HEI conversion question

[Dave81]

Mmmmm......cooler plugs.....didnt think about that. I use BPR5S or Autolite 85s.....what should I change too??

Step by Step.....

http://www.dodgetalk.com/forums/showthread.php?t=203358

http://www.rowand.net/Shop/Tech/MoparHEIConversion.htm

Plugs....Will hunt the info for you mate!

[Steve]

Very interesting article Dave....will have a good read with a coffee after work...cheers

[Dave81]

It seems I may of misread the issue with cooler plugs. Plug gap is mention but I have nothing concrete......I found this on HAMB, so it looks like staying close to stock (what you have) should be okay.

Originally Posted by Fat47 View Post
So, in reviewing posts on HAMB, it appears that the spark plug gap needs to be increased when converting to HEI. I put an HEI in an up graded 318---bored, bigger cam, milled heads, 4-barrel, etc. Stock gap is .035. Read where this needs to be upped to .050. Comments.

Thanks

I somewhat disagree with the common gap theory. Plug gap goes with the engine and the combustion chamber design , compression ratio etc. Having a larger gap on a engine that didnt call for it actually does very little other than wear out stuff much quicker.
Claims are very stretched over the years.
HEI is a good relieable upgrade , in the nature of varying dwell at idle allowing a lower dwell cycle and longer cycles between tune ups etc....
Stay close to the stock gap....

I'd await Dave999's info before following me on plugs!

[Steve]

No probs Dave...all very interesting stuff to know! I hadnt even considered plugs to be honest so glad you mentioned it...gets the grey matter moving for a change!

[Dave999]

never touched the gaps other than checking once in a while and haven't changed plugs in 10 years

never needed to....

don't do enough miles

you could open them up a smidge i guess, just delays the point of fire so you'd need to adjust timing, and gives a spark at higher voltage wiith consequently less current. (under the cap from rotor to lead and at the plug)

and you need both I and V , power in watts is voltage x current x time in seconds

proabbly better off venting the dizzy cap

keep in mind a proper HEI dizzy has a diameter of 4-5 inches
and shielded cap and rotor, the route to the next nearest contact at any time is cut off by plastic sheild on the end of the rotor, and the plug wire connectors are miles apart

a standard mopar dizzy expects points sized sparks and the plug wires are closer.

i'd leave the plug gaps alone

but we are straying out of street car territory here....

i did nout but bang in the module and go for a squirt.

having said that this conversion is done in Oz on LPG cars
much harder to ignite due to increased compresion ratio occasionally poor distribution and 105 to 115 RON rated fuel...if they can light that with no cross talk/misfire we should have no probs with petrol

Dave

[Dave-R]

Get some NGK Iridium or Iridium/platinum plugs. The ones with the sharp centre electrode. Their website will suggest which one for your engine. Keep to the plug gap they come with.

They will last years and years with HEI. At least 50K miles. The factory says 100K miles but I wouldn't like to go more than 40K without replacing them.

[Steve]

Thanks men....those links are spot on Dave Cheers!

and thanks for the plug advice gents.

Found this on ebay...ordered one for a fiver and I will adapt it for use as a heat sink...

Ive also got a brand new Mopar electronic ignition harness that I can use to get the proper rubber dizzy connector and fresh wires for the rest of the upgrade.

Itching to get started now, just waiting for the bits to arrive

[Steve]

Just waiting for my coil now and will be ready to fit.....Ive mounted my spare HEI unit onto the heatsink so if I have any issues I can just swap them over. Made up some terminal protectors just by pushing some heatshrink on then heating the very end just to crimp it shut to protect from any dampness.

Can anyone tell me for definate, if the black wire from the dizzy is the positive and the red is negative please?? Looking at all the diagrams etc, they point towards the black being positive but the only way that is indicated is by the configuration of the black rubber plug on the ends of the wires. The fully shrouded pin at the plug (female with black wire from dist) joins the male side of the new loom which in turn runs to the small + pick up coil terminal on the HEI. As I have put the connectors on myself...this could be wrong. If the red wire from the dizzy is positive, then I would have to swap the connectors onto the opposite wires. I think its right but dont want to leave it to chance.

Added a pic of what Ive done so far. If it all works I may make up a plain black cover just to tidy it all up

cheers

[Steve]

Here is the diagram I am using to work out which dizzy wire is positive...

[Steve]

And then using this diagram to work out the HEI box end....

[RobTwin]

Just waiting for my coil now and will be ready to fit.....Ive mounted my spare HEI unit onto the heatsink so if I have any issues I can just swap them over.....

Neat idea

[Dave999]

connect up ya dizzy

start the car

if it won't start

or is really flat performance wize

swap the dizzy wires over

if its better thats the correct way

you will have to adjust timing but if you have them the wrong way round you will need to turn the dizzy about 1/3 of a turn to get it to run correctly.

even when you think its right

take it up to 3000+ rpm under load

misfires and its wrong

or rev it to 3000 with timing light on it

rev from 3000 to 4000 rpm the timing should stay at the same place

if it changes then you have it round the wrong way

the graph explains

follow the line from the left axis to the point on the wave form for correct

see at high strength wave form and low strength wave form relating to engine speed the cross over point is the same for correct way round

follow the line for wrong way

as the wave for gets bigger due to faster engine speed the cross over to trigger the module changes dramatically

hence timing change when rpm increases that is not caused by Dizzy advance (which is why you test at 3000 rpm after the mechanical adavnce is all in..) vaccum disconnected for testing

there are so many diffeent colours to the dizzy wires

mopar black and yellow
aussie mopar different white with coloured trace on wires

MSD green and purple

eeeeeeaargh

[Dave-R]

If you get the dizzy wires the wrong way around the ignition timing will seem to be much further advanced.

I made this mistake on my Challenger (the wire colours were the wrong way around on my MSD dizzy) and the car still ran OK and got me to the Nats but on the drag strip it was running a full second slower and stumbling when under max load at WOT on slicks.

This is because the spark is getting triggered as the rotor approaches the dizzy cap terminal and before the coil is fully charged up.

So which ever way around makes the timing more RETARDED is the RIGHT way.

[Dave-R]

By the way. I am VERY impressed with the neatness and correctness of your wiring assembly.

[Steve]

Thanks for your advice gents and the compliment Dave. It took me most of the day so I definately couldnt make a living at it....and I dont know if it works yet!!

I will work through this very carefully just to be sure....luckily, I am using a new mopar performance electronic ign loom to wire the box and coil etc up. I am using the black rubber connector from this loom and the blue wires coming from it to wire in the + and - pick up into the HEI. Its a one way only fit so Im reasonably happy that if I use the + wire that would have gone to the orange box + then it should be ok. That wire worked on the orange box so it should work on the HEI as the MP 5 pin cap only fits one way and + can only be + on that set up. Think it would be harder to work out if
points to HEI