doggiedave

Good morning, just took boat out Sunday. It ran very strong but no boost showing on gauge new motor 406 sbc with 177 blower/ 850 demon carb. 7" lower pulley 3.50" upper pulley. thinking I need smaller upper pulley. chart with blower kit shows estimated boost to be 4.8 would like to be in the 5 to 6 lb boost range( 8.8 to 1 with iron heads 30 deg max adv. 12 inches vacuum at idle) what size pulley to fall into that range? Thanks for any advice. p.s would I need to change belt length?

MILD THUNDER

iTrader: (3)

I'd double check your boost gauge. You should be making something at that ratio on a 406CI. I spun my 177 just a bit faster and made 5psi on a 460CI big block.

doggiedave

Thanks, maybe China junk gauge? brand new Autometer will check. one thought I teed it off with the boost reference line to the carb could that be giving a false reading? the engine just by the seat of the pants with a given of a familiar prop is even now making the boat a rocket coming on plane etc,mid range was badass did not try to wring out yet.

akaboatman

iTrader: (1)

yep

doggiedave

Update, took boat out last sat. tapped on gauge now show 4.8 at 4100 rpm believe will have the 5-6lbs I was hoping for at 5000 to 5100 rpm

MILD THUNDER

iTrader: (3)

Figured it was the gauge. Probably just was stuck

ezstriper

different flame arresters will change boost way more that you think...been down that road !!

doggiedave

thanks I have a 4x8 spark arrester from eddie marine