Engine Problems
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Freshman User
Joined: Jul 2003
Posts: 37
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From: Bloomfield New Mexico
Engine Problems
I recently rebuilt my 360 engine (1975 F-250 4x4). During the rebuild, I converted it to a 390 by replacing the pistons and crank. I had it bored .030 and installed a 4 bbl edelbrock manifold and Carb. In addition to having the heads reworked, I installed a new Cam, Oil pump, lifters etc.
Problem: Engine uses a quart of oil every 500-600 miles. I also have weak oil pressure and when the engine idles, it exhausts what appears to be carbon (black splatter).
Diagnosis and testing so far: I have good compression on all cylinders. No fouled plugs and the engine otherwise runs and sounds good.
Any ideas on what to check/test?
Thanks
Custom 1975
Problem: Engine uses a quart of oil every 500-600 miles. I also have weak oil pressure and when the engine idles, it exhausts what appears to be carbon (black splatter).
Diagnosis and testing so far: I have good compression on all cylinders. No fouled plugs and the engine otherwise runs and sounds good.
Any ideas on what to check/test?
Thanks
Custom 1975
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Freshman User
Joined: Jul 2003
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From: Bloomfield New Mexico
Engine Problems
I have only about 5000 miles since rebuild. I run Motorcraft 10-30 oil. The choke (Electric) is fully open. I also went through the tuning procedure with the carburator. Any other Ideas?
Custom 1975
Custom 1975
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Joined: Mar 2003
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From: Green Bay Wi
Engine Problems
I know this is going to sound far out but what rings are you running?Sometimes those moly rings take a while to seat out.Cast rings seat down in no time.Also if you didnt break the glaze/hone real good can also give you the same situation.Just a guess.
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From: Sun River St. George
Engine Problems
Drive it for a while and keep an eye on the oil level. I think Hotrodfordguy is on to something, the rings have not seated yet. The soot out the tail pipe is likely normal moisture and soot found in most exhaust systems. Low oil pressure on a fresh rebuild is not good. The list of possible causes is very long and since you rebuilt this engine you proabibly already know them so I wont try to make a list. I'd just keep an eye on everything, keep the RPM's down and drive it.
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
Engine Problems
Was the crank turned? Try running 20W-50 oil. Moly rings seat faster than the others , not the other way around. The "moly" is embedded in a groove in the face of the ring, which wears down faster to seat with the bore. But y'all are correct in that if the bores weren't honed properly, that could be why the rings aren't seating. Also try installing restrictors under the rocker shafts, if you haven't done so already. This will help the pressure some. How high does the pressure get up to at higher rpm's?
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Joined: Jan 2003
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From: Balfour
Engine Problems
Do you mean it shoots black tar goobers out the exhaust? or just rich smoke? My old beater 360 used to shoot oily tar chunks out the tail pipe it had some kinda valve and piston problem on #5 cylinder. Some things you might wanna check, probaly done'em already
Climate control will make your smoke black if incorrectly set,
Blocked pcv, carbs are richened to compensate for the pcv gas and if its not there you gotta lean out the carb or fix your pcv.
weak ignition parts?
Black smoke is richness or inability to burn all the gas, theres no other cause for black smoke.
Climate control will make your smoke black if incorrectly set,
Blocked pcv, carbs are richened to compensate for the pcv gas and if its not there you gotta lean out the carb or fix your pcv.
weak ignition parts?
Black smoke is richness or inability to burn all the gas, theres no other cause for black smoke.
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Freshman User
Joined: Jul 2003
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From: Bloomfield New Mexico
Engine Problems
I did install a reconditioned crank at rebuild. I am running cast rings, so I may still need to run a little longer to seat the rings. As far as the exhaust, I would classify it more like black Goobers, but it seems to clean up once it is warm, but the black smoke does not (not a real lot of smoke but you can see it) . I did absolutely nothing to the ignition, so I am wondering if that could be a problem area. I plan to install a Performance Ignition soon. I installed a manual gauge and the oil pressure gets up to about 35 psi at normal driving speed RPM, but drops off pretty fast at idle, down to about 5-7 psi. If I need to pull it down again, I want to be sure to know what I should look for. I have never Heard of restrictors on the rocker shafts. I will look in to that as well.
Thanks alot for the good ideas. I will let you guys know what I find when I finally fix her.
Custom 1975
Thanks alot for the good ideas. I will let you guys know what I find when I finally fix her.
Custom 1975
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Joined: Mar 2003
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From: Green Bay Wi
Engine Problems
So its black smoke not blue?One other thing i thought of was if you forget the valve seals on the intake side you can get the blue smoke going on and consumption of oil.I had assumed when you said it ate 1qrt pet 600 miles that it was blue smoke.
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Engine Problems
Sorry if this offends you, but you did use the correct undersize bearings for the reconned crank right? If the crank was turned .010 then you need .010 bearings, not standard. If you were to use standard bearings on a turned crank, you would have very low oil pressure, and maybe some knocking.
I ran 10w 30 when I broke in my engine and it had over 35lbs at idle hot. I have a High Volume pump though.
Try 20w50, that should help alot, 30 is pretty thin unless its winter.
Brian
I ran 10w 30 when I broke in my engine and it had over 35lbs at idle hot. I have a High Volume pump though.
Try 20w50, that should help alot, 30 is pretty thin unless its winter.
Brian
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
Engine Problems
To restrict the oil to the rocker shafts, unbolt them and on one of the 2 middle bolt holes you will see the oil passage angling down toward the head bolt. Get a pair of Holley #82-88 jets ( they don't have to be exact, but the holes need to be around .090 in them) and stick one down into the passage on each head, then replace the rocker shafts and retorque them to 45 lf/lbs.
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From: Long Island USA
Engine Problems
It sounds like you're running so rich that the gas is washing off the oil from the cylinder walls and you are burning it off. That would account for the excessive oil consumption, and the black carbon from the exhaust.
Be aware that running too rich will starve the cylinders of oil and cause premature ring/piston failure.
Been there, done that
As for the low oil pressure, make sure you are at least using 10w40 at less than 80 degrees F, and check the rockers for excessive shaft clearance. You should also have restricted the oil feed to the rocker shaft.
ak
Be aware that running too rich will starve the cylinders of oil and cause premature ring/piston failure.
Been there, done that
As for the low oil pressure, make sure you are at least using 10w40 at less than 80 degrees F, and check the rockers for excessive shaft clearance. You should also have restricted the oil feed to the rocker shaft.
ak
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From: Bloomfield New Mexico
Engine Problems
I took the advice of several people that were kind enough to post Ideas for things that I could check on my 360/390 engine. I finally decided to pull the engine and have another look.
What I found was the first time I had my heads reworked, the Machinist must not have replaced the valve guides. They were shot! So I got to spend another $200 on the heads for guides and valve and seat work. Also during the first rebuild, I did not do anything with the rocker shafts (shame on me) . They were also worn quite a bit. While I had the engine out I took a look at both the rod and main bearings as well as the cam bearings. They all looked fine. I decided not to go any deeper in the engine at that point. I did however, go through the carburator (Edelbrock 1406 4bbl), and went back with 2 size leaner jets.
I went with 20w50 valvoline oil.
Results:
Oil pressure on start-up: 70 psi droped to about 60 psi after warm up.
I will need to run her for awhile and see if my oil consumption slows down (was using about 1 qt. every 600-800 miles.
Thanks to all who posted answers to my questions, you guys are a lot of help!!
What I found was the first time I had my heads reworked, the Machinist must not have replaced the valve guides. They were shot! So I got to spend another $200 on the heads for guides and valve and seat work. Also during the first rebuild, I did not do anything with the rocker shafts (shame on me) . They were also worn quite a bit. While I had the engine out I took a look at both the rod and main bearings as well as the cam bearings. They all looked fine. I decided not to go any deeper in the engine at that point. I did however, go through the carburator (Edelbrock 1406 4bbl), and went back with 2 size leaner jets.
I went with 20w50 valvoline oil.
Results:
Oil pressure on start-up: 70 psi droped to about 60 psi after warm up.
I will need to run her for awhile and see if my oil consumption slows down (was using about 1 qt. every 600-800 miles.
Thanks to all who posted answers to my questions, you guys are a lot of help!!
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