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rough running 390
By schu - 01/21/2001 7:57:17 PM; IP 24.237.87.68
My 390 has been running rough lately. It doesn't idle very smooth and it seems very cold blooded. I have run out of ideas on what it could be so maybe one of you has some suggestions on stuff I can look at.

Here is the engine:

1976 390 in a F-150
Stock truck 4bbl intake
Stock exhaust manifold
Stock distributor
Stock heads (crane springs)
Cam is crane HMV-272-2 (216/228 @ .050)
Cam timing is set straight up
8k miles on rebuild
Holley 4160 vacuum secondary carb, 600 cfm

Here are some things I noticed or have tried:

12" of manifold vacuum when set to 10 degrees initial timing
15" of manifold vacuum when set to 25 degrees initial timing
Replaced all of the hoses and checked for vacuum leaks, non found
Some of the plugs are clean and light tan and others some seem to be black
Choke is working correctly (electric)
Truck seems to be getting hotter than normal, but not quite overheating

When I finished rebuilding the motor I was getting 20" of manifold vacuum and it ran great, so I know it isn't the cam that is causing the low manifold vacuum. Is it possible that my intake manifold is leaking?

Thanks

schu
This thread, so far...
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Collapse <b>rough running 390</b>&nbsp;-- <font color=#0000ff>schu, <i>01/21/2001</i></font>rough running 390 -- schu, 01/21/2001
Collapse <a href=../ForumFE/reply.aspx?ID=4318&Reply=4284><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor4318" onclick="return false;">It could be a number of things !!!</a>&nbsp;-- <font color=#0000ff>mcj67, <i>01/24/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=4318', contentMargin: 60, icon: $('anchor4318') }); </script>  It could be a number of things !!! -- mcj67, 01/24/2001
Collapse <a href=../ForumFE/reply.aspx?ID=4319&Reply=4284><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor4319" onclick="return false;">RE: It could be a number of things !!!</a>&nbsp;-- <font color=#0000ff>schu, <i>01/24/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=4319', contentMargin: 60, icon: $('anchor4319') }); </script>  RE: It could be a number of things !!! -- schu, 01/24/2001
Collapse <a href=../ForumFE/reply.aspx?ID=4335&Reply=4284><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor4335" onclick="return false;">A couple more things</a>&nbsp;-- <font color=#0000ff>mcj67, <i>01/24/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=4335', contentMargin: 60, icon: $('anchor4335') }); </script>  A couple more things -- mcj67, 01/24/2001
Collapse <a href=../ForumFE/reply.aspx?ID=4349&Reply=4284><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor4349" onclick="return false;">RE: A couple more things</a>&nbsp;-- <font color=#0000ff>schu, <i>01/26/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=4349', contentMargin: 60, icon: $('anchor4349') }); </script>  RE: A couple more things -- schu, 01/26/2001
 Pulling head will give you some insite -- mcj67, 01/26/2001
Collapse <a href=../ForumFE/reply.aspx?ID=4332&Reply=4284><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor4332" onclick="return false;">RE: rough running 390</a>&nbsp;-- <font color=#0000ff>RC Moser, <i>01/24/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=4332', contentMargin: 60, icon: $('anchor4332') }); </script>  RE: rough running 390 -- RC Moser, 01/24/2001
Collapse <a href=../ForumFE/reply.aspx?ID=4348&Reply=4284><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor4348" onclick="return false;">RE: rough running 390</a>&nbsp;-- <font color=#0000ff>schu, <i>01/26/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=4348', contentMargin: 60, icon: $('anchor4348') }); </script>  RE: rough running 390 -- schu, 01/26/2001
 RE: rough running 390 -- RC Moser, 01/26/2001
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