Vacum advance connection

[RIGEROUS]

Hello,
I have a completly stock, (including all vacum lines and smog equipment) 1986 scottsdale 4x4 with a 305 and 4 spd auto. Problem is when I set timing to 4 degrees btdc, (per the sticker under the hood) it pings. I end up running with no advance an it bogs. Question is what should the vacum advance line be connected to ?

Second question; is there any problem with removing all the extra vacum lines ?

While im at it any advice about removing the smog pump and air tubes ?

Any help would be appreciated.

[jaredts]

Maybe someone sharper than me will chime in and give you some help.  You might try a product for removing carbon buildup from your engine.  Seafoam is recommended a lot.  The other thing I would recommend would be to double check how you checked your timing.  Did you disconnect the vacuum advance before checking?  The vacuum advance is supposed to be on a "ported" connection on your carb (above the throttle plates).  If you connected it directly to the manifold it should still work, you just get a little extra advance.  People do this all the time and usually get a little better performance.  You should be able to get decent driving manners either way.  Running with no advance to eliminate pinging doesn't sound right--even with carbon buildup.  Removing vacuum lines is your decision.  It isn't always legal but most of your smog equipment is probably not working like it should anyway.  For functionality you only need a few things:  vacuum advance, vacuum to the hvac in the cab, vacuum modulator on the trans.(which I don't think you have on yours).  You can remove the air tubes from the exhaust manifold and plug the holes with pipe plugs.  Of course remove the belt from the pump.  Hopefully someone else will help you as I don't claim to be a mechanic.

[Lt.Del]

on my 79, the hose for the vacuum advance goes to a check valve and splits in two, one to the TVS on the t-stadt housing an the other to the carb.  see pic








http://www.delbridge.net/vacuum.html

[VileZambonie]

Jaredts is correct. Depending on your emissions legalities where you live, you'll need to determine what you can and cannot get away with.

[RIGEROUS]

So, I sent the timing to 4 degrees BTDC and moved the vacum advance hose to a ported connection on the carb. Truck runs much better, no pinging and no bogging, a simple change made a huge difference.

Next step I unplugged the electrical wires from three vacum devices, one on the fire wall near the brake master cylinder, one on the engine near the distributor and the third mounted on the passenger side fire wall. Truck starts up, warms up, runs, drives, shifts, downshifts and controls heat and defrost as it should. I guess I don't need all those vacum lines, i'll just keep the one to the vacum advance.

Wondering how useful the vacum module and flap valve in the passanger side exhaust manafold is ? Looks like a warm up device ? Might be better off fixing the flap in open position and disconnecting it ??

Thanks guys for all your input.

[1980c10]

you need your vacuum module.