Thread: first 496 build a running success

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had a 402 in the chevy and sum jerk who put it together neglected to put a retaining plate under the cam bolts which came loose, sent 2 with flat washers through the engine which seized the oil pump twisted the top off it and well you know the rest. on tear down found the 3rd bolt just about to go too. the thing turned out to be a way worn lucky dip engine anyway and with the cost of rebuilding i thought id take pats advice, just get a 454 block and make good use of the fully worked heads and brand new stroker crank id had sitting there for a few years and make a 496. i was paying for a rebore, pistons and balance either way and with the money i saved on not havn to get the old heads overhauld the price of the conrods didnt really come into it.
so i finally got the 496 together and going and it worked out real good, has gobs of mid range torque which was what i was hoping for, i thought the tall diff would give me harder traffic light launches as it wouldnt keep lacing off the mark but still get off it real quick holdin you pinned in the seat because of the big crank AND have plenty of top end, a goal which i achieved and works well. now i know theres been tons said about big block stroker builds on here already and have drooled over them all and now after havin a 496 im hooked but i was just wondering if any of you guys could run your experienced eyes over MY final choice of combo, let me know if its any good, give me some tuning and dissy curve advice or whatever, maybe give me an idea of the power id be getting (there arent any dynos where i live except one and the shop are notorious for blowing things up so i dont wanna go there) and tell me if theres any room for improvement. mainly exhaust size and carb bein a bit small and valve springs. here goes

66 impala, 295/50/15 rear tyres 26.6" tall, 9" diff with 3:1 gears, stage 2 shift kitted th400 with 2200 high stall converter, engine is 9.8-10:1 compression, needs 98 octane pump gas, 454 block 60 over with 4.25" crank, scat 6.385" rods, keith black flat tops, all balanced etc, hei dissy, heads are 3931063 casting planed a bit so a little under 100cc chambers, with severe duty 2.190" intake and 1.880" exhaust valves both with 3 angle grind, been cced, ported and flowed, roller rockers, edelbrock performer rpm intake, 750 holley vac sec carb,

valve springs were 110lbs at 1.9" and 270lbs at 1.4" before adding 45 thou shims under them at cam grinders advice

cam is flat tappet hydraulic comp 280 magnum recommended by www.kelford.co.nz (check them out) i know i shoulda gone roller and got heaps more power but i didnt fancy spendin the $1200-1500 to run roller at this stage and ran outa muny, just wanted the car going, yous can relate? haha

exhaust are 4 into 1 headers 1 7/8" primaries, 3 or 3.5" collectors about 12" long i think(not quite sure on collectors car aint with me at mo im on holiday) into a twin 2.5" system with no crossover or balance pipe and uv570 mufflers which are a straight through type

heads were flowed at 25" test pressure which they do on their benches here so may need converting if they gotta be at 28":

int: .100 .200 .300 .400 .500 .600 .700
69 141 202 244 270 288 297

eh: .100 .200 .300 .400 .500 .600 .700
65 122 149 172 191 206 217

said heads would support 600-650hp and i really couldnt do better for heads on the street up2 6000rpm unless i go alloy which id need if i was putting it on the strip because the bigger runners would make it breathe better up top but these would have better throttle response on street from the velocity of the smaller runners (were on a stock 2 bolt twin turbo 454 with 750hp and ft/lbs torque under 5000rpm with bugger all boost before i got them)

it idles rough at 1000rpm with around 14-15" vacuum

i want it to be a mid range torque meister and it is, it pulls like a schoolgirl but only until about 4800rpm when it starts to valve bounce, its running fine, it aint leaning up top or stumbling or anything, im just wondering do i need stiffer valve springs to get 5000rpm? will there be any more power up there? or is that all itl spin to with that big crank. comp test their big block cams on 454s (small blocks on 350s) and i know bigger strokes lower the rev range but would it lower it that much from the stated 2000-6000 to 1000-4800 like it is with only 1/4" increase?

would keepin this exhaust for the velocity, stiffer valve springs, a bigger carb-say 850 and some 3.25 gears improve performance? or is it about as good as itl get already and should i just leave it alone since its running good and im quite happy. any other info needed let me know, cheers guys, appreciate your input