The Stovebolt Site Forums The Shop Area Engine Shop switching to HEI- few questions

I have a 66' chevy c-30 with a 63' 327 with a mild cam and roller lifters- other than that its been a stock rebuild. im switching to an H.E.I. dizy with a 55,000v coil. what should the spark plug gap be? and i got a curv kit with the dizy; what should the degree of mechanical advance be in relation to rpm? im using it mostly for a daily driver- not hauling anything, but thats not to say i wouldnt mind squashing a honda here and there! any info or a starting point would be appreciated-merry x-mass!

Run one stock advance spring and one of the medium weight springs from the kit. You want total timing all in by 2500 to 2700 rpm so at highway speeds you take advantage of it.
Total timing about 34 to 36 degrees depending on the gas quality and if it pings under moderate load.


Spark plugs gap at .060" with HEI, I like to set mine at .055", .060 just seems to wide.

Joe

Brian, check this site.

http://www.chevytalk.org/fusionbb/showforum.php?fid/72/

It is a Chevy performance forum almost entirely dedicated to drag racing issues. I am not a member but I read it for amusement and information. Like all of these forums, it is a mix of crackpot amateur opinions and expert professional information.

There is a guy whose handel is Ignition Man and he has posted an unbelievable amount of information on the HEI ignitions and how to optimize them. Not only are your questions about plug gap and advance curves addressed by Ignition Man but he explains the best plates, weights, springs and vacuum cans to use and how to adjust and modify them for the best perormance in your application.

You will find that he explains why there is no advantage in an extremely high voltage coil like yours amd he also explains the proper plug gap.

He is very opinionated about various aftermarket HEI systems, some of which come from, you guessed it, China.

On a similar subject here's a site with great information and pictures to learn to read spark plugs. Those of us who don't have a dyno have to resort to plug reading and according to this site plugs have quite a story to tell on matters more than full throttle air/fuel ratio.

http://www.4secondsflat.com/Spark_plug_reading.html

My street rod is a 350 SCB powered '32 Ford roadster and I am running an OEM Chevy HEI with a Crane Cams adjustable vacuum can and mechanical advance spring kit. I did a lot of tinkering with advance spring combinations and vacuum can adjustment and the results are gratifying. Even on a mild street rod like mine or a daily driver, optimizing the distrubutor mechnaical and vacuum advance curves greatly improves performance and fuel economy. My dyno for making these and other tuning adjustments is a long grade near my home. My wife listens for ping because my hearing has gone south and I read the plugs at the top of the grade. It's a crude but effective laboratory.

Have fun!

JMHO but I would get the new HEI in and running before you start optimizing your timing. I run my gaps at .45 and then adjust from there.

Also be aware that you cannot use the existing ignition wire from the switch to the original coil. It is a resistor wire and will not give you the full 12 volts that an HEI requires. A #10 wire is recommended to power an HEI.
Fred