i have 2 750 dp on a blown 440 ....its running way to fat. any rpm below 3500
runs shitty...i also have the 1to1 linkage...running 6lbs boost....what should be a good jet size to get me in the ballpark...i think im going to take the 1 to 1 linkage out....the pvs are blocked and i think the jet in primaries are 86 and 99 in secondaries (ill have to check when i get home)it runs good wide open but it loading up at cruze speeds..help please ...im out of the ball park now..i need to get inside of it
Moparjet,
I would suggest starting with a factory tune up in the carbs including the power valves. This will give you a good starting point you can build from.
Having the power valves blocked will make tuning the carbs at WOT easier, but this also means if you do alot of cruzing you will be way fat. Blocking the power valves is usually a race set up, you just need to decide what you can live with and how you plan on using the boat.
Good luck.
The Carbs Are Used,and I Have No Idea What The Factory Set Up Would Be...i Think If Get Rid Of The One To One Linkage Would Be The Best Place To Start...that Way At Cruz It Would Run Of The Primaries Instead Of All 8....but I Need To Jet It Down Some...i Can Take It A Little Rich But Its Just Way Too Much Right Now..dosnt Want To Run At All Below 4000
Moparjet,
A book on Holley Carbs can give you the set up.
Yes, if you have 1:1 linkage now, changing this to progresive will help alot.
You will still be too fat at cruz without the power valve, but this may not be a problem if you are mostly running hard. The power valve would allow you to jet the carb correctly for cruzing, then would dump extra fuel in when you mash the gas. This would allow you to pull skiers and wake boards without loading up and fouling you plugs.
Moparjet,
A book on Holley Carbs can give you the set up.
Yes, if you have 1:1 linkage now, changing this to progresive will help alot.
You will still be too fat at cruz without the power valve, but this may not be a problem if you are mostly running hard. The power valve would allow you to jet the carb correctly for cruzing, then would dump extra fuel in when you mash the gas. This would allow you to pull skiers and wake boards without loading up and fouling you plugs.
You have a list number for the carbs? should be on the choke housing, if not there then stamped on the top of the metering blocks. When is it fat? at idle or everything below wot?
Call Big Al at Big Al's Toybox - 860-354-3237 - and he will tell you where to start. He gave me my carb setup and I was right on with my Edelbrock carbs on my blower motor.
or
Get advice from people that are guessing at your setup and loose a bunch of time screwing around.
He is good people and I really like doing business with him. You will too.
Good Luck
Call Big Al at Big Al's Toybox - 860-354-3237 - and he will tell you where to start. He gave me my carb setup and I was right on with my Edelbrock carbs on my blower motor.
or
Get advice from people that are guessing at your setup and loose a bunch of time screwing around.
He is good people and I really like doing business with him. You will too.
Good Luck
Yeah thats it, bring your check book too. Do ya get dounuts with this post?
i have 2 750 dp on a blown 440 ....its running way to fat. any rpm below 3500
runs shitty...i also have the 1to1 linkage...running 6lbs boost....what should be a good jet size to get me in the ballpark...i think im going to take the 1 to 1 linkage out....the pvs are blocked and i think the jet in primaries are 86 and 99 in secondaries (ill have to check when i get home)it runs good wide open but it loading up at cruze speeds..help please ...im out of the ball park now..i need to get inside of it
Right off the bat...86's and 99 jets in a 750 is flat ass wrong. One of the worst things about used carbs is you don't know where they been or what "trick of the week" was applied to them.
My suggestion:
Start with looking up the list number stamped on the air horn. Find out what was in the carbs stock. Remember Holley will jet you rich....for an UNBLOWN application. Carbs are factory jetted to run sea level.
Find out if they came with power valves or not.
Rule of thumb (and that is all it is) is when blocking off a power valve....jet up 7 numbers. You have blocked off a circuit....and you must replace that fuel circuit with a larger jet.
OK...now enters the blower. You have to jet up when you have a blower. You are putting in air not seen by a N/A motor.
Better to jet up too far than not enough.
Now enters the other problem. All holley jets are not drilled to a hole size. Some are..some are not. I don't remember all the numbers....but the jump in flow from a 79 jet to an 80 jet is a pretty big jump. Yet a jump in size from 80 to an 81, 82 or 83 jet is very small. 81,82,83 jets are actually higher flowing #80 jets.
If that didn't confuse you I am not working at it hard enough.
I may have a chart...or maybe someone here does of holley jets and flows.
Generally I jet up 4 numbers over stock to get started. Then I run a 1/2 track pass and look at the plugs. And go from there.
Get the carbs right first. You may find the linkage 1 to 1 is ok.
If you get me the list number I can tell you what that carb came stock with, jets, pv, squirters everything.
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