Reply With QuoteI would double check the fuel persure and fuel flow to the carbs. was the fuel line 3/8 outside diameter or inside??? if its out side... you most likly just found your prob.
My brother-in-laws boat has jet boat with a BBC with a pair of 660 carbs that were rebuilt and floats adjusted properly and it has a fuel starvation problem when crusing at over 3800 RPM For longer periods of time, some one has sugested that we install the springloaded needle & seats in the secondarys & Primarys what do you guys think? a little back ground on the motor it has a new full MSD ignition and new fuel lines from the tanks (3/8" line) new fuel pickup tubes in the tanks, new fuel filter before the fuel pump Holley Race series mech., the motor is real strong on take offs but starts to stumble when your on it for very long. any ideas would be helpful
thanks
I would double check the fuel persure and fuel flow to the carbs. was the fuel line 3/8 outside diameter or inside??? if its out side... you most likly just found your prob.
I would double check the fuel persure and fuel flow to the carbs. was the fuel line 3/8 outside diameter or inside??? if its out side... you most likly just found your prob.
3/8ID and fuel pressure is about 6-7 psi when crusing
3/8ID and fuel pressure is about 6-7 psi when crusing
What's the fuel pressure when it stumbles? What was the "proper" float adjustment, and has it been double checked?
the pressure stays between 6-7 even when it is stumbling, and the float level has been checked and adjusted a few times durning tuning runs to see if we could fix the problem it has the clear sites on it and we even raised it to about the middle of the sites
Are you sure it's a fuel starvation issue and not an ignition issue?
A few years back, my coil started going out. Ran like a banshee cool, but after a mile or so hard, or longer cruising below 4,000, It'd missfire badly at elevated RPM. Bring the RPM down, it'd clear right up. It slowly got worse, and worse, lower and lower in RPM. I suspected fuel issues for a while, I think you have planty of fuel, unless your seccondaries in the carbs are WAY to damn small, which I doubt.
the pressure stays between 6-7 even when it is stumbling, and the float level has been checked and adjusted a few times durning tuning runs to see if we could fix the problem it has the clear sites on it and we even raised it to about the middle of the sites
Where are you picking up the fuel pressure reading? It is possible to have plenty of pressure but low volume. Have you removed the bronze type filters in the inlet of the carbs?........MP
As MP refered to above, since you have the sight glasses in place of the plugs, does the fuel level maintain at 4,000 RPM or does it start to fall? If it maintains level, you do not have a fuel supply issue.
As MP refered to above, since you have the sight glasses in place of the plugs, does the fuel level maintain at 4,000 RPM or does it start to fall? If it maintains level, you do not have a fuel supply issue.
It is definatly not an igntion problem all new MSD Everything replacing an old Points set up and the only thing it does better is starting with the New MSD, and it is hard to see the fuel when it is running and bouncing on the lake but it looks like it is lower like it is not filling backup fast enough, also if i remember right when i rebuilt the carbs they had i think 88 or 90 size? jets in them, the guy that had this intake setup said he had it on his old jetboat. but like i said someone said try the off road springloaded needle valves for the float level
It is definatly not an igntion problem all new MSD Everything replacing an old Points set up and the only thing it does better is starting with the New MSD, and it is hard to see the fuel when it is running and bouncing on the lake but it looks like it is lower like it is not filling backup fast enough
Just bcuz everything is new(and made by msd) does not mean that it is working correctly. I wish I had $1 for every time I bought something new and found out it did not work. That is asuming that everything is hooked and setup correctly. double check everything...
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