patprimmer
New member
This is not work related, but is really getting me down. If anyone feels it should be red flagged, then fair enough.
I just built a 409 CI SBC for my very good friends social ski boat, being the boat I regularly ski behind. It has been nothing but trouble in many areas and with several changes of plan mid stream.
I will stick to the bottom end and oil system at this stage.
Crank. Brand new Eagle 4340 non twist forging std 400 CI SBC configuration.
Rods. Eagle "I" beam 5.7" stroker rods with 3/8 ARP 2000 Cap Screws.
Oil pump, Brand new (well never used, but 15 years old) Mellings 55 oil pump.
It is a so called centre mount configuration, with the motor in back to front so it drives of the timing cover end of the crank, and is close to the bottom of the boat with the flywheel and the bottom of the timing cover only about 1.5 to 2" off the bottom.
This calls for a flat wide shallow pan, that has journal #1 running into the oil, but the oil pump clear of the oil.
It has a roller cam and the lifters restrict oil flow to top end. It has 240 deg at 0.050 and 0.600 lift.
It has new Clevite cam bearings installed by a reputable machine shop.
It has new King main and big ends. These are Std +0.001" bearings.
The pick up is an OEM flat pan shaped thing that is about 4" dia, has a bottom side half cover that stands 1/4" below a fill circle screen, so it keeps the screened pick up area about 1/4" clear of the bottom of the pan.
It has a tray of sorts that presses this pick up down below oil level.
With the engine turned off and plenty of time for drain back the oil is about 3" deep and well over the top of the pick up.
The inlet port of the pump has been tapped to 3/8" BSP thread and a -8 nipple inserted with originally Loctite 515 and later with Teflon thread seal tape.
The pick up has a -8 nipple welded to it.
The pick up is connected to the pump via a 1/2 steel reinforced high pressure rubber hydraulic hose over press in -8 fittings.
The oil pump was assembled with Clevite assembly lube, and the cover was sealed down with Locktite 515. Remember this pump is well above normal oil level due to 14 deg incination of the motor.
Filter is in stock location.
Main galleries and lifter galleries had plugs removed and tapped to 1/4 BSP as required to properly clean and reseal. Plugs were checked for length so as not to cover galleries and were installed with Locktite 515.
No plugs leak oil.
Sump Gasket. Felpro one piece.
Tray is a simple hoop with rear facing louvres. It clears the crank by a country mile and really does nothing but hold the pick up down.
The sump, tray and pick up are all from the previous engine.
It has good oil pressure when started, but it falls away fairly quickly after a minute or two running. If we stop, and restart 15 sec later, it has 75 psi pressure again, but falls to 10 psi at 2000 rpm and develops a knock.
We have had it in and out 5 times now, replaced the hose, checked the pick up position in the sump, re tightened the fittings, checked cap and pump are down square etc.
It uses Penzoil 20W50 GT or something or other oil.
On original assembly, many shortcuts were taken, to the point of the owner snatching parts and tools out of my hands and doing it himself as I was "wasting time checking things". These things were ring end gap, cam timing, piston to valve, and bearing clearances for instance.
It is carby/petrol with no apparent dilution of oil. There is a little water in the oil from a previous head gasket problem due to a dowel pin holding the head off just enough so the compression sealed, but the water did not and came up one stud into the rocker box, but only very slight discolouration due to emulsification.
Every time I question the system, I get abruptly told it worked OK for 25 years.
It has about 7 litres of oil. The old engine (an old school bog stock 350 CI SBC) with the same oil system except it had a BBC pump, previously ran OK with as little as 5 litres of oil.
Bottom line.
How can an engine have good oil pressure, loose it quickly after a few minutes, then have it again 15 or 20 seconds later, then loose it again after a few minutes running on a repeating basis in a stationary position resembling attitude of normal operation. The temperature rise of the oil was minimal and had no impact on the results.
It is the quick decline while running at a fast idle, then the instant recovery after stopping and restarting that has me puzzled as it seems it is not sucking air, at least not where we can determine.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
I just built a 409 CI SBC for my very good friends social ski boat, being the boat I regularly ski behind. It has been nothing but trouble in many areas and with several changes of plan mid stream.
I will stick to the bottom end and oil system at this stage.
Crank. Brand new Eagle 4340 non twist forging std 400 CI SBC configuration.
Rods. Eagle "I" beam 5.7" stroker rods with 3/8 ARP 2000 Cap Screws.
Oil pump, Brand new (well never used, but 15 years old) Mellings 55 oil pump.
It is a so called centre mount configuration, with the motor in back to front so it drives of the timing cover end of the crank, and is close to the bottom of the boat with the flywheel and the bottom of the timing cover only about 1.5 to 2" off the bottom.
This calls for a flat wide shallow pan, that has journal #1 running into the oil, but the oil pump clear of the oil.
It has a roller cam and the lifters restrict oil flow to top end. It has 240 deg at 0.050 and 0.600 lift.
It has new Clevite cam bearings installed by a reputable machine shop.
It has new King main and big ends. These are Std +0.001" bearings.
The pick up is an OEM flat pan shaped thing that is about 4" dia, has a bottom side half cover that stands 1/4" below a fill circle screen, so it keeps the screened pick up area about 1/4" clear of the bottom of the pan.
It has a tray of sorts that presses this pick up down below oil level.
With the engine turned off and plenty of time for drain back the oil is about 3" deep and well over the top of the pick up.
The inlet port of the pump has been tapped to 3/8" BSP thread and a -8 nipple inserted with originally Loctite 515 and later with Teflon thread seal tape.
The pick up has a -8 nipple welded to it.
The pick up is connected to the pump via a 1/2 steel reinforced high pressure rubber hydraulic hose over press in -8 fittings.
The oil pump was assembled with Clevite assembly lube, and the cover was sealed down with Locktite 515. Remember this pump is well above normal oil level due to 14 deg incination of the motor.
Filter is in stock location.
Main galleries and lifter galleries had plugs removed and tapped to 1/4 BSP as required to properly clean and reseal. Plugs were checked for length so as not to cover galleries and were installed with Locktite 515.
No plugs leak oil.
Sump Gasket. Felpro one piece.
Tray is a simple hoop with rear facing louvres. It clears the crank by a country mile and really does nothing but hold the pick up down.
The sump, tray and pick up are all from the previous engine.
It has good oil pressure when started, but it falls away fairly quickly after a minute or two running. If we stop, and restart 15 sec later, it has 75 psi pressure again, but falls to 10 psi at 2000 rpm and develops a knock.
We have had it in and out 5 times now, replaced the hose, checked the pick up position in the sump, re tightened the fittings, checked cap and pump are down square etc.
It uses Penzoil 20W50 GT or something or other oil.
On original assembly, many shortcuts were taken, to the point of the owner snatching parts and tools out of my hands and doing it himself as I was "wasting time checking things". These things were ring end gap, cam timing, piston to valve, and bearing clearances for instance.
It is carby/petrol with no apparent dilution of oil. There is a little water in the oil from a previous head gasket problem due to a dowel pin holding the head off just enough so the compression sealed, but the water did not and came up one stud into the rocker box, but only very slight discolouration due to emulsification.
Every time I question the system, I get abruptly told it worked OK for 25 years.
It has about 7 litres of oil. The old engine (an old school bog stock 350 CI SBC) with the same oil system except it had a BBC pump, previously ran OK with as little as 5 litres of oil.
Bottom line.
How can an engine have good oil pressure, loose it quickly after a few minutes, then have it again 15 or 20 seconds later, then loose it again after a few minutes running on a repeating basis in a stationary position resembling attitude of normal operation. The temperature rise of the oil was minimal and had no impact on the results.
It is the quick decline while running at a fast idle, then the instant recovery after stopping and restarting that has me puzzled as it seems it is not sucking air, at least not where we can determine.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
