HEI was GM's electronic distributor. It stands for High Energy Ignition. The HEI uses a magnetic pick up to trigger a solid state ignition module. The HEI is, in theory, maintenance free. It is for the most part, but you do need to change the distributor cap and rotor. The GM HEI uses an integral coil that is mounted inside the larger distributor cap. The coil can run hot in this location and sometimes drop voltage at higher RPM's. This is easily remedied by using an MSD distributor cap that has an extra terminal for a coil wire, so that you can run a separate coil mounted in the stock location. The HEI is capable of firing bigger gaps (up to .080 in some applications) in lower compression motors.
Re: hei ignition -clearance Does anyone know if a GM HEI dist. with a MSD cap(coil mounted in another location) will clear the bottom fibreglass snorkel cup on a 70/71 455 GS? My HEI sits too high for the RA breather. Thanks Craig
That's wierd. My HEI dist fits under the dual snorkel air cleaner. 71 455 car w/hood & air cleaner setup.
Re: hei ignition -clearance Have you ran it since the distrbutor was installed. Sounds like it might not be all the way in the oil pump. But if it runs and has oil pressure that theory is not valid. Bob H.
The Edelbrock Performer/B4B is a bit taller than a stock intake. Any spacer plates or thicker gaskets will often raise the air cleaner enough to clear an HEI cap.
Thanks for the replies. I am running a Poston aluminum intake,76Buick quadrajet -no spacer, and 76distributor. The distributor is set down completely. When the cleaner is sitting on the carb the RA cup rests on the sparkplug wire retaining ring. With it(the ring) removed, there maybe just enough space. Would there be a problem running without the ring? Thanks. Craig
UR5 is a step colder than stock but should still be fine. The NGK equivalent to the original AC R44TS would be UR4. Devon
UR55 is the same plug with a longer ground electrode. The longer electrode accommodates larger gaps. You can increase or decrease the gap by .008. The UR-55 comes pre gapped at .059., so you can gap it a .051-.067 http://www.jegs.com/i/NGK-Spark-Plugs/739/UR55/10002/-1 The UR-5 comes gapped at .040, so it can be gapped at .032-.048 http://www.ngk.com/product.aspx?zpid=10180
The big cap HEI would not fit nicely with my GS air cleaner So I went with a stock style distributor, with an electronic kit. Does the same thing as big cap HEI but from the outside looks like a stock points distributor I used the Crane XRi kit - it uses the existing resistance wire unlike the pertronix kit
