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  #16 (permalink)  
Old 11-19-2002, 05:27 AM
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So I'm guessing you did not check the Oil Pump Pickup to pan clearance at assembly time? I don't know how you would adjust this with a long screwdriver through the drain plug, because it is supposed to be welded to retain it (besides the press fit). Crunching it with a screwdriver does what? You also said a "local proffesional engine tuner that builds dirt track motors" built the motor, so is it a race motor or a street motor? I do know that most racing engines have High Volume Oil Pumps, and bigger than stock (as in 6 or 7 Quart capacity) oil pans. They usually have different clearances than a street motor as well. As it has been said here already, a HV Oil Pump will pump all of the oil out of a stock pan, up to the lifter galleries where it does NOT belong.
I'm also assuming that you (or your Engine Builder) checked the oil pump over,
as in gears to housing clearance, and inspected the pressure spring before assembly (as in test it and make sure it works, and doesn't malfunction. I personally always replace the Oil Filter Bypass (filter adapter thing on SBC) with a non bypassing one to make sure all oil goes THROUGH the filter, but that wouldn't explain your pressure loss. I don't see how a windage tray would cause this either. It would stand to reason that as your engine warms up the pressure will drop some but 60 to 30 sounds extreme (not to mention 60 pounds of oil pressure unless this is a race car 35 is adequate for most street purposes IMHO, I usually have like 40-50 in Dirt track engines that we build). None of you have stated what you are running for oil pumps (as in stock, HV, aftermarket), Oilpan (as in capacity) or oil (synthetic?, viscosity), so it's hard to guess, but I would say that BstMech has a pretty good explanation, at least it makes sense. He's also right about Pressure Verses Volume and the bypass spring. :-)
I probably would re check the Main Bearings, and Oil Pump Pickup clearance, Oil Pump, and add a bigger capacity Oil Pan, or a stock Oil Pump that was properly checked out first. My 2 cents for what it's worth.

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Old 11-19-2002, 05:45 AM
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Almost forgot.....Most racing motors also have plugs that restrict oil to the lifter galley area, and lifters. I personally also tap and plug up the drain back holes over the camshaft because
oil draining back on a rotating assembly = lost HP, and the valve train does not need the ammount of oil that a stock block supplies, The Mains and Rod Bearings need it! (you shouldn't restrict it as much with a hydraulic cam as a mechanical or roller), if this was done, maybe that combined with your maybe loose Main Bearings could explain this? It's important to enlarge the front and rear drain holes (the big ones) and deburr and paint the lifter galley area to help drainback when restricting the oil flow upwards. Thisa is all guess work of course. 2 cents more. :-)

[ November 19, 2002: Message edited by: Airport Towing ]</p>
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Old 11-19-2002, 06:02 AM
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I would look at two things. Pan to pickup clearance. If a HV pump was installed in place of a stock pump with a stock pan and pickup then you'll have a problem. The HV pump is about 1/2 inch taller than a stock pump and although the stock pickup has a raised section that holds the screen off the pan, the assembly just doesn't fit right. Another would be someone forgetting the welch plug that sits under the #5 main cap that directs the oil form the pump to the oil filter. That can lead to goofy oil pressure readings.
Something you might want to try to see if the theory about "sucking the pan dry" is to add an additional quart of oil. A word of warning though is that overfilling the pan would only be to prove out that theory. Too much oil leads to excessive windage which can whip the oil into a useless foam.
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Old 11-19-2002, 10:47 AM
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airport towing - this is the oil pump that was installed in my Firebird 400 during the rebuild:
_________________________________________________

Vendor: Sealed Power
Product Line: Sealed Power High Pressure Oil Pump
Material: Cast Iron

For heavy loads

Pontiac: 326-455, high pressure oil pump

Higher oil pressure aids in maintaining the oil film thickness in many areas subject to extreme loads. Engines that operate under heavy loads but still use stock bearing clearances will benefit from a high pressure pump. A stock rebuild with a supercharger or nitrous also needs a high pressure oil pump.
__________________________________________________ __

Would this require a non-standard oil pump installation. Unfortunately, I was not personally involved in the assembly so I'm kind of fishing for the most direct solution to the problem. I checked out Summit's inventory of oil pans that fit the Pontiac 400. Which would you recommend? I am always a little concerned about maintaining ground clearence. This car has factory long branch manifolds and does reasonably well over bumps. My other firebird has after market headers that seem to drag on every speed bump (I hate those #@!!%# things)

Pontiac: 326-455, 7 quarts plus filter, 8 in. sump depth, low profile, steel, gold iridited finish, performanc...MIL-30355

Pontiac: 326-455, stock style, steel, gold iridited finish, replacement oil pan ...MIL-30770

Pontiac: 389-455 6 qt. road race oil pan, fits all chassis ...MIL-31660

I did a test on my drive home last night. While the car was still pretty cool (150 degress) I jumped on the accelerator on the freeway. The oil pressure rose quickly to 60 psi and stayed there well beyond the magic RPM where I noticed the drop occuring in the past. Does this shed any light on our problem???

[ November 19, 2002: Message edited by: jobu ]</p>
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Old 11-19-2002, 01:42 PM
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Is the crank crossdrilled? Are the main and rod bearings grooved? Partial or full groove? These factors will change dynamic pressure readings substancially. What about main bearing clearnaces? Rod?
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Old 11-19-2002, 03:47 PM
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Jobu:

For heavy loads
Pontiac: 326-455, high pressure oil pump
High Pressure = High Volume? (One would assume)
SEaled POwer make quality parts, I've never used their Oil Pumps, but I assume they are OK. I couldn't tell you for sure if this pump requires special installation procedures, but it would definately need to be checked for proper clearance or depth in the Oil Pan (just as any other pump stock or otherwise) (Engineczar already said this, so I'm echoing his ideas) :-)

Well, being as I'm a Chevy kind of guy, I can only answer in those terms.... (hee hee)...but seriously...
If you have 60 lbs of Oil Pressure at cruising speeds, then there can't be too much wrong. It would also stand to reason that at higher speeds the pump would pump more oil, as long as the oil is availiable (in the oilpan). What "magic rpm is this pressure drop occuring? I would guess at 2500-3000 RPM. Could this problem be heat related (or is heat contributing to the problem?) An OIl Cooler would probably keep your oil at a lower temperature, which will definately help. I mainly build Engines for Modifieds and Sportsman stock cars, so I'm always concerned with basically 3 things in an oiling system:
1. Adequate Pressure
2. Keeping oil in the pan and on the Mains and Rod bearings.
3. Keeping oil off of rotating assemblies ie windage trays and drainback principles.

As I said before, I prefer more than 5 quarts of oil in the pan, but I can appreciate your ground clearance issues, same deal on race cars. All of Miloden's oil pans are pretty good, especially as far as clearance and oil control. I usually use Moroso's, because they are tough, they sponsor 2 of my stock cars :-) , and they fit without sacrificing ground clearance. Seeing as how almost any car will do fine with 30-40 lbs of oil pressure I wouldn't worry too much about a drop from 60 to 50, especially if you maintain 60 lbs while at cruising speed. Below 30 is a problem for sure. Again, I build Chevy motors, so I'm not a Pontiac expert. My father owns an Automotive Machine Shop, so I see and assemble allot of engines, but not too many Pontiacs. Sorry I can't offer better help.
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Old 11-19-2002, 05:47 PM
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My buddy with his 71 split bumper Z-28 camaro had the same problem when he put his rebuilt motor in. He simply replaced the oil filter and that fixed it. <img src="graemlins/drunk.gif" border="0" alt="[drunk]" />

I have a similar problem with my 69 camaro with a sbc 400, but It only happens when the oil is at the lower end of the safe mark on the dip stick. All I do is throw half a quart of oil in it and that fixes it.

I say try changing oil filter with a high flow one, maybe the oil filter is restricting the flow of oil, thats what my buddy thinks was happening to his car. Just a thought.
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Old 11-20-2002, 02:24 PM
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First let me start by thanking all of you for your insightful advice! This board and it's contributers have helped me out a lot!

Airport Towing - the magic RPM where the oil pressure drop occurs is around 2800 degrees. As I stated, the unusual oil pressure behavior ONLY happens when the car is running at 190+ degrees. When the car is still warming up (below 180) the pressure at 2800 RPMs is pegged at 60 (At lower temperatures the higher oil viscosity is keeping the pressure up and I'm assuming that the pressure/flow is being restricted by a 60 psi pressure limiting valve). When the engine is cold, further increases in RPM don't cause any oil pressure deviations one way or the other.

When the engine is warm it's another story. Here's an example of the unusal oil pressure behavior: Running at 195 temperature, the oil pressure at 2750 is around 54 psi. Under these conditions, when I speed it up to 2800 RPM within 2 seconds the pressure drops dramatically to around 43 psi. Further increases in RPM actually make the pressure go back up slightly, but to not more than 46 psi. If I slow it down below 2800 at any point, the pressure jumps dramatically back to 54 psi. This will happen back and forth every time this RPM is hit one way or the other. I will check into the Moroso pans. If I can get a higher total oil volume in this engine without sacrificing ground clearance that has to be a good thing (except for the MONEY - but, in this case, the "pay me now or pay me later" rule might be in effect.

chevyelc81 - I rummaged around at the Kragan parts store and after some trial and error found that a Fram PH-11 is exactly the same dimensions, threads etc, as the PH-25 (specified for the Pontiac 400) EXCEPT that it is around 3/4" LONGER. I bought one and will replace it on the car tonight and see what happens. My thought is that the larger filter will pass more oil than the smaller one.... If that fails, perhaps your could recommend a higher flow brand and I'll try that next. This is an experiment that's easy and cheap, so what have I got to lose? Maybe I'll get lucky! Keep your fingers crossed for me!?

[ November 20, 2002: Message edited by: jobu ]</p>
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Old 11-21-2002, 01:24 PM
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I installed the Fram PH-11 oil filter last night. I think the problem is solved!? I didn't get around to replacing it till after 10 PM and took it for a quick spin on the freeway to confirm the results (the lights on the gage haven't worked since I took it out of the dash to bleed it of air) so it was a little tricky keeping track of the readings. The pressure seemed to be behaving as one would expect. Higher RPM - higher pressure regardless of engine temperature. It is a little jumpy when you accelerate hard but the problem with the dramatic plunge of oil pressure at 2800 PRM seems to be fixed! I hesitate to completely say for sure until I can test it further. The #!@%! traffic was so bad on the freeway this morning that I couldn't go fast enough to get confirmation! I'll report back tomorrow with more conclusive results. Best Regards....
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Old 11-22-2002, 10:51 AM
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IT DEFINITELY WAS THE OIL FILTER!!!

The pressure was steady as a rock at 50 psi with the engine running at 200 degrees last night and steady as a rock at 53 psi with the engine running at 195 this morning. I think this is as high as it would get at these temperatures, because after I hit 2500 RPM further increases in RPM had no effect on the oil pressure (NO BIG DROP LIKE BEFORE). I was going pretty darn fast when I gave up this test.

If you guys wouldn't mind, I would like some feedback on a related matter. When I sit idling in traffic this engine gets HOT! (over 220 even in 80 degrees weather with the temp still creeping up). My plan is to still replace the oil pan with a larger version the next time I do any serious poking around down there: 1) because although the symtoms of the wierd oil pressure are gone I have a feeling that I'm perched on the edge of this problem reappearing. I think Airport Towing was right on in his conclusion that I was sucking the oil level in the pan down to the point where the pump wasn't working right. The bigger oil filter is just enough to keep things working OK for the time being. 2) I think the extra oil might help in keeping the engine running cooler. My thought is that the oil is doing its share cooling the engine, and more is better than less. What do you guys think? Also, does anyone think an oil cooler is a good thing to invest in? Is there a downside to using one? Would it rob oil from engine parts? Where is the best place to mount it? I presently have a large 4 row radiator with a fan shroud and filler panels. Finally, does anyone think that I casued any accelerated wearing of engine parts by running my engine for 5000 miles with this restricted flow at high RPMs? The pressure never got lower than 40 psi while running at freeway speeds.

Thanks again everyone! Please reply if you try a version of this oil filter swap.

[ November 25, 2002: Message edited by: jobu ]</p>
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Old 11-22-2002, 04:35 PM
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Sounds like you have another problem, not necessarily related. A new pan would probably keep the high pressure oil pump from sucking the sump dry, but overheating at idle is a cooling system problem. Oil certainly contributes to cooling, but I don't think the bigger pan is going to fix your problem. An engine oil cooler might be an option though.

When you had the motor rebuilt, did you replace the fan/fan clutch, make changes to the shroud, etc.? If you do a lot of driving where you have to sit at idle, you might want to consider an electric fan to keep air moving even when your rpms are low.

If you never dropped below 40 psi, I wouldn't be overly concerned with wear. Heat is definitely and enemy though. I'd look into that asap.
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Old 11-23-2002, 05:33 AM
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Glad to hear the larger oil filter worked out for you. I guess I generally assume everyone will use the BIGGEST Oil Filter that fits on their engine, just for that reason, restriction. Very good example of the KISS Principle in action. Oil Coolers are great for keeping the oil substantially cooler, which helps keep it from breaking down or thinning out, which should help oil pressure remain more constant (in theory anyways) With the lines and the filter, you can usually pick up another quart, or quart and a half in oil capacity without a pan change. You can also use a remote filter or dual remote filter adaptor with this setup (or by itself)which will give you more filtration and more oil in the system. Again, this is race proven stuff here anyways, the oil cooling would seem to be insignificant compared to the cooling system, but it really makes a big difference. Cooler is better at least with oil. You can mount the cooler portion in front of your radiator,or anywhere else you can find that air will pass over it. We usually use the ones from the JEGs catalog, but if you want a cheap alternative, look for a 3/4 or 1 ton truck in your local bone yard with the towing package. It's a nice setup that you can get for almost nothing. Sorry for any typos, it's still early here. :-)
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Old 11-25-2002, 11:23 AM
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Thanks again! Installing an oil cooler sounds like the way to go. If I can get some extra oil capacity as a bonus, I might save some money and skip the bigger oil pan.

I also posted my version of the overheating problem on the topic "engine running really hot!!" and got some good feedback from there as well. There was a good link posted on general cooling system do's and don't's <a href="http://www.inccn.net/techforum.htm" target="_blank">www.inccn.net/techforum.htm</a> I tried thinning out the water antifreeze mix from 50/50 to 75% water/25% anti-freeze. She's definitely running a bit cooler. Tooling along at freeway speeds the temp stayed UNDER 195 til I hit the traffic pile up. The temp still wants to climb while idling in #@$%%!@ traffic, but I think progress has been made there as well. Today she stayed below 210 after idling for 10 minutes, and as soon as I was able to proceed at 35 mph it dropped back down to 200 within a half mile. I think that when I put on the higher flow rate water pump I ordered, and an oil cooler I might be out of the woods?!?

30coupe - I've got the factory shroud with a flex-lite #1319 19" - 6 blade fan, no fan clutch.

I know running with the timing set incorrectly can cause excess heating of the engine. Do any of you hotrodders have a good feel for the ultimate timing setting at 600 PRM on a 1967 Pontiac Ram Air 400, 0.030 overbore, factory specs cam, factory long branch exhaust manifolds and 800 qjet carb? This weekend I reset the timing to 10 deg BTDC and she seemed to help run better (stronger/cooler). I have a hard time getting the engine to "ping" under load no matter how far I advance the timing so I'm trying the "tweak it - test it" method of finding the sweet spot in the timing. Kind of fun... but what's my next move advance or retard?

[ November 25, 2002: Message edited by: jobu ]

[ November 25, 2002: Message edited by: jobu ]</p>
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Old 11-25-2002, 05:06 PM
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Depends on the grade of oil also 5w-30, 10w-30, 10w-40, or 20w 50.

I am running 20w-50 in mine, the machine shop that built my engine recommended 20w-50, they warranty it for 3 yrs/36000 so I run 20w-50.

With a high volume oil pump when I start the car cold I am at 60 to 70 PSI of oil pressure at idle. I have a Summit gage. The same gage I had before I rebuilt my engine. When I start to move it can get to 80 psi when its under 180 degrees. Once it warms up and the oil thins it will go down at idle to 35 psi. When you stomp on it, it jumps up to 60 to 70 psi.
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Old 11-26-2002, 10:51 AM
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I've had a lot of conflicting advice on what grade of oil to use. I've always had a gut feeling that 20w-50 was superior, but the argument I've heard against using this grade of oil on a freshly rebuilt engine is that the cleacence between engine parts is so close that the thicker oil can't get in there as well when cold so you have a excess friction event happening when you first fire up the engine. It seems to me that the reverse would also be true; once the oils in there between moving parts it wouldn't drain off as easily and therefore keep lubricating better/longer. I'm thinking of switching all my cars to full synthetic (Mobile 1 15w-50 or Casrol Syntec 5w-50) I reason that the low number would keep the oil thin when the engine is colder (5w or 15w) and the high number (50) would keep the oil more viscous when hot. Does this seem to make sense to everyone or am I missing some important assumption? What do you think Airport Towing?
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