oil pressure drop, sorry kinda long

[godheadcustoms]

I've been lurking around here for a while, and now I have a long winded question, so bear with me... some background: I bought a '65 ranchero that had been sitting for 7+ years in an old man's side yard. I fired it up and drove it the 3 miles home.
observations: A. it ran pretty good once I put fresh gas in the tank and changed the oil
B. compression test= 150-155lbs. on all, but #6-130(sticky lifter, I think)
C. plugs, points, rotor, etc all as new
I drove it for a few months as is while doing bodywork, etc. Now here is where the fun starts...the rear main seal started leaking pretty good, no surprise considering, so I decided to simultaneously change/add
1. DII dizzy/module & MSD coil
2. 100 psi. mech oil pressure gauge
3. tach
4. new oil pump & drive
5. cliffy dual out headers w/2" dual pipes
6. harmonic balancer
7. rebuild cyl. head w/1.75 & 1.5 SI valves, milled .045", 48cc chambers, and pretty serious porting
8. T-5 trans w/hurst shifter

observations:
A. cyl. bores showed slight wear, no pronounced ridge
B. #1 & #6 main bearings looked very good, except for slight grooves from debris. Ford bearing inserts, but no obvious markings as to oversize
C. rocker arms/shafts were not getting proper oiling as there is heavy scoring on both ends of shaft and rockers and heavy oil coked deposits
D. engine was rebuilt at some point (rods are numbered)
E. engine was fairly well coked with oil, but not horrible. Only a little bit of guck in pan, nothing to really worry about.
F. engine runs much, much harder with above mods.
G. considering how the motor looked, I didn't measure bearing tolerances before I put it back together. Wish I had
Now to my problem, sorry for taking so long to get to it, but trying to give all info, whether relevant or not. When cold 45psi at idle and above, but when it warms up it drops to approx. 10psi/1000. Here's the kicker, when I step on the gas the oil pressure drops. If I let up, the pressure comes back up(mostly). The only thing I can think of is that I'm sucking air or the clearances at the rockers is too great? Since I didn't have a gauge before I changed the oil pump I don't know if the condition was pre-existing...I've never had this particular condition happen to me before. Any ideas, facts, rumors, opinions or lies would be greatly appreciated

Zac

 

[xctasy]

What oil weight are you using?

 

[JT81stang]

Zac:

Sounds like you are sucking air into the oil pump.

I don't believe the mid-sump oil pan has a baffle in it.

What's happening is - when you stand on it you push all the oil to the back of the pan, thus uncovering the oil pickup tube. You said when you let off the pressure comes back, and it should as the oil comes back into the sump when you do that.

If you can remove the pan without taking the whole motor out, you can make a baffle yourself & have it welded to the oilpan.

John

 

[godheadcustoms]

Here's some more info: the car had been sitting for 7-9 years with the prvious owner firing it up every six months or so, but never driving it. I think that's where the wear and oil coking has come from, otherwise it looks like a fresh rebuild, just old. I didn't want to run any kind of motor flush through it, afraid it might dislodge a piece of guck that could get traped in an oil galley. So I have changed the oil on it 4-5 times since I've owned it ( 6 months- 1000 miles or so). I run straight 30W oil, purolator filter. The car has always run great, now with the mods it runs really well (still need to do carb uprades!). I plumbed the oil press. gauge into the old sending unit location. Someone on a previous search said that was after the pressure relief valve and the pressure drop would happen like that when warm. I've always ran my mech. oil press. gauges from the sending unit spot, no tee, just disconnect the idiot light; never had any problems on other cars. When I saw that the rockers were scored I buffed with emery cloth and swapped the most worn rockers to the least worn spots on the shaft to try to decrease the tolerances( didn't have any more adj. rockers or another shaft, but are things I was planning on replacing in the near future). This certainly isn't the first time I been around an engine, but I'm not above screwing something up. I didn't have a gasket for the oil pump to block, but as they are close tolerance machining I just put some gascacinch on the mating surfaces. That's where I'm thinking I might be pulling air from, but that seems sorta remote ?

 

[wsa111]

Zac, bite the bullet, drop the pan & check the oil pick up tube where it bolts to the pump. if its tight, pull the engine & check the thrust bearing. I not sure but there may be a plug missing from the lifter oil galley behind the timing cover. I'm not sure of this its been a couple of years since ive been into a block. After you tear it down to bare bones the problem should be very obvious. Keep us informed. william
A second thought is the oil pump drive spinning in the distributor shaft???

 

[Junk-Falcon]

i think i would try

 

[godheadcustoms]

I went out and played with the car in the shop some more and...in the driveway the oil pressure rises with the RPM's like normal, but still a bit low (barely holds 10psi/1000 when hot). On the road it drops when I step on the gas. I don't mean when I'm really goosing it, but at a light cruise and you have to step on the gas a little to maintain road speed; as soon as I let off it will come back up. So all this seems to point to oil crawling up the back of the pan away from the pickup? The pan is stock, no baffles(or dents), but my theory doesn't seem to hold true because then this problem would be happening to alot more people. But even with the low oil pressure there's no clacking from the lifters, rough running or death noises, either on the road or in the shop. I'll be gone for a few weeks, but when I get back I'll try the filter first, then pull the pan and look into things a little deeper. Maybe I'll be rebuilding sooner than I was hoping...