Supercharger Performance and Engine Performance Parts

I ran into this great article on a performance rebuild for a 289 ford engine (and similar sized Small block fords), and thought about what I would change to prep the motor for a nice dose of boost.

The engine build in the aritcle inculdes an:

Flat topped pistons hugging their bores...

• Eagle/Arias stroker kit bring up the displacement to 297 ci
• Holley Systemax aluminum heads with 1.90″/1.60″  intake/exhaust valves
• Weiand action plus dual plane intake manifold
• Holley 670 CFM action carburator
• Comp cams Dual Energy split pattern cam with 265*/273* intake/exhaust duratio and 110* Lobe Seperation Angle

The setup as-is should be capable of around 440horsepower at 6000 rpms making it a great crate engine type build for a 289 engine. However if you’re looking for even more performance through a supercharged application here are some recommendations during the enigne build.

Pro systems blow through carburator ...

• The use of a stroker kit is great for increased displacement and low end torque, but comes at the cost of higher static compression which ultimately limits your peak boost and peak timing at whatever octane gas you have available.
• The use of aluminum cylinder heads is great for increased cylinder head cooling and reduced cylinder head temperatures (which makes for less head distortion, better head gasket stability and seal, and more stability at higher power figures).
• The use of flat topped pistons (or even domed if possible) is great for quench; quench helps create a better swirl inside the combustion chamber giving a better air fuel mixture. This results in increased volumetric effeciency (more power per displacement) and also has the added benefit on a supercharged car in preventing any lean pockets in mixture (especially around weak parts such as the piston rings and ring lands) because the increased swirl will help even out the air fuel distribution in the cylinder.
• To lower the compression ratio, while keeping good quency and swirl dynamics in the cylinder, the use of a larger CC engine head can be beneficial, so swapping to a Holley 300-575 (Aluminum heads with 2.0″/1.60″ valves and a 63 cc combustion chamber) will bring the static compression down from to about 8.6:1.
• For a camshaft, using a split pattern cam with more lobe seperation angle would be advisable to reduce valve overlap and help increase our utilization of our supercharger (by preventing boost from leaking out of the cylinder during overlap). A better camshaft for this application would be the comp cams nostalgia camshaft with 266*/273* duration and 112 degree lobe seperation angle.
• Now that we have a nice compression ratio to work with, we can easily run a safe and reliable 14 to 18psi on this motor, we can expect to make at least 715 hp at 14 psi and up to 780hp @ 18psi.
• Obviously at this point stock like I-beam rods rated to 500 hp are going to be stretched beyond their design limits, they may survive but not for long, a better approach would be to utilize eagle’s H-Beam rods to make sure the assembly stays put together under boost…
• Every 1.5 CFM is equivalent to roughly 1hp depending on the volumetric effeciency of the motor and thus a 650cfm carb is only capable of around 433hp. This makes it a great match for our original crate build but a poor match for our supercharged build. If we’re looking at a modest supercharger build around 630 hp then the holley supercharger draw through carb is capable of 950 cfm and is a good match for a roots style supercharger setup. The carb has an additional fuel enrichment vacuum reference that adjusts fueling based on the vacuum trapped in the region between the carb and the roots supercharger sitting below it. This vacuum is proportional to the overall flow rate and boost pressure of the motor and so it is used to regulate carb’s additional enrichment.
• However, if you’re looking for more than 630hp or looking at using a centrifugal supercharger for boosted top-end power, then there are two options:
  • Use a blow through carb setup such as the pro-systems blowthrough carburator which can be setup in blow through setup (after the supercharger) and is capable of adjusting fueling based on barometric pressure changes and boost pressure changes. The carb is capable of fueling upto 1800 hp depending on your requirements.
  • Switch to different style intake manifold such as a weiand single plane M9424-C82S, which comes with untapped injector bosses. Drill out the bosses go with a full blown EFI setup that is neither limited by carb CFM or jet changes… equipped with some 1000 cc injectors you will be able to support either a centrifugal or twinscrew supercharger upto the target of 780hp @ 18psi with this setup.
• Typically with the use of a supercharger (or any form of forced induction) we may need to retard the ingition timing event depending on the octane level and boost level we are running at the time. Since we have dropped to a very safe and fairly low compression ratio of 8.6:1, then this it is less stringent that we retard the ignition timing. However if we needed to, it would be good to have that facility available and so I would (on my personal car if i were to build this motor) swap the distributor for a pertronix street/strip HEI distributor which comes equipped with a vacuum advance as well as adjustability for base and mechanical (Rpm based) advance. Thus we can have better fuel effeciency and throttle response with advanced ignition timing timing at low loads and low rpms, and as that vacuum reference sees less vacuum (and more boost) the vacuum advance is elimiated giving us a more retarded peak timing curve.
• Finally, the hydraulic dampener would probably have to be changed to match whatever supercharger you use (belt setup or cog setup) and to be geared to the proper supercharger drive ratio to reach your target peak psi and peak power goals.

For the complete original article please visit:

Mustang Monthly

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