"Since reading this thread, I have gone back and installed the stiffest springs in the Mr. gasket kit (gold) in my engine, and watched my idle (in DRIVE) smooth out considerably- the idle drop from PARK to DRIVE is not as bad as it used to be" Good news! This is a very common problem associated with aftermarket springs, and distributor advance "kits". Huge drops in idle rpms from Park to in gear result if the timing falls back some, or part of the curve was in at idle speed, then timing retards when a slight load is placed on the engine. Folks tend to associate this with a carburetor issue, when it is a simple fix.....simply make sure the springs and associated parts do NOT add any timing at or below the idle speed of the engine. You can still enjoy a fast spark curve without adding any timing below apprx 900-1000rpm's. Most stock distributors have a faster spark curve than folks tend to associate with them. Later model distributors often have a very "tight" spark curve as well, which acutally lets us run more initial timing and still get the total timing we want after engine modifiacations. Most distributors will add too much timing via the vacuum advance unit for a well thought out "high performance" engine. Things we do to increase combustion efficiency, such as improved quench distance, "optimum" compression ratios, cams with earlier intake closing point(s), improved engine scavenging, etc, tend to allow us to run reduced timing settings for optimum power/efficiency. Without exception, all of the engines I've had in my Ventura in the past 10 years require exactly 30 degrees total timing for best HP production, and don't want over about 10-12 additional degrees from the vacuum advance unit. I zero deck the blocks, .039" head gaskets, very efficient combustion chambers, well chosen camshafts, excellent intake/exhaust systems, and precise carb/distributor tuning. My current engine is 11 to 1 compression, 236/245/112 Hydraulic Roller camshaft with .630" lift, ported stock intake, 1977 Q-jet carburetor, stock HEI distributor, stock Pontiac "Shaker" assembly, professionally ported aluminum heads with "heart" shaped chambers, .037" quench distance. It runs fine on 89 Octane pump fuel, smooth idle, strong off idle power, and pulls hard to at least 5800rpm's. I don't race the car much these days, and am limited to 1/8th mile tracks, as all runs are easily under the legal roll bar rule for 1/4 mile tracks, even spinning most of the way thru first gear! It really is possible to have a strong running pump gas engine that is dead solid reliable in all areas on the street, and runs like a "race" engine at the track.:TU: .......Cliff
Like Cliff said, if the springs are too light, they add advance at idle, and that results in a larger RPM drop from Park, to Drive. I use the lightest springs for checking and setting my total advance. Then I switch to heavier springs to get it all in between 2500 and 3000.
Steven Doves book lists this as the correct dist. for the '71 350 Man. Trans. 43-44-45000 series cars. Centrifugal specs were 16-20 at 4600 rpm. The automatic cars would have had dist. 1112080. 14-18 at 2900 rpm.
