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Oil Pressure Help
Hello everyone,
I have an all aluminum shelby 427 Big Block engine, that has been stroked to 468 inches. I have a comp cam (roller cam), but with out the cam card I can only tell you that it is over 600 lift. I have been having oil pressure problem. When the engine was first built I was getting at idle 65 to 70 pounds of oil pressure. When the engine was hot, I was getting between 35 to 40 pounds at idle . When on the accelerator from 4000 to 6000 rpm I was getting almost 80 pounds. The engine was rebuilt once because the roller lifter self destructed. It now has been 10 years with 10,000 miles and it is now doing this: Idle cold 40 pounds. Idle hot 20 pounds and when accelerating from 4000 to 6000 rpm I am getting almost 50 pounds. We believed once again the roller lifter has self destructed. We had one problem where the oil filter seal popped and oil went everywhere. The engine was on for about 15 seconds, but I thought you might need to no this. So with just 10,000 miles should I be seeing this kind of oil pressure ? Any Ideas on where I can start? Guy |
1.Test with known good (or new) mechanical gauge.
2. Cut oil filter open and ck for metal. |
That oil pressure sounds about right to me, similar to what I get and I have a wet line gauge.
Mine goes to about 75-80 stone cold too. |
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My did that 10,000 miles ago. Now 40 pound at idle when cold and hot 20. 50 pounds going from 4000 to 6000. I also checked the oil gauge with an air house went wright to 65 pounds. This matches the air compressor. I figured the gauge was working. Guy |
Your pressure is not that bad to worry about.
Your pressure is pump volume minus all the internal "leaks", the pressure is lower all at rpms now because the bearing clearances are slightly larger. It was probably on the tight side of clearance when it was built. Pressure without flow is more than likely to fail than higher flow from lower pressure. 10000 miles in 10 years, how many oil changes has it had? Your bearings could be wearing out chemically from acid in the oil. |
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I removed the valve covers and Found one of the push rods not even close the the rocker arm.
I am not sure how to remove the rocker arm. Here is a picture. Star style nut with an allen screw. What is the procedure on how to unlock these? http://www.clubcobra.com/forums/atta...1&d=1377051988 |
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Loosen the 12 point locknut, wind out the setscrew/pushrod cup seat to set valve lash, lock the locknut. The amount of "screw" out of the nuts are different for what I can see in the photo. This tells me your adjustment procedure/preload is not the same for all valves. Can you also give some info to my questions, and why you believe a roller lifter has failed. |
I think Gaz makes a couple of good points worth addressing. Are your lifters hydraulic or solid? I'm thinking hydraulic and some failure or leak down is causing the bad valve adjustment. An easy fix would be it is just loose and out of adjustment. Start by adjusting it. Undo the lock nut and adjust the screw in the centre with the valves timed correctly. You can usually hand crank the motor over till a valve is at full opening. Then you would check adjustment on the other valve of the same cylinder. They should be adjusted till there is no play in the pushrod. At that point most hydraulic lifters require an additional 1/2-3/4 of a turn. I like to do that with the distributor out with a socket in a cordless drill so you can pump the oil up to pressure so the lifters are more like actual running conditions.
If the lifter has failed you could visually inspect valve operation with an old set of valve covers with the tops cut out. The rockers are on a short shaft for each cylinder. They have a socket screw holding each end down. I don't think you want to remove them just yet. |
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Does that allen screw need to turn Clockwise or counter? Because the allen head is on really hard. I run solid roller lifters. |
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Although we can't see it in the photo, I'll assume it is the middle pushrod in the photo that you are talking about. I would be pulling the intake off, then pulling the lifters and cam out. If you have had a roller lifter self-destruct, shrapnel will be in the sump. You say it did this 9000 miles ago, did you replace the cam as well or only the lifter? Who set the valve lash? Does it have adequate valve to piston clearance? Plus all the other clearance checks around the valvetrain? The locknut holds the setscrew, like the majority of shaft mounted adjustable valvetrains. |
Crack the star shaped outer locknut loose first. The allen head in the middle IS the adjuster and it won't move until the locknut is loosened. The rockers and pushrod will come out first, followed by everything else until you remove the lifter - which has most likely failed based on your description.
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Okay I got the manifold off. All the lifters are now loose except for the lifter above the number 8 cylinder.
The back lifter will not pull out we have tried everything. The lifter barely moves an inch, we can push it down but not up. What next?? Guy |
Most likely roller failure and has to have damaged the cam, and metal throughout. You can pull, open, and inspect the filter just on the chance it might be free of debris , but looks like you'll need to pull the engine and go through it. You said this happened before ? Pull the engine !!!
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If I changes cam, will I have to change the pushrods?
Guy |
Hi Guy,
I'll be "cruel to kind" as they say. No doubt the engine was misfiring with one rocker not operating, and it must have had some form of noise internally. Who built the engine last? What did the cam look like if you didn't replace it when your last lifter failed? Now you have to rebuild the engine again. The lifter bores will be need resizing/sleeving. NEW camshaft, NEW lifters, and the rest of the bottom end recondition as necessary. Solid roller cam needs to have lash adjusted correctly. |
I'm in North sandiego....where are you.....?...
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Bummer!!!!!! I never saw the cam, I was only told. CHANMADD "I'm in North sandiego....where are you.....?..." I am in LA Pine OR. Guy |
Guy,
Hate to say this but it needs saying: solid roller lifters do not last 10K miles.... 5K to 7K is usually the max, even with really good maintenance. If you must have them, it's a really good idea to replace/rebuild them every 5K miles. There's a new type of solid roller lifters that are advertised to run more miles; it would pay to find someone with actual experience with them before going that route. There are some new-style Crane hydraulic roller lifters that are supposed to be OK to 8500 rpm if you need that. I haven't tried them. I have run my old-style Crane hydraulic rollers 30K miles without incident so far. When you are rebuilding the engine again, I'd recommend thinking about this change. Just sayin' Tom |
I have not decided on what to do yet. I do thank you all for the information.
Guy |
That lifter has failed - the lower "fork" surrounding the roller has spread out.
Best thing is to remove the cam and try to pull it out from below because you'll bugger up the lifter bore tying to force it upward. |
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