Possible cause? Advice, please.

[cfan10]

Truck is running like crap! So, my question is when it idles it runs bad, when I put it in reverse it acts as if it'll kill. Does this sound like a timing issue. Also, two studs are broken off of my pass exhaust manifold, only one bolted up....is this why its running o horribly? Many thanks in advance for all advice.
I hate to feel this way, but I'm starting to feel burned out with this truck...and I know its my own fault. Just seems like it is always something going wrong. Forgive the rant, lol.

84 swb 305 w/true dual pipes....ran beautiful before it was parked, tune up/new gas/bunch of new parts.
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[cfan10]

New parts

Waterpump
P/s pump
Thermostat
Fan clutch
Battery
Fuel pump
Ac delco plugs
Msd wires
Some other stuff I can't remember...
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[wilkin250r]

How does it run when it's NOT idling? Have you been able to get it that far?

My first thought is a vacuum leak, and then timing. Vacuum gauges aren't terribly expensive, I'd start there.

[cfan10]

^Haven't ran it on the road, as it running like crap. And it killed, good thing is it actually starts right back up. This is with backyard driving, risking sounding like a noob, but hey I am, lol.
Should I just change the throttle body gasket? How would I connect a vacuum gauge to check the lines?

Carb is an edelbrock 1406 if that makes a difference.

Thanks!
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[wilkin250r]

You're in luck, I'm familiar with the Edelbrock, I have owned a few and have torn them down and rebuilt them.

The Edelbrock has several different vacuum ports on it, two small ones in the front, one large one in the front, and I believe also one large one in the back (old age, fuzzy memory). The large ones should be connected to the vacuum brake booster, and also the PCV valve on the cylinder head cover. If they are not, either connect them or plug them right now for diagnostics.

One of the small ones should be connected to your vacuum advance on your distributor, the other small one should be plugged. Since your problem might possibly be timing, this one we definitely DO want connected for diagnostics. These two ports are slightly different, let me know which one, left or right, is connected to your distributor.

Let's start with that small check list. Check those connections. Do you have a vacuum gauge?

(just so we are clear and we have our terminology correct for the future, technically the "Left" and "Right" are as if you sitting in the truck facing forward. So the "right" side is the passenger side)

[willett]

If it ran fine before sitting how could the timing be effected?

How long did it sit? Is it possible that the carb needs a good cleaning? cracked vacuum lines?........ buy a can of ether and start spraying!

Wilkin feel free to correct me if I'm wrong, I'm fairly new to this game, Maybe I'm missing something about the timing?

[wilkin250r]

The base timing shouldn't have changed, but it's possible that the vacuum advance is rusted and seized, which would indeed have an effect on the overall timing. Or if the timing has been altered recently in this new attempt to revive it.

It's also possible, like you said willett, that the carburetor is gummed up from sitting too long and needs a good cleaning.

The can of ether is the next step, but it doesn't make sense to go searching for vacuum leaks unless you've confirmed whether or not there is one.

[willett]

thanks, that makes sense.



this is sort of off topic, but in my quest for knowlege I came across this article about timing:

http://www.chevytalk.org/fusionbb/sh...hp?tid/239321/

[cfan10]

Uploaded a vid to photobucket, can't start it today. As the landlord is visiting her brother next door and its running rough, don't want to hear her bs...will post vid tomorrow morning. Just wanted to show how the vacuum lines are hooked up.

Photobucket user id: beatrusted10
Thanks in advance.
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[wilkin250r]

Originally Posted by willett

thanks, that makes sense.



this is sort of off topic, but in my quest for knowlege I came across this article about timing:

http://www.chevytalk.org/fusionbb/sh...hp?tid/239321/

That's a pretty good article, you'd probably have to read it a few times in order to digest all of it. I don't know if I agree with the "ported vs manifold vacuum" 100%, I think there are a few other aspects to consider.

The one aspect that I DIDN'T see in that article, however, was the necessity for the mechanical advance. It did a good job of explaining the vacuum advance because of the lean mixture at a idle needing more time to burn, but it didn't go into an explanation of why the mechanical advance is needed.

It's rather simple, really, and probably why the article didn't explain it. It's simply a matter of speed. The combustion process takes TIME to burn, not degrees to burn. Let's pretend you want to spark 75 milliseconds early, that translates to 12 degrees at 1000rpm. But think about it, at 2000 rpm, the motor is turning twice as fast, isn't it? So 12 degrees is only 37 milliseconds, you need 24 degrees to get back to your 75 milliseconds. And at 4000 rpm, you would need 48 degrees.

As the engine is turning faster and faster, each degree of revolution takes less time. So you'll need more and more degrees to reach the same length of time.

This is an over-simplification, of course, but that's the general idea.