holey carb gurus
 

my blue 500hp holey carbs work great except when put in gear they drop from 950 idle to like 600 rpms and the one wants to stall unless i bump up the throttle and it make it tough to load on trailer and dock. I dont realy want to turn idle up any higher due to going in and out of gear on the drives.

Thanks

Change the air bleeds and adjust the carbs properly !!!!

Put a vacuum gauge on the engine and see what you've got for vacuum at idle, both in and out of gear. You may have go to a power valve with a lower opening point.

Check your filters first...all of them (water sep included). There may still be filters (small ones) in the bowls (where the lines go in). Always start with the easy stuff first. :drink:

How many hours are on the engines? It may just be time for a carb re fresh or valve adjustment. Those carbs if they are still stock, and the engines are still stock need little adjustment over their life span.

Either you are loosing your signal at idle, and that would be from the flow in your metering blocs slowing from dirty gas and buildup in the idle circuit.

Or your valves just need to be run and this is normal after a couple hundred hours.

You could try opening the idle circuits a little more and see if this helps your idle strengthen. you don't adjust your idle on those carbs at the throttle screw. make sure that is closed all the way. That gives you a stronger idle through the metering block.

Have yoiu removed your carbs at any time in the past. You could have a leaky gasket between the engine and the intake. This would allow a little air in and will affect the signal at idle, but will not affect anything at WOT.

Take a small 5/16 wrench and test the tighness of the bowl screws. Make sure that they are snug. Over time the gaskets can shrink and a tightening of those screws wil tighten the gaskets back up and this will fix your signal through the metering block.

Good luck and let us know what helps.

Usually it is not a filter if the engine will still run hard under load. Typically a clogged filter will idle properly and at low RPM's. the clogged filter will restrict at WOT and then the engine will just not run as hard as it should because it is not getting the proper volume.

So if i dont adjust at the allen idle screw where is the idle setting you mean, heads and all valves all new good stuff last year and like i said carbs work great no hesitation run up to 5500 no problems just in gear low idel and stalling out of ger idles perfect at 950 i keep them up some for reversion reason with my 741 cams and gill exhaust.

I was just assuming that these were stock. The 741 cam is going to idle rough, but you should be able to get them smoothed out.

I am not saying that the valves would not be good etc. Just might not be adjusted evenly. It is pretty common for guys to adjust the valves on a brand new engine before actually running it and there is no pressure built up in the lifter. After you run the engine and the pressure is built up, then it is best to re adjust them to ensure that they are all even. with a big cam like that one, if 1 or 2 of the valves is opening a little more or less than the other, it will cause a rough and week idle. It is also common to re adjust the valves once a season on a high lift cam like that one.

You idle mix screws on those carbs are on the metering blocks. Disconnect the throttle cable and remove flame arrestor. Turn throttle screw to the left until the butterflies in the carb are completely shut. let them slam close with the return spring a few times to ensure that they are closed. turn throttle screw back to right until it just bumps the butterflies in the carb. Back to left to ensure that they are closed.

I can't rememebr if those carbs are 4 corner idle or not, but there will be at least 1 very small needle screw on each side of the bowl on the front of the carb and if they are 4 corner, there will be 1 on each side on the secondaries on the back.

Start by closing all four screws all the way and then opening each 1 of them 1.5 turns back to the left.

Start the engine and see if the idle is stronger. If this does not cure the problem, and the valves are adjusted smoothley, then slowly close each screw 1 by one and the engine should slowly die out each time, but recover when you open them back up. This will let you know that nothing is clogged. Take them all back to 1.5 turns and then open each .25 turn further and test again and see if this makes the engine idle stronger.

Once the idle is strong, then turn the throttle screw back to the right slightly until you are idling at the rpm's that you desire.

Also check your spark plugs a couple times a season. If you are running a fat carb while you are cruising and at high speeds then it is slowly building carbon on the plugs and will make a weak idle.

Mine only have 2 screws on the primary side both were 1 turn out, also my float levels are at the bottom of the sight glass is that ok.

Did it idle right when you first put the engine in last year?

mine did the same thing after putting a big cam in, so my builder added some spacers that had adjustemnts to them, it helped a bunch, they look cool as well.

I agree with everything Jeff1000 says. Lots of issues seem to come from guys cranking the idle speed screw up to get the engine to idle higher. Ends up with a crappy idle mixure, as the carb comes off the idle circuit. If adjusting the little mixture screws on each side of the bowl has almost no effect, the idle speed screw is prob set too high.

Oh, and sometimes adding more base timing and taking a little out the the advance can help clean up the idle.

U need bigger idle air bleeds !!!!!! go 2 sizes up and u be fine....:party-smiley-004:

Iam running 1" hvh super sucker spacers new this year but it always had 1 " open spacers

Rick,

Put a little more fuel in the idle circuits like 1/8 turn additional(out) on each screw until it stops stalling. Shouldn't affect the idle to the point it will hurt the drives.

I still say after the carb is ajusted out that a really good valve adjustment makes all the difference in the world when you are trying to strengthen an idle. Re set them after you run the boat for a while and the lifters are pumped up.

Strengthen the idle screws until it stops stalling. The only issue you will have is that the carb will be loaded up strong when you come off plane, but a quick bump to the throttle will get them straight again.

Good luck and let us know what you find.

retighten the carb to manifold bolts,,,sounds like a vacuum leak

Fixx
 

here's a good read for ya to give you a ides on how a carb works..

http://www.candsspecialties.com/tuning.html

Go to 3/4 turn out and retest (in 1/4 from where you are at 1 turn out). If still not satisfied go to 1/2 turn out. That should do it. If not, you will need to open the secondardy idle srcrew a bit so we can close the primary idle screw to get on the idle circuit.

Both were at 1 turn out im going to turn them all the way in then 1 1/2 turn out then go from there on water this weekend.

Thanks guys

Fixx
 

if you go 1 1/2 turns out it will probably stumble and load up at idle..out makes it fatter and in liens out the mixture.

i always start at 1/2 then adjust the rear throttle blade for idle..never touch the front,,read the c&s post,it has good info.

if your getting reversion at 800 rpms then you may have to live with it or restrict the water coming our of the pipes and run some through hull fittings and dump the water their to..

Mine only have 1 idle set screw and 2 air bleed screws in front none in rear.

The 2 screws that go in to the metering block on the front are the idle mix screws. The one screw that acts as a throttle stop is the idle screw. No such thing as air bleed screws.

Like mrfixx and I said, start at one turn out on the mix screws and go in (cw) evenly with both until the problem resolves.

Rick, I run the idle screws in a little at a time with the boat in gear idling until the motor dies. Then back out 1/8 or 1/4 turn on each idle screw. Needs a lot of warmup to idle but doesn't load up.

also put a timing light on it, make sure the timing is not backing off when you put in gear...that will act just like a carb issue..Rob

Man, r any of u guys coming to Bermuda soon..I had the same problem last season..I recently sent the carb back to be recalibrated..haven't sea trailed yet to see if it's any better..but will keep u guys updated..n i only have 12hrs on this motor..

rssteiny.. i feel your pain..mines does the same thing..idles fine.. around 950rpms, but once in gear and under load it drops instantly to around 650rpms and stumbles n wants to cut out unless i come up on the throttles..i ready to sacrifice speed for a dock friendly boat..good luck.but if u have any findings please advise..

Q

The air bleeds on that carb are not adjustable. They are bulit into the metering blocks on the top/ That is also something to check and make sure that they are not cloged or restriccted. You can pull the bowl screws off the front of the carb. the metering block is sandwiched between the carb and the main body. Blow air from the bottom openings of the metering block out so that any debris comes out of the block instead of going in further.

You may just want to buy an upgraded carb from holley with 4 corner idle circuit since you have gone to the steeper cam to help the engine out.

I have a set of 2 year old bg demonds 875s maybe i should try them just need to do some different plumbing. Im going to play with the holleys this weekend on the water see what happens first ill let you all know.

Thanks

What size cams are you running, how is it working this year.

I run Bob Madara's cams that are ~228 I, 232 E duration with ~.598 lift on both I & E, pretty mild idle but they pack the charge in really well on the top end. Peak hp is at 5500 rpm. I am still in the 90-91 mph range but looking to do another project with Bob this year to take it up another notch.

You spinning 30s at 5500 with nose cones right.

yep.

Try cleaning the air bleeds with some carb. cleaner, by sticking the red nozzle into the air bleeds. This carb. worked well once upon a time. Also a blown power vale will cause ir to be rich at idle.

I would first warm engine to operating temp set floats, and then set timing. I would run as much intial timing as possible at least 14 degrees with full advance around 35 to 36. Then set idel mixtures to max vac or rpm usually 3/4 turn out. should idel about 950 out of gear. put boat in water and install vac gauge. make sure when ideling in gear u do not drop vac under your power valve vac rating which is usually a 6.5 vac rating. If you are below that you need to change powervalve to lower vac opening then in gear idel vac. Just my 2 cents good luck!

That how we do them, Great advise... Pete

Just a thought but my carbs were set up by Dean at Nickerson's and have always worked perfectly till I got my first tank of fuel with alcohol then they idled just as you stated all the carbs needed a extra 1/4 turn at each corner in the idle circuit. then they were back to there normal idle