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Old 11-24-2013, 06:52 AM   #1
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Carb Set-up

I have a 289 with Hi-PO heads, a mild cam, high rise intake and a 600 Holley with 66 jets. When the car really runs for a while I get a major hesitation when I hit the gas hard. Even at start or idle it seem to be running rich. The timing is correct, I checked it.

Any thoughts? I'm thinking maybe the carb is too big or at least needs jetted differently...
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Old 11-25-2013, 11:09 AM   #2
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To tell you the truth I think I have the same prob with mine...600 double pump and it does the same thing after driving for a while.
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Old 11-25-2013, 01:24 PM   #3
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Yup jet her down to 525 550 max and you will be a lot happier and so will your 289
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1968 Coupe <53000 miles on her 289 came off the line Jan 21st 1968. I bought it in 1983

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Old 11-26-2013, 06:03 AM   #4
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Originally Posted by Mlarv5 View Post
Yup jet her down to 525 550 max and you will be a lot happier and so will your 289
thanks! I'm not that advanced just yet as far as this stuff goes. How do I know what jets get the carb down to 525 or 550?
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Old 11-26-2013, 07:09 AM   #5
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I have had that same problem, I even went to a 2 barrel and the performance was worse. I am convinced that the fuel sending unit and/or fuel pump that come stock in these just aren't very good at regulating the fuel.
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Old 11-26-2013, 08:20 AM   #6
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Here is a sight to see what you have.

Holley Four Barrel Carburetor List Numbers, Stock Jet Sizes, CFM, and Stock Power Valve Ratings | Hot Rod Reference

Also here are a few tips from Holly

Holley Performance Products Frequently Asked Questions

Search there site for Jet Sizing

Holley Performance Product Search

Hope this helps
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2013 Shelby GT500 Born 12/06/2012 number 439 of 530 in DIB and 1 of 9 with Red Stripes over the top and on the seats
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Old 11-26-2013, 08:29 AM   #7
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Originally Posted by Geoff_lundy View Post
I have had that same problem, I even went to a 2 barrel and the performance was worse. I am convinced that the fuel sending unit and/or fuel pump that come stock in these just aren't very good at regulating the fuel.
The fuel pump might be bad but hold off just yet.

What year car and engine?

Was the engine rebuilt?

Have you replaced the gas tank or sent it in for a good cleaning out?

Have you replaced the fuel filter?

Do you have rubber fuel lines?

If rubber fuel lines when was the last time they where replaced?

Does this happen in warm weather or cold or both?

New carbs normally bring out other problems in the fuel delivery systems such as weak fuel pumps, collapsing rubber fuel lines, bad filters etc.

Good luck
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2013 Shelby GT500 Born 12/06/2012 number 439 of 530 in DIB and 1 of 9 with Red Stripes over the top and on the seats
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Old 11-26-2013, 10:35 AM   #8
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1966, 288, New gas tank, new rubber fuel lines, motor rebuilt 10 years ago, new sending unit, recently tore down cleaned and put back together with all new gaskets. I am going to try the links provided above for Holley carb info.
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Old 11-28-2013, 09:02 AM   #9
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On a carb, the float controls the fuel. The pump provides (hopefully) constant low pressure and the float allows flow as needed. The sending unit only sends a signal for the gauge.
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Old 02-12-2014, 02:59 PM   #10
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Quote:
Originally Posted by Cleve Steve View Post
I have a 289 with Hi-PO heads, a mild cam, high rise intake and a 600 Holley with 66 jets. When the car really runs for a while I get a major hesitation when I hit the gas hard. Even at start or idle it seem to be running rich. The timing is correct, I checked it.

Any thoughts? I'm thinking maybe the carb is too big or at least needs jetted differently...
I have a 68 with a 289 and an edelbrock 600 on it and have the same problem. I was watching an edelbrock tuning video and from the troubleshooting tips it seems like the floats need to be adjusted if we're having this issue...any comments?
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Old 02-12-2014, 03:10 PM   #11
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Originally Posted by ndeining View Post
I have a 68 with a 289 and an edelbrock 600 on it and have the same problem. I was watching an edelbrock tuning video and from the troubleshooting tips it seems like the floats need to be adjusted if we're having this issue...any comments?
It might be the floats after you adjust them according to the video, if not then it just might be to much gas for the engine to handle when you first hit the peddle. It was a very common problem before fuel injection.
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Old 02-12-2014, 03:22 PM   #12
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Originally Posted by Mlarv5 View Post

It might be the floats after you adjust them according to the video, if not then it just might be to much gas for the engine to handle when you first hit the peddle. It was a very common problem before fuel injection.
Yeah in the intro the guys specifically said you wouldn't want to put a 600 on a ford 289 or 302 lol may not be worth messing with I guess
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Old 02-12-2014, 04:08 PM   #13
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Yeah in the intro the guys specifically said you wouldn't want to put a 600 on a ford 289 or 302 lol may not be worth messing with I guess
A 600 is a little big see if they can rejet it to 525 to 550. They should have a kit for it.
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2013 Shelby GT500 Born 12/06/2012 number 439 of 530 in DIB and 1 of 9 with Red Stripes over the top and on the seats
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Old 02-21-2014, 06:00 AM   #14
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Adjust the carbs idle mixture screws while using a vacuum gauge to achieve optimum intake vacuum. The Holley site explains the procedure.
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Old 02-23-2014, 08:13 AM   #15
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If it's a relatively mild motor (less than 300 hp) a 390 cfm Holley will work wonders, I thought it was a little small at first but the throttle response was incredible compares to the 600cfm eddlebrock that was on there. I had to her up 4 sizes for a 289 with an edelbrock performer cam, intake and longtube headers.
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