SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: The Chaz on April 26, 2008, 03:51:14 PM
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Before I start trying random things I thought I would ask for some suggestions on how to get my engine to idle below 1800 RPM :o
I backed the idle screws all the way back and it will stall: no idle at all. just maybe a 1/4 -1/2 turn and it idles at 1800. I am wondering if it might have something to do with the bowl settings. When I 1st installed the carbs they shot fuel out of the overflow tubes. I tightened the large screws on top and got it to stop but I was left with this high idle speed. Any thoughts or suggestion on what I could try?
Thanks
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What kind of carbs?
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Holley 600's[attaching=#1]
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Chaz, What is the number? You might look here and see what you can find. http://www.holley.com/TechService/Instructions.asp
I know on my carb (Edelbrock 750) the book said it should run out of the box, but the front adjustment screws were turned WAY out, about 10 turns. Once those were shut clear down and then turned back out about 1 1/2 turns the thing came to life and then the idle was set to 800 - 900 rpm. I just happen to have a good friend that lives down the street that use to be a drag racer. He came down and within a few minutes we were perking along and running in the cam.
Maybe this will help:
http://www.holley.com/data/Products/Technical/199R10319-2.PDF
Or look for your carb by number here: http://www.holley.com/TechService/Instructions.asp
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I thought this might be the problem...
[attachthumb=#1]
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But I replaced it and it still has a fast idle. Checked vacuum, it was good. :banghead:
Tried to adjust timing, just stalled if I retarded it too much... must be a jetting or fuel delivery problem :mad:
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Chaz, Were did those carbs come from (were they shipped UPS?)?
The fuel overflowing is a sign that the float level is way off.
I've said this on several other threads, but I would start by removing all four float bowls and checking the float level.
Removed and inspect the needle and seat assemblies for debris.
Set your mixture screws at 1 1/2 turns out on both sides (run all the way in lightly then turn out 1 1/2 turns).
Set initial timing to about 16BTDC and 36 degrees at 3000rpm, then adjust idle speed setting.
*** make sure you have all the vacuum ports plugged off before trying to tune ;D
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There should be some air delivery needle valves to adjust. Sounds almost like you are running too lean.
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OK let's ask some things here.
Vaccum leak - did you spray carb spray around EVERYTHING to see if it affected it?
Did you check or temp plug the PCV?
What size cam, IE duration @ .050 do you have?
Did you set the timing? Did you try it with the vac advance unplugged? Did you verify the vac advance is plugged into the port above the idle screws?
Have you verified the secondaries are fully shutting?
Have you attempted to verify that both of the primary throttle blades are open approximately the same(or use a uni sync to adjust - that is what I do to mke sure the flows are the same)
There are other things it could be too - but check these first.
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OK let's ask some things here.
Vaccum leak - did you spray carb spray around EVERYTHING to see if it affected it? Carb Spray? So No, but I did attach a vaccum gauge and it read very close to OK (approx 23) at the high RPM idle. I also double checked every bolt for torque.
Did you check or temp plug the PCV? Doesnt have one
What size cam, IE duration @ .050 do you have? 218* for now >:D
Did you set the timing? Messed with it a bit, will try with the timing light tomorrow in the water.
Did you try it with the vac advance unplugged? Yes, It is always disconnected and unplugged
Did you verify the vac advance is plugged into the port above the idle screws? See above
Have you verified the secondaries are fully shutting? No, cant see top of carbs with scoop bolted on. I will remove it tomorrow at the lake.
Have you attempted to verify that both of the primary throttle blades are open approximately the same(or use a uni sync to adjust - that is what I do to mke sure the flows are the same). Again I will eyeball them tomorrow, but I did check idle adjust screw and turn them both as close as possible to the same amount out that it will still idle.
What should I look for/ set at for the float levels after I take the bowls off? I have never seen the inside of a holley carb...
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Vaccum leak - did you spray carb spray around EVERYTHING to see if it affected it? Carb Spray? So No, but I did attach a vaccum gauge and it read very close to OK (approx 23) at the high RPM idle. I also double checked every bolt for torque.
I'm surprised you are pulling that high, but OK.
Did you check or temp plug the PCV? Doesnt have one
What size cam, IE duration @ .050 do you have? 218* for now >:D
OK, that rules out a few things.
Did you set the timing? Messed with it a bit, will try with the timing light tomorrow in the water.
You can seriously mess with the idle if you have the advance set wrong. If you get on it while it is really advanced, you will have major pinging too...
Did you try it with the vac advance unplugged? Yes, It is always disconnected and unplugged
Did you verify the vac advance is plugged into the port above the idle screws? See above
OK
Have you verified the secondaries are fully shutting? No, cant see top of carbs with scoop bolted on. I will remove it tomorrow at the lake.
You can do that from the side of the carbs - hit the secondary linkage and see if it closes.
Have you attempted to verify that both of the primary throttle blades are open approximately the same(or use a uni sync to adjust - that is what I do to mke sure the flows are the same). Again I will eyeball them tomorrow, but I did check idle adjust screw and turn them both as close as possible to the same amount out that it will still idle.
What should I look for/ set at for the float levels after I take the bowls off? I have never seen the inside of a holley carb...
Your float levels should be set so when the big screw on the side of the bowl is removed, gas is just below or trickling out. You don't need to remove the float bowls to adjust.
Is it idling that high because you set it (it wouldn't run below a certain RPM), or because you started it and it was that way?
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What should I look for/ set at for the float levels after I take the bowls off? I have never seen the inside of a holley carb...
With the float bowl off, flip it up side down and adjust the needle and seat to get the bottom of the float (actually the top of the float) level with the body of the bowl.
Make sure there is no junk in the needle & seat while apart.
Let me see if I can get a pic to make it more clear.
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Basically that is the way it idles. It will not stay running if I try and lower it with the screw. It is, however, maybe 1/8- 1/4 turn past just touching to keep it running at 1800 RPM's
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The first pic shows the bowl in the correct position, the second pic shows the bowl upside down with the float nearly level (even gap along bottom).
This bowl is a little differenct than yours because it doesn't have and externally adjustable needle and seat but it gives you and idea of what to look at.