Oil Pressure Worries

[TheBirdistheWord]

I recently had to have my A87 peanut head rebuilt,  It appears the head wasnt good to begin with,  frustrating considering I paid to have a machinist "look over" it before I assembled it.  I would think it goes without saying I didnt bring it back to him.  I put about 8k on a brand new build with weak valve and stem seals, and during this time the oil pressure always seemed reasonable, just under 30psi for the first 500 miles and then 20-25psi after that.  I have a reman ebay turbo ZX pump, and it appears from other posts on here my pressure should be in the upper 20 psi range.  Once I diagnosed the head problem and got it serviced, I thought my pressure would have gone up a bit considering I have real compression now but it hasnt.  There has been a notable power gain since the head service, and it hasnt subsided, if there is a piston problem I would assume the power wouldnt be there or would have dropped off by now with 1000 miles on the new head and almost 10k on the block.  The pressure has been hanging around 25psi when I am being nice to it, but eventually falls to 20psi or gets there quicker when I am getting on it.

 

I was playing around today and spinning it to about 4500-5000rpm and as I came to a stop off of the freeway exit I was greeting by a nice billowing cloud of white smoke from my exhaust and oil psi dipped to a tad under 20.  I was expecting there to be smoke knowing I probably didnt remove every last bit of carbon build up from the top of the pistons, just not this many miles after.

 

Is there some wiggle room with the recommended oil pressure? or did I miss something crucial on my first build? should I consider bumping up the weight to a straight 30w or 20w-50 oil?  Could my rings have taken damage when I was removing the carbon?  It seems from the look of my plugs it has been running a bit on the lean side, with a primarily white ish grey color with just a spec of golden brown on the very top of the plug.  Anyone think this could have something to do with this or could it just be another symptom?

 

Any input is appreciated!

[flatcat19]

Compression test said what?

 

And buy a new KA-E oil pump. 

[EricJB]

Not trying to alarm you, but 20 psi oil pressure would scare the Hell out of me. I set my motor up pretty loose, with a stock used pump that had a couple shims stacked in the pressure relief, and anything above idle is 60psi. First thing I would try is a different gauge. If you are using an electric one. make sure you have a good ground strap to the body. Typically mechanical ones are more accurate.

Valve stem seals have no effect on oil psi. Valves properly seating will help with compression, but again have no effect on oil psi.

 

Fatten up the carb (s?). Do a few plug tests at different throttle positions to find where it is lean. That could get ugly. Check for vacuum leaks as well.

[datsunaholic]

Even my most worn, 320,000 mile engine holds 30psi at anything over 1500 RPM.  But 30 is all it gets, too.  Even on cold start, maxxes out at 30.  But falls as low as 12 psi at idle.

 

As stated above, there's no correlation between compression and oil pressure.  Valve stems seals aren't in the oil pressure loop.  In fact, unless you had a head with extremely worn out cam towers or a cam with the gallery plug missing, any head work won't have an effect on oil pressure.  Oil pressure is dependent mostly on the relief valve setting and the condition of the main and rod bearings, since the crankshaft is where most of the oil goes.

 

Oh, and just because it's a ZX oil pump doesn't mean it was rebuilt correctly or the relief valve was set properly.

[datzenmike]

As Doug said. The billowing white cloud indicates that the crank main and/or rod bearing have too much clearance, possibly put together too loose or just plain worn out and are bleeding oil too much and dropping the pressure. This oil 'leak' is throwing way too much oil onto the cylinders and over coming the oil control rings.

 

If this is the case the bearing can be checked/changed without removing the crank but the engine will have to come out.

 

 

What's the history on this engine?

[TheBirdistheWord]

I should have clarified, all of the psi readings I mentioned in the first post are at idle, anything over 1000rpm has consistently been 60psi, and it has never dropped lower while running over 1000rpm with this build. Using a mechanical pressure gauge connected at the pressure switch port and I have used multiple gauges to rule out a faulty gauge. Im now thinking billowing was the wrong adjective to use. It was one hefty cloud half the size of the dime at deceleration off the freeway, but didnt continue or come back again.

From what you guys are saying, it actually seems my oil pressure is within spec if not above average. I will say I have never read or heard anything about the pressure relief valve, which kind of concerns me. But again, my pressure readings have been consistent with what I have mentioned, and it would seem it is acceptable. I had this block bored .40 over and the crank polished by the same guy who "checked" my head initially.

I personally assembled it from the crank out, new rod and main bearings the mains were .25 oversized and the rods were std and with plastigauge I measured clearance to be within range respectively. The rod bearings were on the looser side but within tolerance. New pistons and rings, reused the rods.

 

I guess the real question is; Am I over reacting?

[banzai510(hainz)]

Am I over reacting?

 

YES!!!!!!!!!!!

 

put new oil say 20-50 and when cold Im sure youll get 40 psi at idle/ when warms up I have had it low also up to 40 at idle.

 

buy the Napa oil filters if your going to buy over the counter

[datzenmike]

Is the turbo oil pump from an automatic? Those were the only ones that had the high volume I believe. If not new order a 240sx KA24E or any Hardbody with KA24e or KA24DE oil pump. I think the pressure could be higher at idle.

 

All oil pumps have a pressure reliefr valve. Volume (and pressure go up in direct dresponse to engine RPMs. I had a relief valve fail once and it blew the oil filter off. The relief valve can be shimmed with washers to raise the pressure when revved up. There is no way to adjust the idle pressure, it's a function of idle volume from the pump and how much oil bleeds past the bearings. Twenty is absolutely fine for idle as it's got no load on it, I just expect higher.

[TheBirdistheWord]

I have been using wix filter without a hitch but may try the napa filter next oil change.  I just checked my old rockauto order to verify which pump I have and it turns out I bought a reman KA24E pump, not the turbo zx pump I previously mentioned.  It just slipped my mind I ended up getting that one instead.  I plan to do a compression test soon, and I have verified no vacuum leaks are present.  

 

However, it is a bit hard to find my timing mark on the crank pulley with a light, I am still able to accurately set the timing it just hops around and disappears frequently.  anyone know if I can do anything to remedy that?

 

Thank you for your help!

[datsunaholic]

NAPA filters ARE Wix filters.

[banzai510(hainz)]

mark the crank with white model paint.

 

a l16 will have like 5 or 6 notches and the L20s use a single notch but have a sawttooth timming sheetmetal bolted to the front cover.

[TheBirdistheWord]

I have a L16 crank pulley with a L20 sawtooth position indicator, and I marked it when I had the head and front cover off recently so I know its on point mechanically.  that mark seems to come one go when trying to time it with a light.

[banzai510(hainz)]

Unless you previous marked it when the crank is at Zero during assemble. with a ink pen or a scibe mark to the front cover

I dont know if the L16 crank correspodes to the L20b sawtooth stamping. Highly doubt it so I dont know if you get a good reading.

 

wheres the l20 pulley?

 

if timming light looks like it bouncing around?? you have points????????? dist shaft wiggle? no springs in dizzy/ or dizzy weights off. Timming light junk?

 

Coil getting HOT? feel it. alot of kids put newer coils in there and cook the points or remove the ballst and coil get hot. esp if running points

[TheBirdistheWord]

I marked it when I installed that head and everything was at tdc. Electronic ignition, I guess it wouldn't be too far fetched to assume the kragen light is a cheap pile of turd. I have timed it accurately with these existing components without this issue. So ill check that first.