why i keep pestering people to change their HEI units

[ari666]

hei unit, igniter module, whatever you wanna call it. its the little black thingie on the side of your HEI dizzy. look for the shiny cover with two phillips screws. undo those two screws and you will see a black module with 4 wires attached. that thing is the hei unit i am talking about.



now, anyone who has seen an old car that used to use the headlight switch as the on/off rather than relays like all modern cars have will know that any switch wth 12V running through it, with enough current, will oxidise and fail. it make take a week, it may take 30 years but it will. the HEI unit is basically the same as a head light switch. its a switch. and it has voltage running through it at a spastic rate while your engine is running.

so how much? ok i suck at math, so correct me if i am wrong. i am also gonna work with 8 cylinders but the principle is the same:

the dizzy has 8 firing triggers, 1 trigger per spark plug
each revolution of the engine = 8 triggers
308's idle at 850 rpm sooo

850x8= 6800 triggers per minute
113 triggers per second


THATS AT IDLE!!! my car sits on 3k rpm @107kmph so 3000x8=24000 triggers per minute or 400 triggers per second.

now all these triggers MUST be precise or your timing will be up to pooper. the HEI modules are timed to nanoseconds, they must be constant, regular and precise. the problem with the chinease units are that 1. quality control is crap (it gets tested to see if it works or doesnt work, thats it) and 2. materials used are cheap. both of these are to lower the cost to you. nothing say quality like a german product which is why you cant go wrong with bosch. you can grab a bosch dizzy off a car thats been sitting in a field for the last 20 years, clean it up, get the bearings working and itll run just fine. i doubt you can do that with a chinease one.

dizzys are quite simpe really. there are only a few problem areas with them. 1. the bearings need to be good, which i have found the ebay ones are fine. 2. the gear needs to be good, once again the ebay ones are fine 3. the hei unit needs to be good, i have had problems with a 9000kms old hei unit 4. the thermal grease under the hei unit needs to be good. the chinease ones are fine BUT you may as well put some better stuff on it while you are changing it over.

the thermal grease on the bottom of the unit is to allow heat to pass through the module and onto the body of the dizzy where it will dissappate. if it isnt done properley the hei unit will over heat and cook. so use artic silver, available from a PC shop. take the dizzy into a shop and they may even grease it for you.

remember, 3k rpm equals 400 12V pulses per second, thats a lot of volts and a lot of heat.

i hope i have explained clearly. i will read through this again, and prolly mak changes to crap explanations.

[immortality]

lol, ok mate. it takes 2 full revolutions to fire all 8 cylinders ( cause we are working with a 4 stroke engine )

[ari666]

i thought about that but the tacho is run off the dizzy which considers one full rotation of 8 cylinders 1 rpm.

if im wrong, then itll be 200 triggrs per second for 3000rpm, even still thats a lot.

[VR38]

lol, ok mate. it takes 2 full revolutions to fire all 8 cylinders ( cause we are working with a 4 stroke engine )

Hahahaha, the dizzy turns half engine speed, one revolution of the dizzy fires two revolutions (a complete firing cycle) of a V8 motor.
Eg. If the engine is turning at 3000rpm the dizzy is turning at 1500rpm.