SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: CHROMEY on June 11, 2010, 08:58:40 AM

Title: myown carb jetting questions...thanks
Post by: CHROMEY on June 11, 2010, 08:58:40 AM: i have my own carb jetting questions..... ???

im running a 750 dbl pumper on my 460 with dove-c heads....(used motor - new for me)

early in season after 2 trips out noticed high heat paint flaking off heads.....checked new set of plugs
still looked white as brand new....so i figured it was leaning out big time

original jets in the carb were 80 in front bowl and 71 in the rear

increased jet sizes x4 so 84 in front and 75 in rear....really seemed to make a differance out of the hole..now plugs are just starting to get a light tan color just berely....where do i go from here?

i got a loaner 850 dbl pumper from a friend that im working on rebuliding...but i think the 750 is enough just needs tuning......should the jet sizes be closer together betwen ft and rr bowls?
or should i go up x4 more and see?

one more week left untill i leave for big river..i wanna dial it in ...please help!
Title: Re: myown carb jetting questions...thanks
Post by: Ralph Brunt on June 11, 2010, 09:07:15 AM: go to the holley website and put the carb back to factory spec (jetting) if you have to go up a buch of sizes then carb is too small. Normally bigger jets in secondary and smaller in primary
Title: Re: myown carb jetting questions...thanks
Post by: Luckie Stiff on June 11, 2010, 09:09:16 AM: go to 80 front 84 rear
Title: Re: myown carb jetting questions...thanks
Post by: CHROMEY on June 11, 2010, 09:13:10 AM: nordie.....i need to borrow your jet box!!

MY BAD! JUST WENT OUT AND LOOKED AGAIN...OOOOPS!

75'S IN THE FRONT AND 84'S IN THE BACK!
Title: Re: myown carb jetting questions...thanks
Post by: Luckie Stiff on June 11, 2010, 09:27:00 AM: If you have 80 and 84 jets, go 80 front, 84 rear with 30* timing. It won't be fast, but it won't melt down either.
Title: Re: myown carb jetting questions...thanks
Post by: CHROMEY on June 14, 2010, 09:57:01 AM: how about 84 and 84? thats what i got here at home?
Title: Re: myown carb jetting questions...thanks
Post by: Luckie Stiff on June 14, 2010, 10:33:40 AM: Quote from: CHROMEY on June 14, 2010, 09:57:01 AM
how about 84 and 84? thats what i got here at home?

It'll be a little rich, but you'll be good to go.
Title: Re: myown carb jetting questions...thanks
Post by: CHROMEY on June 14, 2010, 01:50:17 PM: ;) i just aquired nordies jet box......so ill be running 81 and 84's...we'll see how that goes! :beer:
come on river!
Title: Re: myown carb jetting questions...thanks
Post by: SS-201 on June 16, 2010, 06:01:45 AM: Thats a lot of fuel however usually smaller in front larger in rear . Keep the timing no more than 35 in the 460. all in at 2500 -3000 rpm. Withe addiives and the porclain used by each manufacture they may take longer to color. To read the plug tou look down at the base of the porclain to look for a fire ring.