750 holley 3310-2 question

[velrob]

I have a 383 bored 60 over
comp cams XE268H
edelbrock intake
exhaust headers
prw roller rockers
2800 stall

car runs good but right now too rich plugs turn black pretty quick.

A friend of mine is saying the 750 is to big for my motor? We tried to tune the vehicle a week ago but the mixture needles would go all the way in and the vehicle would keep running.

So im wondering if I could get a 650 or put a smaller power valve? I dont even recall what size power valve was put inside. Would a smaller power valve help that?

Theres no vacuum leaks.

 

[toolmanmike]

I have a 383 bored 60 over
comp cams XE268H
edelbrock intake
exhaust headers
prw roller rockers
2800 stall

car runs good but right now too rich plugs turn black pretty quick.

A friend of mine is saying the 750 is to big for my motor? We tried to tune the vehicle a week ago but the mixture needles would go all the way in and the vehicle would keep running.

So im wondering if I could get a 650 or put a smaller power valve? I dont even recall what size power valve was put inside. Would a smaller power valve help that?

Theres no vacuum leaks.

What does the float adjustment look like? What is your fuel pressure?

 

[RemCharger]

The 750 is not too big. If the pv is leaking internally, it could present those symptoms.
It sounds like the throttle blades are open too far.
Has it been rebuilt, are the floats set properly.

 

[493 Mike]

The 750 is not too big. If the pv is leaking internally, it could present those symptoms.
It sounds like the throttle blades are open too far.
Has it been rebuilt, are the floats set properly.

The 750 is not too big. If the pv is leaking internally, it could present those symptoms.
It sounds like the throttle blades are open too far.
Has it been rebuilt, are the floats set properly.

Mike

 

[PurpleBeeper]

These guys are in the right track. My first guess (also) is the throttle blades open too far so that you’re idling on the main fuel circuit and not the idle circuit. I believe there are slots inside the front barrels that should not be un-covered. Six pack guys often drill holes in the throttle blades to get more idle air flow with the throttle blades more closed (to cover those slots)

 

[padam]

Drill holes in the throttle blades.
You can try adjusting the secondary throttle blades open more at idle, which may be enough.

Also make sure you have the correct power valve. Big cam may cause low vacuum at idle which will open the power valve and be too rich.

 

[velrob]

is the primary blades adjusted by the idle screw? If not how do I adjust the primary blades? I do recall there was no screw at the bottom for the secondary blades, the hole was empty. I only realized after that there needed to be a screw there but I wasn't sure if secondary mattered at idle? Being no screw there the blades would be fully closed. Could be one of the reasons? The fuel level in the bowls are good.

 

[padam]

is the primary blades adjusted by the idle screw? If not how do I adjust the primary blades? I do recall there was no screw at the bottom for the secondary blades, the hole was empty. I only realized after that there needed to be a screw there but I wasn't sure if secondary mattered at idle? Being no screw there the blades would be fully closed. Could be one of the reasons? The fuel level in the bowls are good.

There should be a screw there. It could be a reason.
Do the obvious things first.

 

[velrob]

ok ill take a look since i know the carb isnt oversized for my motor.

thanks

 

[padam]

In my experience adjusting the secondary throttle idle screw can get you in the ballpark but is very touchy, maybe because there’s no idle circuit on that side.
So open it up until you can make adjustments with the mixture screws then fine adjust idle on primary side

 

[velrob]

ya ill try putting an allen screw so i can adjust it while the carb is on the car if i need to

 

[4speed68rt]

Sounds like your power valve is leaking. Maybe a good cleaning while you are in there changing it.

 

[Demonic]

They had a power valve check valve kit. Split the throttle body from the main, drill w a small included bit w a stop colar and install a check ball & retainer.

Holley 125-500 Power Valve Check Ball Kit

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Holley 125-500 Holley Power Valve Check Ball Kits | Summit Racing

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3310's had 72 or 74 jets mostly. Maybe drop to 70's and see how it runs, check plug readings.

 

[4speed68rt]

Drop 1 jet size for each 1000 feet you are above sea level. I think that is what Holley recommends. You can look up the factory jets that the carb came with, and go from there. Check your vacuum and put a power valve that is half of that amount. That is what Holley recommends on that as well.

 

[Daves69]

 

[velrob]

i changed everything, its all rebuilt. new jets, new power valve, new gaskets etc. soaked in carb cleaner before reassembling.

the only thing i didnt check was the power valve when i put it in. i used the quick fuel 300-2 rebuild kit im not sure what power valve comes in that kit if anyone knows
? i tried to look it up but no reference. The jets at the time i was putting it back together i looked up what they recommended and i think 71 and 73 sounds from what i can recall. if there was no screw for the secondary wouldnt that fully close the the secondary blades? is the screw used to open it more ?

i just looked and toronto is 250 feet above sea level.

 

[velrob]

View attachment 1546427

View attachment 1546430

thanks dave!! thats exactly what i need. it might be i used the wrong power valve gasket.

 

[Geoff 2]

The wrong power valve does NOT cause a rich idle! A leaking PV will!

Do NOT drill holes in t/blades until other possible causes have been ruled out.

That cam in a 383 is going to NEED about 25* of timing at idle. Possibly more; less than that can cause your problem, which is likely the pri blades open too far. Increasing idle timing from the generic factory setting will increase idle rpm; this, in turn, will allow blades to be closed further so that the idle cct works as designed.

 

[Black_Sheep]

I respectfully disagree Geoff, XE268H is a fairly mild cam, there’s no way it would need 25 degrees of initial timing.

Xtreme Energy 224/230 Hydraulic Flat Cam for Chrysler 383-440

Xtreme Energy 224/230 Hydraulic Flat Tappet Cam for Chrysler 383-440 (Single-Bolt). Great for street machines. Slightly rough idle. Will work with a stock converter, but best with a 1800+ stall.

www.compcams.com

 

[BSB67]

i changed everything, its all rebuilt. new jets, new power valve, new gaskets etc. soaked in carb cleaner before reassembling.

When did the problem you discuss in your first post occur, relative to your quoted statement above? Before or after? Why did you “…change everything “?