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Old 10-29-2012, 09:10 AM
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JimN JimN is offline
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Quote:
Originally Posted by Surfer View Post
Hi,

JimN, thanks a lot!
Yes, the engine is non-Vortec.

Ok, I might ask for price of roller rocker arms for the base engine, if it is an option and maybe for newer TBI manifold. But MC did this type of engine only 1995 - 1997, after that MPI?

So EFI computer just "puts gas in", when crackshaft position sensor says so? When and how fast the valve is opening, fully open, closing and closed, does not matter?
Craph for roller cam vent opening is more rectangular, as flat tapped cam craph is more parabolic, as in time vs. vent opening x-y scale.


BR, Pasi
They won't have the same intake MC put(s) on the newer TBI and the one used on the Vortec won't work because of the way the bolts go in.

TBI engines, especially from the '90s, don't have a crank position sensor, they use the can on the distributor shaft and, unlike crank sensors, that doesn't tell the ECM which direction it's turning. The ECM uses the MAP sensor to detect engine load (uses barometric pressure and engine-induced vacuum relativee to RPM and throttle position), TPS detects idle throttle position (</= 2%) run throttle position (>2%) and fast throttle position changes (delta >20) for acceleration enrichment or deceleration enleanment, and coolant temoerature to determine whether to add or remove fuel when it compares its state, relative to the fuel mapping tables in the program. These run rich enough that changing the lobe shape won't cause the engine to experience problems unless it's run really hard and something is outside of the normal ranges.
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