Hot Rods ignition timing on 216 chevy

hi, i gotta a 49 with 216, i just fitted petronix elec ign, whats best plug gap? and what shall i reset timing to? she seems a bit sluggish now,

 

I would think you would use stock plugs and settings. Is the vacuum advance working?

 

vacuum working, original plug gap 35in, been told coz its now elec it gotta be 50, and that i have to redo timing, poss to 10 to 18 ??? just want to besure

 

i thought somebody on here would know???

 

I'm no automotive engineer but I'll give it a try -

The electronic ignition gives you a hotter spark, that enables you to set a wider plug gap; the wider gap enables you to use that hotter spark.

Ignition timing, as I understand it, is more dependent on compression ratio, combustion chamber design, camshaft, gasoline quality and intake charge temperature - and none of this has changed so stock timing should work.

As for the vacuum advance, those old Chevy's used a ported vacuum, when you 'crack' the throttle open you get a vacuum signal which advances the timing. And you are setting the timing using a timing light on the flywheel ball and the pointer in the opening of the bellhousing right above the starter?

Now - if anybody disagrees with what I said, you will soon get a bunch of comments...............

 

yes am setting timing with adjustable light, but need to know how many degrees

 

yes am setting using an adjustable light but need to know how many degrees btdc

 

With an adjustable light set it to '0'; time #1 to the 'ball'

The clamp for the vacuum advance has a scale on it, set that to '0'

There should be no vacuum at idle, and set the idle as low as you can.

I just thought of something else, if I remember right, the centrifugal advance on those 216's comes on very quickly - do you know the advance curve in the distributor?

If the advance is not coming in quick enough that might explain why it seems a little sluggish.

 

In the original 1938 Chevy operators manual it says to adjust the timing so that a slight " Ping " can be heard.

 

i just gave dizzy slight turn and gave half a turn on mixture , she now goes like a 90 hp rocket lol

 

I use a vacuum gauge to set the timing on my 235. Pull all the vacuum you can, then back off a little. The "slight ping" method is good too, if you can hear. The needle and ball thing wasn't very accurate for my car. 235s and I assume 216s like what they like, and you got to find what it likes by tinkering with it. And I don't know if the Pertronix necessarily means a hotter spark, (you need a hotter coil, right?) just a more accurate one.

 

I go with the "ping" method. These 6's will run best when the timing is set just under the ping point. The initial advance on my 235 is WA-Y-Y ahead of what the book calls for and it runs great.

 

ive added a hotter coil, aswel

 

well ive had a pertronix ign in a 235 six for 20 years .plug gaps are 0.45 thou and set the timing by ear runs like a bat out of hell!lol

 

Electronic ignition works fine with stock ignition timing. You don't need an adjustable light to set your timing. A regular light will work just fine.

As for plug gap I run pretty hot spark on most of my stuff and seldom gap my plugs more then .045. A good place to get a definitive answer would be from GMCBubba. he builds petronix dizzys for a living.