Discussion in 'Chevy' started by TXFlyGuy, Aug 21, 2012.
Right forum, wrong thread.
What information do you have that says the engine/PSRU was at fault? We had a fatality of a Subie powered RV a few years ago, where the failure was >IIRC< due to a loose ground wire. Sure, the engine stopped producing power, but it wasn't really a fault of the engine itself.
What info do you have to directly refute this?
Witnesses stated they heard/observed an explosion just after takeoff. The general consensus is the power train was the culprit. I am deferring to the first hand info told to me by Mike O'Sullivan, owner Supermarine Aircraft. Formerly of Australia, now in Texas.
I have no information to refute anything, and am not trying to refute anything.
What I'm trying to do is determine if there are facts to support your claim. Saying WTTE "Some guy's engine or PSRU failed, and I wouldn't build that engine." needs supporting facts. Specifically, information on the nature of the failure.
Your honor, the prosecution rests it's case. Especially with the testimony of a first hand witness.
Why the 1.7:1 PRSU ratio? I could spec a 4.3 that might make close to that kind of power at that RPM but you would be scared of the cost. Give me a 4800-5000 RPM then we can make it easy. Just don't be delusional in thinking the 4.3 that your buddy has under a tarp behind the wood pile is a candidate.
I would start with the GM Bowtie catalog for the aluminum block and 18 degree heads. You'll need the airflow these heads have to make the power you want without resorting to extremes of compression or cam specs.
Are you planning on a constant speed prop? If so your choice of PRSU gets limited. I'll tell you right now I've not seen a belt PRSU on anything high powered I would fly behind. 300hp, yeah, we can do that. I've squeezed 1800hp from a 3.2 litre Cosworth V-8 but that's another story.
Without knowing what the engine/prsu//prop combo was it's impossible to make any informed comment. If someone had that information then maybe we could learn something useful. I'm building a highly developed combination not unlike what most were doing for the Stewart 51. I simply don't need a big block for the power level I'm seeking and the supercharger is mostly for takeoff power and high altitude performance.
For those who do not know, we have the GM LS376/480 engine, with the Autoflight New Zealand 2.21 PSRU.
RPM limited to a max continuous of 4500, which equates to 370 hp. On the dyno, we got 430 hp @ 4500 rpm, but that was with long tube headers installed. With the Mustang "short stack" exhaust, there was a power loss above 4000 rpm. 525 hp @ 6200 rpm.
Constant speed, hydraulic 90" prop.
Not sure why you would choose a smallblock Chevy platform over an LS engine if you are going to start with an aftermarket block and go from there. The LS is a superior design in many ways over the revered smallblock ...especially if you step up to something like an RHS version of the LS. LS engines easily make more HP due to the replicated flow where each cylinder gets the same airflow vs the antiquated design of siamesed ports with different air flow. 23 degree valve angle vs the more upright designs of various LS heads. Its all about air flow if you want to make HP. LS heads are some of the best flowing heads out there and easily outflow even smallblock race heads.Different crank firing order which helps run smoother and avoid resonance. No loss of power by driving a distributor. Better design and more efficient oil pump and with the RHS, a better priority main oiling system. Long snout Corvrtte style crank can drive two oil supplies which can furnish oil to a redrive if desired. Crank raised in the block for more ridigity. You can upgrade the smallblock to a roller cam and roller rockers to equal an LS but you still may have issues with the distributor interface if not properly done. On an LS there is no distributor. 1 Coil vs 8 coils. Gaskets and seals that aren't leak prone. Lots to like about LS engines
I have a lot of respect for smallblock Chevy engines, but if I had that kind of money to throw at a project, I'd start with an LS block from RHS. Tall Deck 502 cu in or something less with a standard deck. 6 bolt head clamping. Billet cranks are available too.
As for "never putting LS internals" in an airplane engine, apparently you aren't putting standard GM smallblock parts into your engine either....or even using a GM manufactured block. What are you going to install this engine in, and do you plan to be able to actually use the 650 HP you mentioned ? Personally I have always been a proponent of building LS engines with strokers (since it adds displacement with no weight penalty), but even the factory components are pretty reliable. GM tested these engines exhaustively at high rpms , far more than smallblock engines. But, I do agree that there are better quality parts available for those who can afford to do so.
I'm using the splayed valve symmetrical port BowTie 18 degree heads starting with semi machined castings. This is most of what the LS technology is based on without the constraints of being production. I also have a 40' storage container stuffed with left over engine bits from road course with my old '65 vette.
The big factor is I'm building reverse rotation and the firing order will be changed because of the heads. I've been involved with this type of engine development for over 4 decades and I agree, the LS series are a good starting point for most people. Unlike most people I have a bizarre wiring disorder in my brain to not allow me to follow the crowd.
I appreciate people who don't follow the crowd and work thru their own ideas . It makes a lot of sense to use something you already have and have experience with. GM changed the firing order from 18436572 to 18726543 to smooth engine pulses and think they picked up some power. If you are going to reverse rotation and get a special cam made, it might be worth innovating that into it. Good luck with your project, sounds interesting.
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