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Troubleshooting my 304

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sweetevil28 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweetevil28 Quote  Post ReplyReply Direct Link To This Post Topic: Troubleshooting my 304
    Posted: Jan/14/2018 at 2:54pm
I have a 74 Gremlin 304 that needs some engine love. I've done a lot of work on it already and I'd like to continue to do the work my self so I'm asking for some suggestions as to what I should troubleshoot to fix my current problems. I appreciate the feedback!

After smooth warming idle, the engine slows with choke open until it idols very low (sometimes stalls) and sounds like a ticking grinding pulse. I've tried to increase fuel but by the time it's enough to prevent stalling in park it's super rich and still pulsing idol around 1000rpm. I can't back off timing (34 degrees) or i get a backfire.

Some Videos... The rattle sound is because I have to replace the NEW water pump as the fan is wobbling a little. 

Warming Idol (1300 RPM 22 Vac): https://photos.app.goo.gl/fGhM0TpUQHg3bKif2
Warmed Idol in park (700-750 RPM 15ish Vac): https://photos.app.goo.gl/DrP768ahSTbTnQZc2
Warmed Idol in gear ( 470-485 RPM 7ish Vac): https://photos.app.goo.gl/wYK0JTp1VvubBhgR2


Recent Engine Upgrades/Work
HEI distributor
Edelbrock 1406 600CFM
Headers
New tappets and rods
One new rocker and bridge replaced where sound is coming from.
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one bad rambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/14/2018 at 4:44pm
Several question`s...When did this start before or after you did the work? Is the intake factory?Are you sure the timing is right?When is it 34deg?(RPM)If it`s 34deg at idle you would have a labored crank...Is the cam stock?
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Boris Badanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Jan/14/2018 at 6:11pm
Does it have an EGR valve?
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sweetevil28 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweetevil28 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/15/2018 at 9:10am
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Yes. I have the egr out from carb running to it. I drove it for about 200 mi after all the work. Intake is not original. Cam is stock.  The timing used to be good at around 20 degrees but not since it’s been acting up.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72gremx401 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/15/2018 at 7:05pm
My quess is, skipped timing chain.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jan/15/2018 at 7:36pm
A cold engine (specifically cold intake air temperature and cold intake manifold) does not vaporize the fuel well, which is why they need the choke to literally dump enough fuel into it that it will run.

That choke has to stay on until the intake air and manifold warm up enough to vaporize the fuel properly and run without the choke.

Your factory choke is designed to open at the same rate that the intake air and manifold warm up. Their warming is controlled by the heat crossover passage in the intake manifold, the heat valve on the outlet of the passenger's side exhaust manifold, and the warmed air intake with duct built into the air cleaner. If one or more of those devices has been removed or no longer functions as it should, the intake and manifold will be colder than it should be but the choke will still open like everything is fine. This means you have cold intake air and a cold manifold but an open choke...resulting in a low idle, stalling, hesitation, and all the things carburetors have a reputation for.

If that is your problem, solutions:

1. Replace or repair the missing or not functioning heating devices.
2. Make the choke open slower to keep dumping raw gas into your engine for the longer amount of time it takes to warm up the intake components. Note: raw gas pouring into your engine causes more cylinder wall and ring wear.

Most people do #2 because they removed the original engine heating components in the name of high performance. 


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232jav3sp View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 232jav3sp Quote  Post ReplyReply Direct Link To This Post Posted: Jan/15/2018 at 8:06pm
Do you always have your timing light set to 34*? Regardless of RPM? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lucas660 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2018 at 5:25am
It reads like you have excessive advance at idle which is probably covering up a vacuum leak. Stock cam should give you good vacuum at idle.
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sweetevil28 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweetevil28 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2018 at 8:28am
I changed the light to match the advance that performs best and shows TDC. Just to understand how far advanced it was. No marker above 15.
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232jav3sp View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 232jav3sp Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2018 at 11:35am
You shouldn't have to do that except for when checking for full advanced at 2k-2200rpm. At idle, your light should be at zero degrees and you adjust your ignition timing via the distributor until the mark on your balancer is at the particular degree you want. If the timing mark is no where near the degree indicator on the timing cover you either have a balancer that had spun, your distributor is off a tooth or two, or your distributor drive gear could have gotten damaged.
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