Another dyno session, 454 w bm 420 megablower
#1
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Another dyno session, 454 w bm 420 megablower
Local guy brought me a destroyed 502 na motor, died a miserable death, oil cooler was bypassed plus he ran it low on oil. He bought a 454 525sc w bm 420 megablower to put in his boat. Norm went thru nicerson carbs and modded them further (they had mismatched needles/seats, flow curve thru boosters was erratic). So he converted them to his customised drop leg boosters and changed circuits a little. Stock 525sc cam, stock compression.
So i put it on dyno, w 48 lower/60 upper it made 4.8 to 5 ish lbs boost. On its best muffled pull it made 614 hp/585 ft lbs tq (j607 w dry race car headers w 5"tailpipes thru gibson mufflers, no accesorys). Average afr of about 11.5 w #5/#8 around 11.8/12.2, #2/#6 in 11.0 range .
Owner would like to see more power so borrowed a 52 tooth upper and re-pulled today, saw 679hp at 5900/641 ft lbs tq, 7.5 lbs boost. No innercooler, stock heads, unknown head gaskets and stock head bolts so richened up tune a titch, took timing down from 34 total to 31, made almost same hp. Ordered a 56 tooth upper that its getting shipped out with, current tune should be "safe" at 6.5 lbs boost, thought id share, Smi
tty
So i put it on dyno, w 48 lower/60 upper it made 4.8 to 5 ish lbs boost. On its best muffled pull it made 614 hp/585 ft lbs tq (j607 w dry race car headers w 5"tailpipes thru gibson mufflers, no accesorys). Average afr of about 11.5 w #5/#8 around 11.8/12.2, #2/#6 in 11.0 range .
Owner would like to see more power so borrowed a 52 tooth upper and re-pulled today, saw 679hp at 5900/641 ft lbs tq, 7.5 lbs boost. No innercooler, stock heads, unknown head gaskets and stock head bolts so richened up tune a titch, took timing down from 34 total to 31, made almost same hp. Ordered a 56 tooth upper that its getting shipped out with, current tune should be "safe" at 6.5 lbs boost, thought id share, Smi
tty
#3
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I expected bsfcs to be awful, surprisingly even after fattening it up they were in .54 to .6 range, impressed for such low compression!
Last edited by articfriends; 08-06-2018 at 06:32 PM.
#8
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Probably 30 to 40 hp i would guess, someday ill dyno a motor then bolt everything on including manifolds and dump the water from exhaust on ground but it will be a while before i have extra time to try. Im dressing this out today and giving it to customer so he can get it in his boat asap