Rich,
I have to say, I am really impressed with this Pontiac 350. I used to hate it, but now, we are making firends.
I didn't really expect it to make anything over the baseline, because the car disn't feel as strong after the headers went on, which makes sense, since it moved the torque band higher up in the rpm range.
What I concentrated on after the first baseline was taken, was all 'seat-of-the-pants' feel for tuning. I don't have any high-tech stuff, so I did it the way my Dad taught me to do.
I would use a stopwatch and time my 50 to 80 mph pulls in high gear with the kickdown cable unhooked. I would change the hanger and rods until performance peaked and then richen until the times fell off, then drop back to the parts that gave the best times.
On the primaries, I would richen the engine until it 'felt, sounded and smelled good,' then take an exhaust reading on my friend's smog machine. I would lean the primaries out as much as I could and still get smooth running, then I would fiddle with around with jets and metering rods until I had the lowest HC ppm emissions, trying to keep the APT in the 3.5 to 4.0 turn neighborhood.
I always like a lot of initial timing, so I played with weights and springs until I got 20° on the crank and 36° total. That just seemed like a good starting point to me and the engine 'felt good' at that setting, so I just left it there.
You can't say the 'seat-of-the-pants' dyno doesn't work, plus, its a helluva lot cheaper!!!
I agree with you on the 092 short turn. On mine, I am going to match the first .250" of the intake ports to the gasket, but that's it. I will smooth the rough edge from the short turns in both intake and exhaust, but I won't do any porting at all.
I'm using new stainless steel, swirl polished 1.600" exhaust valves in the stock 389 lengths. The intakes are good used OEM replacements (1.970") from a SBC, which just happens to have the same OAL as the stock 389 valves. I am using brand new, OEM replacement Pontiac dual valve springs set at 1.600" installed height.
It's really a very basic swap, nothing trick at all...Robert
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