I understand playing with Crank, Rods, Pistons, heads, can give you different stroke or compression ratio's. I made no reference of boost pressure, application, or hardware when I quoted "lower compression boost the heck out of it"; stubbornly, I
will still stand by this statement.
True, hear me out........
Assumptions:
Application: Streetable, and off roading/wheeling. Driven at speeds
under 4,500 rpm and will infrequently see higher RPM's
Induction device: Roots Blower - M90 or small equivalent. (Nota centrifugal and not referring to a turbo)
Intercooler: none
Rods: Cast-stock
pistons: Cast-stock
Crank: Cast-stock
Heads: 95tm stock mostly, 3 angle valve job- mild porting
Cam: 422 - Low end torque? Correct me if I'm wrong.
Fuel: 93 pump fuel
Main Caps: two bolt -stock
The Why?:
Knowing that you're building a motor for forced induction- roots blower system. Having that info up front is valuable if you're doing a power adder purpose built motor. I don't know why anyone, given the choice, would build it with a high static compression ratio. Given the scenario above, I would build it with the7.5>8:1 Compression ratio. If anyone would know to do that cost effectively, I'll bet you would, but I have not researched it.
It is fairly easy to change the boost to get the ideal combination of performance and power by changing pulley's. Unless you disassemble, how are you to easily lower static compression ratio?
You will make greater total power with a low compression, high boost engine than you will with a high compression, low boost engine. Remember even at idle you are boosting even when a vaccuum/boost guage says "0". , and At very low engine speeds the smaller blowers will produce more low RPM torque than at higher speeds. Sound like a pretty good application for wheeling? All the power's delivered in torque, not by higher RPM's
This is absolutely right. If you can't get the boost through the heads and past the valves, what good is it? Heads, according to JD4242, are one of the biggest weakness.
Turbo's are a whole other discussion. Best power adder by far, but I'm focusing on the roots blower.
I totally agree with this. The hardware, custom fabrication, lack of affordable aftermarket go-fast goodies, and without an easily modifiable Fuel/Ignition system, it makes this build especially difficult, but I'd still do it given the opportunity.
Not for long they aren't. I'll believe 'em when me crap turns purple and smells like rainbow sherbet.
(This is gonna generate some hate reply's)
Conclusion:
Run low boost pressure of 3 to 5 pounds. 5 at the most. There's way more to this discussion, I'm merely simplifying. The good thing is with a roots blower that you're not spinning this engine to the moon, all your additional HP is delivered in TQ.