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468 oil pressure loss

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468 oil pressure loss

brenttruck brenttruck
I love my Chevy Chevette! | Posts: 1 | Joined: 12/13
Posted: 12/01/13
11:54 PM

Help! I just got my car back from having an oil leak fixed on the inlet manifold and also replaced the lock nuts on top of the hydrolic lifters. Now it has lost its oil pressure so much so that the oil light comes on. Its a 468 chev big block with and Auto trans.
The oil pressure was fine before i had the work done. The distibuter was removed to replace the inlet gasket. Could that have caused anything to go wrong? And there is oil in it.
Any help would be great!  

waynep712222 waynep712222
V-6 Camaros rule! | Posts: 122 | Joined: 03/13
Posted: 12/02/13
08:48 PM

this reverts to the basic oil flow test...

ignition and fuel system disabled.. so it can crank.. but will NOT run..

this is only a 10 second test..

use a remote starter button.. hooked up so you can crank the engine from under the truck..  remove oil filter.. position oil pan..  crank engine. for 10 seconds..

do you get significant oil flow from the filter housing... this is to prove the pump can free flow oil and the pick up screen is not clogged..

you might want to carefully cut open the filter that was on the engine when the oil pressure vanished.. and see if the filter media failed.. crumbled and went into the engine..

depending on the year of your block.. there are.. oil pressure bypass valves that are embedded into the block..  under the filter or in or under the oil cooler adaptor..  when these hang up.. all kinds of issues happen..

if you have drained the oil.. you can use a clean wire and fish around inside the pan.. and verify the oil pickup is still attached to the pump.. that the oil pickup is more than 1/8 inch from the pan bottom and less than 3/8" from the pan bottom..  the cameras with the fiber optic lens come in handy here sometimes.. depending on the location of the drain plug..

i am taking that you have a crankcase breather along with the PCV valve.. so there is no pressure built up in the crankcase.. and even more important. no vacuum. there has been instance of the PCV system creating so much vacuum that is pulled the pan flat over the pickup screen and blocked the oil flow into the pickup ..

a little more info would be nice to know.. and might assist the other forum members in diagnosing your issue..

is it a generation IV or gen V big block..  as the oil routing is slightly different..

remote oil cooler  yes or no..

remote oil filter  yes or no..

have you performed a mechanical oil pressure test.?? using a mechanical gauge instead of electrical sending unit..

and.. a HUGE question.. is there any chance that something fell into the pan.. some excess silicone sealer..  some gasket material..  fasteners.. sludge that got washed down from the lifter valley..

these are questions only.. its best to start with the full flow filter off test.. the engine can usually crank for 10 seconds without oil pressure.. if you have the time. its easier on the rod and main bearings to do so with the spark plug out so there is no compression pushing down on the rod and main bearings...

you can also either rent, buy or build a oil pump priming tool out of an oil distributor.. so you can use either a speed handle.. ------___-o to drive the oil pump to see if its building pressure..

you could have as simple as dirt holding the oil pressure relief valve open in the pump ..  and thats not simple. but its easily fixed with a replacement pump..  

waynep712222 waynep712222
V-6 Camaros rule! | Posts: 122 | Joined: 03/13
Posted: 12/02/13
08:57 PM

oil flow after it comes out the filter.. some goes up to the lifter galleys.. some goes down the galley in the side of the block to the main and rod bearings. but also to the forward 4 cam bearings..

the rear cam bearing and lifter galleys are oiled in the conventional manor up the rear and forward..  you will have to study the bottom image carefully.

BBC Sideoilgalley Zps1ea35d93

you can see in this gen V block that there are 2 oil pressure relief valves..
you can easily see one. but look down the center hole under the filter..
Bbc Geniv Oilbypassvalves Zps6a63a959

BBC Oiling Zps83f2d446

use slider below this to shift image back and forth..