Im having trouble with the timing with my car. I set my timing at 38 degrees total timing at 3000rpm. I have a MSD pro billet w/ vac advance. I just bought the bracket that eliminates the vacuum canister and also bought the advance spring kit to. I bought the distributor brand new so Im almost positive that i need to change the springs. Car idles good, when i go to punch it, it pretty much breaks up. Does anyone have suggestions?

 

Whats your initial timing at?


My weird beast hates any movement in timing, i run locked out at around 30*

Its the only way i could get alot of bottom end power without knocking at high RPMs.

 

Why, WHY!!! would you want to eliminate the vacuum advance?

What camshaft? What carb? what intake manifold? What is the converter stall speed?

*Generally* 38degrees is a little too much total timing for a SBC. usually with accurate timing marks, best power is at 32-36deg. More timing than this indicates either too rich or too lean an air/ fuel ratio or inacurate timing marks, timing tab.

 

I have an Isky Camshaft, Hydraulic Flat Tappet, Advertised Duration 292/292, Lift .505/.505. My stall converter is a Jegs Street/Strip 3200-3600 stall. I also am running a Holley 650 double pumper.

 

What intake manifold? Did you get any advance limiter bushings in the kit or with the distributor?
You need to do more than just swap advance springs.
You need to install the advance limitor bushing that is the thickest that will limit the *mechanical advance travel* the most. Then use two medium tension springs. With vacuum advance temp unplugged set the timing at 3500+rpm to 36deg. Now, what do you have for idle timing at 700rpm? You'll probabily have to readjust the carb throttle opening to slow the motor down..

You want the initial as close to 22-24deg (more the merryierr)at 600-700rpm as possible and 36deg total at 3500+rpm.

Once you've got this you want 10 to 15deg vacuum advance at high cruise ( limit the travel of the vacuum canister arm to 10-15deg (use ported vacuum)

From that point you may need to dial in the carbs accelerator pump cam linkage set up and shooter size.

Do the distributor first.

You may have to replace your spark plugs if they are fouled with carbon. Check the plug gap (.035")
Make sure the engine is grounded to the body and if you have a CD ignition box like MSD6al make sure it is well grounded to the battery - and engine block.

your big isky cam with its long duration, rough idle and low manifold vacuum pumps exhaust gas back into the intake at idle.
Thats what make the cool rough idle. This "EGR effect" slows the fuel burn rate. therfore you need much more initial timing at idle than a stock or near stock motor with a small cam. thats why you need to limit the advance travel to allow more initial yet the same 34-36 at high rpm total for best power.

Once you've got it running right you need to hook up a vacuum guage and read it at idle in gear.
What ever the vacuum guage reads for manifold vacuum at idle you want to install a power valve in the carb that is just slightly lower. EG if the guage says 5" while idleing in gear, you want a 4.5" power valve.
This will insure that the power valve remains closed at idle preventing a over rich idle the kills the throttle responce.
Make sure you have the PCV hooked up to the carb base and vent the other valve cover so the PCV system breaths and vents the crank case. It is an essential part of your carbs idle system. Do not disable it.

22-24 deg at idle advancing to 34-36deg at high rpm.
So you want 12deg of mechanical advance travel.

then 10-15deg vacuum advance at high vacuum cruise ( hiway) (not at idle) ported vacuum.