fbc25el

The web site that SB posted will explain it in detail. All you need is some 6/32 x 1/8 brass set screws and a 6/32 bottom tap. You also will need a 1-60 drill index. If your jet is smaller than .040 you will need a 61-80 index.

redcorvetteman3

hey guys been having exact same problems with stalling when drop in gear.. Running barry grant marine 750s.front jets 78...rear 86...496 dart pro 1 alm. 320 cfm elderbrock air gap. msd ig. So let me ask a couple questions to clairify for me.
Ive always had some trouble but getting worse about dying.
Motors have always been rich at idle and low rpm plugs black .
which port do i use if i use a vacume guage ? and how much vacume am I looking for what should I expect?
The air bleeds on the top towards the outside are idle air bleeds correct? change them larger by replacing or drilling?
Talk about ignition timing ? at idle in gear out of gear ? Total. what springs and bushings in MSD?
Does Barry Grant have the ability to lower the idle circut in there metering block?
thanks and if I need to supply more info please let me know

wingnit

Connect the vacuum gauge to a port on the carb that is near the base of the carb. You are wanting to read manifold vacuum as close to the carb as possible. There is no set vacuum value. Vacuum readings will vary by the type of manifold used and cam selection. You want to adjust the screws to get the highest vacuum reading possible and then turn both screws back in about 1/4 turn.

Do not mess with the air bleeds until you have eliminated everything else.

Maximum timing advance varies by application. I have been a car guy for many years and like to see the timing set for full advance (all in) at 3000 rpm. Boats are different. I will let someone with more knowledge help with this question.

253

I fought the idle thing too, run 540's, Dart Pro 1, Holley 800 cfm #9022 carbs,, 76 primary/88 secondary, opened the secondary's to .020, use MSD Black Bushing, and use the Blue springs , this gives me 17 degree advance at 850-900 idle out of gear,, 35 advance total, I had been using the light silver springs for years,, when I changed to the stiffer Blue Springs it really helped keep the timing constant at idle, mine is idling very nice now in and out of gear, it took me a year of trial and error,
Good Luck

SB

iTrader: (1)

Sorry for the quick sidetrack but wholly crap are there alot of people in this thread with big motors that are under carbureted.

Okay, carry on....just had to get that off my chest.

MILD THUNDER

iTrader: (3)

Couldnt agree more.

253

Yes, and a lot of over carbed engines too. I ran the flow numbers on mine.
540 cu. in. at 5300 rpm,,, 90 % volumetric efficiency,, mild cam, requires 745 cfm carb.,,, at 100%, which would be very rare to achieve, , it requires 828 cfm.
I may run 5300 rpm once per season if at all, usually cruise 3500 to 4500 rpm.
I may need to jet up one number but reading my spark plugs they look right on for color.

MILD THUNDER

iTrader: (3)

Good read..

http://performancecarbscience.com/ho...-booster-tech/

FIXX

iTrader: (2)

Hell yea!! i have a little 435 hp 355 with a 750 on it..little screamer..

SB

iTrader: (1)

Yup, 330hp-450hp small blocks I use 750's.

450hp-550hp big blocks 850's.

550-650hp 950-1000cfm 4150's.

650+hp nice big ole 4500 Dominators.

All above some generic guidelines without getting into exact engine details. Quick example: dual planes can use more carb than single planes on same exact motor build.