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Discussion Starter · #1 ·
351w that was recently swapped in and now am working out the small things. No matter the timing it’s a weak idle or stall after giving it a rev. Vacuum is 12-13”around 750rpm and the cam is a xe268h. Summit distributor nothing fancy. I haven’t done any carb adjustments yet, any suggestions would be great thanks.
 

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That doesn't surprise me. Timing and carbuertor adjustment would be the obvious first things. You're not going to get 20 inches anymore with that cam. Based on the overlap of that cam profile that isn't way off the mark.
Is the cam installation new?
 

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Discussion Starter · #3 ·
That doesn't surprise me. Timing and carbuertor adjustment would be the obvious first things. You're not going to get 20 inches anymore with that cam. Based on the overlap of that cam profile that isn't way off the mark.
Is the cam installation new?
Yea everything is new
 

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Idle is a balance of timing, curb idle adjustment and idle screw adjustment. If you haven't messed with the carb at all, then I'd say it's perhaps as simple as the curb idle not being open enough but the idle screws being at a position that allows it to still run. What type of carb?

First, I would check some mechanical basics. Return spring working? Throttle opening all the way? Firing order correct? Spark plugs gapped right? Plug wires installed properly on the plugs?

Then ensure the carb idle screws are set to the factory positions as well as the float level. Carbs are supposed to come from the factory set up to run out of the box, but you never know.

Then I would set the timing to a generic base level like 10-12 degrees and leave it. I would not touch this again until after you've gotten a livable idle.

Then I would adjust the curb idle to get it to get the idle RPM you want.

Then I would adjust the idle screws with a vacuum gauge.

Then I would tweak timing and idle from there to get the best vacuum.

Then I would adjust the carb as needed- secondary spring, accelerator pump cam, etc.

If this does not work then you have a mechanical issue.
 
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My car's engine was rebuilt/upgraded in about 1985. Currently it runs about 9 to 10" of vacuum at 850 rpm (but has fuel injection). Previous to the fuel injection upgrade it had a substantial lope (when I was running a carb, stock 1965 A code Ford unit) but it would idle at about 1,000 rpm. I didn't have the stalling issues you mention, so I think it should be possible to get yours running correctly. Best of luck to you. :)
 

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Discussion Starter · #8 ·
Idle is a balance of timing, curb idle adjustment and idle screw adjustment. If you haven't messed with the carb at all, then I'd say it's perhaps as simple as the curb idle not being open enough but the idle screws being at a position that allows it to still run. What type of carb?

First, I would check some mechanical basics. Return spring working? Throttle opening all the way? Firing order correct? Spark plugs gapped right? Plug wires installed properly on the plugs?

Then ensure the carb idle screws are set to the factory positions as well as the float level. Carbs are supposed to come from the factory set up to run out of the box, but you never know.

Then I would set the timing to a generic base level like 10-12 degrees and leave it. I would not touch this again until after you've gotten a livable idle.

Then I would adjust the curb idle to get it to get the idle RPM you want.

Then I would adjust the idle screws with a vacuum gauge.

Then I would tweak timing and idle from there to get the best vacuum.

Then I would adjust the carb as needed- secondary spring, accelerator pump cam, etc.

If this does not work then you have a mechanical issue.
My car's engine was rebuilt/upgraded in about 1985. Currently it runs about 9 to 10" of vacuum at 850 rpm (but has fuel injection). Previous to the fuel injection upgrade it had a substantial lope (when I was running a carb, stock 1965 A code Ford unit) but it would idle at about 1,000 rpm. I didn't have the stalling issues you mention, so I think it should be possible to get yours running correctly. Best of luck to you. :)
Thanks for the feedback. It’s an edelbrock avs 650. I accidentally bought iridium plugs an am using those, don’t know how much they affect it.
 

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Discussion Starter · #9 ·
Wanted to just say I think I got it. The idle mixture screws were out only about 1/2 turn. Solid 13” of vacuum at 14 degrees around 850rpm.
 

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Wanted to just say I think I got it. The idle mixture screws were out only about 1/2 turn. Solid 13” of vacuum at 14 degrees around 850rpm.
Your Vac is still pretty low and can affect carb performance. Carbs rely on vacuum for maximum efficiency. It can manifest into sluggish performance, poor idle quality and MPG. Also, any VAC dependent accessories, think "brake booster" etc, will suffer. But then, that's the price one pays for a cammy sounding engine.
 
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