still get timing advance. Then the MSD box comes with some wiring adapters to plug in to various factory connection points so it can light the fires when directed so by the distributor/ECM.

Old style non-computer controlled distributors you rip the module out completely and plug the MSD triggering plug directly into the distributor's magnetic pickup.

MSD boxes are overkill for performance on an engine like yours, but I've found they're usually worth a solid 1 MPG over a stock ignition under typical dirving conditions. Might pay for itself in gas pretty quick at the the kind of prices we're all paying these days!

Damon

Hey, I just did the math on the cost savings from an MSD box, like I mentioned above. Payoff is not so quick.

Assumptions:

1 MPG improvement (from, say, 19 MPG to 20 MPG).
MSD box costs $150.
Gas costs $2.00/gallon.

You need to save $150 in gas to pay for the MSD, obviously.

1 MPG improvement is 5.26% better mileage (20/19=1.0526). That would be equivalent to gas being ~$0.11 per gallon cheaper ($1.89).

$150 / $0.11 = 1363 gallons of gas needed to "break even" between the cost of the gas and the cost of the MSD box.

1363 gallons of gas = 27,260 miles driven @ 20 MPG

So it takes almost 30K miles to break even on the cost of an MSD box on gas savings alone, even at todays high gas prices. I'm sure I missed something minor along the way but that's probably roughtly right.

FireBoid

Damon, I don't understand what you said about the performance module not talking to the ECM. I've been using an after market performance module in my Firebird for some time now. The timing advance works fine??