oil pressure

1

1981z28owner

1981z28owner
i am starting to have oil pressure fluctuations in my sbc 355 in my 81 camaro. just the past week the oil pressure will fluctuate and drop 20 pounds when i stand on it. I have read about melling redesigning their pumps and having a cracking problem. My pump is one that is known to crack. Would a cracked pump cause this problem?

thanks
mike
 
Possibly....just before it broke off and fell in the pan! But I would eliminate some other, more common, problems before going to the trouble of dropping the pan. Things like wrong oil level (high or low), restricted filter, drainback issues, etc. Knowing more specific conditions present at the time of the occurence would help out. Do you "stand on it" from low, mid, or high rpm? Does it make a difference? Does the problem show up immediately, or after a certain time has elapsed, or a certain rpm has been reached? After dropping, does the pressure stabilize at the lower value? Increase? Waver? What pressure does it start at? What does it drop to?
 
thanks

i will be changing the oil again today and putting on a new filter, to eliminate that problem. if the problem still exists, i will look for exact conditions, hopefully it is jsut the filter.

thanks
mike
 
nope

i changed the oil and filter today, same problem. i actually found a peice of metal on my drain plug. it is about 1/16 thick and is part of a circle that is about 7/8 diameter and looks just like some pieces on the oil pump.
just a few observations.

from 2000-3000 oil pressure is constand at about 45 pounds.
at 3300 and i peg it pressure drops from about 61 to 40 pounds and stays at 40 until i let off it. which at 6000rpm 40 pounds it way too low.

i think it is time to pull it and find the problem, i dont want to have the pump break off and screw up the while motor, and drag racing season is coming.

thanks
mike
 
Yes..big bulletin on this issue on their site. Replace it anyway for good measure. And id contact them to see if you can get refunded for some of your time and efforts.
 
pics of the metal piece

P1010295.jpg


P1010294.jpg


P1010292.jpg
 
I don't know what the long piece is but the others are valve spring dampners. You have more problems than just oil pressure. Looks like your springs are shot or possibly binding also . Likely you have a bunch of junk blocking off your oil pickup.
 
The second picture on here looks like a piston skirt. But then again if you haven't dropped the pan then that isn't it because you won't get that out of the drain plug. I would say to pull that motor and have the heads gone through and freshen the lower end. Be cheaper to do it now while most of it is still in one piece. Good luck and keep us posted on what else you find.

Tom
 
binding

i think it was probably binding. i will need to pull this out, heck the heads were just redone last august with all need springs, valves, etc.
 
Yea..the motor is hurt. Its just more than an oil pump problem. Thats either piston skirts or vavle train dampeners in the first set of pics. Pic 4 possibly looks like a piece of a spun bearing(looks the the surface..looks blew and all gaulded up). Good luck
 
what would cause a head to bind like that? the machine shop said the springs were good to about 650 lift, and i am only at 502. they are single springs.

could the valve train geometry have been screwed up by the machinge shop. i only got maybe 4000 miles on them.

thanks
mike
 
Could be the machine shop didnt install the right shims inder the springs...or valve guide not in straight(ive seen that a dozen times). If the decked the block..pushrods may be too long..i dont know. but it needs to come apart. If its a piston skirt and bearing..thats another issue. could be bored wrong..had a bad piston to begin with..ran low on oil pressure long enough everything got hot...id pull her apart..and let us know what all you find. Then we can give you a more definite opinion..but they are just opinions.
Will try our best.
 
i am just curious about one thing. if it happens to be the wrong shims, or giude put in incorrectly, thus the machine shop;s fault. would they possibly refund or fix the heads. I think they should since it only has 2000 miles in just over a year.

it might not even be a problem with the heads. but the pistons were new, and both piece are magnetic, so they are not part of the piston, they are both part of a dampner by their looks.
 
1981z28owner said:
i am just curious about one thing. if it happens to be the wrong shims, or giude put in incorrectly, thus the machine shop;s fault. would they possibly refund or fix the heads. I think they should since it only has 2000 miles in just over a year.

it might not even be a problem with the heads. but the pistons were new, and both piece are magnetic, so they are not part of the piston, they are both part of a dampner by their looks.
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Well..that all depends on how much the machine shop backs their work. Most have a warranty on their stuff and most go at least a year or 20,000 miles. Now...if its a perfomance car..meaning...its a street strip car...that depends. Our machine shop will even if we caput a motor..they will take it apart..examine it and put it back together unless it was run without oil or got too hot. but either way..i say it is something they did. Now.on the oil pump issue...how did you find out what kind of pump it has..did you change it recently??? If so...that may void the warranty..if they have one. Either way..motor needs to come out and go from there. Let us know
 
i guess i need to pull them and take them back to the machine shop to get them checked out. which machine shop do you work at? i am looking for a good machine shop to go too.

I will be looking for some dart pro 1 heads and will need some pistons decked.
 
I donot work for a machine shop. I have had Mark Leuk @Authorized Auto Prts in Wood River do some stuff for me and he does excellent work. We have a sponsorship deal with Matt Johnsons Performance in St. Louis as of now and they have been nothing but great. Have had some issues but they have stuck behind their stuff. I wouldnt just pull the heads..id pull the whole motor out just in case you werent. Whatever all that is has gone through the motor. all the oil galleys and passages ...bearings and all that crapola need cleaned out to the best it can be. Let us know what you find out..thanks
 
They wouldn't be vortec heads by any chance. If they are that is the problem unless it is machined on the spring pad the vortecs can only use a damperless spring.
 
no, they are 441 heads that had all new pbm valves, springs, retainers, bronze guides, etc. put on by a local machine shop. cost be 750.00 and now this. i will first pull the heads off and see if they are the problem for sure, then go and talk with the shop why they lasted only 2000 miles. My cousin actually bought brand new heads from the same place, and a year later all the guides had to be replaced. cost him 800 for the heads and then a year later cost almost 400 by the time the machine shop got done with them.
 
1981z28owner said:
no, they are 441 heads that had all new pbm valves, springs, retainers, bronze guides, etc. put on by a local machine shop. cost be 750.00 and now this. i will first pull the heads off and see if they are the problem for sure, then go and talk with the shop why they lasted only 2000 miles. My cousin actually bought brand new heads from the same place, and a year later all the guides had to be replaced. cost him 800 for the heads and then a year later cost almost 400 by the time the machine shop got done with them.
Click to expand...


Well i probably wouldn't have gone to that machine shop if your cousin had problems with heads before from there. Good Luck though in getting it fixed.

Tom
 
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