Yet Another Carb Question
 

I have been battling with a lean miss on hard acceleration on a Pro-Systems 950cfm 4150 style carb. I thought I had it licked and my wife noticed it again. I have a 524ci GEN 5 with AFR 315 heads, Diamond 10:1 pistons, a .623/.612, 242/252 @ .050" and 112 LSA cam. I'm running a Brodix HV2000 single plane intake that's been gasket matched to the heads and Lightning headers. I didn't dyno the motor I am postulating that I make somewhere near 700hp. Best speed to date was 90 with 4 adults and a full tank in a Velocity 280. I'm running #92 jets and have power valves in the primary and secondary. I've added a 50cc pump to the primary side which has helped significantly. My boat can accelerate very well, time to plane is around 3 seconds, 30 to 60 times aren't much worse. I've been planning my strategy to solve this problem and I was doing some reading about adding jet extensions to the secondaries, when I came across a note that said if you need to add jet extensions to the secondaries, you need to eliminate the secondary power valve as it is above the jets and will lean out first. My question to the consortium is this, how many of you run secondary power valves in high performance applications? Secondly what size accelerator pumps are you running in single carb configurations?

Makes sense to me. Id try removing the rear PV and upping the jets to 98, and putting in jet extensions.

No suggestions about your carb issue, but would like to no more about your setup as I have the same boat. What out drive are you running and have you had many issues with it?'

Thanks

I'm running a 98 B1 with Amsoil Extreme Gear and a drive shower. So far the oil is almost as clean as I put in. Just waiting for the day when it breaks. My wife just bought me a new radio so I can call for a tow when it does.

I thought the jump was more like 8 sizes? I don't have an O2 bung so I'm going strictly off of plug reads. So far the plugs actually are very clean so I thought I'd try jumping up 2 to see what the plugs read to see if I may be too lean. With dual power valves, I'm sure that it's real lean at cruise. By rough calculation I'm getting 3mpg at 60mph, and I've checked it over a couple of tanks.

I agree. Get rid of/use a PV blocker for the rear PV and increase the secondary jet size 6-8 sizes. You already have quite a bit of jet, so 98-99's should be fine.

Thanks for the info. My out drive is 2 years old so I'm hoping it it will hold up to my new 509.

Upper 80's sounds good to me!

another trick is behind the power valve is 2 little holes that the fuel runs through,,you will nees to open up those holes to flow more fuel through them..also try the extended squirters,those will get rid of a stunble..i run the 30cc pumps and 36 extended squirters on my 355.

I talked to my Engine Builder and he said that if I have cast metering blocks, they may not be flowing enough fuel. I'm going to strip the carb down and check every component and block off the power valve.

fixx
 

that why they say when tuneing the carb you go + ot - 4 jet sizes..the metering blocks will only flow so much before you have to open them up..try to install annular boosters...idomises the fuel better and will be better out of the hole..