Melling M55 done after 5000rpm? - 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 02-24-2011, 07:07 PM
Registered User
 
Join Date: Sep 2010
Location: wi
Posts: 57
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by jeepers creepers
I've read lot of things on the forum about the causes of oil pressure drop, oil level, windage tray, oil pick up height and its related brazing to the pumo body can afflict pressure.
Mine is very good, about 70 when cold and over 35 at idle at operating temperature, the problem pop out when engine turns close to 5000 rpm, the gauge pointer has a superfast vibration from around 5 to 35 PSI.
Cavitation?
Looking for the cause on the web i've seen that some oil pump has problem over 5000rpm or so, any experience with them?

i'll tear down oil pan to check pick up height first (honestly i want to see bearings too) then braze the pick up or make a bracket for it.
Competition Products in oshkosh wi. sells an oil pump pickup bracket .Nice bracket .LARRY

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 02-25-2011, 12:00 AM
4 Jaw Chuck's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Mar 2002
Location: Manitoba, Canada
Age: 46
Posts: 4,974
Wiki Edits: 0

Thanks: 2
Thanked 89 Times in 72 Posts
A regular oil pump pressure relief valve is set to release at 55-60 psi and unless there is a gauge issue what you are seeing is the relief spring surging without a load on the engine causing your gauge to fluctuate rapidly.

Don't worry about it, its normal.
__________________
Outlawed tunes from outlawed pipes
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 02-25-2011, 05:42 AM
SSedan64's Avatar
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Macon, GA.
Age: 50
Posts: 6,016
Wiki Edits: 0

Thanks: 0
Thanked 46 Times in 46 Posts
Quote:
Originally Posted by jeepers creepers
great link, thank you, pump is down ready for the mods, problem is to make to vertical groove on the gear bore, i haven't the right tool for that, but grooves on the bottom are easier to do, do you think i can make just them? any con?
thank you.
To see much improvement I'd think you would need both ends done. A small Die Grinder/Rotary Tool with a cone shape Carbide or Diamond Burr will work if you can find one.
Examples>> http://www.harborfreight.com/power-t...ary-tools.html
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 03-17-2011, 05:25 PM
Registered User
 
Last photo:
Join Date: Mar 2008
Location: Piedmont Italy
Posts: 208
Wiki Edits: 0

Thanks: 8
Thanked 3 Times in 3 Posts
i've made a quick video just to show what the oil gauge is reading:
http://img546.imageshack.us/i/ony.mp4/
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 03-17-2011, 07:17 PM
SSedan64's Avatar
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Macon, GA.
Age: 50
Posts: 6,016
Wiki Edits: 0

Thanks: 0
Thanked 46 Times in 46 Posts
Wow! That looks and sounds like cavitation at the Pump's Pickup? You can hear the load on the engine change when the Pr. drops.
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 03-18-2011, 06:48 AM
Registered User
 
Last photo:
Join Date: Mar 2008
Location: Piedmont Italy
Posts: 208
Wiki Edits: 0

Thanks: 8
Thanked 3 Times in 3 Posts
Quote:
Originally Posted by SSedan64
Wow! That looks and sounds like cavitation at the Pump's Pickup? You can hear the load on the engine change when the Pr. drops.
i guess so, nevertheless as somebody told me in this thread engine has no load on so it's better to try the car on the road before.
i saw the "oil pump mods tutorial" , very interesting but i don't want to mess up and end with a piece of junk so i'm thinking about a new and different oil pump, stock pressure and volume is a must.
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 03-18-2011, 07:43 AM
302 Z28's Avatar  
Last photo:
Join Date: May 2003
Location: North Texas
Posts: 10,839
Wiki Edits: 0

Thanks: 1
Thanked 86 Times in 73 Posts
If your still relying on the electric pressure gage your chasing ghosts. Find a mechanical gage and get an honest pressure reading.

Vince
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 03-18-2011, 09:43 AM
Registered User
 
Last photo:
Join Date: Mar 2008
Location: Piedmont Italy
Posts: 208
Wiki Edits: 0

Thanks: 8
Thanked 3 Times in 3 Posts
Quote:
Originally Posted by 302 Z28
If your still relying on the electric pressure gage your chasing ghosts. Find a mechanical gage and get an honest pressure reading.

Vince
You're right, the oil pressure sender is probably on the worst spot ever,i just need to make a hard breath and do that.. mechanical gauge is on the shelf.
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 03-18-2011, 12:05 PM
Registered User
 
Join Date: Jun 2010
Location: TX
Posts: 1,182
Wiki Edits: 0

Thanks: 0
Thanked 105 Times in 96 Posts
retainer

Quote:
Originally Posted by larryf
Competition Products in oshkosh wi. sells an oil pump pickup bracket .Nice bracket .LARRY


A pump screen assembly retainer or brace is available from Summit and Jegs. It is retainer part #23620 for a 3/4" inlet tube. The M55 tube such as you have has a 5/8" diameter inlet but it will still fit if welded to the tube. Since my oil pan is 9-1/4" deep, the pick up assembly is more subject to vibration damage than a shorter tube assembly. I used the #23620 retainer after cutting and shortening the pick up tube 1/2" in order to fit a Melling 10552 HV/std pressure pump. I tried to fit Milodon and Moroso screen assemblies that were equipped with braces but I could never get the desired 1/2" oil pan bottom clearance with any of those pick ups. A vortex under the screen and severe cavatation will result if the pick up screen is less the 3/8" from the botton of the oil pan.

I used the special Melling tool and drove the inlet tube into the pump housing then bolted the #23620 brace to the tube, welded it and tossed the supplied retainer bolt in the trash. I bolted the bracket to the oil pump bottom plate with red Loctite. Severe vibration can weaken the oil pump pick up tube, especially if it is a long pick up assembly for a deep oil pan. The #23620 pick up retainer dampens vibration that can work harden the tube at the pump housing connection, even if the pick up tube has been brazed to the cast iron pump housing.
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 03-18-2011, 12:54 PM
Registered User
 
Join Date: Jun 2010
Location: TX
Posts: 1,182
Wiki Edits: 0

Thanks: 0
Thanked 105 Times in 96 Posts
BB Chevy pump

Cavitation is a common problem with SB Chevy oil pumps unless you use one that is designed to reduce cavitation. Those type oil pumps also reduce oil pressure below 1200 RPM and are recommended for racing applications only. A good solution would be to install a stock BB Chevrolet oil pump. They have larger diameter spur gears with more teeth and run smoother with 10% higher volume than a SB chevy oil pump. Unfortuantely, the inlet tube is clocked differently in the pump housing and the baffles in the oil pan may need trimming to get a BB Chevy pump to fit. I tried to fit a stock BB Chevy pump but the inlet tube hit the back of my 4.3L V6 4X4 oil pan. The BB Chevy pump will fit most SB Chevy V8 oil pans.

If you trial fit and can use a BB Chevy oil pump on a SB Chevy V8 engine, you will need to get a Moroso oil pump drive shaft that is designed for that conversion. That shaft is shorter than a SB Chevy drive shaft to allow for the slightly longer BB Chevy gear shaft.
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 03-18-2011, 02:55 PM
cool rockin daddy's Avatar
1.21 giga-watts???!!!!
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,535
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
"Cavitation is a common problem with SB Chevy oil pumps unless you use one that is designed to reduce cavitation".

Any proof of this? Documented proof? This is just getting ridiculous.
Reply With Quote Quick reply to this message
  #27 (permalink)  
Old 03-18-2011, 03:05 PM
cool rockin daddy's Avatar
1.21 giga-watts???!!!!
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,535
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
If you think your M55 is done, put a DZ 302 Z/28 or equivalent oil pump in it and be done with it. GM had no qualms about running a high volume oil pump in a stock engine with stock clearances. Why should you? Man, when it comes to oiling systems on Chevy's you can't beat the factory. Shouldn't even try.
Reply With Quote Quick reply to this message
  #28 (permalink)  
Old 03-18-2011, 03:33 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,822
Wiki Edits: 0

Thanks: 4
Thanked 449 Times in 384 Posts
Quote:
Originally Posted by jeepers creepers
i've made a quick video just to show what the oil gauge is reading:
http://img546.imageshack.us/i/ony.mp4/
I don't know what to say about this, I notice the sound of the engine changes when the pressure drops, did you back off the throttle, am I imagining this? I really don't know why there would be an apparent drop in sound which I would take as power or RPM at that point. Some things that come to mind would be the inlet is picking up air, the sump is running low on oil, the bypass opens too far and catches before it returns to closed or the by-passing oil which is returned to the input side of the pump is causing a disruption to the intake of oil. Or the output side is having a problem to where the bypass valve in the filter and the filter element combine to reduce flow to the engine. That would load the pump but I'd be surprised that could apply enough load on the pump and up to the distributor gear to slow the engine or alter its sound would surprise me some. It could be the distributor isn't positioned correctly or not tight enough to where the right side tappet galley is being opened to where pressure oil is venting back to the pan. Or the reverse to where the distributor is setting to low and under the combined force of it and full system oil pressure that single bolt that holds the pump on is allowing the pump to move enough to temporarily open the discharge cavity, then it recovers as the pressure drops.

While any of these are possibilities, I don't see any of them being strong enough to cause the power sound change that seems to coincide with the pressure drop. though if the distributor, or its shaft, is moving in some unrestrained direction it shouldn't, that would affect timing either by changing point dwell or upsetting timing advance settings either of which would affect RPM and power output, thus sound.

I keep thinking I've seen this before, but can't put where, when or what to it.

Bogie
Reply With Quote Quick reply to this message
  #29 (permalink)  
Old 03-18-2011, 03:50 PM
302 Z28's Avatar  
Last photo:
Join Date: May 2003
Location: North Texas
Posts: 10,839
Wiki Edits: 0

Thanks: 1
Thanked 86 Times in 73 Posts
Quote:
Originally Posted by MouseFink
A pump screen assembly retainer or brace is available from Summit and Jegs. It is retainer part #23620 for a 3/4" inlet tube. .

Not available from Summit. A friend of mine has the patent on that retainer and Summit came out with a knock off not too soon after Jegs was licensed to carry it. The threat of a lawsuit made them drop it from their catalog.

Vince
Reply With Quote Quick reply to this message
  #30 (permalink)  
Old 03-18-2011, 05:02 PM
Registered User
 
Last photo:
Join Date: Jul 2004
Location: At Speed
Age: 51
Posts: 1,343
Wiki Edits: 0

Thanks: 2
Thanked 28 Times in 28 Posts
The video suggests it sucking air somehow. Try adding an extra quart of oil and retest. Maybe do that two or three times even. The plug in the bottom of the pump that covers the drill passage from the regulator bore to the inlet tube is intact?
Or, the drive gear in the pump is slipping on the input shaft, though I have only seen that once. There were alot of pumps made with sintered metal gears that had problems but I dont know exactly what the problems were. I think Melling went back to a billet gear in all their pumps.
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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Melling oil pump issue Studebaker Engine 14 07-11-2010 10:42 AM
new melling oil pump BBstroker Engine 3 05-26-2007 09:51 PM
Engine falls over above 5000rpm Pinko351 Engine 16 04-30-2007 04:00 AM
Melling cam Gassman Engine 3 03-30-2003 02:59 PM
5000rpm alternator! chevelle327 Engine 2 11-22-2002 07:32 AM


All times are GMT -6. The time now is 05:59 AM.


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.