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Old 03-14-2012, 09:04 PM
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leaking oil pan on a 400 small block chevy

i have a 1977 chevy c10 with a 1982 built 400 small block i bilt the block a half a year agoe and have had oil leaking from the front and rear of the oil pan. i have gone through 7 seals from (4 pice to a 1 pice rubber and cork) and 3 new oil pans . i have pulled the engine out and redone all the seals and still is leaking oil frome the pan. i put die in and found no other leaks. the oil leaks while driving and when it is shut off. i have oil all over the passenger side wheel and frame. i have a pcv and a breather.

i have found while the engin is runing and you take out the breather or pcv it smokes out of the valve cover

i have ran 5w30 and 10w30 oil and the leak is the same

i need to fix the leak im going through a qurt of oil in 2 weeks

i need ideas to why it is doing this and how to fix it thanks

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Old 03-14-2012, 11:25 PM
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a lot of times the oil pan does not meet up with the timing cover or rear cap evenly which causes the rubber seal to fit tight on one side and loose on the other side causing a leak or the seal gets tweek because of uneven pressure from the oil pan.. Sooo to fix this issue, you first must trial fit the oil pan on the engine and secure with four bolts one in each corner, then take a look at where the oil pan meets the timing cover and the rear cap. Look for an uneven gap where the rubber seal would be, note the gap.. now take the rubber seal and sand very lightly on the sideof the seal that has the tightest gap when you trial fitted the oil pan, use 80 grit paper and lightly sand a bit of material off the outside edge of the seal where it meets the oil pan.. then re-install seal and oil pan, look to make sure as you bolt down the oil pan that the pan does not sqeesze out the rubber seal on one corner or so, if so, then sand a bit more of the seal untill there is an even pressure against the rubber seal from the oil pan... follow this tip and it should fix your issue

hope this helps
Jon
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Old 03-15-2012, 12:29 AM
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Quote:
Originally Posted by jacob 1977
i have a 1977 chevy c10 with a 1982 built 400 small block i bilt the block a half a year agoe and have had oil leaking from the front and rear of the oil pan. i have gone through 7 seals from (4 pice to a 1 piece rubber and cork) and 3 new oil pans . i have pulled the engine out and redone all the seals and still is leaking oil frome the pan. i put die in and found no other leaks. the oil leaks while driving and when it is shut off. i have oil all over the passenger side wheel and frame. i have a pcv and a breather.

i have found while the engin is runing and you take out the breather or pcv it smokes out of the valve cover

i have ran 5w30 and 10w30 oil and the leak is the same

i need to fix the leak im going through a qurt of oil in 2 weeks

need ideas to why it is doing this and how to fix it thanks




I thought gm stopped production of the 400 in 1980. At any rate, if you have smoke from the breather and you recently rebuilt, you may have additional problems. Regarding the pan, are you sure you have the correct front seal (There is a thick seal or a thin seal depending on the pan). Also check the the 3/8 threaded hole on the front of the block, passenger side, just above the pan. Actually two holes, one on top of the other, about 1" apart. One of these holes is bored directly thru to the fuel pump push rod cavity. If not plugged you will drop lots of oil.
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Old 05-06-2012, 07:52 PM
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there are a few different oil pan seals for the small chevy's there is a thik one and a thin one, if the motor is an 81 and the timing cover and the oil pan are stock it will use use the thin front seal. most aftermarket pans require the old thick one that was used 55 - 79. i just rebuilt a small block 350 and its a 73 and it used all the thick gaskets to put it together. and i have no leaks, also if it is the stock pan and timing cover then check them for trueness along the bolt holes if any are bubbled then i would reccomend replacing the parts and try again.
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