350 with vortec heads timing issues does this sound right?

[01maroonz71]

My motor has been idleing a little rough, and it dieseled the other day, so i need to get this dialed in before i go out to the local mud hole next weekend.

it's a GM 350 longblock with 8k miles on it and vortec heads. i just replaced plugs and wires, and now i am trying to set my timing to where it needs to be. we have the initial timing set at 12degrees and at 2500RPM it's aroud 28-30. 3000RPM puts it up to 33-35 RPM. when i hook the vac advance back up, it throws damn near 55degeees of timing into the mix. not sure if that is normal or not. this is with idle set at around 750in park, and 550 in gear.

next will be adjusting the air/fuel screws on the edelbrock, but i want to get timing right first.

does anybody see anything wrong with these numbers at all???
thanks!!!!!!

 

[JoshHefnerX]

Timing doesn't look out of the realm, wouldn't hurt to back it off a degree or 2. Vortec's don't need quite as much timing as old smogger heads. You can get into the 50's under no load and higher rpms -such as highway speeds. If it recently started idling worse, check it for vacuum leaks. As for the idle mix, turn them out equally and look for highest manifold vacuum. If it was off you'd have to back off the idle speed screw some more. But check for leaks first.

 

[paratrooper307]

Dieseling usually means overly advanced timing. When I had a carb on my 350 with Vortec heads, I had mechanical timing at about 10 degrees advanced. I also put a stop in the vacuum canister to limit it to 12 degrees of vacuum advance, since most canisters can allow way too much timing advance for most 350 setups. Now I run fuel injection with electronic (no vacuum) advance, and it's "all in" at 42 degrees advanced. Josh is right, Vortecs don't need as much timing.

 

[blazer74]

Possibly just some bad gas could cause your issues.

200 rpm drop a bit much, check when your mechanical advance comes in. Might be to soon.

Limit your vac advance to 49 50 total.
All that timing is going to be in at cruise rpm.

Ported or full vac is whatever you engine likes the best for idle.

Check your pcv valve.

10 deg initial is all I run. 350, vortecs quadrajet ,268he cam ,8.75to1 ,14 deg limit stop, msd street dist.

I have zero ping.

IMHO