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Could it simply be the oil line from the motor to the gauge has a slight kink, is pinched somewhere, or even clogged with a little gunk?
Is it the original oil line to the gauge or was the line replaced with the gauge?
Just thinking of the simple stuff to check before you start pulling pans and rod caps.
Have you tried putting a gauge at the motor and checking your pressure there?
Last edited by OldCarBum; Apr 26, 2019 at 02:14 PM.
Well had time today (been extremely with $ paying work to get to this earlier) to pull the pan and pump. I haven't pulled any caps yet but everything including the pump innards look good. There was a little bit of crap on the screen but nothing metal, just a very small amount of what looks like either gasket or RTV material. The pan is clean except for a bit of that really super fine metallic material that glistens in the oil. The last changed the oil at 400 miles, and the latest oil that I just drained has 1,000 miles on it so I'm not going to get too excited over it.
About the stock M77 pump, I can depress the pressure relief spring with a screwdriver but haven't take it apart to see if the valve could be sticking. As I've said, pressure is great when cold, just drops when hot, so I'm having difficulty believing the relief valve could be sticking, but who knows. Is it possible that the spring characteristics are changing enough when its hot that it relieves sooner? I don't buy that theory eight as it doesn't explain the low pressure at idle when hot.
Ugh, I suppose I should pull a few rod caps, clean off the oil, the plastigage them. I've thinking the best way is to pull plugs the ever-so-gently, tap them up the bore with rubber tubing over the cap studs. I'll start with #1 first since it's near the end of the oil path. My thinking though is that there would have to be some pretty serious clearances to cause a significant pressure drop when hot with 15W-50 oil, but then again...
I had a shop dip the block, magnaflux it, install new cam bearings freeze plugs and oil galley plugs, so I THINK the block is A-OK.
So I pulled rod caps #3 & #4, and main caps #2 & #3 and the pit in my stomach quadrupled. Not pretty. Both cap bearings and main bearings look about the same. You can see the specific Clevite bearings used for the rods. Surprisingly, the plastigage results were very reasonable for all four bearings. Readings landed right in the 0.003" range on the scale (I used the red gage). Also shown is cap #3 with the bearing removed. I don't know if the rods were machined, but the photos might indicate that they were. I imagine the discoloration on the bearings is due to extreme heat perhaps as a result of low pressure at idle, therefore very low oil flow causing hear buildup. I'm to end up pulling the remaining rod and main caps because, well, these bearings are shot. I'll plastigage all of them too, but I honestly don't expect different results. Everything mic'd out during assembly, and the high low-idle oil pressure has been there since the beginning. I don't get it. The oil must be hemmorhaging, but where? Could there be a crack in an oil gallery that wasn't detected when the block was magnafluxed? I don't see the point in just throwing new bearings at the problem. The rod journals are in amazingly good shape, but the mains have a ridge. Ugh, someone is going to make some money.
So I pulled rod caps #3 & #4, and main caps #2 & #3 and the pit in my stomach quadrupled. Not pretty. Both cap bearings and main bearings look about the same. You can see the specific Clevite bearings used for the rods. Surprisingly, the plastigage results were very reasonable for all four bearings. Readings landed right in the 0.003" range on the scale (I used the red gage). Also shown is cap #3 with the bearing removed. I don't know if the rods were machined, but the photos might indicate that they were. I imagine the discoloration on the bearings is due to extreme heat perhaps as a result of low pressure at idle, therefore very low oil flow causing hear buildup. I'm to end up pulling the remaining rod and main caps because, well, these bearings are shot. I'll plastigage all of them too, but I honestly don't expect different results. Everything mic'd out during assembly, and the high low-idle oil pressure has been there since the beginning. I don't get it. The oil must be hemmorhaging, but where? Could there be a crack in an oil gallery that wasn't detected when the block was magnafluxed? I don't see the point in just throwing new bearings at the problem. The rod journals are in amazingly good shape, but the mains have a ridge. Ugh, someone is going to make some money.
i believe the copper color is the second layer of babbitt under the grey layer. not heat discoloring the grey. could be clearances were too tight. that is why bearings are softer than crankshafts. so the crank can do a little finish honing of the bearing surface. 2 choices. replace the bearings or replace the crank. and don't go .011 under. you still have to check ALL 5 mains.
I agree that the hone marks on the rods indicate they were resized.
Looks like a dirty block with crap that ran through the oil system took out the bearings. The resulting increased clearance is what killed the oil pressure.
I can't imagine that the crank won't need a turn, how does it look?
i believe the copper color is the second layer of babbitt under the grey layer. not heat discoloring the grey. could be clearances were too tight. that is why bearings are softer than crankshafts. so the crank can do a little finish honing of the bearing surface. 2 choices. replace the bearings or replace the crank. and don't go .011 under. you still have to check ALL 5 mains.
Thanks, and glad to hear that the copper color not likely heat related. I'm afraid I'm going to have to go with a grind and new bearings, and 0.011 won't likely do it. I'll have to go 0.020"
Originally Posted by L88Plus
I agree that the hone marks on the rods indicate they were resized.
Looks like a dirty block with crap that ran through the oil system took out the bearings. The resulting increased clearance is what killed the oil pressure.
I can't imagine that the crank won't need a turn, how does it look?
Hate to say it, but she's gotta come out.
Yeah, the truth was painful but I'm off the ledge now. What the heck, I need something to do with my time and money anyway, right? So yes, some junk ran through the system and glad to at least have a reason for the low pressure. I don't know where I went wrong, but I missed the debris before assembly. So, any reservations about going 0.020" on the mains and pins? Thank you for your frank response; it's the best medicine.
20-20 regrind no problem. Do ensure they leave a gentle radius / fillet. Unless you're gonna do it, also have them chamfer & dress oil holes.
>But before assembly, suggest block is professionally cleaned via bake & blast. Many auto machine shops can do it; some cannot.
That means new cam bearings ... again ... but it's the best way to loosen hidden crud-crust.
All damage from trash in the oil.... dirt or machining junk that wasn't properly cleaned before engine assembly..... the more you ran it, the more it ate up the bearings and the more bearing material added more trash into the oil.
Engine needs to come out and be torn down... cam bearings are no doubt ate up as well and the oil galleys are caked with trash that will need to be cleaned out in a hot tank/Vat.
Would like to see what the crank journals look like as well...can't be good.
Had the same thing happen to a SB. You need to inspect the pickup very closely. Carbon and tiny pieces of metal can get thru the screen and collect in the back of the pickup, well out of sight. Soak it in lacquer thinner for a few hours and rap it on a hard surface and see if junk falls out. I would only use a CJ-4 diesel oil.
Last edited by itsforfun; Apr 30, 2019 at 05:28 PM.
The engine's coming out this weekend and I'll tear it down. I'll look at everything very closely and have a hard look at the resized rods to make sure that the bores are round, and to proper size. Yes, crap in the engine got distributed throughout. I may be the case that a rod wasn't machined correctly and introduced the initial bearing material that cause the snowball effect. I'll have an idea soon. I'll have the block cleaned properly, new cam bearings (already talked with a shop that will do that), turn the crank with fillet/chamfer treatment, and have the roller lifters cleaned (likely metal particles in them, in need of cleaning). Hopefully my new Howards cam is still good. Rklessdriver, the main journals are not pretty, but not catastrophic in the sense that a 20 grind should bring it back to service. I'll take a few photos when I'm back home in a couple of days.
As for oil, I'm running a roller cam so thinking I don't need the zinc, but always open to comments.
Thanks for all of the info and support. I have a good machine shop lined up. Hoping to get her back on the road in a month. It's only time & money, right? Good luck with all of you and your own projects.
FWIW rods Must be torqued to spec during honing & during measuring ... not just snug ... TQ to spec w/proper lube.
Probably a dozen years back, some sbc eagle SIR rods were failing ... culprit should have been caught during motors' dry-fit ... rods were apparently sized without being TQd to spec/ wrong or no lube/bad gaging etc.
Always properly gage new/resized rods for round.
Is this a cast or steel crank? A lot of people won't touch a crank cut more than .010. You are cutting through the hardened surface into soft steel or iron. A new crank should be considered. And as long as you are contemplating this, can you say 496?
Good time to check prices-- a NEW 4" stroke, 2 piece RMS 4340 crank can be had for around $695. And a decent set of forged rods is about the same price as having a set of rods reconditioned with ARP bolts. All I'm saying is since you're going to crack it open, spend your $$ wisely. A full forged rotating assembly can be had for what you spend reconditioning rods, grinding the crank, and making it all go back together. Ohio Crank has a full short block kit for less than $5k if you're willing to build it yourself.
Sounds cheap and easy to build a 496, right?
A cheap rotating assembly with a cast crank, so so rods, hyper pistons, rings and all the little components will cost you about $2,400.00.
Upgrading to a forged crank, I beam rods, forged pistons better rings and you are looking at $3,000.00.
Upgrade again to forged crank, H beam rods, forged pistons, better rings and it was easy to spend $3,500.00.
Add additional cost to have your block clearanced for the longer rod stroke, a new oil pan, and the list is just beginning.
Of course you will want a different cam, heads that flow better, new intake, bigger carb and new headers with larger primary tubes.
Now that you will be putting out all that torque, will your trans, clutch, u-joints, differential and half shafts hold up?
To do it right isn't cheap, but it's worth every penny.
Good Luck
Last edited by OldCarBum; May 2, 2019 at 11:57 AM.
