Initial timing on 87 350

[bdozeraz]

My brother has a 87 blazer with throttle body 350. It failed emissions for HC at idle. He installed a new O2 senser, cats are only one year old. It passes the loaded reading well within spec. I think it is the timming out of spec at idle that is causing it. We disconected the wire to the distributer and set the timming to zero. When it is hooked back up it reads up around 20 - 22 degrees. This seems high to me, I am used to 8 to 12 with old school ignition. He has a custom chip. What initial timming does that year usually read with the computer hooked up?

Thanks,
Brent

 

[chvymudin3388]

i got youre smae problem in my 87 i have no clue whats with it sometimes it runs what i set it at which is 4 then other times itll run at like 20 but when it does run at what i set it at runs like crap and when you gun it from a dead still or even in park it shoots black smoke like its a damn diesel

 

[dyeager535]

Never threw a timing light on my truck, but 20+* at idle sounds about right after setting base timing.

Higher timing at idle is something GM can get away with since base timing is what it starts off of. You'd never start it at 20* base.

 

[chvymudin3388]

mine was starting at 20 base i unplugged the wire and freaked when i saw 20 even after i unplugged it

 

[dyeager535]

Heck, my starters typically can't/won't crank the engine fast enough if the timing is anything over 8*.

Regardless, idle timing is higher with electronically controlled ignition systems than with mech/vac setups.