Another dyno session, 454 w bm 420 megablower
08-06-2018, 06:25 PM
#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
08-06-2018, 06:29 PM
#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.
08-07-2018, 07:10 AM
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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
08-08-2018, 10:32 PM
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I was hoping that my estimate on power for these motors was close, looks like it was. Glad this is going to work out well for the buyer, and thanks for posting the dyno results!
