I have a 390 that I got with an old truck for cheap that was suposed to have been rebuilt (was a gamble) and had been sitting for many years.
so I took the heads of to check it out a little and it looked good. pistons marked .30 over and all parts look very new. I cleaned it up and put it back together. I put it in my 69 F-250 that originally had a 360.
I got it running, but it required a huge amount of advance to idle. so much that the starter has issues cranking after it warms up. It will only run with about 30-40* btd advance. Also, I the carb screws have to be backed out about 4-5 turns. seems like a lot of fuel.... if I had to guess, I would compare it to a car that has the timing belt off a tooth.
The only thing I didn't check was the timing chain... could it be off a tooth causing this? I don't think it has a radical cam, but maybe? any ideas are appreciated...
First thing to check is the vibration damper for being at "0" with the engine at TDC. Then do a compression check next. If that is good, check for a vacuum leak. I think it sounds like either a damper slip or a timing chain issue.
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Bear 45/70 Gimp Racing
“There are only two things stopping you, common sense and fear! And not much of the latter.”
sorry, for got to say that yes, I checked the timing mark. it is correct at top dead center.
I guess I will tear it back down to visually check the chain see if marks line up.
This might be kind of a long shot but simple to check off the list. At TDC and 0 on the damper is the rotor pointing to the #1 plug (the cap may have a 1 marked on it but the actual #1 plug position may be different.) trace out the Fire order. Just a thought.
If you determine the comp stroke TDC on #1 piston when you look at your balancer the pointer is going to be in the timing region. If your 180 out the timing region will not be visable at the pointer. Also your rotor should be pointing at your #1 plug wire. Make a mark on the intake next to #1 plug port on the cap. Or mark the edge of the diz in the same spot pull the cap and the rotor should be pointing right at it. You should be able to tell if your a tooth off on the diz also.
If you determine the comp stroke TDC on #1 piston when you look at your balancer the pointer is going to be in the timing region. If your 180 out the timing region will not be visable at the pointer. Also your rotor should be pointing at your #1 plug wire. Make a mark on the intake next to #1 plug port on the cap. Or mark the edge of the diz in the same spot pull the cap and the rotor should be pointing right at it. You should be able to tell if your a tooth off on the diz also.
Yes it will, as a 4 stroke has 720° of crank rotation for 360° of distributor rotation. So 180° out at the distributor would be half of 720° at the crank, or 360°, otherwise right back to 0°. This is all basic engine mechanics. Why do so many not know this kind of stuff?
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Bear 45/70 Gimp Racing
“There are only two things stopping you, common sense and fear! And not much of the latter.”
Take it easy... bear... Your right. My bad. I said ( (If your 180 out the timing region will not be visable at the pointer.)) and I was wrong. The marks will come around on exhaust and compression.
"When" you determine the compression stroke TDC on #1 piston, your rotor should be pointing at your #1 plug wire on the cap. Make a mark on the intake next to #1 plug port on the cap. Or mark the edge of the diz in the same spot, pull the cap and the rotor should be pointing right at that spot. You should be able to tell if your a tooth off on the diz also by the location of the rotor point.
PS EDmist sorry about that. Their are some good old timers to keep it real.
Last edited by Kennewick; 11-16-2009 at 12:27 AM.
Reason: correction.
Second point of reference: Where are the valves on #1 cylinder?
When you check to see if the engine is in time, the damper should be on TDC, both valves on #1 should be closed, rotor should be on #1 terminal. Screw up on one of the three and you'll be back at the drawing board. Never mind how I know this...
The most you should have to take apart would be the distributor cap and one valve cover to watch the rockers. As you spin the crank, watch for the intake valve on #1 to close, stop the damper at TDC. Is the rotor pointing at #1? Can you spin both push rods with a finger and thumb on #1 cylinder?
That is the short and simple explanation. I was going to use this smiley: but I didn't like the look on his face.
HTH
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Ok, so just to clarify. If my timing light is hooked up to No.1 plug wire... and my light shows my 390cid to be at 10deg advance... and my motor is running (yet not perfectly)... my distributor could still be out 180 deg?
Ok, so just to clarify. If my timing light is hooked up to No.1 plug wire... and my light shows my 390cid to be at 10deg advance... and my motor is running (yet not perfectly)... my distributor could still be out 180 deg?
No, these 180° guy are full of it. A 4 stroke engine will never run with the distributor 180° out as the spark will happen on the exhaust stroke.
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Bear 45/70 Gimp Racing
“There are only two things stopping you, common sense and fear! And not much of the latter.”
No, these 180° guy are full of it. A 4 stroke engine will never run with the distributor 180° out as the spark will happen on the exhaust stroke.
It might be better if "you" just explain to the man how to do it. I know how as I'm sure the other poster do also. But we can't explain to the exacting detail that your capable of. That way he can get his question answered and the rest of us can stop making such fools of ourselves. Heck then I would know how to explain it better in the future.
Thanks
It might be better if "you" just explain to the man how to do it. I know how as I'm sure the other poster do also. But we can't explain to the exacting detail that your capable of. That way he can get his question answered and the rest of us can stop making such fools of ourselves. Heck then I would know how to explain it better in the future.
Thanks
The easy answer is "If it runs at all, it ain't 180 out." OK?
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Bear 45/70 Gimp Racing
“There are only two things stopping you, common sense and fear! And not much of the latter.”
edmist here is some info that can help you. 4stroke animation and a text. Look for the distributer section. I have right there for you. Its not FE but the info will work for you. Take it easy.
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390 requires a lot of ign adavance to run
Second point of reference: Where are the valves on #1 cylinder? 
but I didn't like the look on his face. 
