360BW

Oil/Hydraulic Experts,

I'm not new to engines or racing but this issue puzzles me and I'm now wondering if a complete rebuild was necessary!

I recently had a new race engine purpose built for my road racing interests. It was broken in properly and did not show any signs of pressure issues at idle or start up, After properly getting the oil up to operating temps I started to consistently see low oil pressure under full throttle, while driving down the long straights of my local track. I've never never seen anything happen like this before. When i say problems i'm talking like max 35 PSI on a new motor that was previously idling at 55PSI. Motor is an LSx stroker but nothing exotic.

Since that time the motor has been completely replaced with all new components and i'm ready to run it again. The builder could never pin point the problem so he basically started from scratch with a new shortblock. As i'm going over everything i just noticed that the builder never installed a check valve (one-way flow valve) in the T-fitting for the accusump running in the line between the pump and the oil cooler. Could the accusump be causing these issues without a one-way flow control to keep it from pushing against the pump?

I'm not debating that i really need one and will soon be installing it but i'm now wondering if this was the source of the pressure issues.

Experts I'd love to hear from you!

Lou, David, Randy or anyone else out there with a first hand understanding of oil flow control...what do you think?

Cobra4B

^ FYI before my LS4 oil pump (high volume oem pump) I would see mid 30's oil pressure at full throttle when my oil was hot (270+ pre-cooler install). When I put my cam in I installed the LS4 pump and now see no less that 50 psi at all times (full throttle, I see high 40s at idle).

I run Amsoil 5w40... so I guess what I'm saying is that your pressure doesn't seem off for a high temp oil... do you run an oil cooler? What weight oil do you run?

360BW

10W40 and yes an oil cooler. However I have never experienced and wouldn't expect to see those kind of pressures under full load with no G-forces. Yes in turns but never under full accelaration in the straights.

I don't want to mis-direct the dialog on this post. My question is specific to the check valve missing. I've got a call into Canton but I thought i would start here.

Thanks for your response.

AU N EGL

How much oil do you have in?

I have 10 1/2 qts in the engine, oil pan, 3 qt accu-sump and lines.

When I change the oil, I let as much drain out as possible, then switch on the sump. Normally I get 9-9 1/2 qts out. I am not worried about the remaining qt-qt 1/2

When I full it back up, Sump switch is OFF. I put in 6 1/2 qts.

Start the engine and let the oil circulate.

add a quart ( 7 1/2 total) switch on the sump, rev the engine to get the oil pressure up, the sump starts to fill, add another qt ( 8 1/2 total now).
Rev the engine up more keeping an eye on the oil pressure gages, dash an and the sump. add an extra 1/2 qt.
Now I am close to what drained out and the sump is filled.

Take the car for a short drive, watching the oil pressure. Get home rev the engine to get the oil pressure up and to fill the sump.

Switch off the sump, shut the car off. Come back hour latter and check the dip stick. Normally need about 1/2 qt at this time and now back to what drained out and the sump is full.

RAFTRACER

A missing in-line check valve for your accusump will not cause low oil pressure.......I know alot more about this than I have the time to type right now. I'll be back later tonight.

I went through the low oil pressure with higher oil temperatures for 3 months last year....made me

360BW

Then we have the exact same set up and that sounds very familiar

360BW

That's what i am trying to confirm that the in-line valve is not the source . The builder was confident he had component issues. Temp wasn't extreme although on this particular adventure. Conditions were probably 250 oil temp and 220 Coolant. I've seen hotter temps with better pressures on a seasoned engine so I'm just trying to make sure we had component issues and not a $20/part.

Thanks for your thoughts!

0Randy@DRM

The check valve is a good idea but not needed and isn't your issue. I like angel's theroy on the problem. My S10 when it got low on oil would do the same thing. When you say LSx, is it a GM block or aftermarket. The engine builder deal with LS engines often, because I have a few more ideas if he is a novice to the LS engines. If he is a novice LS builder then there is about 5 less then 20 dollar parts that can cause crazy issues.

Randy

0Randy@DRM

New block or used???

360BW

Randy it had plenty of Oil and it was a seasoned block - LS6 with darton sleeves. As for engine builder its someone everyone would recognize so i'm not going to call them out as I'm not interested in dragging anyone through the mud. I just wanted to make sure it wasn't the lack of a check valve.

I'm going to install one anyway after i speak to Canton.

Thanks for your reply!

RAFTRACER

So a couple of questions....When the motor is cold and first fired up , engine oil temperatures around 100 degrees what is the pressure @ 1k,2k,3k,4k etc ???? What is the pressure at those same engine speeds when the oil is 200+ degrees???? How hot is the oil when you are registering sub 40 pressures, and what rpm ??? Does it max-out below 40 psi at any engine speed ??? Additionally how is your cooler ran in relation to your accump ???? Is the accusump T'd into the return (from the cooler) line close to the engine ???? Or is it tied inot the galley plug at the front of the block ??? What camshaft and lifters ??? Whose cooler are you using and what size AN lines

I fought a sleeved LS2 block earlier this year of my own for a long time. It always made resonable oil pressures when the oil was cooler, but when hot it had really low oil pressure and would max out in the low 40's no matter what engine speed . I played with all sorts of internal pieces ( lifters, pumps, bearing clearances), but what majoritily fixed my hot oil pressures was sleeving the lifter bores in the block to tighten up lifter to bore relationships, and at the same time using the sleeves to retrict how much oil is fed to the lifter ( individually by smaller orifice ) . When the engine is hotter with higher lift camshafts to lifter bores bleed, alot. This is scary since the lifters and camshaft are fed before the rotating assy. My oil pressure is alot better now (55-60 @ 220 degrees ) , but I can still generate more than 300 degree temperatures which creates low pressures 45-50 @ 7.5k rpm...still makes me nervous. High engine speeds = high oil temperatures = low oil pressures. My car has stock ls6 pump with higher pressure bypass spring. I may go to the high volume GM pump soon, or dry-sump. It has so far survived 6 hours of track time and a 40 minute race ...and I am not easy on it . Occasionally I will look down at 300 deg oil and see 39-40 psi on a corner exit, but you also have to remember that the oil pressure gauge is "buffered" and is not real time.

Another thing that I have seen happen is for the cam bearings to walk partially out creating an oil galley leak ( this happened to me after we sleeved the lifter bores ). Supposedly the aftermaket camshaft bearing do not contain as much hard metal, so they dont have as much tension on their bearing crush. My engine has the GM cam bearings now.

Another thing to consider is that some EOC's have higher pressure drops than others. I acutally picked up oil pressure by switcing coolers.

0Randy@DRM

Ok,
There is a couple plugs that are pretty common to miss for a Novice LS builder. But it doesn't sound like that is the issue.

Randy

360BW

Thanks everyone and Danny i will keep you posted!

rustyguns

davidfarmer

Normally you have highest oil pressure at high rpm UNLESS you are starving your oil pump. This should not happen unless your bearings are too loose fitting (too much oil slips between the bearings and rotating parts), or there is a problem with oil drainage back to the oil pan.

I think maybe it's an oil pump problem. There is a spring in the pump that lets oil bypass if there is too much pressure....basically a pressure regulator. The spring can be too loose, or be sticking.

Thanks to GM's Gib Huftetter, I've always put a 150/1000th's" thick shim behind my oil pump spring (in the cap), and normally get oil pressure up in the 70psi range cold, 50-60 hot. It varies from engine to engine, but I like it better than having 20psi hot.

As for the accusump, you dont' need a flow valve. If you get starvation, you need to completely fill the oil system, so having a bit go "backward" to the pump is OK. If you don't get the full system full of oil before the accusump runs dry, you are still going to be running your bearings dry. However, for best results I like to go into a dedicated block galley, like shown in my DIY guide.

I'm a firm believe in accusumps, for Prelube as much as for on-track protection. However, if you already have an oiling problem going straight, an accusump won't fix it. I have an accusump fitting guide on my site http://www.davidfarmerstuff.com/

spankythegator

I am having the exact same problem with my new motor....except I don't have an accusump....will do the checks that Danny suggests to see what I get

360BW

Ok, thanks to everyone for jumping in. I got Randy, Danny and David! I also spoke to Canton who also confirmed that this was not an issue and in fact i don't necessarily need the check valve. So hopefully the new motor is done correctly. We shall see.

Spanky, i hope you figure it out!

varkwso

My new motor never sees more than 45 psi but it never gets below 20psi at idle. It is really slow to build oil pressure on a cold start also. My 44K ZO6 has better pressure. The hottest my oil temp has seen is 190 since it has not been to the track yet.

My engine builder states it is well within the guidance for LS1/6 motors...but I do not like it a lot.

RAFTRACER

Those sound alot like the reasons I repeatedly took mine apart..

You keep an eye on that thing when you run your first event. I am thinking if you dont like your pressure @ 190 deg, your defineatly not going to like what you see @250 deg +.

C66 Racing

I agree. Though covered a little bit above, I'd emphasize not to overlook the oil's viscosity drop as it heats up. Example, Mobil 1 at 100F has a viscosity of about 64.8 cSt, at 212F 11.3 cSt and at 300F 3.09!!!

It is for this reason that I run a 10w40 in my car on the track where higher oil temps are common. In my case I've chosen to use the AMSOIL SAE 10w40 Formula 4-Stroke Marine Synthetic Motor Oil which has a viscosity of about 4.6 at 300F, about 50% higher than the factory fill.