Here is a basic daily driver friendly combo for a 461" bigblock that will churn out 500hp with mostly stock parts,and will handle a 200 shot of nitrous with no problem.Start out by getting yourself a stock 454 junkyard shortblock out of a mid 70's thru late 80's pickup truck,or an early passenger car.Try to find a complete assembled shortblock.When you find your shortblock,you need to measure the deck height of the block before you disassemble the engine.You can do this by cleaning off the tops of the pistons and using a straight edge across the bore and a feeler guage between the straight edge and the top of the pistons when they are at the top of their bore.Slide different feeler guages into each one to figure out how far down the stock opistons are in the deck,and then when you find the one that is the closest to the deck,write down the measurement,and tell the machine shop to deck the block and to remove at least that much material off the decks.Then have him bore and hone the cylinders,and check and correct the main cap bores if they are not in spec,and then finish prepping the block with the core plugs and cam bearings an such.
Then have the stock crank checked and if it isnt damaged or cut more then .030",have it ground to the next lower undersize,and have it gorund to the "low side of spec",your machinist will know what that meansget decent replacment bearings like the CL77 or FM HP series bearings.Have the stock rods fitted with aftermarket bolts and resized.You are now going to need to buy pistons.I would go with a set of TRW #2399 pistons,these will give you about 9.8:1 in the combo I am about to propose.Use new stock replacemnt rings that match the piston application{1970 LS6 454),and have the block honed to fit the pistons and finished for the rings.You can then have the bottom end balanced with a stock damper and flexplate,or you can upgrade to SFI spec stuff if you plan of running the car at the track with the nitrous on.
Now you need to finish off the shortblock with a mild hydraulic flat tappet cam such as the Isky 280 Mega cam.This is about as big as you can really drive every day without getting tired of the lope.Install the cam with new stock replacement lifters,and a good steel roller timing set.Button it up with a stock timing cover and a Moroso 6 quart trap door pan and matching pump.pickup.If you have a 55 chevy you might ned a special pan for this swap,so look before you buy.
Now you need to add a top end to it.I would splurge and get a set of the GMPP oval port aluminum heads,such a the ones that are put on the 502/502 motor.These are a great bargain for alloy bigblock heads and can be had for about $1700 fully assembled.You could install these heads as is and get good results,or for about $300 you can have a shop disassemble them,check all the critical specs such as valve spring height and pressure and guide clearance,and also have them back cut the intake valves,and touch up the stock valve job.Such a move could be worth another 20 or 30 hp,which is money well spent if you can afford it.With the shortblock ready for the heads,you have to measure the deck heigh of the new shortblock.If the pistons are all in the hole,and none of them are above the deck,then you would do well to bolt the heads on using a set of the felpro blue type gaskets made for the aluminum heads.If the pistons are out of the deck at all,then you need to buy gaskets that will give you .040' clearance between the pistons and the heads,so if for example the pistons are .010" out of the hole,you will need a .050" thick gasket.Such gaskets are available from shops that specialize in building race engines,as well as from some mail order houses.With the heads bolted on with new bolts,you need to top it off with a set of stock replacemnt stamped rockers,and then get youself a pushrod length checker{cheap plastic ones can be had for a few bucks},and figure out what length pushrods you need.You will need to order new pushords for this combo,and they will need to be hardened and also be the correct width to match the guide plates that come with the new heads{3/8" I think}.
With that done,you need to add an intake such as the edelbrock performer RPM air gap,and an 800 cfm double pumper carb.Finish it off with an MSD ready to run HEI distributor,and a set of 1 7/8" headers and you will have the overall combo to make about 520hp on pump gas with a moderately choppy idle,and good street manners.In a 3500# car with a 3000 stall covertor,a th400 trans,30" tall tires and 4.10 gears you should be able to get this thing well into the 11's on just motor and into the 10's on a 125 shot.The entire engine minus the nitrous will set you back a little under 5 grand if you shop right and build it yourself,but since it makes 520hp without nitrous,you should need to add the nitrous right away anyhow.Good luck and let us know how you make out.
. Actually like was also said, its safe when done right. However can be very dangerous in the hands of a novice. If you are going to run a small shot of it in the future (100hp shot or so) then I'd suggest getting forged pistions for the safety. Dont need a forged crank or rods however.
