Carb help
 

I'm having trouble keeping my engines running in gear . It is idiling at 1000 rpm out of gear and drops to 550 in gear. They are 540ci 600 hp 950 quick fuel carbs. 35 total timing with black bushing in dist for more initial timing. Makes 5 inches of vacumn at idle. I don't have experience tuning using the air bleed jets. I would like it to have another 100 rpm or so in gear for a stronger idle. It smells fat at idle but if I turn the idle screws in any more it doesn't idle at all in gear. The engines were dynoed and perform flawlessly everywhere else. Just looking for any suggestions on the weak idle in Gear. I have also drilled a .040 hole in each throttle blade that did help.

What is your initial ? I Haven't done MSD dist's in eons.

Did you adjust your sec opening ? If not, should have done this before you drilled the holes in blades.

Between timing adjustments and secondary idle air flow, many times (not all of course) you can tame down the idle.

I wouldnt have drilled the throttle blades.

Are you sure the primary throttle blades are set properly as far as their location in reference to the transfer slots? How about the secondary throttle blades? You do not want to see the transfer slots on the secondary side.

Sometimes if the engine is too lean at idle, and misfiring, the exhaust can smell rich too. 5" of vacuum at idle is pretty low. What kind of cam is in that thing? Are you sure you dont have a vacuum leak?

Its sounding like you'd need to either go a little smaller on the air bleed, or larger on the IFR to richen the circuit up. In nuetral lean can mean high idle. but in gear running out of gas will make it want to fall on its face. how far out are the mixture screws when it wont stall out when in gear?

I agree it sounds like a vacuum leak. 5in is way low assuming that is out of gear. Even in gear that is nfg. Spray some starting fluid around the base of carb and intake to see if rpm changes. Make sure no stray sparks are present, but you know that already.

With the MSD Black bushing you will have 17 degree advance at idle, the Black bushing gives another 18 degree advance, I use the Black Bushings on mine with 540's and Holley 800 cfm #9022 carbs, idles perfect at 850 rpm in neutral, 650 rpm in gear w/28 pitch, how is it jetted in front., also not sure you need a 950 carb.

Jets are 78 front and 86 rear. Idle bleed 73 primary bleed 32

When it is up to operating temp. and out of gear put your finger over one of the idle air bleeds. If it pick's up RPM it's most likely to be lean on the Idle air bleeds. If it looses RPM its most likely rich. The IAB's are the ones to the outside.

Main jets will have nothing to do with this.

I have a quick question on your Quick Fuel's. Would they by any chance have a provision for and be calibrated for a PCV valve ?

Was it running OK and just started doing this? A 540 with 600 hp should have a pretty mild cam and hold a little more manifold vacuum .

Engines were new last year. Has been like this since new. Been real busy and havnt had much time to get it dialed in. I think the air bleeds are my next step. Just looking for suggestions to try next weekend when I go back to the lake. As far as the vacumn goes both engines are the same. And they have a very aggressive idle. Engines make 620 ft lbs at 4800 and 608 hp. And hp keeps climbing to 6000. Engines are being run at 5300 -5500 rpm.

We fought the stalling issue for 10+ years and tried every option we could to get the RPM spread lower that 500 RPM between in and out of gear without stalling. We finally fixed it last year with these new Holley Gen 3 Ultra carbs. It is kind of like the carb "knows" and won't let you stall. It is available is various sizes. I little pricy, but worth twice the cost. We also ordered J tubes as separate part as Holley hasn't offered this series of carbs in a marine version.

http://www.jegs.com/p/Holley/Holley-...36511/10002/-1

1st thing I would do is run the dist locked, set at 34 and you will notice a big improvement in idle quality, also I bet if you put a timing light on it when you put in gear you will see it fall even lower than you 17 initial and start moving around making it even worse...with a good gear drive starter should not be a issue starting, if you do you can run a MSD start retard but would try without it 1st..