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kevin
04-08-2000, 12:40 PM
GENE SORRY TO READ ABOUT YOUR BAD LUCK THERE IS NO LOWER LIFE FORM THAN A THIEF OR SOMEONE WHO WOULD DO SOMETHING LIKE THAT.
I THINK EVERYONE WHO THOUGHT BEARINGS MIGHT BE THE PROBLEM WITH THE OIL PRESSURE ON MY 302 WHERE RIGHT. I GOT A MECH. OIL PRESSURE GAUGE AND AT IDLE ABOUT 5LBS. AFTER ENGINE WARMS UP. I DO GET ABOUT 75-90 AT HIGHER RPMS, THIS I DO NOT UNDERSTAND I DID NOT HAVE THAT KIND OF PRESSURE LAST YEAR. I GUESS IT MAY BE AWHILE BEFORE WE HIT THE WATER NOW. THE REBUILD DOESNT BOTHER ME AS MUCH AS GETTING THAT THING BACK OUT OF THAT LITTLE DONZI ENGINE COMPARTMENT. ANY IDEAS BEFORE I START THIS TASK.

klink
04-11-2000, 01:21 AM
Sounds like the relief valve in the oil pump is not working properly, 90 lb is just shy of blowing the o-ring out of the oil filter. I had this happen to a 390 that sat over the winter.

GeneD
04-11-2000, 12:55 PM
Kevin,
Tanks for your kind words, I am taking care of business with these scum, legally. Narcotics will be making some visits over there, if they are not under surveillance already. Hopefully, I can get the apt complex's insurance company to pay off on the damage. Yes, that will make me very happy.
Onto your problem.
Don't freak out too soon. Now I realize you have a Ford, and while I'm no Ford expert, I'll tell you what Mercruiser's stance is on oil pressure.
The factory says minimum of 5 lbs at idle, and approx 10 lbs per 1000 RPM's over that. I've had race motors that seemed to have relatively low oil pressure, but ran great, and made no noises.
Now, I ain't telling you that nothing is wrong. 5 lbs at idle wouldn't keep me happy for long, but if I wanted to use the boat it wouldn't stop me. As long as I was getting good pressure at speed, that is what is important.
Here's something else, doing a bearing job is not that hard of a project, once you are into it and make the mental okay "I'm going to do this..."
Yeah, getting that motor out of that engine compartment is going to be tough, but everyone at one time or another has to do it. I'm not the 16 expert, and do not have any single hatch experience. It's a two person job, that much is certain.
Here's anther thing I just remembered, my machinist told me years ago that the oil filter has a high pressure bypass that turns on at approx 30 lbs, which means that oil does not pass through the filter with oil pressure higher than that. I was aghast when he told me that, I just couldn't beleive it. And I asked him, "You mean any motor that gets really good oil pressure at idle won't get any filtration?"
"Yup, only when you start up..."
I still don't believe his numbers, but the bypass valve is there, I've seen it. Has anyone else heard of this?
And again, this is my machinist talking, not me. He is well respected and builds race motors for Modifieds. He really is not a flunky. Oh, and we were talking about Chevys, I don't know if Ford's have this feature.
You know, Emmo bought that crate motor at a reasonable price, have you considered one of those? I just installed a crate 350 Chevy into a Sea Ray and the thing worked out just great.

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GeneD
007
Melbourne, Florida

AVickers
04-11-2000, 04:24 PM
The bypass in the oil filter comes into play when the filter is clogged, not when the overall oil pressure is too high.

As the filter fills up w/ junk, the pressure differential between the high side and low side within the filter changes (gets greater). Eventually, this will push the "bypass valve" open to "bypass" the oil around the filter (Get it?). The thinking here is that dirty oil is better than no oil... The bypass does not affect overall oil pressure in the engine. It is designed so that the engine will maintain oil pressure even if the filter is totally clogged.

Some manufacturers' systems have the bypass built into the filter (Nissan and Oldsmobile), some have it built into the filter housing (big and small block Chevys, for instance), and some actually push the filter element off its seat to bypass the filter (Triumphs). I haven't worked on a Ford in so long that I don't remember which system they use...

When the engines are cold, they'll also bypass oil around the filter 'cause the viscosity of the cold oil will create a high pressure differential at the oil filter just like it's clogged. That's another of the reasons not to rev a cold engine. Not only is there a greater chance of shearing metal in there, there's a greater chance that it will bypass the filter.

The pressure relief valve is another bypass mechanism that works almost the same as the bypass valve: pressure goes up to a certain point and overcomes a preset spring to push a valve off its seat. But it has a much stronger spring than a bypass valve. Usually the PRV is built in to the oil pump housing (sometimes into the block) and it usually bypasses oil back to the sump, sometimes to the input side of the pump (as in Chevy). Most of the time, the pressure relief valve is upstream of the oil filter, but I've seen 'em on the downhill side as well.

The oil pressure sending unit, on the other hand, is usually downstream of both the oil filter and the pressure relief valve -- between the oil pressure/filter control systems and the bearings that the oil is supposed to protect.

Interestingly, SB & BB Chevys do not filter any oil that goes to the rear main. It's lubricated directly off the pump.

[This message has been edited by avickers (edited 04-11-2000).]

[This message has been edited by avickers (edited 04-11-2000).]

Kenn
04-11-2000, 04:39 PM
GeneD,

I read what Avicers wrote and it makes good sense to me BUT Ya know what, I've heard the other explaination about oil pressure since the early 60's.

When Chevy converted the original 283 to a 327, the oil pressure was at 5 lbs at idle (sometimes it read below 5 lbs on the gage) and they said it was for that very reason.
Also, the Chevy tech people also said that when you came off the throttle, the pressure would drop and the oil would go thru the filter again.

I have a similar situation with my SBF in the Corsican.

Also, when we reworked my Jeep 360 (to make it into a tow vehicle) which has an AMC 360 Javelin engine, I notice the same situation and got the same explaination from my machinist and from a friend who builds quarter mile engines.

Now, I know that I do not have the expertise to answer the whys or howcome, BUT it seems to me that the same answer keeps coming from all these different sources and over a 40 year period, so there must be something to it.

It probabally has something to do with a lower theoretical risk factor which occurs only under a load.

Kenn http://206.150.187.82/ubb/wink.gif

[This message has been edited by Kenn (edited 04-11-2000).]

klink
04-11-2000, 05:10 PM
My 428 cobra jet pumped between 5-10lb at idle after a rebuild with a high volume pump the guys that built the engine wern't the least bit concerned, and when I pull the valve covers to adjust the valves there's lots of oil getting up top. But I think 90 lb is whay to high.

AVickers
04-11-2000, 05:17 PM
Ok,

It is possible that at higher RPM there would be a higher volume of oil flowing through the filer and this could cause a pressure differential in the filter which would cause the bypass to open. The spring is very weak...but the bypass port is only about the size of a pencil eraser.

However, my guess is that the engine is designed NOT to bypass the filter when it's at normal operating temperature and the correct viscosity of oil is being used and the PRV is working properly so that the upper limit of oil pressure is maintained -- 50 to 65 PSI. Anything consistently higher than that could tend to scrub the babbit off the bearings -- not a good situation.

Also, I like to see something more than 5 PSI at idle. Like about 20... Low pressure at idle tells me one of four things: 1) weak oil pump (worn out pump), 2) too much bearing clearance somewhere (bad machine work or worn out engine), 3) leak between oil pump and oil feed system (bad seating of a internal fitting or the seat on the bearing cap), or 4) there's junk in the pressure relief valve holding it open(sometime a bit of lint or a gasket goober will get in there and hold the valve off its seat just a bit... At low RMP, there's not enough pressure to register on the scale 'cause it's all being bypassed, yet there's not enough pressure at high RPM to open the PRV so the oil can wash the crap out of the valve...).

I've got an engine that runs low pressure at idle and I expect to have to replace lower end bearings soon. The damned Holley power valve diaphram on my wife's car broke and by the time she got tired of having it die at stop signs, the oil was badly diluted with fuel. I found the problem of it dying (****ty idle as a result of a way rich mixture). There was also about a quart "extra" oil in the pan and it smelled of gasoline -- really bad sign. I changed the oil, but by then the damage was done.

It used to be that that small block Buick would hold 35 PSI at idle. Not any more...

RickR,GroveCity
04-11-2000, 06:23 PM
If I had 5psi, at normal operating temp idle I'd be looking for the reason BUT,
Mercruiser Hi-Performance Service Manual says
Minimum 5psi@idle for the Hi-Per Big Blocks

Are you using Straight 40?
Is it cold outside?
Does pressure change after engine warms up?

If you blow the oil filter gasket you have BIG PROBLEMS and a big mess. I learned that lesson 27 years ago when I stretched the little PRV spring too far ona 327.

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RickR mailto:riggerb@aol.comriggerb@aol.com</A>

[This message has been edited by RickR,GroveCity (edited 04-11-2000).]