I'm thinking about upgrading my ignition components (rotor, cap, wires, plugs) to more performance level stuff. First quesiton I have is about the wires: I already have 8mm ACDelcos on there from the last owner...would Accel 8mm make any difference or perform just the same?

for that matter, what can I really expect to get from replacing these components? smoother running? better response? better fuel economy? All I'd hope for would be a slight tuning improvement of some kind. Would I even notice the diff? This is a daily driver but I do like to open her up once in a while for short bursts (86 stock 305 tpi). thanks.

 

You are running a stock '86 TPI, so the ignition power starts to fall off right about at the same time the valves begine to float, which is right about where the TPI runs out of breath - All at about 4,500-4,800 RPM. A rather nicely matched combo, wouldn't you say?

You can solve the ignition problem to a great extent by changing to a higher power ignition coil, a matching HEI switching module (to handle the higher coil primary current) and installing a good quality brass terminal cap and rotor. The coil and HEI are available from several aftermarket companies, like Crane, MSD, etc.

The distributor cap and rotor don't have to be anything super special, or have some fancy checkered flag molded onto them. A Wells/Conrand DR2009G is as good as anything you'll find with the name "MSD" or ACCEL" on them. The arc chutes are actually deeper than what is found in what some of the "high performance" names offer, so flashover/scatter is even less of an issue. Solid brass terminals are standard on these caps. Standard Motor Proiducts also has the high quality cap/rotor sets.

Ditto with the ignition wires. With a higher power ignition coil, plain old Packard Electric Division resistance wires will easily carry the necessary current to fire plugs under demanding conditions. Resistance wires really don't restrict the initial plug firing current any appreciable amount, but will kill all the secondary and subsequent spark excursions so that you don't have to wrap aluminum foil around your engine just to use your cell phone or listen to the radio. What is more important is the corect spark plug gap. Keep the gap for an '86 near 0.035", and maybe 0.045" with a hotter coil setup. Additional gap isn't going to help much on your stock setup, but too wide a gap will kill spark energy.

Once you solve the ignition problems, the valve float and TPI choking syndrome may become more apparent. Only decent valve springs will solve the first issue, and some tweaking of the TPI plenum and runners can help the second one.

 

Vader, thanks for the info. One thing you lost me on was the reference to an "HEI switching module." Not familiar with the part. Where is it located?

Do you have any reccomendations for a higher power coil?

One last thing, sounds like these mods will make a diff on the high end mostly, where the stock parts lose strength, did I read that correctly? I appreciate your feedback.

 

The HEI module is the ignition module, located inside the distrib body.

The stock 7- or 8-pin GM modules swing ~ 6.5 amps of current (per the
literature). I have not personally seen any pin-compatible aftermarket
modules that are credibly rated higher than that.

To get more current, I think you would need to consider lashing up an
external unit, such as the LT4 switch or something like the MSD
5900 box. Both are rated at 7.5 amps +.

7.5 amps, with a low-inductance coil, can carry ~100+ mJ of spark up to
about 6K RPM (at least on paper). That's about the same energy that an
MSD 6 makes - both systems lose energy after that.

The reason to use either is for high-RPM operation; neither is any better
than stock for normal street driving.


As a simplified example, the current-limiting design of the 4-pin GM HEI
unit is illustrated here, as well as the rate of coil charge ( V / L ):

http://www1.jaycar.com.au/images_uploaded/MC3334R0.PDF

Some other info on ignitions was posted here a couple of years ago, if
you care to read further:

http://forums.corvetteforum.com/showthread.php?t=419893

My coil evaluation (based on published specs) wound up here (short
saturation time & high energy are good; long saturation time is not) :

http://www.corvetteforum.net/c4/doct...ilcomparo2.jpg

Since that chart was made I've seen a GM note that put the LT4 coil at
about 4 mH on the primary, IIRC.

The B&G ignition simulator is still here:

http://www.bgsoflex.com/igncoil.html

HTH

 

Thanks a lot for the info and the links man!