KB oil pressure bleeding away.

Hi guys.

Bit of a question thats got the crew scratching our collective heads.

We acquired a KB Stage VI block and can't get to the bottom of why the oil pressure is bleeding away to near destructive levels.

From cold, the motor in the pits has between 110-125lbs oil pressure, but the hotter the motor gets, the pressure goes as low as 45lbs after a few minutes. When we race at local track we start the car just behind the burnout box, we have about 110lbs of pressure, but by the time we have done the burnout, reversed, and coming forward into stage we are running as low as 45-50lbs of pressure.

Top end of the motor is perfect, and all of our rod and main bearings are coming out perfect, we have pressure tested the block and we have no pressure bleeding away from the system. We ran the oil pump on our previous block at Easter and had no trouble with it then, and we are running the same oil lines and fittings as before.

Anyone else had anything similar happen to them? If so, I'd love to hear from you because we are very quickly running out of ideas.

Thanks everyone for reading.

 

Info

Give us a little more info on this situation. What oil are you using? Is the oil warming up and getting thinner? Is it possible the oil isn't draining back into the pan and it is running out of oil? Dave Germain

 

Hi Dave.

We are using Shell Racing Ultra 10/60W, which we've used in our engines since 2000 or so and never ever encountered a issue like this before. The oil is upto temperature no problems and thinning out nicely (it isn't breaking down)

Like I said, we would usually lose possible 10lbs or so between cold and hot, but we are losing 70lbs or so.

As for not draining back into the pan, I admit we haven't thought about that, but I also am not quite sure how we would go about checking it. What possible things to look out for which caused that?

Thanks for the suggestion Dave

 

oil pressure

Is that the pressure from the Racepack? did you use teflon tape on the threads?

 

Don:

We don't run any on board computers, we are simply using some pressure gauges (Autometer 200lb pressure gauge is what we use). As for using teflon tape on all the threads, i'm not sure as I didn't assemble the system. We have zero leaks externally if that answers your questions. We are finding no oil in the diaper / anywhere it shouldnt.

We originally thought it might be due to the open water jacket areas in the Stage VI causing more expansion area over our Stage V block, but after more thinking and general research on the blocks it doesn't say you need to run things differently between the two stages to allow for the extra area.

Thank you for your help too Don, I'm hoping it's something simple.

 

what kind of pan are you running, and how much oil?
Darren

 

check the main webbing for a crack

 

oil pressure

I had a simpler problem years ago on a fresh BB Chevy. A small piece of tape got into the back of the gauge. That is the reason I asked. I never use tape anymore. Just liquid thread sealer. Just a easier + quick check. Good luck Don

 

oil pressure

If you are running the same oil pump and lines, same heads, same head gaskets same pan then the only thing different is the block? I would pull the plugs at the ends of the oil galleys to see if there is some junk in one of them. Then check main bearings to insure oil holes are still lined up. I have seen blocks that had 'stuff' in the internal oil passages in the blocks, especially those who have been fixed. I always pull the plugs when a block gets back to me after being machined or repaired and run a block cleaning brush through them. Also check the passage to the oil pressure guage itself as well as the gauge. Let us know what you find? Dave Germain

 

You don't say if this is a fresh block or not. Are the cam bearings new. What are your clearances. I have seen when cam bearings get worn the engine will have lots of oil pressure cold but when it warms up it drops off. These bearings are not easy to change as some engines are. KB's are stepped. They may have been left even though the block may be honed etc.
just a suggestion
Dale

 

Okay let me answer these questions:

Hi Darren, we are using a Olsen style pan with about 2 gallon (8 quarts) of oil. We've used the same amount of oil in all our previous engines.

John: We have crack tested the block and crank, and can't find anything that would cause such a large dissipation of oil pressure.

Don: I wish it was as easy as a bit of tape over a thread, that would be a real weight off our shoulders. I'm hoping it is as easy as that, thanks for giving me food for thought!

Dave: Yes the difference is the block, and we've had every blank out, and blown through the oil lines, cleaned them through, cleaned the main oil lines out within the block and no junk is coming out. We can't feel any obstructions in the block either. Our bearings line up all okay, all oil drillings line up okay too.

Dale: The block is a second hand unit which was repaired at KB themselves. It was repaired through the gallery, but we have checked the oil line and it seems fine. The block has no saddles, and the main bearings came out as good as they went in during assembly. The cam bearings are used, but i'll have to see about clearances around the cam bearings themselves.

Some possible ideas there, i'll have to see what I find. Either way i'll let you all know how we get on. Trouble is it's near the end of the season now, and we only really have one or two more racing weekends to test the car. Might have to wait until next season to see if they have worked.

Thank you all, I appreciate your efforts to help me out.

 

ok...i know that you stated you ran the same amount of oil earlier with no issues. if this is a KB Hemi, there is no way that's enough oil. we run a wet sump TFX with a KB Billet pump and Olsen deep pan.....we run 16 quarts. a chevy on the other hand would use less oil, i'm not sure how much less. 8 quarts seems pretty low to me. have you had the oil pump apart and checked things out? maybe there might be a small crack? hope this helps
Darren

 

oil pressure

Good luck, I hope it is simple for you. I know how you feel, been fighting a thrust bearing problem and my bank account all year. Only have 1 races left. & maybe a test. Haven't had a full run all year. Don

 

If you still have the old block, perhaps measure the main bore on both blocks.

Did you change the crank at the same time as the block?

 

Hi Darren:

We have had the oil pump apart, and originally thought that maybe the relief was relieving too early and too much, thus causing the pressure to drop away too much. But it seems regardless of what we do with the relief it still occurs. We have checked the two rotors and they are clean, tidy, no scoring, no horrible marks anywhere. We really need to try a different good pump, but alot of racers we know have gone to the billet KB pumps and our pump / sump combination doesn't work with billet pumps (Perhaps a area of investment during the off season!)

As for too little oil, we might try adding a few more quarts to our usual oil change. 16 quarts is huge however. But it obviously works for you which is more than I can say about our oiling situation!

Thanks again Don, I admit we were lucky enough at the start of the year to run a really stout number (6.62 @ 205), but then the motor let go 2 passes later. Ever since we've had no end of trouble. I chanced my luck a few times and ran a brace of 6's, but we are a low budget team and can't afford another complete engine failure. Hopefully you can get your car flying for your final meetings and finish on a high.

Thanks for replying Robert; we found a crack in the crank we ran before, so yes this is a new block and crank configuration, however we have measured all possible dimensions on both blocks and cranks and can find no derivation whatsoever. The only difference was that the original crank ran on standard mains and rod bearings, whereas the current crank runs on standard mains but 10 under on the rod bearings (of course running the 10 under bearings on).

Thanks again to everyone, if we can get it fixed i'm dedicating the next good run to all you guys!

 

Oil restrictors?

Different oil filter?

Different oil pressure guage location?

Crank throw widths different?

 

Have you changed lifters recently? Sometimes they can leak.

I may get bashed here but,

If nothing else works and you don't mind doing stuff others may consider stupid, you could pull the intake and pan ( put the oil pickup in a coffee can and have a hose and funnel to add oil to the can as needed ) and run a thinner oil and spin the pump with a drill to see if you can see any excessive leakage, if you don't see anything abnormal cold then put the engine in a cardboard box with a couple of paint strippers to heat the block ( yes I have heated castings this way before when welding and it works pretty well)

Just an idea, if it seems to mickey mouse please disregard.

 

we had a issue like this we started to run 16 quarts and it went away..Dave

 

oil volume

I've never heard of anyone running less than 12 quarts, most run 14 to 17 qts.

i think your sucking your pan dry.

 

I am new to this, so my experience is very limited, but I will tell you what I experienced and maybe it will help in some way.

My engine is a KB10. I saw everybody on here saying they ran 16 quarts, but didn't think it would apply to me. I only run 1/8 mile and I don't run high RPM (in fact, if I said what my top end RPM was you guys would laugh me outta here). So I put in 12 quarts of Brad Penn 70. I idle at about 130 lbs and 1800RPM. On my data recorder it shows the run nicely on the graph, but to see the shut down part of the run on the graph I have to zoom out. I had made about 7 passes before I did. Wow! About 1 second after I lifted the oil pressure dropped for a second, picked up slightly, then dropped again for about a second. After that it was fine. I talked to Dave at Secondwind and he said to put in 16 quarts. I did, and my oil pressure doesn't dip now.

In a nutshell, although it seems like alot, 16 quarts is fine. Some of these guys run 16 plus additives.

Also, I would be very hesitant to run a multi-viscosity oil. Most guys are running straight 60 or 70 on here. I can't say for sure, but it seems like Brad Penn 70 is the most popular.

-Brian