power valve
 

posted before about power valves etc,,thanks for advice

now i know i have 15 inch of vacum at idle,,,not in water , but in driveway..
so i should get 70-80 power valve for primiary side...??
what should knock jets down too??..82 ---84 ..again primiary side.

carbs are 1050,,3 circuits,,,,both power valves blocked,,92 jets all around.
issue is motors are running fat....547's.
yes i know i need to check plugs at idle,,,then mid range check,,then a hard run and check
but trying to get started...

thanks for advice........

Jetting and PV's have nothing to do with being rich at idle. Engines need to be run under load to determine if jetting or PV changes are needed.

If you wanted to install a PV in the primary, a 6.5 is pretty standard, then reduce primary jetting to the 84 range.

ok thanks griff,,,,,just want get going on this...i know i will have to run boat ,,,kill motors ,,look at plugs..

thanks....................

Before you change power valves I would keep the vacuum gauge hooked up and record the readings through the entire rpm range idling and under load in the water.

I'd get the idle cleaned up first so it's not making plugs hard to read when water testing. You'll be far and away more able to tune it if you can get an O2 sensor and A/F ratio meter on it.

was going to put o2 sensors on,,,but my extensions from headers are wet...would be big job to change was suggested to put in 90 degree adapter for sensor,,,just not thru all that right now...thanks for advice...

and i was planning on taking vacum guage out with me on next run,,,look at numbers mid range etc....maybe i would be better just jetting primary down..??

90* adapters are screw in. No big deal to install.

well i would have to remove my extensions,,meaning remove tips from transom to get out my extensions...then get bung welded into my extensions,,then reassemble....fun...think we chatted on this before the 90 degree adapters..
thanks.............

If you`re rich why would you add an unmetered fuel fill to your carbs?
Whomever had no power valves in there had it right.
Powervalves belong in cars not boats

Edit: OP said he's got rich looking plugs. He didn't say at idle.

Don't add in the variable of power valve unless you take out even more from primary, and perhaps secondary too.
Power valves add 6 to 8 numbers to the fuel at whatever vacuum you put in the block. So if it's rich with 92's start by taking out some jet. Like 10 or more primary, and 2 or 4 secondary.

I think he wanted to lean out the primary side jetting so the PVs only add fuel below their rated vacuum. If I understand things, that gets him more flexibility through the mid range.

Really needs AFR gauge. Best $ you can spend.

I am learning/fighting this myself right now. Got a lean spot just before (mechanical) secondaries open on mine. oops, don't answer- No Hijacks!

I`ve tried it all, the best fuel curve I got was block off all power valves and tune with jets.
Wanna lean out primary take jet out.
but at the end of the day without a O2 reading he`s pissing in the wind.

edited my post from 7/26

I have a Pro Systems 1000CFM 4150 and I have power valves in primary and secondary, although I have restrictors in both. Carb runs great and I get really good fuel economy. Power Valves aren't always bad, if done right. I get 2.5mpg at 60mph all day long.

i love like ...love to add o2 sensors,,,but it would be a big job,,,,and sensors would be in wet exhaust extensions,,,heard suggestion put in 90 degree adapter would solve wet problem...maybe..
i think i am going to start dropping jet size..go run boat mid range,,,,then pull a few plugs..
thanks for all advice....boats runs...just seems to fat...
plugs are always black...
thats some good fuel mileage thisisliving..........what rpm u at running 60...4500???

hello...thiisliving,,,,,,
did u just put on your motors??? i am guessing you had to fine carbs somewhat???
thanks,,,,,,for advice...

The problem with most carbs out of the box is they are designed for cars that have a multi gear transmission and can rev much quicker than in boats. In addition boats are under constant load. I spent years tuning my carb to get it just right and the proper ignition timing and curve are part of that. I have a big cam and in gear at idle I have 2.5" of vacuum. I had to change power valves, jets, accelerator pumps and squirters to get it to run exactly as I wanted. With a big cam and prop it takes longer to get on plane and build rpm's so I needed to extend the accelerator shot and timing to get me to the point I had some air flow to pull fuel. I ended up going to a 50cc on the primary with a .028 squirter on both primary and secondary. I had to use 2.5" power valve and as I stated earlier I have them on both primary and secondary. I bought an Otoscope to help read the plugs. I started the jets on the rich side and kept dropping them down based on the plug reads. Because I have almost no vacuum at idle it was hard to get the initial timing right. I tried special bushings in my MSD distributor to reduce the total advance so I had more initial timing. Then I ran the distributor locked which helped. I finally switched to a Daytona Sensors system that allowed me to create a custom timing curve with added idle control which made a huge difference. Now even without a choke she starts right up and I only need about 30 seconds of warm up and she's good to go. Once it's been started for the day I just give the key a quick hit and it's running. I know EFI can give you better cylinder to cylinder fuel balance. But when I pull my plugs, they are all identical even looking at them through my 10x Otoscope. I think some of that is due to the improved signal I get when I added a 4 hole tapered spacer. That also made a noticeable difference in performance. With motors as in life, everything matters and effects everything else.

............
wow........alot of info...but i like it...
so do u run the daytona sensor system with your msd distributor????
so u replaced the msd box with the daytona system??
what motor and how big is cam??

thanks for info........

He has a 4150 . That is a 2 circuit carb. What you have is 3 circuit. The intermedent circuit feeds too much fuel at part throttle. You should convert it to 2 circuits.

hello fbc25el....

not sure if it was you or someone,,,but it was suggestted to make it a two circuit....
not sure how hard it would be...
but i think a site or two was posted on this..
i did look at one of these sites...wow..
stuff they were talking about changing,,,i didnt even know what it was,,, was over my head..
just did a google,,found a thread on here from 2010...also don terrils speed talk...
thanks info.....
sounds like i should gt new carbs...any suggestions???

It may be cheaper to send them off to a carb shop. The main parts you will need is 2 circuit metering blocks.

Yes, I have the Daytona Sensors box connected to my MSD distributor. I did replace the MSD box with the Daytona sensors, so much better. I have a 524ci BBC with AFR 305 ported heads. The cam is a custom Comp with .623"/.612 lift and 242/252 @ .050" duration with 112 degree lobe separation.

Patrick at Pro Systems is someone I would call to modify your carbs. He will wet flow them as well.

.............
ahhh thanks for info,,,i would be willing to send my carbs to someone to go thru them.
i called tyler crockett about going thru carbs,,they said buy new ones...ok thanks for help...
i am litttle bigger..547,,389cc runners,,,720 lift isky....maybe i shoud be using bigger carb...
thanks for advice,,,,going to call pro system....
someone else suggested nickerson carbs..guess they did his guys carbs..
again thanks