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  #1 (permalink)  
Old 08-28-2010, 09:26 AM
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Default 351W oil pressure

I have a 351W with 6000 miles on it and over the last year or so the oil pressure has been slowly dropping after a long run (40-50 miles). On short runs (15 miles) it seems ok, the engine is at temp (185) in both cases. Originally it was around 55 at 2500rpm and 30 at idle (850rpm). It is now at 45 and 18. I pulled the oil filter, cut it open (what a pain) and found some tiny metal flakes in it, about 1-2 per pleat in the paper filter.

I haven't torn into an engine since 65, so here is my guess
1. dist/cam gear wear and the oil pump is shot
2. something really bad is slowly happening

I really don't want to pull the engine unless I have to but if it is #1, change out the dist gear, new oil pump and ??
If #2 is it possible to change the bearings without pulling the engine?

Any other ideas? If #1, should I pull it anyway and replace all the bearings?
Thanks
Joe B
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  #2 (permalink)  
Old 08-28-2010, 09:53 AM
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Guess what, its hot in Texas. The hotter the oil the lower the viscosity and the lower the oil pressure. Check you oil pressure when cold, and see what you find. What viscosity are you running? Low oil pressure is usually attributed to bearing clearances in the main, rod and camshaft. I would not worry about the metal flakes, probably nothing. That being said it is a 5 minute job to pull the distributor if you know what you are doing. Turn engine over to top dead center on #1, to make sure you are not 180 out make sure your timing cover pointer is at zero. mark orientation of distrubutor to engine and rotor to distributor. As long as the rotor is pointing to #1 on the cap when installed you are good to go, if you get the whole dist off relative to the engine your spark plugs wires may not hook up. Start up set timing.
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Old 08-28-2010, 03:57 PM
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My oil pressure will drop to 45 psi when the oil is above 210 F on the track. I have a fairly fresh 351W built by KCR ( 6000 miles). I called Keith to discuss it and he did not seem overly concerned by the pressure when hot. The bearing clearances were purposely set a little looser then factor specs according to my build sheet. That was about 3 years ago and it has not caused me any problem. The engine runs like a champ.

I did switch to syn 20-50 which bought me about 3 psi above 210 F oil temp. I also replaced my electric oil pressure gage with a mechanical but they read the same.

Once a year I sample my oil and send it in for analysis. No problems so far.
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Old 08-28-2010, 04:23 PM
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Rest assured 20W50 will have substantially more pressure than 10W30. Why would anyone set bearings loose??? especially on a high performance engine. I imagine your mains are .002-.003" KC knows how to build engines.

Its a double edge sword, sure if you are going to race for 60 minutes straight and run your oil temp up 20W50 might not be to heavy. If you start and run around town 10W30 is the answer. Heavier oil just overflows instead of penetrates. You can wear your engine out with 20W50 with day to day starting.
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Old 08-29-2010, 05:43 PM
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Quote:
Originally Posted by madmaxx View Post
"......... You can wear your engine out with 20W50 with day to day starting.
not true, at least not in my case.

Using 15w-50 Mobil 1 for 9 years, nearly 40,000 miles. No measurable wear on rod or main bearing checked recently. Piston/cylinder clearance unchanged. Car started and ran 4 to 7 times a week, minimum 30 miles, usually more. Longest trip 1700 miles over a 3 day period.

I do agree that it doesn't seem right that someone would set up a high perfmance engine, a street engine that is, with loose bearings.

Z.

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Last edited by zrayr; 08-29-2010 at 05:45 PM..
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  #6 (permalink)  
Old 08-29-2010, 07:31 PM
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Quote:
I do agree that it doesn't seem right that someone would set up a high perfmance engine, a street engine that is, with loose bearings.
It all depends on the way the engine will be used, this is usually decided bewteen the owner and engine builder.......

daily driver cars will have a certain bearing clearance,basically the same amount you would find in any production engine....

High performance engines that will see track duty usually have a "little" more clearance and I mean a little more, as in a thousandth or less......this promotes oil flow and the more oil flowing over the bearings,the more they are lubricated and produce less friction and less heat will be generated....a by product is a little less oil pressure....

There is a big difference in oil pressure and oil flow, more oil pressure does not mean more oil flow....

I would prefer oil flow and a lower oil pressure than high oil pressure and less oil flow in a motor......

Also, oil temp has a big impact on oil pressure.....my 65 Fastback (351-W) using 15/40 conventional oil,oil pressure is 60 psi on start-up with cold oil at 900 rpm idle, once the oil is up to 180 degress, my idle oil pressure is around 35 psi, on track, I've come in from a 15 minute run with the oil temp in the 200 to 220 range, at idle rpm,oil pressure is from 25 psi to 30 psi........this engine has near 30,000 hard miles on it right now........

BTW: NHRA Pro Stock cars have been know to run as little as 10psi of oil pressure at speed, of course they only run for 6 seconds at a time at speed......

Quote:
I have a 351W with 6000 miles on it and over the last year or so the oil pressure has been slowly dropping after a long run (40-50 miles). On short runs (15 miles) it seems ok, the engine is at temp (185) in both cases. Originally it was around 55 at 2500rpm and 30 at idle (850rpm). It is now at 45 and 18. I pulled the oil filter, cut it open (what a pain) and found some tiny metal flakes in it, about 1-2 per pleat in the paper filter
I'm guessing wear from the bearing is causing the lower oil pressure since you have found metal flakes in the oil filter,1-2 per pleat is a lot to me anyway.... I don't think I've ever seen that many in an oil filter from a "good" engine.......

David
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Old 08-29-2010, 11:30 PM
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I would send the oil to Blackstone labs and have it checked out and see if it is block or bearing material.

there are some things you can try --

1. figure out better cooling, more oil capacity.
2. update the pump to a M88HV from melling -- with a chromoly oil pump drive shaft.
3. drop the pan and check bearings. --

Steve
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Old 08-30-2010, 10:42 AM
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I need to pull out my build sheet and get the exact clearance as I forgot the number. I seem to recall it was 0.0005" to 0.001" over the factor specified range.

I have complete confidence in KCR but I would be interested in getting others opinions on this issue. I have always wanted to see 50 to 65 psi for V8's with a peak HP at 6000 to 6300 rpm. I realize the flow versus pressure is much more complicated then this rule of thumb.

My cold pressure is 60 to 65 psi @ 1500 rpm. The lowest I have ever seen it once warmed up ( 200 to 220 F oil temp) is 43 psi at 5000 rpm.

As a side note the bleed down leak with the block warm and testing at 125 psi was 1 to 3% with 7 of the 8 cylinders 2% and less. I am under the impression this is very good sealing and an indicator of the build quality.
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Old 08-30-2010, 05:22 PM
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I must have missed what weight oil are you running?
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Old 08-30-2010, 05:58 PM
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Just a couple of thoughts -

I think most of you guys are too concerned with oil pressure and not concerned enough about oil flow.

Having a bigger crankcase will not keep the oil cooler, it will just take longer for the oil you have to heat up. If you want cooler oil you need to add an oil cooler.

Just for the record, my Windsor from FMS never goes below 50 PSI when in motion and that's using 5W-30 Redline usually running around 180 degrees.

Bob
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Old 09-01-2010, 04:19 AM
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I am running 10-40 now. Just to be sure I stated the problem correctly, it is not that the oil pressure drops as the engine/oil get hot, but the idle and 2500rpm pressures have dropped by ~10-15 lbs in 2000 easy miles. I have never (until now) cut open an oil filter so are a few metal flakes acceptable?
My current plan is to drop the pan, check a main and a rod bearing, replace the oil pump and go from there.
Thanks for the inputs
JOe
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Old 09-01-2010, 04:38 AM
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There is a reason there is a filter on the oiling system. It catches the wear particles and general junk that enters the oiling system.

I use 15W-50 Mobil 1. Great stuff.

If you have particles ( and they are not huge ), it could mean several different things.

If you are hammering the throttle, I am sure you are going to "age" the engine faster than if you let grandma drive it...well, maybe grandma.

Check it again in 1000 miles and see if you get more metal.

Just my opinion.

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Old 09-01-2010, 06:22 AM
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I like the Mobil 15W50 also due to the high zinc and phosphorous, the problem lies in the fact with a 9 quart system it takes forever to get the oil warm enough for it to flow. When using 10W30 it pumps out of the rocker arm and fills the void with little overlfow. The majority of flow goes through the needle bearings in the rocker arm fulcrum instead of splashing over exactly where you want it. The 15W40 just overflowed the rocker arm with little going through the bearings. It was similiar to pouring water through a screen and pouring syrup. If you are trying to wet what is below the screen you want the water.

With 10W30 my oil pressure is 35 psig at 90C and 40 psig at 80C at 900 rpm. Anything above 1500 rpms it is 53? psig. At 100C and idle it is 30 psig.

With 15W40 add 8-10 psig everywhere.
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Old 09-01-2010, 06:37 AM
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Quote:
Originally Posted by madmaxx View Post
I like the Mobil 15W50 also due to the high zinc and phosphorous, the problem lies in the fact with a 9 quart system it takes forever to get the oil warm enough for it to flow. When using 10W30 it pumps out of the rocker arm and fills the void with little overlfow. The majority of flow goes through the needle bearings in the rocker arm fulcrum instead of splashing over exactly where you want it. The 15W40 just overflowed the rocker arm with little going through the bearings. ........" .
interesting assertion. what data do you have to support it ?

btw, I'm currently using Mobil 1 15w-50 in my 289 with great results. Over 40,000 miles w/o any measurable wear. And have used it in many FE family engines ( 390, 428 & 427 ) over the years without any wear issues

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Old 09-01-2010, 08:38 AM
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Quote:
Originally Posted by allen_cobra View Post
I am running 10-40 now. Just to be sure I stated the problem correctly, it is not that the oil pressure drops as the engine/oil get hot, but the idle and 2500rpm pressures have dropped by ~10-15 lbs in 2000 easy miles. I have never (until now) cut open an oil filter so are a few metal flakes acceptable?
My current plan is to drop the pan, check a main and a rod bearing, replace the oil pump and go from there.
Thanks for the inputs
JOe
I think your current plans are your best bet right now....There is a reason for the drop in oil pressure and I'm guessing it's a bearing/bearings that have wear in them....Things happen for no good reason, you can have an engine with the best parts built by the best engine builder and still sometimes $hit happens....

By the amount of "stuff" you've seen in the filter, I think you have a problem with a bearing or bearings....just my guess......

Even on my daily driver,I like to let the engine run at idle at least 1 to 2 minutes on cold start-up in the morning before heading out to work.... On my street car (65 Mustang) I'll let it idle till the oil temp gets to around 140 before taking off......On my race car (road racer), I don't get on the track till the oil temp is at at least 180.....

Not saying you've done this, but I've seen way too many folks get in their high performance car and start it up cold and begin revving it up to show people just how bad the motor is, that's about the worse thing you can do to an engine.......

David
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