1990Z71Swede
I'm Awesome
When gathering parts for a mild upgrade I took a dive into my own parts bin, mainly just to assess the greatness or lack thereof of the stock TBI inlet manifold. (just by eyeballing it, so not very scientific really ) While doing so I took some pictures. Maybe they can be of use to someone else doing something similar?
What I had to work with was:
#1 A generic 1968 Q-jet Cast iron manifold, found on for example 275 Hp Camaros.
#2 A GM/Winters Z28/LT1 factory replacement aluminium High Rise, similar to a performer RPM, this is the one with the oil fill tube.
#3 A Holley 300-36 Again a High rise comparable to a performer RPM, but slightly larger (not taller) overall.
#4 The odd one out a Weiand X-celerator Single plane Low rise.
Now, I'm personaly either going with a cleaned up Stocker or a non RPM Performer Q-jet manifold plus adapter.
The runners of the Stock TBI manifold are pretty much identical to the old cast iron Q-jet lump, so that part I guess is just fine for what I'm doing, but the "plenum" is a different story altogether.
The TBI manifold has some quirks. Apart from the obvious 87- onwards angled center bolts, the entire plenum has coolant in a water jacket around it. The exhaust heat riser port appear to be used just for EGR and does not pass through. The underside part of the plenum water jacket connects with the open rear water passage, and exits through the port used for the heater core. The pics of the underside shows the difference. All of this could influence which way to go, when choosing a manifold that suits your specific needs. Old news maybe for most people, but take it for what it is.
What I had to work with was:
#1 A generic 1968 Q-jet Cast iron manifold, found on for example 275 Hp Camaros.
#2 A GM/Winters Z28/LT1 factory replacement aluminium High Rise, similar to a performer RPM, this is the one with the oil fill tube.
#3 A Holley 300-36 Again a High rise comparable to a performer RPM, but slightly larger (not taller) overall.
#4 The odd one out a Weiand X-celerator Single plane Low rise.
Now, I'm personaly either going with a cleaned up Stocker or a non RPM Performer Q-jet manifold plus adapter.
The runners of the Stock TBI manifold are pretty much identical to the old cast iron Q-jet lump, so that part I guess is just fine for what I'm doing, but the "plenum" is a different story altogether.
The TBI manifold has some quirks. Apart from the obvious 87- onwards angled center bolts, the entire plenum has coolant in a water jacket around it. The exhaust heat riser port appear to be used just for EGR and does not pass through. The underside part of the plenum water jacket connects with the open rear water passage, and exits through the port used for the heater core. The pics of the underside shows the difference. All of this could influence which way to go, when choosing a manifold that suits your specific needs. Old news maybe for most people, but take it for what it is.
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