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Hello I am new to the forum. I have a question for Moses Ludel. Moses my uncle and I have rebuilt a 505 performance 4.6L stroker due to the main, rod and cam bearings worn out prematurely. The motor had roughly 12,000 miles on it before I loss oil pressure and upon tear down noticed the bearings were worn out. We have since rebuilt this motor, utilizing a new scat crank with all new bearings and rings. The block was vatted and did not require the cylinders to be oversized but instead a light hone was done. We chose a complete Comp cam kit (68-232-4) we were not able to use the valve springs from this kit due to the retainers not fitting the valve stems correctly. So we used the existing springs that were used with the 505 Performance cam which was the (266/272-14H). We just fired this motor up yesterday for the break in process and the lifters will not prime up and the top end rattles. In addition we seem to have a timing issue (popping at the exhaust above 1800 rpm). I am kind of at a loss on what our issue is.



Any help would be appreciated,


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manderson72...So if I follow the sequence, it sounds like this 505 4.6L stroker long engine had an oiling issue that starved the main, rod and cam bearings for oil.  The original problem may still be plaguing the rebuild that you just completed...Let's start with basics.  You need to clarify why the engine lost oil pressure or had restricted flow in the first place. 

A functioning oil pump ("pressure okay") is not enough.  Oil also needs to flow with proper volume through the lubrication system.  First, some questions regarding how the original bearings failed:

1) Did you have what seemed like normal oil pressure when the original bearings failed? 

2) Did you run the engine either without oil, low on oil or on a very steep incline that could have dry-sump'd the oil pump and starved the bearings of oil? 

3) Was the oil pump screen in the correct position within the oil pan, submerged properly in oil and not creating a dry sump issue or failure to pick up oil?

I am unclear about all the work you and your uncle have currently done.  My concern is whether the camshaft bearings were changed and whether you are you using a new oil pump and pump gasket.  Questions regarding the current light rebuild:

1) Did the machine shop install new camshaft bearings?  (Bearings not installed in proper alignment will prevent oil flow through the lifters and to the crank bearings.)  Was there any mention of a "spun cam bearing(s)"?  Were the original cam bearing oil holes aligned with the block feed holes?

2) Is the oil pump pickup screen attached properly to the oil pump?  With a new gasket?  Is the gasket properly installed between the oil pump and block?

3) The debris from the original bearing failures would clog an oil pump pickup screen.  Is the oil pump pickup screen new and tightly fitted into the pump body?  

4)  Did you prime the engine oiling system before start-up?

6)  Is the oil filter stand the correct type for the engine and chassis?  You have a YJ or TJ Wrangler?

The issue with backfiring would not be surprising if the valves are not opening properly or reaching adequate opening height due to no prime.  Of course, the valve timing (chain and sprockets) could be off mark.  Before considering valve timing, however, if you did not prime the oiling system or there is no oil pressure registering on the gauge, prime the oiling system before trying to start the engine again. 

Note: Another cause of valves not seating is wrong pushrod length.  You will find several discussions about the use of a CompCams pushrod gauge to check each pushrod's length.  If pushrods were reused and installed in their original valve positions, this may not be an issue. Otherwise, if backfire persists after resolving the oil flow problem, check the pushrod lengths.  This can be done with the cylinder head in position and rockers loosened.  Follow these guidelines that we have discussed:



Oil priming can be done by removing the distributor and using a priming tool to spin the oil pump with a stout (1/2-inch) variable speed drill motor.  (I use a pressurized Goodson Tool oil canister, but for one-time use, that's way too costly.)  I pull the coil wire or disconnect the battery to prevent engine firing and rotate the crankshaft with a ratchet and socket while priming the engine.  This allows each lifter to prime without the pressure of valve opening on the lifter plunger.

Valve springs should not be an issue.  If the 505 build springs were for a performance camshaft, the springs should have enough seating force and spring height to work with the new camshaft you describe.  Though not a likely problem from the work described, make sure the springs are not coil binding:  compressing completely at full lobe lift and not allowing the rocker arms to move.  Beyond that, 1,800 rpm should not create valve floating.  Begin with separating issues.

Until the lifters have oil (through priming with the pushrods and rocker arms installed and rockers torqued in place), there's no way to judge the lifter or valve opening heights.  Begin by priming the oiling system unless something else in my questions or comments sparks a solution. 

Let us know what you find...I'll watch for your reply.


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  • Moses Ludel changed the title to Freshly Built Jeep 4.6L Stroker Six Issues on First Fire Up

Thanks Moses for replying. I received this 1998 Jeep TJ on a trade around a year ago, I was told that the motor had around 8,000 miles on it and after dissasembly it appeared to be very low mileage, due to the cross hatch on the cylinder walls was very prevalent and absolutely no ring groove at the top of the cylinder walls. The head appeared to have been freshly worked as well.

The engine gave me no problems for 4,000 miles, then while driving I noticed the oil pressure was running lower than normal between 20 to 30 lbs, (it had previously been running 40 to 50 lbs depending on rpms), Iran this lower oil pressure for around 15 min then the oil pressure dropped out to 0 the top end was rattling, I pulled over, and called a friend to bring his trailer and I trailered it home. I changed the oil pump and would have around 20 to 30 lbs until it got to operating temp and then it would drop out. The old oil pump pick up tube was in the correct location and did reach near the bottom of the sump, the new milling pump was identical of the one it replaced and as was the pick up tube.

Pulled the motor disassembled and found the main and rod bearings completely worn with copper showing full width and full circumference, the two center cam bearings were gouged in the centers full circumference, the two outer bearings showed no obvious issues. 

We reused the head as it was including the push rods that were checked for straightness. We primed the new oil pump prior to installation, but did not prime the lifters. 

The machine shop only vatted and removed cam bearings and did not install the new ones, they also performed the light hone.

My uncle installed the cam bearings and I assume they were installed in the correct orientation but did not see them before the cam was installed.

When we started the new motor it had immediate oil pressure between 50 to 60 lbs depending on rpms. I was planning on using a long flat head screw driver extension in my high speed drill to spin the oil pump at high revs. to see if this corrected the lifter issues.

I will definitely the oil priming you suggested, thank you for your help!! I will definitely let you know the outcome.

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manderson72...Focusing on the initial tear down condition and how the oil pressure stumbled down to zero, it sounds like the most likely culprit was oil starvation at some point, which damaged the bearings, and they gradually wore out.  I would guess that with all bearings failed, the engine either ran dry of oil or experienced an extensive, extremely steep climb or descent that starved the engine for oil.  The bearings scored badly, and bearing clearance increased at the damaged bearings. 

Oil pressure dropped from the camshaft, rod and main bearing oil bleed-off.  Excessive bearing clearance or scoring will cause the damage you describe at the cam bearings.  Rods and mains worn into the copper is a clear sign of rapid bearing wear, which usually originates with an oil starvation issue...As bearing clearance gets extreme, the oil pump volume is meaningless.  Oil simply runs off the bearings without resistance, and therefore the oil pressure drops.

At this point, unless you ran the engine for a while, priming would be a first step.  Your priming method will work, use care not to damage the oil pump tangs.  If the engine has already run considerably, priming will not make a big difference. 

Here is the explanation for oil flow/routing within your engine.  Note that the oil goes from the full-flow oil filter directly into the block and to the main oil gallery.  This gallery is the direct feed for the hydraulic lifters.  No oil at the lifters, likely no oil to the camshaft bearings, crankshaft bearings, valvetrain or other critical areas in the engine.  Read this through carefully:

The pump draws oil through the screen and inlet
tube from the sump at the rear of the oil pan. The oil
is driven between the drive and idler gears and
pump body, then forced through the outlet to the
block. An oil gallery in the block channels the oil to
the inlet side of the full flow oil filter. After passing
through the filter element, the oil passes from the
center outlet of the filter through an oil gallery that
channels the oil up to the main gallery which
extends the entire length of the block.
Galleries extend downward from the main oil gallery
to the upper shell of each main bearing. The
crankshaft is drilled internally to pass oil from the
main bearing journals (except number 4 main bearing
journal) to the connecting rod journals. Each connecting
rod bearing cap has a small squirt hole, oil
passes through the squirt hole and is thrown off as
the rod rotates. This oil throwoff lubricates the camshaft
lobes, distributor drive gear, cylinder walls, and
piston pins.
The hydraulic valve tappets receive oil directly
from the main oil gallery. Oil is provided to the camshaft
bearing through galleries.
The front camshaft
bearing journal passes oil through the camshaft
sprocket to the timing chain. Oil drains back to the
oil pan under the number one main bearing cap.
The oil supply for the rocker arms and bridged
pivot assemblies is provided by the hydraulic valve
tappets which pass oil through hollow push rods to a
hole in the corresponding rocker arm. Oil from the
rocker arm lubricates the valve train components,
then passes down through the push rod guide holes
in the cylinder head past the valve tappet area, and
returns to the oil pan."

If you follow the above description, you can see the possible trouble spots.  There must be full volume and pressure of oil at the "main gallery".  This feeds to virtually everything else except the rocker arms, which receive oil up through the pushrod tubes from the lifters.  The lifters, of course, depend upon good oil pressure and oil flow volume at the main gallery.  The key is getting good oil flow into the main gallery.  Below are illustrations of lubrication flow for AMC/Jeep inline 232/258 engines.  (Couldn't find these illustration in later Mopar FSMs.)  In any case, this is similar to your 4.0L/4.6L:

1979 AMC-Jeep 232-258 Inline Six Engine Oiling System (4).jpg


1979 AMC-Jeep 232-258 Inline Six Engine Oiling System (1).jpg

Trust this is helpful...Here if you need further assistance...


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Thank you again Moses for your help! We did run it for a total of approximately 30 mins, the first time was around 10 minutes between 1600 to 1800 rpm until we got it to operating temp. then we let it cool down and ran it again for 20 minutes between 1500 to 1800 rpm with an occasional rev to 2000 to 2200 rpm. At no time did we ever see the oil pressure lower than 50 lbs.

So maybe my best course at this point is to pull the motor and disassemble and inspect for any damage components and thoroughly clean all the oil passages. 



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manderson72...As much work as that seems, there's apparently either no flow or inadequate flow of oil into or through the main gallery.  A remote possibility is oil pump cavitation from the screen tube not sealing at the pump, the pump gasket not sealing or an oil filter adapter somehow blocking flow.  Though these are unlikely possibilities, you can read normal oil pressure without enough oil flow volume.  Cavitation from oil pickup leakage can reduce oil flow.  If you do need to change the screen, use an oil pump screen installation tool.  They sell for as low as $20 and reduce risk of damaging the tube during installation. 

If there is bearing debris floating through the engine, the new oil pump pickup screen could be clogging.  Pulling the engine down now may save the new crankshaft and cam bearings.  When you have the cam out, inspect the cam bearings and their alignment holes with the galleys.  Make sure there are no restrictions anywhere in the oil passageways.  You mentioned block "vatted" cleaning.  Was this done at a machine shop?  They usually remove the gallery plugs before tanking a block.  This step specifically addresses stubborn or impacted debris in passageways.

There are bore brushes and flushing tools available from Goodson Tools (professional grade) and elsewhere that can scour and flush the main gallery and other critical oil passageways.  Install new replacement block plugs when you open up the main oil gallery for flushing.  Dorman, Pioneer and others offer these plugs, often as a "kit" with new freeze plugs.

If you get the Goodson Tools, brushes or improvise with a similar brushing and pressure flushing approach, you can do this work at home.  Some items related to gallery cleaning that you will find helpful:


Considering the amount of bearing material that circulated with the original oil pressure loss, the block passageways and even the crankshaft passageways would need cleaning.  Observe what comes out during cleaning and flushing:  You want a clear explanation for the current lack of oil circulation through the lifters.  Take apart your new oil pump and inspect for debris or any damage.  Clean the pump.  Reverse flush the oil pump screen (still attached to the pump).  Inspect the screen carefully with a magnifying glass.  If debris is visible or suspected, replace the screen.  The crankshaft passageways could have debris if the main gallery was not thoroughly clean during engine assembly.  The main gallery is past the oil filter.  If you plan to reuse the new bearings, inspect bearings for any signs of embedded debris.  Cut the oil filter apart and inspect pleats for signs of metal debris...Install fresh oil and a new oil filter before start-up.

Your new lifters should be set aside in their removed order.  Install them in the same bores to match lifter/lobe contact patterns (even though the engine only ran briefly).  I would carefully disassemble each lifter and clean out any debris.  Make sure plungers move without restriction.  Lube the lifter bases and sides with engine assembly/camshaft lube during installation but do not fill or "pump up" the lifters with oil.  During valvetrain installation, the lifter plungers must be able to move.  If filled with oil, the plungers will stay extended during initial cranking and can cause valves to hit the pistons on some engine types.

Measure the pushrod lengths.  If you did not machine the head or valves/seats, and if every pushrod is the same length, you likely have properly fitted pushrods from the original 505 build.  (It's reasonable to assume that 505 checks lifter clearance and fits pushrod lengths.  If you discover pushrods are different lengths, you need the CompCams gauge to determine where each pushrod should go.)  You're not changing the heights of the valve stems or machining the head or block deck.  If you either need or want to verify pushrod lengths and proper lifter clearance, you can invest in the CompCams gauge (a $20 item).  Confirming lifter clearance is always a safe bet.

When you reinstall the timing chain, make certain the valve timing is correct.  Once the valvetrain (including pushrods and rocker arms) is fully assembled, you can prime the oiling system while hand rotating the crankshaft (battery disconnected!) to fill each of the lifters.  This is easy to do with the spark plugs removed.

Let us know what your find...You need to find something tangible that explains the lack of oil flow to the lifters.  You can post photos if helpful.


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Thank you again Moses,

The machine shop did remove all threaded plugs and freeze plugs prior to the vat cleaning. 

I have ordered the Comp Cams 7704-1 pushrod gauge, and prior to pulling this motor out I am going to check my pushrod length and in addition pull the timing cover off and check the gear alignment to be sure that everything is correct. I am going to remove the oil pan and oil pump inspect for debris and bearing material. 

One thing that concerns me is that I could not get a good measurement on the existing head gasket used, so I chose to use the Mahle 54249 head gasket which is 0.040" thick. So with that said I am not sure that I went back with the correct gasket thickness and will check to see if my pushrods are adequate or not.


Again I really appreciate you taking the time to help!


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manderson72...Mike...I'm puzzling why the main gallery could be plugged after that kind of commercial vat cleaning unless debris was, literally, packed into that passage or brush cleaning did not back up the vat tanking.  Bore brush cleaning is the only assurance of open passageways....Any solution with the engine still in the chassis is worth pursuing.  Did you thoroughly clear out the oil passages in the tubular pushrods before installing them?  If necessary, I like your idea of dropping the pan and looking for debris and bearing material before taking the step of removing the engine from the chassis. 

The Mahle head gasket at 0.040" is a slight bump in compression over the OEM head gasket (typically 0.052" +/-).  This would make the head set slightly lower than with a Mopar gasket.  A lower head height would increase the lifter preload.  I would check pushrod lengths before disassembly.  This will provide some insight;  measure the pushrod lengths when removed...After the head is back in place and torque'd to spec, install the rockers and use the gauge to determine correct pushrod lengths at the right lifter preloads.  Do not order pushrods until the engine is assembled and the final preload(s) can be checked.  If you change head gasket sources, there will not be an issue.

I agree with your latest approach and would rule out all other possibilities before removing the engine and disassembling it:  oil pump, pickup, oil filter adapter and flow to main gallery, clogged (accessible) passageways that can be tested and reached with the block in place, etc., etc.  Definitely remove the oil filter and open it up carefully to inspect for metal (especially bearing overlay, babbitt and debris) in the filter pleats.  This can be very revealing.  Do this before dropping the oil pan.  You may have enough answers here.

Fortunately, dropping the pan with a one-piece gasket is not major work.  (Fel-Pro makes a great replacement gasket that comes with plastic threaded plugs that temporarily hold the gasket corners in place when working overhead.)  Checking the oil screen, tube and pump, looking for debris in the pan and so forth makes sense before the bigger step of pulling the engine.  Also, though I'm sure you have looked at this, be certain that the distributor drive gear (Camshaft Position Sensor/oil pump drive gear on later C-O-P engines) is intact and that the oil pump drive slot and the distributor tang engage properly.


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