When I start my 460 cold it has around 85psi at an idle. Once it warm up it run about 65-75 down the road and 30 at an idle.

I have noticed lately that when I lay into the 4bbl. that the pressure will drop from 65-75 down to 45-55 and kinda fluctuate in that range. What is going wrong.

 

What is probably happening when you stomp the gas and the oil pressure drops is that your oil pump is sucking air. It is like when you drian the sink and water takes the shape of a funnel and you can here the air getting sucked down the drian.

Fixes: deeper sump pan w/ baffels (L&L products in Texas makes a 10qt pan), use a rear or close to rear sump pan (I did this one).

Also not knowing what condition your 460 is in, your oil pump could be worn or the relief spring could be weak. I use a high volumn pump (not high pressure) and it works great. hope this helps.

Greg
71' F250,4X4 460ci-NP435
43 ****** MB204109 289ci

 

Well the oil pump is brand new as of August, along with the bearings. It also has a rear sump pan on it since it is 4x4.

It seems to do it only at high rpm's.

 

mine does that too! it has done that exact same thing before and after it was totally rebuilt. the only diffrence being that before it droped all the way to 5 pounds warm. and now its low is at 30 and cold its up around 80. I was woundering what could be wrong also?

 

Did you check the crank and if within tolerances have it polished or if out .002 have it turned undersized? Decreasing oil pressure on increasing rpms is normally an indication of worn oil pump, no gasket between the oil pump and block, no gasket between the pump and pickup or excessive bearing clearances.

 

Check with the manufacture of your oil pump. Make sure the spring they used in the pump can handle the oil pressure your engine is producing. A thought (Might want to get a second oil pressure gauge reading just to make sure the first gauge is registering correctly?) Sounds like you have a fresh powerplant. Your engine is tight creating allot of pressure and the oilpumps relief valve is used to open at a certain pressure and let some of it out.

As for the used engine doing the some thing. Well, the same thing above applies except your relief spring is tired and opens sooner (at lower oil pressure).

Let me know what you find out.


Greg
71' F250,4X4 460ci-NP435
43 ****** MB204109 289ci

 

[updated:LAST EDITED ON 07-Jan-03 AT 09:25 PM (EST)]yes it is very fresh, crank was turned .010 and as for the oil pump its a new Melling HV oil pump. I even tryed runing it a half quart more oil than its sopsed to have because some chevy dork told me that a HV pump would suck the sump dry. I told him he was crazy I had one on a 302 I had rebuilt that ran 95 cold and 70 warm and it never sucked it dry. it also didn't have the drastic presure loss either.

I wonder if it could have something to do with where the presure line is hooked up on the engine, although presure is presure nomater where you read it.

I have tried diffrent gauge also it did the same thing. in fact if I hook up the stock ford gauge along with my mechanical one and it drops to nothing when in fact it has 25-35 lbs still.

I have been runing it anyway and have just decided that this must be "normal" even though I know better. it hasn't changed for the worse any and its got aprox. 10,000 on it now so I geuss its allright.

at least its not a every day driver or anything, it just worries me when I think about it. especially since I went to the time and money to go thru the beast right.

also I geuss 30 lbs isn't that bad warm its just a big diffrence from what it is cold. not used to that, heck my 283 with over 60,000 on it and stock pump still has 50 when warm and it reads 60 cold. hate to even admit that I even have that chitty but I do.

thanks for your input and sorry if this got toooo long.

hey Greg I see you have a ****** too, I have a '41 ma with a 161 ****** 6. those oldies are goodies aren't they?

 

Billy, I will ask a couple buddies and see what they say about your pressure problem.

Yes, I do own a 43' MB. I just bought it about three months ago. It has been highly modified by some goofball (nicely putting it). I am not agianst mods but these were poorly done. I plan on pulling the body and putting it on a custom frame I have ready. You got any pics of your MA? Send them to my direct email address if you would. Also check out G503.com if you haven't allready. Greg

Greg
71' F250,4X4 460ci-NP435
43 ****** MB204109 289ci