It's been 3 years now since installing a GMPP ZZ383 in my '69. I'm thinking about changing the cam to get rougher idle. The stock cam pulls a very steady 18 inches of vac, at idle. I'm looking for suggestions for a cam that would not lose me low end torque but get the idle I'm looking for.
I topped off this crate motor with the following parts:
Edelbrock Air-Gap vortec intake
MSD 8360 Distributor
Holley 650cfm vac, sec. carb #80783-1 (also have similar 750)
D368 headers
M22W 2.54 first gear
ProComp 1.6 roller tip rockers(still have 1.5 GM rollers)
When I had my 383 originally quoted (which has since grown into a Dart 400 thanks to my tax refund), my builder selected the cam with me after going round and round on what I wanted. 100% street driven and wanted gobs of midrange since I'm running a 3.42 and five speed OD trans.
He came up with the Comp Cams XR276HR (hydraulic roller) but ground with 224/224 on 108 lsa (normally it's 224/230 on 110 lsa) along with 1.6 rockers to get the lift up some. If you're running Vortec heads you might want to keep the extra exhaust duration. Mine was going to have AFR-195's. He said that would give me what I wanted and still pull around 14" at idle and we were going to keep compression ratio around 10:1.
Whenever you start increasing duration to get a rougher idle it is very likely low RPM torque is going to suffer a bit. You could circumvent that compromise by utilizing a looser torque converter, or in your case slipping the clutch a little more or even going to a different clutch set up, and using a lower gear.
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