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Unread 09-20-2014, 09:05 PM   #1
Hbryant123
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Amc 304 Tuning Help

I rebuilt my amc 304 myself last winter, now i want to tune it in run good and smoothe. The carb is an mc2100 from a ford with 1.08 venturis. I am running an HEI distributor. The engine starts and runs decent but the idle isnt smoothe but its not like a vaccum leak either. I always wanted to have a smooth running older v8. I am not sure wear to start, the carb is kinda unknown and i did use the origional rockerarms, pushroods and bridges. Where should i start in tuning my engine in?

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Unread 09-21-2014, 06:35 AM   #2
Mike Romain
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Did you set the idle mix screws for the 'best lean' mix? Is the choke opening all the way?
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Unread 09-21-2014, 07:03 AM   #3
lucdog
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How does the exhaust sound, do you detect a miss, or does it sound normal?

How does it run off the idle circuit at 1400 rpm, does it smooth out?
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Unread 09-21-2014, 07:05 AM   #4
swatson454
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Personally, I'd start at the spark plugs and work my way backwards, through any emissions components that you have and finally to the carb.

*Check the condition of, color and gap of the spark plugs.
*Carefully inspect the plug wires, especially around the exhaust.
*Inspect the inside of the cap for evidence of arcing on the plastic and welding on the posts, especially if you have aluminum posts.
*Check the rotor for red dust. If you've got it, pull the rotor off and make sure you haven't welded the advance mechanism together. Address as needed
*Check the PCV and EGR and for vacuum leaks on anything that hooks to vacuum either directly or indirectly.
*Make sure you're using the correct fuel filter (if bypass type, orient the bypass at 12 o'clock)
*Blow out any air bleeds in the carb with carb cleaner.
*Check the float level.
*Fire it up and make sure the choke pulls completely off when warm.
*Once warm, make sure the timing is set between 8* and 12*, run through the lean-best idle procedure and see where you stand.


Shawn

Ps: Although I've tried to lay this out in an orderly, step-by-step fashion, the addition of beer in between any or all of the steps is perfectly acceptable.
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Unread 09-21-2014, 10:03 AM   #5
jeepdaddy2000
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Quote:
Originally Posted by swatson454 View Post
Personally, I'd start at the spark plugs and work my way backwards, through any emissions components that you have and finally to the carb.

*Check the condition of, color and gap of the spark plugs.
*Carefully inspect the plug wires, especially around the exhaust.
*Inspect the inside of the cap for evidence of arcing on the plastic and welding on the posts, especially if you have aluminum posts.
*Check the rotor for red dust. If you've got it, pull the rotor off and make sure you haven't welded the advance mechanism together. Address as needed
*Check the PCV and EGR and for vacuum leaks on anything that hooks to vacuum either directly or indirectly.
*Make sure you're using the correct fuel filter (if bypass type, orient the bypass at 12 o'clock)
*Blow out any air bleeds in the carb with carb cleaner.
*Check the float level.
*Fire it up and make sure the choke pulls completely off when warm.
*Once warm, make sure the timing is set between 8* and 12*, run through the lean-best idle procedure and see where you stand.


Shawn

Ps: Although I've tried to lay this out in an orderly, step-by-step fashion, the addition of beer in between any or all of the steps is perfectly acceptable.
Which is why it will NEVER run right....
If you follow alll the above instructions and you can't get to idle right, you woill want to drop the cover on the power valve and check to see if there is any gas in it. If so, the valve is bad and will need to be replaced.
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Unread 09-21-2014, 10:46 AM   #6
swatson454
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Originally Posted by jeepdaddy2000 View Post
Which is why it will NEVER run right....
Good point
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Unread 09-21-2014, 08:42 PM   #7
Hbryant123
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Thanks for the replies! I have one more questions before getting my hands dirty, I am wondering what the vaccum is supposed to be for this engine? I believe I checked it and it was at 13.
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Unread 09-21-2014, 08:44 PM   #8
Hbryant123
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Quote:
Originally Posted by lucdog View Post
How does the exhaust sound, do you detect a miss, or does it sound normal?

How does it run off the idle circuit at 1400 rpm, does it smooth out?
When the engine is warm and idling it sounds great at the tail pipe, very uniform and smothe. Idle accerlerates pretty well. no hickups or miss
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Unread Yesterday, 12:33 AM   #9
Matt1981CJ7
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Quote:
Originally Posted by Hbryant123 View Post
Thanks for the replies! I have one more questions before getting my hands dirty, I am wondering what the vaccum is supposed to be for this engine? I believe I checked it and it was at 13.
At your elevation 18-20" would be normal. 13" is way low.

Matt
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Unread Yesterday, 09:24 AM   #10
Hbryant123
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Originally Posted by Matt1981CJ7 View Post
At your elevation 18-20" would be normal. 13" is way low.

Matt
I agree. My worn out s10 held steady at 19. I had two different intakes and two different carbs. No matter what i never saw vaccum at 18-20. Could valves not opening up all the way cause low vaccum? During the rebuild i reused my push rods, rocker arms and bridges.
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Unread Yesterday, 12:12 PM   #11
RedNeckCorvette
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Originally Posted by Matt1981CJ7 View Post
At your elevation 18-20" would be normal. 13" is way low.

Matt
Air leak?
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Unread Yesterday, 12:23 PM   #12
zillla
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My 304 gets 14 on a good day.. No more.. I live at 6500" so I think it's normal.


FYI: I had 2 different 2100's on my 304. The first was a 1.08. Ran OK but seemed to lack a bit. Upon recommendation of a carb guy I traded for a 1.21. Much better.. IMO the 1.08 is a tad small on a 304..
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