Oil pressure under braking

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Oil pressure under braking

Post  BigRigTech on May 31st 2016, 9:27 am

I need some opinions please guys.  Wink  I had some trouble on sunday if you saw my other thread. We found #7 exhaust rocker stand busted off the head and the push rod in 2 pieces. No piston to valve contact. The cam and lifters look fine. The head is going out to be fixed tomorrow, I'm putting new valve seals on them while I have it apart as I see some oil leaking by. I put new 175lb coil over springs in the front of the car this spring and now under braking the low oil pressure light comes on pretty much every run because the car noses down so much more and it's not easy to stop and keep that light off anymore. The light comes on a 15psi.  it only happened before if I really piled the binders on with the old stiff springs. The pan is baffled but I think I need to improve it. I have a Melling HV pump with King bearings. I usually see 50-65psi of pressure at the stripe with 20w-50 VR1 oil and a Jomar filter. I'm crossing the stripe around 6800 now on the 275 drag radials, but I'm putting 3.70 gears in place of the 3.89's to bring that down to 6500 and closer to my peak HP.

I'm wondering if I'm filling the valve covers before the finish line? The valley is polished and the drain back holes are chamfered. It's a SFT cam with notched Johnson hygrade lifters.

1: should I try a stock pump? The bearing clearances are handy to .003"

2: can I just buy 2 new lifters for the two that it spit out? I don't know which one came from which bore...Or should I just put these back in and run them where the cam is broken in long ago? I also discovered that oil from the valley is leaking into the rear ports on either head. They are both wet with a film of oil.






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Re: Oil pressure under braking

Post  dfree383 on May 31st 2016, 10:24 am

A accusump system might be a good solution
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Re: Oil pressure under braking

Post  BigRigTech on May 31st 2016, 11:19 am

Yeah I was thinking about that too. I wonder if a pan with kick-out's would help?
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Re: Oil pressure under braking

Post  dfree383 on May 31st 2016, 11:36 am

BigRigTech wrote:Yeah I was thinking about that too. I wonder if a pan with kick-out's would help?

A better pan could help some, what does the current baffles and tray look like?

What do the bearings look like?
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Re: Oil pressure under braking

Post  BigRigTech on May 31st 2016, 11:43 am

I had the pan off this winter and the bearings looked great but I'm wondering how they look now after last weekend. I'll see if I can find a pic of the inside of the pan. I got it used from a forum member.
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Re: Oil pressure under braking

Post  Paul Kane on May 31st 2016, 1:03 pm

You need to minimize the oil slosh at deceleration and keep it around the pickup.  Switching to a standard volume pump isn't going to help that.

Take a look at the inside of your oil pan and think about what can be done to keep the oil down in the sump....and this includes preventing the oil from climbing up the rear of the pan at launch/acceleration as well as preventing it from running forward during deceleration.

Before any of the above, it might be insightful to try adding a single quart to your current oil level and watch how that affects pressure drop during deceleration.  By the way, if the pressure drop is only for a couple of seconds then I doubt it will destroy your engine which is probably generating perhaps 20-40 hp during that time.
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Re: Oil pressure under braking

Post  BigRigTech on May 31st 2016, 1:49 pm

Paul Kane wrote:You need to minimize the oil slosh at deceleration and keep it around the pickup.  Switching to a standard volume pump isn't going to help that.

Take a look at the inside of your oil pan and think about what can be done to keep the oil down in the sump....and this includes preventing the oil from climbing up the rear of the pan at launch/acceleration as well as preventing it from running forward during deceleration.

Before any of the above, it might be insightful to try adding a single quart to your current oil level and watch how that affects pressure drop during deceleration.  By the way, if the pressure drop is only for a couple of seconds then I doubt it will destroy your engine which is probably generating perhaps 20-40 hp during that time.

It comes on and it goes out as I apply the brakes any ways hard at all. I have 8L in it now. This pic has 10L in it after the dyno oil suction problem a couple years ago.



here's the link to that thread.

http://www.429-460.com/t20823p25-dyno-day-tomorrow-guess-timates

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Re: Oil pressure under braking

Post  maverick on May 31st 2016, 6:09 pm

dfree383 wrote:A accusump system might be a good solution

Absolutely.
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Re: Oil pressure under braking

Post  Lem Evans on May 31st 2016, 7:46 pm



A solid louvered tray like the Ford Racing designed unit would be better, in my opinion. But, don't over look what Paul said about just adding a qt.

Decel pressure drop is always an issue with rear sump pans. I'm just looking for 12 psi rather than zero psi in some cases Laughing

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Re: Oil pressure under braking

Post  BigRigTech on May 31st 2016, 10:35 pm

I found a pic of the inside of my pan. I could modify it now if you guys had some suggestions? I was thinking about an accusump previous to this so that may get installed regardless. 10L of oil had my windage tray submersed and the crank was swimming on the dyno to fix the suction problem. I have 8L in it now.

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Re: Oil pressure under braking

Post  away on June 1st 2016, 9:44 am

I have a std volume pump, oiling mods done to the block (restricted cross-over and cam bearings), bushed lifter bores, and a 3- quart accumilator on my engines exactly because of this issue with the BBF oiling system and short distance shutdown tracks. 11 Quart system (7.5 pan and filter plus 3 quart for the accumilator -so I use 11)
75 PSI cold start-up and hot idle never falls below 50 PSI on the brakes
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Re: Oil pressure under braking

Post  cool40 on June 1st 2016, 9:45 am

Have you checked out the lifters yet? How are they designed where the oil hole goes through them? I still think you have too much oil up top or it wouldn't be starving on the shutdown. The other dyno thread appeared like it also IMO.
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Re: Oil pressure under braking

Post  DaveMcLain on June 1st 2016, 10:55 am

Just looking at the pan I wonder how difficult it would be to add some baffling to the bottom of the sump in sort of a C or [ shape just on the front side of the pickup to help keep oil around it for a few seconds while you're really on the brakes. Maybe 2 inches high with a small lip right at the top.

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Re: Oil pressure under braking

Post  BigRigTech on June 1st 2016, 11:14 am

DaveMcLain wrote:Just looking at the pan I wonder how difficult it would be to add some baffling to the bottom of the sump in sort of a C or [ shape just on the front side of the pickup to help keep oil around it for a few seconds while you're really on the brakes.  Maybe 2 inches high with a small lip right at the top.  

Not hard all all and that's what I was hoping to get some tried and true idea's. I have Johnson hygrade "notched" lifters that I bought from Scott J on the other BBF site. I have a deal in the works for a 3 quart accumulator with another forum member here so hopefully that goes through and helps this situation too.
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Re: Oil pressure under braking

Post  99zx9r on June 2nd 2016, 12:15 am

Like Lem said it seems as if low oil pressure on decel is a fairly common issue. I've experienced it on some motors, not others. On my current setup, oil pressure drops to about 10psi on decel (I pop it into neutral after the stripe), then slowly creeps back up to 45-50 by the turnoff. To prevent any potential damage, I click the motor after crossing the stripe and coast to the return road. Of course I test brakes first before clicking off and we are fortunate to have a long shut down area at our local track.
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Re: Oil pressure under braking

Post  IDT-572 on June 2nd 2016, 2:59 pm

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Re: Oil pressure under braking

Post  BigRigTech on June 3rd 2016, 9:26 am

Do you have any pics of the inside of it? I'd like to put some more baffles inside mine. I have a 3 quart accumulator coming thanks to another forum member here. Very Happy
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Re: Oil pressure under braking

Post  IDT-572 on June 3rd 2016, 9:37 am

I think I have an old one I can take a pick of.
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Re: Oil pressure under braking

Post  Dave De on June 3rd 2016, 10:53 pm

I lost my 547 to oil control similar to yours. I had the Moroso pan with 3 trap doors and a screen/scraper. For me braking was done in stages while looking at the oil pressure in shut down. If I had to stand on the brakes at the end the pressure would drop to 0 to 5 psi.
The pan I have today is a simple fox pan similar to yours but it has a tray mounted to the main caps with extra long studs.
Similar to this
http://www.jegs.com/i/Canton+Racing+Products/074/20-936/10002/-1?CAWELAID=1710886681&CAGPSPN=pla&CAAGID=15769068431&CATCI=aud-58142372711:pla-176568833831&catargetid=230006180003463673&cadevice=c&gclid=Cj0KEQjw1cS6BRDvhtKL89em1oIBEiQAtZO5x7hg-bS31wm9Nc08eHvSzj8sqwAaBvnN-HFfkqq4Pk8aArRU8P8HAQ

I think the windage was blowing the oil out of the pan when a tray isnt used. Now it doesnt drop below 20 psi. Another factor is steep walls and a deep sump to help the oil not get blown out.
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Re: Oil pressure under braking

Post  BigRigTech on June 6th 2016, 11:08 am

That's the tray I have now.
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