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Old 07-14-2008, 07:30 PM
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oil pressure complete loss

chev LT1 immediate loss,lifter clatter oil level full. I replaced with new oil pump and shaft pressure gauge and checked with mechanical gauge. stumped.

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Old 07-14-2008, 09:12 PM
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Are you using a Fram oil filter? They are junk , this has come up one several forums and I've seen it myself, they collapse in on themselves internally.
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Old 07-14-2008, 09:24 PM
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I have collapsed two frams. One was on a gm 4.3 v6 and the other was on my hotrod. On the hotrod it looked like a crushed soda can. Both went to about 5psi for oil pressure at the most.
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Old 07-15-2008, 10:32 AM
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reply to scapegoat

thanks for the tip i will check it out.
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Old 07-15-2008, 10:35 AM
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ericnova

thanks for the info i will check it out.
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Old 07-15-2008, 11:05 AM
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make sure you didnt lose a lifter out of its bore!
that will give you no oil pressure
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Old 07-15-2008, 11:50 AM
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Quote:
Originally Posted by Jack Dore
chev LT1 immediate loss,lifter clatter oil level full. I replaced with new oil pump and shaft pressure gauge and checked with mechanical gauge. stumped.
What does the pressure gauge read? The lifter clatter tells the story, zip oil pressure regardless of indicated gauge pressure.

The way the SBC is laid out is that the lifters could starve while there is pressure in main galley from either something blocking the lifter galley feed passage or (and more likely) a passage plug in a (2 of them) lifter galley blew out.

If the engine's main galley doesn't show pressure, it could indicate that plug is blown on the main (center) oil galley. There is a plug on the front and rear of this and the lifter galley passages a set under the timing cover another behind the flywheel/flexplate. A leak inside the timing cover would just go to the pan, a leak off the rear will be everywhere on the outside.

One could consider the main pressure passage off the pump into the block management ball, which divides the main passage so oil will flow thru the filter, could have migrated up to block off the return passage from the filter which would cut off all flow into the engine.

The pick up could be blocked or leaking. This would reduce or stop intake of oil to the pump, though if you replaced the pump I would expect you would have seen any pick up problems.

The LT1 is a tricky build up of the pump drive, there is the gear and stub shaft, a collar that aligns that with the pump shaft, then a retainer and bolt that keeps it all together in the absence of a conventional SBC distributor; is all that there?

In addition to the usual Chevy filter there is an adapter for an oil cooler, a couple lines and the cooler. Assumption is that there could be something obstructing these passages which would cut off the oil feed to the engine.

Then of course is the usual loss of bearing clearance which leads to excessive oil flow thru the bearings and aback to the pan, though this is usually indicated by very low pressure rather than none. At idle there might not be any pressure, which then picks up with RPMs.

Bogie
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Old 07-15-2008, 12:45 PM
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Oldbogie

Thanks for all your info I think your a shop manual in disguise. It looks like I got a lot work to do. Thanks again.
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Old 07-15-2008, 01:07 PM
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oldbogie:
im having what I think is a top end oiling problem when the motor is warmed up.. I get lots of lifter clatter.. although I do have lots of oil coming up through the pushrods im trying to troubleshoot this issue.. I have plenty of oil gauge pressure at the rear of the engine.. 35-40 psi at idle and 50-60 at cruise....

im just not sure where to look for obstructions / and or missing plugs, restrictor plates etc. i do know all 3 galley plugs are in the back and not leaking.. and that the plugs in the timing cover are installed... hard to tell if they are leaking or not but they are tight and if leaking wouldnt be enough withy my oil PSI as high as it is to cause lifter rattle...

ive even replaced the lifters thinking they were the issue.. is there a pressure port on the motor somewhere that i can measure for lifter galley pressure? will I visually see anything if I pull the intake and drill spin the oil pump? ive never had to get into the internal oiling circuit of an engine before..
-Christopher
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Old 07-15-2008, 04:08 PM
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Quote:
Originally Posted by eldoradoboy
oldbogie:
im having what I think is a top end oiling problem when the motor is warmed up.. I get lots of lifter clatter.. although I do have lots of oil coming up through the pushrods im trying to troubleshoot this issue.. I have plenty of oil gauge pressure at the rear of the engine.. 35-40 psi at idle and 50-60 at cruise....

im just not sure where to look for obstructions / and or missing plugs, restrictor plates etc. i do know all 3 galley plugs are in the back and not leaking.. and that the plugs in the timing cover are installed... hard to tell if they are leaking or not but they are tight and if leaking wouldnt be enough withy my oil PSI as high as it is to cause lifter rattle...

ive even replaced the lifters thinking they were the issue.. is there a pressure port on the motor somewhere that i can measure for lifter galley pressure? will I visually see anything if I pull the intake and drill spin the oil pump? ive never had to get into the internal oiling circuit of an engine before..
-Christopher
If the engine is holding good oil pressure, which it appears that it does, and there is good flow from the push rods, but the lifters clatter, it would appear that the problem is the lifters aand or their adjustment.

- Leak down lifters such as Rhoads tend to be noisy on idle as they tend to develop some lash which is what makes the cam timing look shorter at idle.

- The lifters you have a a bad or incorrectly machined bunch.

- Excessive wear between the lifter bores and lifters that doesn't shut off the bleed hole, allowing the lifters to leak down, or the bleed hole being miss positioned on the lifter.

- Rocker and pushrod geometry incorrect making rocker sit too low when adjusted resulting in running out of stud threads before lash is adjusted. Gets to be an issue with milled or aftermarket heads, incorrect push rod length for cam lift and or rocker ratio. Can also be wrong lifters for the block such as 4.3 lifters in a 5.0 or 5.7 block. The V6 lifter is shorter than the V8 requiring a longer pushrod if cross pollinated.

Bogie
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Old 07-15-2008, 04:38 PM
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i have had several lt1's in the shop with the same problems as you, all of them had spun cam bearings.

sam-missle
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Old 07-17-2008, 08:56 AM
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sam-missle

thanks for the tip sam another place to look. jack
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