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Old 07-18-2014, 02:12 AM   #1
MachRog
 
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Vehicle: 1970 Ford Mustang Mach1
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Default 1970 mach1 351c falls on its face when i hit accelerator.

Hi all. First post here.
Need help with my 1970 mach1. Its a*351c*2v with fmx trans. I just put an edlebrock manifold and 650 carb on it but am unhappy with performance. Just to set the record straight, i am by no means a tuner. Im a novice at best with the engine but im learning and not afraid to jump nto the engine.*
The engine idles nice and sounds like a beast when i rev it in park. No issues at all...no bogging, hesitation, or loading up. But when im driving and hit accelerator, it bogs down and falls on its face. It will backfire sometimes. I can creep the*gas pedal*up but if i press down too much on accelerator, it almost always bogs.

Ive looked over alot of posts on here and have found alot of good info but none are exactly my issues. Im thinking it may be the new carb needing adjustment, but am unsure.
Any and all help would be appreciated.

Im just looking to get her running good. Engine sounds and revs good in park or neutral.
Rog
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Old 07-18-2014, 02:34 AM   #2
jimkaray
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Your dumping in too much fuel when you go full throttle. I'm get you started but I'm rusty with carbs so hopefully someone will jump in with some specific adjustments and part changes. You'll want to swap out the power valve/spring assembly for one that will add less fuel. Is this a mechanical or vacuum secondary carb?
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Old 07-18-2014, 09:55 AM   #3
88 orangepeel notch
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+1 ^^^

" IF " it was running good before the carb swap. Check for vacuum leaks also. Maybe a port on the new intake or carb not plugged.
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Old 07-18-2014, 10:02 AM   #4
MachRog
 
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Quote:
Originally Posted by jimkaray View Post
Your dumping in too much fuel when you go full throttle. I'm get you started but I'm rusty with carbs so hopefully someone will jump in with some specific adjustments and part changes. You'll want to swap out the power valve/spring assembly for one that will add less fuel. Is this a mechanical or vacuum secondary
carb?
It is a vacuum secondary.
But if it were getting too much gas, wouldnt it do the same thing when i mash the throttle in park or neutral???
It doesnt... It revs nice and crisp. It just bogs down when in gear.
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Old 07-18-2014, 10:05 AM   #5
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Quote:
Originally Posted by 88 orangepeel notch View Post
+1 ^^^

" IF " it was running good before the carb swap. Check for vacuum leaks also. Maybe a port on the new intake or carb not plugged.
It was doing the same thing before the carb swap, just worse now. The old carb was Holley ... new is edlebrock 650. Ill do a vac check on it.
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Old 07-19-2014, 03:14 AM   #6
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When you rev in neutral/park there is no load on the engine so its able to deal with the issue with out bogging. If you have a vacuum leak you should notice a rough idle. Now that you're telling us the issue existed before it does change things. You've switched from a Holley 2bbl or 4bbl and what intake was on there?
When was the last tune up? Are you running an electronic distributor or still have a points & condensor set up?
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Old 07-19-2014, 11:36 AM   #7
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Quote:
Originally Posted by jimkaray View Post
When you rev in neutral/park there is no load on the engine so its able to deal with the issue with out bogging. If you have a vacuum leak you should notice a rough idle. Now that you're telling us the issue existed before it does change things. You've switched from a Holley 2bbl or 4bbl and what intake was on there?
When was the last tune up? Are you running an electronic distributor or still have a points & condensor set up?
No rough idle on the engine.
(Had) a Holley 2bbl on it, stock manifold... (Now) has a Edelbrock 650 with Edelbrock 2v manifold.
It has points right now but I was contemplating elec. distributor.
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Old 07-19-2014, 12:43 PM   #8
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Is the tune up recent and the points gap and dwell rechecked?
When it falls over are you seeing black smoke out of the tailpipe? That would help confirm it is a rich condition. What was the symptoms with the old set up? If you're saying it was the same then maybe its a distributor or a fuel pump issue.
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Old 07-19-2014, 01:13 PM   #9
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Could be timing, have you checked the vacuum advance to make sure its working? Does this have a mechanical distributor with centrifical advance?
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Old 07-20-2014, 02:55 PM   #10
MachRog
 
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Quote:
Originally Posted by jimkaray View Post
Is the tune up recent and the points gap and dwell rechecked?
When it falls over are you seeing black smoke out of the tailpipe? That would help confirm it is a rich condition. What was the symptoms with the old set up? If you're saying it was the same then maybe its a distributor or a fuel pump issue.
Hasn't been tuned up yet.
No black smoke coming out... It just sputters and falls on its face under load until I let off a little on gas.

Symptoms before the new carb and intake were similar. Im getting overwhelmed with the motor. I just need a starting point.
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Old 07-20-2014, 02:55 PM
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