79 400m runing right issues
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
[quote=StarTrash;7948296]its connected to the carb in the front its really low on the carb.. it idles great..quote]
That's manifold vacuum, connect it to ported vacuum and you should see an improvement with your off idle acceleration (assuming the vacuum advance is working properly) though you will need to re-adjust your idle speed.
That's manifold vacuum, connect it to ported vacuum and you should see an improvement with your off idle acceleration (assuming the vacuum advance is working properly) though you will need to re-adjust your idle speed.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
I'm not sure which carb you're dealing with but it doesn't really matter, connect your dizzys vacuum adavance to the highest port (above throttle blades) this will allow the V/A to "kick in" after you open the throttle, just plug the port you were previously plugged into, though you can run a vacuum gauge from that port into your cab if you want too (great diagnostic tool) you'll need to re-adjust your idle because pulling manifold vacuum was advancing your timimg at idle therefore increasing your idle speed.
Postmaster
Joined: Jul 2001
Posts: 4,956
Likes: 10
From: MD
The vacuum hose for the advance should go to the passenger side of the carburetor below the choke housing. This is the ported source. At idle with the throttle blades closed, there is little to no vacuum operation like Montana-Highboy advised.
While checking the timing, you must remove the vacuum hose from the vacuum advance and plug the line. Retime it after you do that. Anywhere between 6-14 BTDC.
If the idle drops when you remove the advance vacuum, it's been advanced all along since the manifold vacuum is always present. Remove & plug the vacuum line. Readjust idle in Drive to 600-700 RPM. Also hook a vacuum gauge to a manifold vacuum source. Adjust the vacuum reading to 17-21 Hg by turning the idle mixture screws on the carburetor base.
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Senior User
Joined: Nov 2005
Posts: 106
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From: belton mo
well the vaccum on my previous trucks have always been plugged where i have mine now.. i will try the passenger side in the morning.. thanks everyone hoply this is the problem.. ill feel dumb .. but hell itll be fixed 
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Senior User
Joined: Nov 2005
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From: belton mo
ok i played with a few things.. did the vac advance to a different port .. had to retime it but it runs a little better.. actually some accerlation.. got a hold of a vaccum gauge it reads anywhere from 10-15 when i play with the mixture screws.. ive checked for vac leaks cant find any.. i was told b4 i had the motor it was ran with just the headers.. no exhaust... so im thinking maybe a burnt valve?.. anyway to check?
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Senior User
Joined: Nov 2005
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From: belton mo
forgot to mention that the needle jumps back and forth..
according to this
http://www.users.bigpond.com/ergoff/vac1.htm
i have a burnt valve worn valve guides or leaky valves.
according to this
http://www.users.bigpond.com/ergoff/vac1.htm
i have a burnt valve worn valve guides or leaky valves.
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Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
If you're reading between 10-15" of vacuum @idle with an erratic needle you definitely have a problem like you've already stated, a healthy motor will pull 18-20" of vacuum @idle (give or take an inch).
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Senior User
Joined: Nov 2005
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From: belton mo
yea .. well ive got some heads off a good motor just had a fuel problem.. found out after pull outta a different truck.. same motor.. so i might just be doing a swap..
Dont know yet but Thanks for all the help.!!
Dont know yet but Thanks for all the help.!!
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Senior User
Joined: Nov 2005
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From: belton mo
ok so 7 was fine.... 8 had no more then 60.. so cylinders 6 and 8... 30-60.. What could it be?... valves? .. there wasnt oil all over the spark plug so the rings arent gone... or hole in piston.. my guess would be valves?