Pontiac D Port 8 Stack Manifold Assembly
Pontiac 8 Stack Manifold Assembly
Complete and ready to run. This 8 stack individual runner (IR) manifold fits Pontiac D port heads
Each manifold comes completely assembled and includes the following:
- 4 Weber carburetors. Your choice of 48 IDF or 48 IDA carburetors.
- CNC machined aluminum manifold with composite runners.
- Stainless steel intake bolts and intake gasket set.
- Low pressure fuel regulator.
- Stainless steel braided fuel line with AN fittings.
- Liquid filled stainless fuel pressure gauge.
- Throttle cable bracket.
- Synchrometer.
- Simple to follow tuning manual.
These manifold assemblies are made to order. Please allow up to 6 weeks for your manifold to ship. I make every effort to ship sooner than that.
What you will need:
1. This manifold will require you to run a “divorced” coolant cross over. This can be achieved by simply cutting the coolant crossover off the existing 4 bbl manifold. Many Pontiac enthusiasts have found this beneficial, as it allows you to change the intake manifold without the need to drain your coolant.
2. This manifold is designed to be run using a throttle cable. If your vehicle is equipped with a mechanical throttle linkage, you will need to convert to a throttle cable. There are many third party companies such as Lokar that offer these for many different Pontiac models.
3. Once the manifold is installed on the engine, you will need to perform the synchronization procedure that is called out in the included tuning manual.
4. You will need to determine a mounting point for the included fuel pressure regulator. Due to differences in all installations you will need to provide the fuel line running from the regulator to the 8 stack assembly.
Camshaft Selection
You will want a camshaft with a lobe separation angle (LSA) between 112-114 degrees I would not recommend anything tighter, like 108, or 106, even a 110 is considered marginal. The good news here is there are many stock Pontiac cams that have an LSA in this range that will work fine with an IR manifold like this. I am personally running this manifold with a stock Ram Air III cam 9785744 with a 115 degree LSA and it performs very well.
What happens when you have a lot of overlap is it causes reversion which are pulses from the exhaust stroke while the intake valve is still open, these pulses have nowhere to go but back up through the carburetor.
Most engines with a typical 4 barrel have a common plenum manifold that is shared across all cylinders and the reversion pulses can be absorbed by other cylinders. Without a plenum, the flow is pulsed backward up into the carburetors because there is no place else for the reversion pulse to go
Options:
Overall Height / Velocity Stacks:
The height of the manifold assembly as measured from the lip of the valve cover is the following:
IDF Carburetors = 8.5"
IDA Carburetors = 9.5"
Stock velocity stacks are 2.25" tall. If you require additional hood clearance, you can order shorter billet velocity stacks. We offer two shorter versions.
Jet Kits:
Every engine could require slightly different jetting depending on your use. Each 8 stack assembly comes jetted with idle and main jets that will run fine for most applications. If after you go through the tuning process and you find you need to go up or down in jet sizes, these kits will allow you to fine tune your engine. Each kit contains enough jets for all 8 carburetors.
Main Jet Kit contains 4 jet sizes ranging from 145 - 165 and 4 Air Jet sizes ranging from 175 to 210
Idle Jet Kit contains 4 jet sizes ranging from 55 - 70, pump bypass and pump jet size 55.