Issue with Holley 2BBL idle tuning.

[stant1man]

Penta 5.7GL

I have read many a report to turn the idle mixture screws in until the engine nearly stalls then back out half a turn but when I screw in the mixture needle on the right side there is no change, it seems to do nothing. The one on the left would stall the engine no problem.

Am I missing something... I hear that if your idle mixture needles wont stall the engine your powervalve is blown, could this be the case here?

Best wishes,


Stan

 

[Maclin]

Re: Issue with Holley 2BBL idle tuning.

Idle air bleed screws not making a difference usually indicates a vacuum leak somewhere. Or the throttle plates are open too far, but your idle would have to be very high for that to be the problem.

If your power valve is blown then fuel leaks into the manifold from the bottom of the carb all the time, makes a very rough idle then usually dies unless you hit the throttle. Then when the engine is off the fuel bowl drains into the manifold causing a flooded condition for the next start.

Now, if you have had an idling problem and have the throttle idle positon way high, say to overcome a leaking power valve, then all bets are off.

What was the most recent thing you did that was fuel or carb related?

 

[stant1man]

Re: Issue with Holley 2BBL idle tuning.

I rebuilt the carb but the power valve that came with the kit was a 6.5 whereas the valve in the carb is 4.5.

Ironically when i took the boat out last night I could not get it to start for ages then when it ffinally did it ran like the big ends were away :-S like it was flooded...

Thing about the idle screws is one of them has an impact, the other doesn't.

I'll install the 65 valve just for idle purposes and see what happens.

Any other advice is appreciated.

Best wishes,


Stan

 

[Don S]

Re: Issue with Holley 2BBL idle tuning.

Thing about the idle screws is one of them has an impact, the other doesn't.

Not sure what you mean by that, could you explain please.

You should get the proper power valve, the 4.5 is what the specs call for.

 

[stant1man]

Re: Issue with Holley 2BBL idle tuning.

I'm referring to the idle mixture screws, there are two. One on each side of the bowl, the left one would stall the engine if I screw it in but I can screw the right one in completely and it has no effect on the running characteristics.

 

[Maclin]

Re: Issue with Holley 2BBL idle tuning.

I would find a new 4.5 powervalve to put in (the spec may actually be a 3.5, if you cannot find a 4.5 then a 3.5 should be ok). Right now you could use the 6.5 just to test with, I think that is what you meant earlier. Just do not run at cruise like that. Check the gasketing between the carb and intake, if that is not sealing well then idle will be high and idle screws will have little to no effect. Did you use a new base gasket?

 

[Glastron175]

Re: Issue with Holley 2BBL idle tuning.

I had a similar problem except that neither of the mixture screws would shut it down when closed. The new power valve fixed the problem. I don't know if that could be the problem if only one mixture screw has no effect.