loosing oil pressire on hard accel and at idle

-
kevin amer

kevin amer

Well-Known Member
Joined
May 6, 2010
Messages
64
Reaction score
0
Location
Milton Ontario
Just wondering if anyone has had this problem . I have a stroked 440 fairly fresh one season about 400 miles on it. The problem I am having is the oil pressure drops to 15 psi at idle in drive after engine is warm or after approx a 20 min drive. The other thing it is doing is when i get on it a hard accell i noticed the oil pressure drop off as well, not sure how low it went as i let out of the throttle as soon as i saw the pressure drop. A few things about the engine. Iis a 440 source stroker kit aluminum h beem rods flat top pistons comp 11.5 to1 88 cc heads cast with some work a high press melling oil pump. I pulled the pumpp to check for wear or something but it is in great shape i dropped the oil and checked for any bearing material in the oil nothing visible. At this point i am not sure what is happening. I suspect that a rod may have stretched on the thrust side but i am looking for any info that may help i really dont want to pull the engine again but if i have to i will. thanks in advace
 
Usually a drop in oil pressure under acceleration is to much main bearing clearance, because under a load the crank is forced away from the block increasing the clearance. Now on the engines that I have seen this happen is on a one with a lot of wear or miles.
 
15 psi at a warm idle doesn't bother me with my 360. If its dropping on hard accel, then I'd be looking to find out why? High volume oil pumps require you to run every bit of oil that the pan will allow. We've found that most of the oil in the friend's 440, stays in the heads and will starve the lower end if not full. Lost a good race motor that way!
I've heard it's possible for the pickup to be too close to the bottom of the oil pan and pulling that rascal up.
 
Did you actually measure the crank journals with a mic? Aluminum rods take different clearances and bearings because of the rate of expansion and the alignment dowels. Source parts are great at being good. Not good at being great, and alimunim needs great. I would look at the oil pickup to pan clearance as far as the accel goes, and the pressure at idle isnt bad depending on the oil. What does ti do at 200rpm? 3500?
 
Lets start with the pan Kevin, has it got acceleration and decel baffles in it and what is the large number stamped into the bottom of the pan also are you using a windage tray. I'd drop the pan because you also need to check how close the pickup is to the bottom of the pan. 15#'s at hot idle is way to low for a HV pump and are you using a reliable mechanical guage when you list the pressure.
 
First off, he said high pressure, not high volume. Two different animals. I think there are two seperate issues here. Whatever is causing the low PSI at idle is one issue.....possibly a cracked gallery plug or something of the sort and the high RPM loss is another issue. Maybe lack of a good oil pan baffle. Are you running a windage tray? Doesn't matter how good the oiling system is, if you got a boatload of low end torque, without a windage tray, you're fightin a losin battle trying to keep oil around the pickup.
 
15lbs at idle is just fine, no need to worry. the other stuff is a big concern. "H"beam aluminum rods? just plain weird! i agree with the other folks that you need baffles.
 
The oil pan is a stock mopar tin pan no baffles and yes there is a windage tray. the engine ran great at the begining of summer good oil pressure lots of power. now it seems to have lost some of that when all this stated to happen
 
kevin amer said:
The oil pan is a stock mopar tin pan no baffles and yes there is a windage tray. the engine ran great at the begining of summer good oil pressure lots of power. now it seems to have lost some of that when all this stated to happen
Click to expand...

I'm suspecting that the hard acceleration loss of oil pressure was happening from the beginning and it just got not noticed resently, either way you need baffles and the stock pan will take 5 1/2 litres with a dry filter. Have you got some info on the oil pump like model number. What was your original hot idle oil pressure at the beginning of the summer.
One last question, what was your cold idle oil pressure and has that changed.
 
tell me about your aluminum rods please. a hv pump and stock oil pan is asking for problems. take the pan off and check the bearings and pump out out and while it's off toss it out and get a deeper pan and matching pick-up and put in 8-10 quarts of oil.
 
I would at least plan to take the pan off and inspect. If the oil is the same, and the filter is the same, it should not have dropped unless the clearances changed. That is something i'd want to look at closely.
 
You guys should read the first thread over. He said he has a HP pump not an HV pump. Steve
 
hunky said:
You guys should read the first thread over. He said he has a HP pump not an HV pump. Steve
Click to expand...

Steve, that's why I asked for info on the pump as there are HP pumps out there but most times builders install an HV pump since by pumping more oil a HV pump ends up giving you more pressure (over a standard pump) across all running conditions as long as the down stream passages (resistance to flow) haven't changed. Changes such as enlarging of oil passages.

Kevin, I'm with the guys thinking that there is something wrong and that a complete bearing inspection is in order.

I'm running a Melling HV pump in my 383 and even though I had a baffled pan and 5 liters of oil I was getting a drop of pressure on acceleration also. I nailed it down to the Mopar windage tray, the return slots were to small and not enough of them and the oil was running out the back of the tray instead of going straight down. I switched to a Milodon pan which has more slots and they're larger and problem gone. My cold idle is 80psi and hot idle 50psi running 10W30.

I've also got a spare 187 dimpled pan that I'm going to have my welder add 2" to the sump and install it this winter and no I won't forget the pickup
 
Since some people here seem to bring threads back from the dead after a year or more I suppose I should be more careful with my replies, rather than taking the question at face value.

Sure glad I was able to provide you with some entertainment "real mopar guy", I will be sure to refrain from helping anyone else in the future.

B.
 
Low oil pressure after ran awhile? Mine runs warmed up at 60- 70 lbs constantly. Let me ask this. Does the engine do any smoking? Sounds like when the oil warms up of course it gets thinner. Whats the engine temp say? Does it use any oil? I had this issue in a new small block. Low on power but it did smoke. Found it was the valve job was a nerl job and the oil was leaving headed for the pistons. They fixed it. Ran like a striped assed ape. Answer those questions for us.
Small Block
 
You must log in or register to reply here.
-

Back
Top