|
#1
|
|||
|
|||
Here's a situation I recently found myself in: my good old reliable Slant Six started dropping its oil pressure by the week!
Let's start at the beginning. A 1972 225 Slant Six engine. I got it when it had 110,000 miles on it (about 3 years ago). It now has 181,000, runs good, and I beat on this thing hard! I ran 10W-40 Castrol GTX oil in it for the first 2 years, then switched to Castrol Semi-Synthetic 20W-50. I go down to 10W-40 in the wintertime. According to my dash-mounted AutoMeter #3421 oil pressure gauge, oil pressure has ALWAYS been 52-53 psi after an oil change. When the oil gets old (3-4 thousand miles) pressure would drop to about 49-50 psi. I use Fram PH8A filters for more oil capacity and the good Fram reputation. This engine takes a full 6 quarts to fill on an oil change. Fine by me. It didn't matter if the engine was at 1000 or 4000 rpm, I always had my 52-53 psi. However, about 2 months ago, something started happening. The gauge wasn't quite getting up to the usual 52-53 psi. Even with fresh oil. More like 50-51. Every week it seemed, the oil pressure would drop a little more. 50...46...44...42...40...39... Even at high rpm on NEW oil! This was not right. Since Slant Sixes and big blocks have external oil pumps, my hope was that just changing the oil pressure relief valve spring would fix it. An easy way to solve the problem, if it worked. Went and found the high pressure spring I had bought for it over a year earlier (procrastinator). Drove the '71 Valiant up on ramps, and pulled out the old spring. It was soft enough that I could squeeze it to solid height between my thumb and one finger. The new spring was definitely stronger, and you could see it was wound out of heavier wire. Put it in and cranked up the engine. 70 psi. Cool. Problem solved. Just to double check, I put the old spring back in. 39 psi. O.K., I'm satisfied. The spring was shot. Put the new one in again, and have my 70 psi. A week later, I changed oil. 10W-40 Castrol GTX (non-synthetic) and a new PH8A for the wintertime. 80 psi. Whoa. This is too much. Gonna blow that nylon oil pressure gauge tube if I leave this like this. On a cold start, it can push the gauge up to about 88 psi. I'll have to get a new standard strength spring and shim it to get about 55-60 psi. I'd be happy with that. I wonder why the old spring held its pressure good for 27 years then just quit all of a sudden. Yes, I know it was old, but I thought it might go away a little more gradually than it did. Anyway the problem is fixed now. Anyone else have some interesting oil system stories and how you fixed your problems? P.S. - This is an all stock engine, no H.V. pump or anything. Only modified stuff is the exhaust headers and 2bbl. aluminum intake setup. I'm currently wearing out my Dremel set porting a /6 head to put on this engine. Mostly just for practice before I port heads for my 273 project, but I'd like to power up the old /6 a little in the meantime, too. |
#2
|
|||
|
|||
I have a 440 in my 70 coronet with a MP high volume pump it had about 65 70 psi cold, had 120,000 plus miles. I reground the crank all new berings now it has around 85 -90 psi cold and 65-70 warm is that too much.
20-50 valvoline [This message has been edited by Squad (edited December 10, 1999).] |
#3
|
|||
|
|||
i been having the same problems with my /6 i use 10w 40 mobil 'it runs threw it in the summer so i went to 20w50 and havent burnt a drop since but my oil pressure has been all over the gage up and down .FIRST i put a 1/4 " nut behind the spring that gave me 10 to 15 more LBS but it would drop every other month .I would change the oil filter and it would be fine for 2 more months.SO ive been trying diffrent filters i hate to say it but FRAM was the worst one i used 3 to 4 weeks tops well the motor has 120'ooo milles on it and its a bone stock super six .I have a cylinder head off a 75 /6 that i open the bowls ported polished but i cant seem to get any valves under 42.50$ each .this will be going on it next year plus cam and headers .mill the head .090 i dont need the down time this is the wifes car and she is more moody then the motor .use a good ol; mopar high ferformance filter mayby it will work for you too.
|
#4
|
||||
|
||||
OK. How about this one. For you that have seen my other posts. I have a 70 Newport Conv. orginal 383 Magnum. Runs great now, except for the oil pressure. I was on the interstate crusing at about 65 at 175-180 degrees, oil at 50 psi and about 2800rpm (I know highway gears. Owner said 3.23s)Gave it gas to pass someone, rpm up to about 3200, no change in oil pressure. I let up on the gas and the oil press goes to about 60! I've never seen this before. Any ideas. This is consistant, I can get it to this anytime at crusing speeds. I can even coast then put it in second and the press will go up. It drops down to about 45-48 when I get back on the gas. As for the oil spring dying so fast, it might be the case of once something starts wearing out, the rate that it weakens increase at an increasing rate. Like if a part wore so much in 30K miles. At 60K it wouldn't wear twice as much, it would be worn more than twice. Once it starts wearing out, it keeps acclerating with usage.
|
#5
|
|||
|
|||
Many times when rebuilding engines we find the p/u tube packed with crap,like valve stem seals,silent timing gear nylon and god knows what else.If you were to look at the p/u tube it would look o.k. but if you turn it sideways and tap it on the ground it will deposit its encrusted host on the ground.After seeing how much crap can be inside one you'll never run a used one again....PRO...
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
0 oil pressure | ADRAGRACER | Performance Talk | 6 | 07-19-2007 04:07 PM |
Fuel Pressure Drops to zero, will not hold a steady fuel pressure | Mopard | Front Wheel Drive Chat | 7 | 03-25-2003 03:48 PM |
oil pressure on 360 | butch33 | Performance Talk | 8 | 02-20-2003 07:25 AM |
oil Pressure | riverside | Performance Talk | 13 | 08-31-2002 08:57 PM |
oil pressure | keithcar72 | Circle Track Chat | 5 | 08-23-2001 10:49 AM |