390 tuning/vacume question?
#1
390 tuning/vacume question?
I am new at tuning my 390, so here is my problem. It idles rough but runs great through the rpm range except right off idle, I have swapped carbs with no change also full tune up, my old plugs were white and my new plugs are white also, so I am thinking vacume leak. The problem is I don't know how much vacume my 390 should be making, at idle it only has 12" and at 2,000 it has 20". The motor is all stock.
#2
have you tried adjust your idle mixture screws ?
if you have a autolite 2brl they are under the front of the carb .
gently turn them all the way in then back out 1 1/2 turns . this is a good base point to start from .
hook your vacuum gauge up and adjust the screw in or out to get max vacuum .
make sure both screw are adjusted the same .
if you have a autolite 2brl they are under the front of the carb .
gently turn them all the way in then back out 1 1/2 turns . this is a good base point to start from .
hook your vacuum gauge up and adjust the screw in or out to get max vacuum .
make sure both screw are adjusted the same .
#4
#6
Everything went from bad to worse, even though my truck has been running rough for a couple years now, I thought I would try to fix what I thought was a vacume leak, then I find a cylinder down on compression. So I decided to just run it like it is for the winter while i tried to build a new engine. This is when my bad luck hit, I took it for a trip into town for fuel and it developed a backfire through the carb and alot of blue smoke from the right side exhaust [#1 cylinder is the culprit]. I hate to waste $1,500 on a stock rebuild right now, when I really want to build a nice stroker [but can't afford], I have another truck 2wd that runs good with a very faint knock in the bottom end, so my thought was to get the crank turned and run that in my highboy until I can afford to build the engine that I want, any suggestions here would be great
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