Oil pressure problem SBC409, serious help needed...

[rodek]

Hi I also wanted to ask here because after some research it seemed that here is some serious sBC oil system knowledge.

I seem to have a serious problem with oil pressure in my new SBC409. I have had experience in engine building, built 4 before and no problems whatsoever in any of these. I'm asking serious help

The engine was dynoed at 560hp/520tq, It has a small base circle mechanical roller camshaft (248/252@050"), 11,5 comression, forged parts, AFR210cc heads, stock block with 4-bolt aftermarket boillet caps, etc etc. oh Melling M55HV high volume pump too!

The problem with the oil pressure is that the pressure is constantly around 20psi below what it should be. Already in the dyno we saw this pressure drop and were cautious in running the engine. No problems arose, everything went as well as they could have gone. No problems whatsoever, except the constantly too low oil pressure. We even opened the oil filter and it was clean. No noises, nothing out of the ordinary, except more power than I anticipated and and too low oil pressure

We analysed the dynos oil pressure graph and came to a conclusion that the oil pump pressure relief valve must have been stuck of binding because we saw a bit erratic and too low pressure graph through RPM range. The pressure even got weaker when the RPMs went up:
Cold pressure at idle 40-50 PSI
hot pressure idle 15-20PSI
hot pressure 50PSI@4000RPM and dropping to 45PSI@6500RPM.....

After dyno I removed the pan, changed the pump, and started the engine... same problem with my in car mechanical gauge...
Cold pressure 45PSI@1500RPM (i'm used to seeing around 70PSI)
Hot pressure 50PSI@4000RPM (Again I'm used to seeing around 60PSI)

Now there is only one thing that I can think of but let's check the easy ones first:
All bearing clearances within spec (closer to upper limit)
All oil passage plugs in place and also the fron ones tapped for pipe plugs
Cam bearings cover the grooves in block
Oil pickup around 3/8 from pan bottom (Spec)
Center oil galley plug in front drilled for timig chain cooling (very small hole)
No outside oil leaks
Anything else???

Now the only thing I can figure out is that the small Base circle cam brings the lifters too low in their bores and thus allows too much oil to enter the small holes that supply oil to the top end

Could it be this problem?
How can I tell if too much oil is getting to the top end?

I can't think of anything more, except that melling suplied me with 2 bad pumps...

So If you have had this problem and foud the reason please let me know.

 

[grumpyvette]

ok lets explore this a bit , and youll notice IVE included links, DON,T ignore those as they contain a good deal more info
you failed to mention if you've installed a milodon or similar windage screen, thats been properly mounted so its about 1/8" outside the rotating assembly ARC of rotation, I know it may be hard to believe but I see guys stick stock 4-5 quart oil pans on $8000-$9000 SBC engines often enough , who then get that deer in the head lights look when they find they have oil control issues as a result, that I always ask because its sure not rare for guys to forget that a stock oil pan designed for an engine that will seldom see 5000rpm is hardly ideal on a performance application spinning 6000rpm or higher.
I purchased a 8 quart baffled oil pan for my 383 and extended the sump to gain 2 extra quart capacity
viewtopic.php?f=54&t=65

IF your using a crank scraper and WHAT oil pan your using and if its baffled and its depth and capacity.
your stated current oil pressure certainly falls in the expected and exceptable range, with bearing clearances known to be on the upper edge of the clearances but at the lower edge of that expected pressure range once hot.
oil pressure is a measure of the RESISTANCE to oil flow rates and you can have an influence on that if the oils being beat to a froth containing air with a low capacity oil pan and not using a windage screen to partly prevent the rotating crank assembly from interrupting the oil return to the pump or beat it to a froth, as air unlike oil is easily compressed and will lower the gauge readings, bearing support and oil flow.

on an engine of that power range ID strongly suggest a 7-8 quart oil pan with a well designed windage screen be used, and with larger bearing clearances a 15 w 40 oil viscosity, as it helps prevent oil being beaten to a froth and dragged around in the spinning rotating assembly

a high capacity oil pump simply has longer gears and pushes more oil per rotation,the PRESSURE is a function of resistance to oil flow and when the bye-pass spring opens, below the bye-pass spring opening pressure it has zero effect on the pressure, larger bearing clearances increase oil flow rates and decrease pressure especially as the viscosity drops as the oil heats up.

READ THESE THREADS BELOW CAREFULLY

viewtopic.php?f=54&t=64

viewtopic.php?f=54&t=3536

viewtopic.php?f=54&t=1334

viewtopic.php?f=54&t=2187

viewtopic.php?f=54&t=5423

 

[rodek]

Hi Grumpy,

Serious answer to a serious question, thank you!

I'm have a masters degree in mechanical engineering and do know little something about fluid dynamics and general mechanics. That is why after researching my problem I came across your posts and got interested in your serious knowledge about SBC oiling systems.
But this is not to say that I'm an expert by no means!

I have already read most of the posts before and will try to answer the best as I can.

Oil pan is 67 camaro specific 7qt (milodon or moroso) pan that has internal baffling and the engine also has a windage tray just like you have pictured in first pic (gold iridised screen type) and it is installed very close to the crank radius. Everything should be blueprinted:
Rod bearings
Main bearings (clevite grooved upper performance series for large radii crank)
New cam bearings installed exactly to factory old positions
Plug in place to divert oil to filter
ground smooth oil feed line in rear main bearing (no obstructions from pump)
pump checked to have free moving relief piston (and this is the second pump to have exactly same problem)
I checked that the pan specific pickup had 3/8 clearance

I bought an endoscope to check the easy things before pulling the engine out....
I will check the pickup clearance again with the endoscope I bought to make sure the clearance is fine with pan bolts torqued and gasket compressed.

My thoughts:
If I have lower than normal oil pressure cold idle @40PSI and it wont go more than 55PSI at 4000RPM I'm guessing that the pickup is fine, its getting the oil it need?

Someone suggested that I might have the oil level too high in the pan, but wouldn’t it be producing 70PSI at cold idle anyways if this was the case.

Should I also check the filter, and mounting adapter, and if so what to look for?

Oil is 15-40 Mobil diesel oil that I use for break in.

Could it be the lifter issue??
Hi the lifters I have are Comp edurex 818-16
http://www.summitracing.com/parts/CCA-818-16/
They also produce lifters that are specially engineered for small base circle cams
http://www.summitracing.com/parts/CCA-891-16/

These have the oil band cutout little bit higher in the lifter body, also the small hole that feeds the pushrod too. Is it possible that the oil cutout groove is too low and I'm getting oil leaking throught the bottom of the lifter bores?? I did check this in one lifter when the pan was out and it seemed that there was more than enough clearance to be on the safe side. The lifter was on base circle and I could hardly see more than the roller itself.

What about the small hole feeding the pushrod? are these supposed to be in the front to back drilled hole or in the lifter bore? Are the 16 small holes too deep in the bores to allow too much oil to the top end?

What else could cause this always too low oil pressure?
Idle or max rpm, hot or cold.
One weird thing is that I've seen engines produce more cold idle PSI but about the same hot idle PSI???
The same engines will build more top end PSI hot or cold than mine...

This really gets me confused, is there a leak somewhere or what??

Hope we can find the solution, I'll start checking the easy thing when I get the endoscope home.

Thanks already!

 

[grumpyvette]

I have not used those comp hydraulic roller lifters , but from the picture I can easily imaging the lifter effectively causing a leak and leaking oil past its lower oil passage band if the lifter bore was short and the lifter bore was not all that close to the cam lobes as it looks poorly designed to me

SHORT BODY

LONGER BODY FOR SMALL BASE CAMS


so all I can say is careful measuring may reveal the problem, but you might be correct that youll need the lifters designed for the small base cam with its slightly longer lower body to prevent excessive oil flow and the resulting lower oil pressure
Ive generally used CRANE,CROWER and MOREL hydraulic roller lifters, occasionally ERSON

Im a big believer in doing a few tests before jumping into changing parts so obviously youll want too measure the lifter bore length in relation to cam base circle and lifter body length below the oil feed groove to see if thats your major leakage issue, remember pressure is almost entirely the result of the ratio of flow in to restriction to flow out so the thinner the oil is or the larger the clearances are, the lower the resulting oil pressure reads on the gauge, maintaining consistent pressurized oil flow is more important than max pressure, and 50 psi will do all thats required even at high rpms if the flow rates are high, as that maintains the oil barrier on the bearing surfaces supporting the rotating assembly loads and cooling the bearing surfaces,you might simply want to try swapping to a 20w50 weight synthetic oil and see it that causes the reading to be closer to what you want to see before you start swapping components because if the bearing clearances are on the larger end of the scale , or the length of the lifter body is almost dipping below the lifter bores that might be all thats required
I don,t think your looking at a major problem, the oil control just needs careful study and possibly some mods, but only checking carefully will reveal the cause.
in some cases the cure is simply swapping to a slightly tighter bearing clearance that results in a slightly higher restriction to oil flow rates

RELATED INFO
viewtopic.php?f=53&t=2726

viewtopic.php?f=53&t=2727

viewtopic.php?f=53&t=3449

 

[DorianL]

Well I think I'll just grab my plastic bucket and spade and go play in the sandbox.

 

[grumpyvette]

Well I think I'll just grab my plastic bucket and spade and go play in the sandbox.

I have no IDEA why you feel that way! you've built a far more powerful engine and have a far better car than 90% of the guys on this or any other site and you've learned a great deal in the process in these threads and shown far more aptitude for the hobby than 95% of the guys I deal with.
Keep in mind that for the most part youve done the majority of the work and made most of the decisions, a great percentage of the guys with fast cars simply have deep pockets and call up some guy who builds or even builds and installs and tunes their engine, thats hardly the same skill and knowledge level

 

[rodek]

Hi

Still waiting for the endoscope..

Anyways main bearing clearance is 0,003-0,0033
Rod bearing clearance is 0,0028-0,0030
Side clearances within spec
New cam bearings installed to original places

I really can't think of anything that went wrong in the assebly process.
I even always follow my SA workbench book on SBC building to the letter.

The only thing that can leak pressurised oil must be the lifters, it just can't be anything else.
I asked Comp BTW about the reason they sell these small base circle lifters, we'll see what they answer, I'll let you know.
Heck I'll try to prime my oil pump when I get the endoscope to look for obvious leaks.

I won't be taking the engine out before summer, I'll run it atleast this summer if there is no worsening problems with the oil pressure. I'll also go to thicker oil 20-50 or something.

The easy things to check:
filter
oil level
oil quantity in top end while on idle


with endoscope:
pickup clearance
obvious lifter problem (oil band visible from below)


Anything else / more comments?

 

[grumpyvette]

I normally try to have the bearing clearances a bit tighter, now IVE seen guys use thos looser clearances successfully but they generally run a 40w or 50w oil weight
Ive tended to run
Main bearing clearance: 0.023-0.027 inch
Rod bearing clearance: 0.025-0.027 inch

and yes I think your lifter design is a contributing factor here if all the other potential problem areas check out, don,t forget that lifter diam. and lifter bores are not always right on speck and wear can cause clearance issues, ID also check the lower distributor fit to the block as it forms one wall of an oil passage, and a loose fit will bleed off a good deal of oil

viewtopic.php?f=54&t=2187

 

[rodek]

OK will do!

I'll also try thiocker oil, will keep you posted in the coming week(s) when I get more info.

Thanks you already!

 

[rodek]

Hi Guys!

I just wanted to let you guys know what the problem was in my 409... so hopefully no one will have to go through this again.

I drove the car for some time and finally got fed up with the really low hot oil pressure. The pressure really went down when the engine and oil got hot, around 8-10 PSI at idle... Well decided to take get elbow grease and tackle the situation!

Out with the engine, oil pan, intake manifold lifters and crank... Installed the oil primer tool and a large cup of oil under the oil pump pickup. LOTS OF OIL coming from the rear of the engine block around the rear cam bearing area. Turned the engine upside down and injected pressurized oil into the oil pressure gauge sender hole, WHOOO oil everywhere... the last cam bearing journal has this small hole (5/16?) for excess oil from the very back of the cam block plug to escape. This hole was ejecting oil at max pressure. Took the cam away and nothing, not a single visible thing that could have caused the oil leak at the last bearing. Took my air pressure gun and gave it some, voila!

THE PROBLEM: I installed the cam bearing exactly where the original factory bearing was, I always mark the original bearing before removing it so I know exactly where to put the new bearing back. Either the factory bearing was installed incorrectly, the new bearing is narrower or has a larger radii at the outside circumference, but the groove cut to the bearing bore was leaking oil past the rear of the bearing. This was not visible!!! the radii conceals the grooves edge so that it is impossible to see that these is a small 0.030" (ish) mismatch under the cam bearing outside radii. Gave the bearing a few punches with my installation tool and the cam bearing leak is solved!!

Will double check everything, especially the lifter bores and lifter oil groove misalignment just to be sure.

So be smarter than me and MAKE SURE TO CHECK THE LAST CAM BEARING / OIL GROOVE ALIGNMENT ALWAYS BEFORE PROCEEDING A CHEVY BUILDUP!!

BTW: I remember when buying the block several years ago from a seller that I later heard was a total cheater, that the price was very right for a 409 block. Could have been that I got a "oil pressure problem block" sold to me at a fair price...

 

[Indycars]

Hey thanks for coming back to follow up with the answer!

To clarify, is it this chamfer that you are talking about leaving the groove in the block uncovered and leaking oil ???

 

[grumpyvette]

yes THANKS FOR POSTING WHAT YOU FOUND!
from the description It seems the rear cam bearing was not installed to the correct depth in the rear cam journal, I really wish that clear picture's were posted to verify that was the issue

 

[rodek]

Yes the outside chamfer I mean is exactly as pictured in "indycars" post!
This chamfer is the reason you see and think the bearing is installed correctly but it's not!

The bearing was not installed all the way in, it was installed exactly to replace factory bearing depth.
So either the factory bearing was already installed incorrectly, the new bearing is narrower or has a larger radii at the outside circumference.

BTW I'm more than happy to give my share in this forum, this is the ONLY place to get serious help and no BS. answers to serious SBC technical problems.

 

[Indycars]

So you didn't have an oil hole that must be aligned ??? That would determined how
deep the bearing was installed in my case. But I'm using a Dart SHP block.

The rear main was different of course, but it looked something like this.



I know Grumpy would appreciate any donation!

http://www.grumpysperformance.com/index-4.html

 

[rodek]

How I recall it, the last (rearmost) cam bearing in a SBC is really hard to see if the oil hole is correctly aligned or not..
The hole is drilled at an angle from cam bearing groove to main galley and it is tilted towards the front of the engine.

It looked ok when it was put together.

 

[grumpyvette]

RELATED INFO
viewtopic.php?f=57&t=869&p=1357#p1357