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Post by 1924vette on Mar 7, 2009 23:31:29 GMT -5
I have a 1986 Chevette engine in a 1924 Model T. I just finished putting it together. It has a noise in the top end that sounds like a lifter tick. At idle or under accelleration, it's OK. When coasting at about 30 mph or getting up to highway speed, I hear the noise. It also ticks just before the automatic transmission shifts gears. It sounds like one lifter. After installing a new stock cam, lifters, followers, and oil pump, it still does the same thing. It also has a new timing belt and water pump. The engine has 90,000 miles on it. The compression is around 140 in all cylinders. I checked one of the main bearings when I did he oil pump and it did not look wore out. The oil pressure runs up to around 30psi and idles at about 10psi. I have tried 10W-40, 20W-50, and 5W-30. Nothing gets rid of the noise. Do I need more oil pressure? Do I have a weak valve spring, or is it something else? I am not a Chevette mechanic, but I'm learning as fast as I can. Thanks, Mike
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Post by #29 Phillip on Mar 8, 2009 6:41:19 GMT -5
i believe you need more oil pressure then your getting..., might be time to rebuild it, thats just my opinion...
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Post by hydroli on Mar 8, 2009 7:11:52 GMT -5
Someone can confirm me, since I've red what I say. In the oiling circuit, there's an area where the pushrod that activate the fuel pump passes. If there's too much play between the pushrod and the casting, there will be a presure lost from this area.
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Post by DOCTOR FIELDS on Mar 8, 2009 8:29:52 GMT -5
You both are correct. You should have a minimum of 30 - 35 psi at idle. I'm betting you have a bad oil pump. I put one together several years ago and it dropped oil pressure, come to find out the oil pump shaft was bent.
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Post by rad15E on Mar 8, 2009 13:23:31 GMT -5
all the above are correct lol-the fuel pump rod will change the oil pressure if it has a lot of wear but a good tight bottom end should hold at least 30-40 lbs. at idle and up to 70 at high rpm,the is a way to build more oil pressure in the pump but it has to be out of the block to change it-----one other thing i have nevver liked fram oil filters they restrick oil pressure
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Post by 1924vette on Mar 8, 2009 17:24:43 GMT -5
Thanks for the replies. I have worked on it today and it is low oil pressure for sure. Now I have to find the cause of it. I will check the fuel pump rod. Has anyone ever adusted the oil pump bypass to raise the pressure? I've done that with Harleys by using a shim on the spring. Mike
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