reliable small block horse power?? [Archive]

Blown353

03-24-2006, 06:07 PM

Hate to say it, but it depends on how much money you have.

Very true... your wallet will play a big role, as will component selection. Some parts just don't lend themselves to extended street duty-- the vast majority of solid roller lifters come to mind.

Good guidelines to a reliable street boosted motor:

-Keep the valvetrain sane when it comes to spring pressures and lift and try to avoid solid rollers. Low RPM stuff (i.e. stuck in traffic) really does solid rollers in in a big hurry, and dropping a lifter sucks! Yes, there are new pressurized roller oiling solid rollers (Isky Red Zones being at the top of the short list IMO when it comes to "street friendly" solid rollers) but even then it's good to pull and inspect them periodically. It's hard to beat a hydraulic roller for street longevity even though it will give up RPM and ramp rate ability to a solid roller. In this situation I prefer to choose reliability over the bit of extra power. You could also go solid flat tappet with the EDM's oil holes.

-Keep the RPM limit reasonable (6500 or so) because as RPM goes up the internal stresses on the rotating assembly increase exponentially, and you'll need to run heavier valvesprings to keep the valves in check at high RPM, and heavier valvesprings tie right back into my first point.

-Use a machine shop that has decking equipment that will provide a smooth enough surface finish on the block and heads to let you use MLS gaskets (I like the Fel-Pro MLS gaskets, they have additional sealing material than most others on the market and will tolerate a little bit rougher surface finish.) The MLS gaskets are extremely durable, cut down on bore distortion, and transfer heat between the head and block really well. Also run good head studs for better and more even clamp load. Good bolts work too (I run them, only because I never thought I would go supercharged and the block was torqueplate honed with bolts-- thus I stuck with the bolts.)

-Spend the bucks to ceramic coat the pistons at the very least, and do the chambers and valve faces if you can too.

-Look into a reverse-cooling setup (i.e. coolant to the heads first.) This will keep the heads cooler which helps keep detonation away.

-Buy heads with excellent low and mid lift flow numbers, since that matters a lot on the street. Peak lift is important too, but so is the "area under the curve." Buy as much head flow as you can afford-- especially on the exhaust side. Better flowing heads on the intake side mean you can flow the same volume with the supercharger pulley'd slower compared to more restrictive heads with the supercharger pulley'd faster. The faster spinning supercharger will heat the air more and make you that much closer to detonating.

-Run inconel exhaust valves for piece of mind. Typical high-HP pump gas boosted motors run relatively low timing which means high EGT's. Sustained high EGT's can "tulip" stainless exhaust valves-- this happens a lot in supercharged boat applications but can also happen to a street car. Spend the few extra bucks here up front for piece of mind.

-Strongly consider piston oil squirters. CV products makes a good kit. It drills into the mains and shoots a jet of oil on the underside of the piston, which helps keep the pistons cool, avoiding detonation and keeping piston expansion down. I'd say 95+% of all OEM turbo/supercharged cars rolling off the assembly line today employ this trick, and for a darn good reason.

-Sort of tying into the above, you can buy rods with EDM'd pressurized wrist pin oiling. Not totally needed but again, nice to have at this kind of power level.

-Don't skimp on the harmonic damper as the supercharger will be placing additional harmonics on the crank. I have had very good luck with ATI and Fluidampr. In fact, if you're starting from scratch have the crank and balancer double-keywayed for piece of mind. Double keyways is a no-brainer if you're using a roots blower. Double keying the crank is not necessary with a centrifugal but if you're here you might as well do it. If you're going to run a cogged-belt drive with a centrifugal I would also say the double-keyway is a must as the cogged belt will impart more harmonics to the crank than a serpentine-driven centrifugal will. And best yet... if you're starting fresh get an SBC crank with a beefier BBC snout on it. These are made just for supercharged applications.

-Find a builder who has built similar stuff in the past and knows the pitfalls-- i.e. a bit more piston to bore clerance, bigger ring gaps, etc.

-A good aftermarket block would be money well spent, but you can certainly go pretty far with a good stock block if you stud the mains. You may also want to consider going to splayed caps on a stock block, they're more stable and more resistant to walking/spalling than stockers.

-Build only what you can afford for the WHOLE PACKAGE. Don't spend a lot of money in one area and then skimp on another. That's just silly-- like dropping $4k on a custom Bryant crank and then running old stock rods and cast pistons from Pep Boys because you spent all your money on the crank.

I put just over 8,000 miles on my car last year (about 650rwhp)-- no engine related issues whatsoever. I could and did drive it anywhere, anytime. Long trips, short trips, didn't matter. Then again I've had the time needed to work the "bugs" out of the setup and made compromises in the power department for street mannerisms and reliability.

All that being said, how much reliable power you can make depends a lot on your wallet and even more so on the gas available. Granted, you can compensate for low octane even at high boost by dropping the timing... up to a point. At some point the timing will be so low you won't be making any additional power and your EGT's will be sky-high. It's usually better to run less boost and more timing than more boost and less timing, although all engine combinations are different. And finally... don't skimp on the tuning. No amount of high-dollar aftermarket parts will live if you detonate the thing severely.

Troy