Small Block Chevy Oil Pressure - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 02-03-2008, 11:31 AM
Registered User
 
Join Date: May 2007
Location: north carolina
Posts: 30
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for the reply. How did you check the lifters?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 03-19-2008, 08:10 PM
Registered User
 
Join Date: Mar 2008
Location: ontario
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
wot oil presssure drop

Word for word, I had the same problem with my brand new (1,200 miles) 350 stroker with a moroso 7 quart pan (side kick) and 25% volume melling oil pump. I used the same dip stick from original 350.
Well guess what, for some reason the oil level is to high and the result is foaming .Take 1 quart out and the problem is gone, not only that but the max oil pressure 65 psi comes in earlier (at a lower rpm) on cruise.
Pretty low tech solution !!!
Please try it, you cant hurt anything , but I would make sure that if it works and you recalibrate your dip stick by cutting off the dipstick tube ,to allow the stick to move "actually " 3/4 quart down, that you scribe a new line for "Add "a little higher up.My oil pressure is strong and steady @ 40 idle, 65 cruise and 65 during and after WOT above 3000 RPM, unlike before.
Hope it works for you!!!
Let me know.
jeepen

Last edited by jeepen; 03-19-2008 at 09:11 PM.
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 03-19-2008, 09:17 PM
Notorious's Avatar
Hot rodder, not street rodder!
 
Last photo:
Join Date: Aug 2007
Location: Bakers Mountain, NC
Posts: 507
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by hotrodf1
You should probably start your own thread instead of interjecting in this one. It gets confusing for people to understand which vehicle we are talking about etc.
Why? He was injecting his experience as it may relate to the OP's problem.
There are so many possibilities here, most of which have already been covered. It can be a very confusing issue, even to those of us who have built hundreds of engines over the years. The pick-up height is certainly critical with 3/8" to 1/2" being the norm these days. I still like 3/8" but haven't ventured past that yet either. Pump pressure and volume, restrictors (or not) for a given type of valve train, pan design and it just goes on and on. No matter what, I always pay special attention to optimizing return flow. The best thing to do is to concentrate your research on those building for your intended purpose. And you can never do too much research.
A return problem, and thus occasional starvation, is certainly a possibility here. But it's not the only one by far.
I use a pan with windage, a scraper and five trap doors built in. It's on a street, strip and track use car. And although my results have been fine with it, some others have still reported starvation issues with the same pan. Is it the pan? Who knows? But it's worked well for me. I don't even use an accumulator yet but will be adding one for future, more serious track (road race) use. For some, even this has not even been sufficient with similar combinations. Once again, in areas regarding engine longevity, the learning never stops here.
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 03-19-2008, 09:26 PM
Member
 
Last photo:
Join Date: Jan 2005
Location:
Posts: 3,707
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Another modification that can really help the oil return in the rear of a small block is to drill a 1/2" hole between the rear main cap and the outer pan rail in the wide webbing on the passenger side of the engine. Oil has a tough time trying to fall in that area because the crank counterweight keeps moving it upward and it builds up above the mainweb with no place to go-if you drill a hole in this spot it will flow through the hole instead of being whipped up by the counterweight.
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 03-20-2008, 10:56 PM
Registered User
 
Join Date: May 2007
Location: north carolina
Posts: 30
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
oil psi drop

Well, considering these things I have to say that the engine has never been apart and that the guage didn't ever used to read this way. I don't know why the oil would foam now but maybe I could try using a half quart less or a different brand. I supose the brand could more/less succeptable.

I realy feel like it is a wear issue. What's wierd is it kinda happend one day. I looked at about 5000 rpm and the oil was at about 20psi. I about ****.

Awierd thing about it is that it will happen easier going up a hill (pulling more load). It will happen at earlier rpm and throttle position.

Thank you guys for your advice. If you hear/figure anything new by chance, let me know.

Nate
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 03-20-2008, 11:07 PM
racecar100's Avatar
Registered User
 
Join Date: Feb 2008
Location: Tennessee
Age: 54
Posts: 255
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
If the Oil pump pickup too close to the oil pan will cause the oil to foam and lose pressure. Also when the pickup too close to the pan, the pan will flex enough and will cut down on the oil flow to the pump. I recomend min. 5/16" perferred at 3/8" to be safe.
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 03-20-2008, 11:49 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 7,078
Wiki Edits: 0

Thanks: 4
Thanked 535 Times in 452 Posts
Quote:
Originally Posted by knizet
My son and I built a high performance 350 small block chevy for his 67 Nova. (desktop dyno at about 425 horse) We used all new parts. New block (standard bore, new casting), new forged steel crank and forged pistons, new Dart iron eagle heads, Moroso 6 qt pan and matching oil pickup etc. All parts purchased new from Performance Automotive Warehouse (PAW) in California. We plasti gaged all the rod and main journals during assembly, and all were well within spec. The problem is that the oil pressure drops under wide open throttle (WOT). Hot idle pressure is about 20 psi, moving right up to about 50 psi at 2500 rpm or so. However, under WOT, the pressure drops from about 55 psi down to about 35 when the rpm gets up to about 4500. However, if we gear down and run the engine at a constant 4500 to 5000 rpm, there is no pressure drop. It only drops under WOT. We thought that the problem might be too large an oil pump (we first used a high volume pump) so we changed the pump and pickup, using a new GM high pressure, standard volum small block oil pump for a 69 vintage Z28 Camaro. But the problem did not change. The engine runs and drives normally except for this problem. My son's got about $6000 wrapped up in this engine, and I'm stumped. Someone suggested that we tear down the engine and check for excessive bearing clearances, but I don't understand how that could cause a pressure drop only under WOT. Please help.
Thank you
Tom
A fairly common problem that has several sources that need to be investigated.

- For an engine that spends some frequent trips to or long durations at WOT I like the Moroso 21319 pan. The built in windage tray is a considerable asset to getting the return oil out of the windage and giving it a chance to de-aerate.

- As RPMs go up so does the amount of oil the pump is pulling out of the pan. A sufficient quantity to start with at a distance from the crank is necessary, I like about 7 quarts in a deep or kickout pan.

- A box shaped pick up about a quarter to 3/8s inch off the pan bottom is about right. Too high from the pan bottom and you'll get a vortex forming as the oil is sucked into the pump. To low and the oil can't flow fast enough to keep the intake supplied as well as a risk of pulling the pan floor up.

- At high speeds if the bypass setting is too low, the rerouted oil blowing off the bypass valve of the pump is dumped into the incoming oil stream, this can be very disruptive to the pump intake. Frankly I don't like your oil pressure as it's low in my book, I suspect too much is being bypassed. I'd like to see an idle pressure more on the order of 30 to 40 pounds.

- Don't subscribe to reducing oil flow to the lifters, the valve springs are cooled by the oil, cutting that flow down or off will have serious consequences to valve spring life and if you running ball and socket rockers they will go away quickly as well.

- Return to the pan is an issue for top end oil. The SBC is on the minimal edge of having enough return passage area to accomplish this. Most top end oil drains down the back of the block because the engine normally sits at a 3 degree rearward rake when installed. That oil which drains down the front does so only after the depth of oil in the valley is sufficiently deep to drain forward. That of course is also dependent upon vehicle dynamics, under hard acceleration, probably none is draining forward as the nose of the car is lifted and the acceleration force on the oil is pushing it to the rear of the engine. It's a really good idea to use a die grinder to open the dranback holes at the rear as much as is practical within the envelop limits. Same can be said for the head drains at the ends. These can be opened up with a drill bit to speed return to the valley. Like the oil in the valley, the heads are mostly draining through the rear return till the oil gets deep enough to pour down the pushrod holes.

- Use a bypassing filter, at 5000 RPM up there is no way you can run all the oil through the filter, it just doesn't have enough capacity unless you look to the large truck filters or put remote racing filter on the car. A bypassing stock style filter will prevent the filter to becoming a pressure reducing obstruction in the lubrication system.

Bogie
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 03-21-2008, 12:01 AM
Registered User
 
Join Date: May 2007
Location: north carolina
Posts: 30
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
oil psi drop

Well, when thinking of bypass.... I did overheat the engine once. I wrecked it and when I pulled it off of the trailer into the shop I looked down and the gauge was about pegged. I have heard of fatiguing the spring in the oil pump and causing earlier/less psi bypass. Have you ever heard of this?

Thanks, Nate
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 03-21-2008, 06:59 AM
CNC BLOCKS NE's Avatar
CNC Blocks Northeast
 
Last photo:
Join Date: Sep 2006
Location: NORTHEAST
Age: 54
Posts: 1,491
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 21 Posts
[QUOTE=oldbogie

- Use a bypassing filter, at 5000 RPM up there is no way you can run all the oil through the filter, it just doesn't have enough capacity unless you look to the large truck filters or put remote racing filter on the car. A bypassing stock style filter will prevent the filter to becoming a pressure reducing obstruction in the lubrication system.

Bogie[/QUOTE]

How have I been getting away with pluging the bypasses on my circle track engines for the last 30 years or so and not have a problem and and some of them turn 7800 lap after lap.

And my street performance engines they are pluged as well and no problems but I will add you have to use a good filter to get the job done!!

Last edited by CNC BLOCKS N/E; 03-21-2008 at 07:07 AM.
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 03-21-2008, 11:50 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 7,078
Wiki Edits: 0

Thanks: 4
Thanked 535 Times in 452 Posts
Quote:
Originally Posted by CNC BLOCKS N/E
" I will add you have to use a good filter to get the job done!!"
I quoted your quote, and will say there-in lies the rub. A Wall Mart filter probably isn't up to the task.

Besides, I'm just aiming him at places to look, any and all can be or not be contributors.

Bogie
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 03-21-2008, 05:21 PM
CNC BLOCKS NE's Avatar
CNC Blocks Northeast
 
Last photo:
Join Date: Sep 2006
Location: NORTHEAST
Age: 54
Posts: 1,491
Wiki Edits: 0

Thanks: 1
Thanked 21 Times in 21 Posts
Quote:
Originally Posted by oldbogie
I quoted your quote, and will say there-in lies the rub. A Wall Mart filter probably isn't up to the task.

Besides, I'm just aiming him at places to look, any and all can be or not be contributors.

Bogie
I see where your going!!
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 03:28 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.