Interesting oil pressure problem

[Alan Roehrich]

Dart little M block, Callies DragonSlayer crank, H beam rods, in a 377 (4.175" bore, 3.48" stroke, 6" rod) set up for a turbo. Comp roller cam and premium solid roller lifters, Comp 3/8" pushrods, Yella Terra rockers, first pump was M-55HV, in an 8 1/4" deep 7 quart Moroso pan, with Moroso pick up. Has Dart coated cam bearings, about 0.0015" to 0.0002" clearance. Clevite H series rods and mains, 0.0025" on the mains, 0.002" on the rods.

With no restrictors in the lifter galleries, and 7 quarts 10W 30, it makes 40PSI at 1500 RPM, at the beginning of a 3000 to 6600 pull, 200 RPM per second, it has 64, but at 5700 it starts falling, drops to 50 by 6600. New K&N race filter doesn't help. Put plugs in the rear of the galleries, leave the front open, no change. Put 0.150" restrictors in the front of both galleries, leave the back blocked completely (best, according to Dart) switch to M-99HVS pump (big block pump, made to fit a small block) with a 3/4" pick up. Pick up is 3/8" off the pan, with both pumps. Now makes 45 at idle, makes 68 at 3500, and stays at 68 until 5700, drops to 57-59 by 6600, still at 200 RPM per second pull.

Both oil pumps have about 0.004" to 0.005" side clearance, and 0.0015" end clearance. The M-55HV is bypassed to the pan (did not change), the M-99HVS is not.

Dart is no help, other than telling me "man, this block flows a LOT of oil" and I have "a windage problem" after 1.5 hours of phone time. Seems Dart has seen this before, they claim the fix is a trick windage tray, scraper, etc. Melling says both pumps are in spec.

I don't buy the windage line. I've done 1/2 dozen or so 383 engines (4.040"x 3.75" 6" rod) with the exact same pan, pump, pick up, and oil. Those were all low budget engines too, all Eagle bottom end, and they had no pressure issues, had 65+ and were either the same or better pressure as you went up from 4500 to 6500, never a drop in pressure. The 377, with better, smoother stuff, and a shorter stroke, will have less windage than the 383 engines have.

It's back off the dyno, I have found nothing, bearings look great. Two separate gauges, pressure taken at the front shows 5-7 psi less than the rear, same drop at the same RPM. I see nothing wrong in the galleries or gallery plugs.

Customer intends to turn 7000 to 7200, up to 20PSI + on boost, and as much HP as he can make with a 100MM turbo and a 1000CFM throttle body, so I need to solve the oil pressure problem with absolute certainty.

[Tuner]

7 quarts

Have you tried it with 6 quarts?

[Alan Roehrich]

7 quarts

Have you tried it with 6 quarts?

Tried 5, 6, 7, and 8.

[Tuner]

Rats, I was looking for the easy one. Engines need a baffle, windage tray, whatever whoever wants to call it, between the crank and the sump to keep the oil slinging off the crank from blowing the oil away from the pickup - like trying to fill a bucket with a fire hose.

This is probably crazy but is the nipple for the oil line to the gauge protruding into the oil passage where there is a flow of sufficient velocity to make a pressure drop? Like the little brass nipple in the choke side primary bore of a vacuum secondary 780 Holley, which boosts the signal to the vacuum diaphragm to facilitate opening the secondary. Fluid velocity=low pressure (Mr. Bernoulli, et. al.)

[Stevespeed]

You need to work on your oil drainback. I try to add oil drainback lines off the back of the heads in any type of serious wet sump application. The bigger the better. Minimum -8. If the heads have the accessory bolt holes in the upper outer corners it makes for any easy fix. The bolt hole will have a boss cast around it and with it's location there won't be any water above it. If it's a cast iron head drill and tap the 3/8 bolt hole to 3/8 npt (you need to verify your casting has enough metal) no deeper than the original hole. I have 3/8 npt taps full length, shortened a little and shortened a lot. A standard pipe tap will be too long for the short drilled depth. Tap in the three steps to get proper thread engagement for the 3/8 npt by -8, -10, or -12 AN fitting. Screw the fitting in full depth. Now, looking from the inside of the valvecover area, drill a diagonal 1/4 inch hole from the inside corner where the oil makes the 90 degree turn to the drainback hole on the head. Your target will be inside the end of the hole you just drilled and tapped. You will drill through the threads of the fitting you just installed. You use the small size drill to allow for aiming errors. Once your pilot hole has found it's target, drill and diegrind / blend a bigger hole into the fitting. Be aware of water. Weld a bung in your oilpan above oil level but preferably below / behind screens / trays etc where oil won't have to return into a hurricane. The bigger the better on the line size as it lets the crankcase ventilate as opposed to trying to push the return oil back up a small line. If your heads are aluminum it's even easier. Bypass the drilling and tapping and just tig weld a bung of the appropriate size in line with the same bolt hole. I try to blend a cusp into the inside corner of the head to try to intercept the oil before it returns to the valley and ends up all over the crankshaft. Flowing lots of oil is good. Most people don't have a way to get it back in the pan though.

[beth]

The oil spinning off the crank and rods and the air disruption of the spinning crank and rods whip the oil in the sump but there is another disruption from the displacement of the lower cylinder volumes that must pass back and forth under the main caps. With taller and wider main caps this disruption is forced closer to the oil level.

I believe you have to have some type of baffle between the crankcase and the oil sump.

[Stevespeed]

Good feedback from you all, but with this just being a 3.48 stroke crank at relatively low rpm, it seems very clear to me to be a drainback issue. Especially after seeing a slightly better result from adding .150" restrictors.

[Stevespeed]

By the way, I like solid windage trays with a scraper edge built in and clearance around the tray to allow oil to drainback, separating the crankcase from the sump. Anti climb shelves welded under the tray to keep oil from climbing out of the rear on acceleration and climbing out the front on braking. Custom built or heavily modified oil pans to go along with the drain lines. My experience comes from blown alky pro-mod drag race stuff and Baja winning off road trucks. Your wet sump CAN act just as nice as a dry sump.

[redvictor]

On that combo forget the wet sump.With the acceleration forces he'll have in the car a wet sump will never cope with the oiling.Believe me,we found out the hard way..
min 3 stage and preferably 4 stage.
The oil goes to 3 places in a turbo drag race engine when it'sat the track. Right up the front,right up the back,and in the valley. Everywhere else has minimal oil.
Also don't forget that your oil system is feeding the turbo and you have to account for that.
Just a heads up..

[Alan Roehrich]

There's not that much oil in the heads, and this thing has huge drain back slots in the lifter valley, there are no screens in it. There's maybe 2 quarts in the top of the engine. There's no reason for it to have a windage problem that causes an oil pressure problem, I've never had a windage problem like that before at that RPM, that stroke, with the oil pan being that deep.

[dale]

i had a simular problem when i changed from a standard chev block to a dart little m block ,same oil pan . oil pressure light would come on at around 6500 than go out when i backed off. the only thing we changed and solved the problem was to lower oil level and move the pickup as low as possible it now revs to 7800 with good pressure.

[robert1]

I guess my question would be if you are letting oil drain back through that huge slot over the cam, is it oil by the time it reaches the pan or is it foam. It may be getting whipped up pretty good by the time it gets past the cam and crank. I'm building one now that's a dry sump and I'm covering the slot.

[xenginebuilder]

There's not that much oil in the heads, and this thing has huge drain back slots in the lifter valley, there are no screens in it. There's maybe 2 quarts in the top of the engine. There's no reason for it to have a windage problem that causes an oil pressure problem, I've never had a windage problem like that before at that RPM, that stroke, with the oil pan being that deep.

But, not with that block, right?
The amount of "oil in the top end" is not just what you pump through the pushrods.
I have never used that block, so what I am going to say has to do with engines that I have worked on using different components.
Valley oil drain backs- Unless the cam tunnel is sealed off below, any openings above the cam in the lifter valley only drain oil back to the crankcase at less than 3000 rpm. At 4000 add above, oil is being pushed through those openings at a high rate and there is no drain back possible. Tubes and stand-offs just aim the oil spray, otherwise are worthless for "windage control" at any rpm that you care about. The larger the openings, the more oil is pushed through those openings. Blocking all those openings and adding an external drain at the back of the china wall that drains to the oil pan is one solution that works very well, as well as additional external lines as proposed by Stevespeed . Usually a drain in the back and the large opening in the front china wall is adequate to handle "valvetrain" related oil drain back.
If you don't believe this scenario, make a lexan valley tray under the manifold that you can watch what happens on a dyno.

I also have to comment, not that I haven't built similar engines in the past, but why the low ball oil pump on a "budget" (?) engine that involves aftermarket crank, rods, pistons, block, heads, turbo, etc. etc.? If you have to use a wet sump, a single stage external oil pump is so superior to a distributor driven pump in so many ways. I agree with redvictor that for this combination a dry sump would be the best, but when you compare the cost of that build against a stock type pump....JMO

[jamie]

Are you running this motor NA on the dyno or is the turbo hooked up?If hooked up,how much boost is it making when this happens?

[promachine]

Alan, What is the oil temp doing during the pressure drop?