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Old 10-18-2009, 04:18 PM
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Troubles with SBC 350 rebuild

Here is my dilemma. I just finished rebuilding a SBC 350. The original engine was pretty clean and did not need to be machined as well as the crankshaft did not need any machining. So I used standard bearings, pistons and rings. Used plastiguage on the bearings and all were within specs. I put in a mild cam with new bearings as well. The holes on all the bearings were aligned and everything was torqued and re-torqued. Now I am getting OK oil pressure at the start when the oil is at room temp, some oil comes through the rods with oil priming with the correct priming tool and a good drill, and now as the engine runs, but not much oil. Pressure at start up is over forty on the in car gauge and close to forty on a mechanical gauge on the block by the distributor. As the engine warms, the pressure will state near forty at 2000 rpm's in the car, but drops on the mechanical gauge. At idle the pressure is low around 10. The lifters get noisy as the temp warms as well. The valves were set at zero lash one cylinder at a time, then tuned by listening as the engine ran. The oil pump is new as well. I am thinking three things. One, the bearings have too much clearance, two, the oil pump is bad some how or has issues with the pick up, or 3, one of the welch plugs in the front is leaking. Some how my pressure is not what it should be and the top is not getting enough oil. I am looking to see what other opinions you folks may have, and what step would you take next if you were me.

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Old 10-18-2009, 04:52 PM
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I am not going to be much help, but who knows. When I rebuilt my chevy 360 I was running around 70psi at start up and 45-55 when warm. My warn out 5.7 is getting 60-70 or 80 if I forget and punch it while its still cool. You definitely have an oil pump or flow issue. Have you tried any lucus additive? My 440 in my 66 imperial likes to run about 40 at start and when it gets hot it goes down to about 20 on and off. Sorry I couldn't have been more help.
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Old 10-18-2009, 05:12 PM
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maybe the engine ate a cam lobe then chewed up bearings.

all the rocker moving about the same at idle?
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Old 10-18-2009, 05:15 PM
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Quote:
Originally Posted by 454C10
maybe the engine ate a cam lobe then chewed up bearings.

all the rocker moving about the same at idle?
All the rockers seems to be ok and I changed the oil this week and looked through it and the filter (Wix) well and I did not see any material in it.
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Old 10-18-2009, 05:30 PM
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The description sounds like an oil galley plug popped out behind the cam. You definitely have a massive internal leak.
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Old 10-18-2009, 06:38 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
The description sounds like an oil galley plug popped out behind the cam. You definitely have a massive internal leak.
Normally when there is a failure with the gallery plugs, do they leak or just pop out?
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Old 10-18-2009, 06:50 PM
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A leak would not be that noticeable. Probably popped out. Note: There are two different size oil galley plugs used on small block chevies. If you accidently get the smaller size in the hole, it won't stay.
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Old 10-18-2009, 07:11 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
A leak would not be that noticeable. Probably popped out. Note: There are two different size oil galley plugs used on small block chevies. If you accidently get the smaller size in the hole, it won't stay.
They both would fit, just one much more snugly than the other. If that is the cast, it's good to know that, as I certainly could replace all three if one has popped out.
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Old 10-20-2009, 05:37 AM
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Did you install new cam bearings? Incorrect cam bearing installation can cause an internal oil pressure leak if the oil channel/groove is exposed due to the bearing either driven in too far or not far enough.
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Old 10-20-2009, 07:42 PM
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Was the oil pump pick up spaced correctly from the bottom of the pan?

Sometimes a new oil pump will have chips from machining left in them- the bypass could be fouled.

If you're running a Fram oil filter, try an AC Delco to see if there is a difference. Fram filters have always worked well for me, but some users have reported problems w/them and a filter swap is an easy thing to try, at least.
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Old 10-20-2009, 07:54 PM
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Quote:
Originally Posted by cobalt327
Was the oil pump pick up spaced correctly from the bottom of the pan?

Sometimes a new oil pump will have chips from machining left in them- the bypass could be fouled.

If you're running a Fram oil filter, try an AC Delco to see if there is a difference. Fram filters have always worked well for me, but some users have reported problems w/them and a filter swap is an easy thing to try, at least.
Thanks for the reply. I have a Wix filter on engine and one of the big questions is, would a new high volume oil pump be the issue? Is it a good chance or a slim one. I know I could just pull the pan, but I am looking for as many opinions as I can get before I tearing into things.
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Old 10-20-2009, 07:56 PM
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Quote:
Originally Posted by GMC boogie
Did you install new cam bearings? Incorrect cam bearing installation can cause an internal oil pressure leak if the oil channel/groove is exposed due to the bearing either driven in too far or not far enough.
I did have new cam bearing put in after the block was cleaned and honed. I don't know about the groove so that could be an issue.
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Old 10-20-2009, 08:23 PM
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Quote:
Originally Posted by Gun Laker
Thanks for the reply. I have a Wix filter on engine and one of the big questions is, would a new high volume oil pump be the issue? Is it a good chance or a slim one. I know I could just pull the pan, but I am looking for as many opinions as I can get before I tearing into things.
It isn't so much the high volume pump being a problem as it is any new pump. It might have bits of iron chips left over from the machining process that could cause the bypass valve to hang up.

The issue of proper spacing of the pump pickup to the floor of the oil pan isn't dependant on the type of pump, either- rather it's the issue of the pickup's placement. I like to shoot for 3/8" between pan and PU, measured with a gasket in place.

Because a high volume pump is longer than a standard pump, sometimes -if the pickup is attached by eye to match the angle the standard pump/pickup had- the pick up will be too close to the pan's floor for proper oil flow. Aeration and cavitation will be the result.
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Old 10-21-2009, 05:21 AM
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oil

First vote would be for a missing plug. If the block was cooked. and it's done this since day one.

It is not the cam bearings. In order to expose the groove in a chevy that bearing would need to be 1/2 ways out the bore. It would have stuck out like a sore thumb when you were putting it together.

Second would be excessive clearance in the bearings. You stated that you checked them but not was the actual clearance was.


In all my years of doing this I have never seen a oil pump be the casue of low oil pressure on a small block chevy. It's always another issue.



Keith
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Old 10-21-2009, 06:02 AM
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Did you install the oil galley plugs or did the machine shop?
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