|Topic Review (Newest First)|
|07-21-2019 08:24 AM|
|DPeterson3||I like the Valvoline VR1 50W Racing oil, as it contains plenty of zinc, preferred for our flat tappet engines. I don’t mind giving it time to warm up before pressing the loud button closer to the floor. I’ve also been using their VR1 20W-50 with no reduction in pressure. Like all Alfas I’ve had, the idle pressure can appear quite low, but it comes up as soon as the revs come up.|
|07-20-2019 08:58 PM|
|07-20-2019 04:38 PM|
There is not an infinite supply of new, LOBO bolts.
The three special shoulder-bolts are new, sourced from AFRA. It was one of the three standard bolts that failed across the head. I have plenty of these standard M8-1.25 bolts, so replaced it with a good unit. As you can see, it was not over-tightening that caused the failure, rather an entrained corrosion. In 50+ years of playing with tools, this is the only one like this I’ve seen.
This engine was given its first start on Valvoline VR1 20W-50. After the 25 or so initial KM, I drained this oil and replaced it with Valvoline VR1 50W. I had noticed the low oil pressure during the last two drives, which had been long enough to warm the oil, so thought I’d see what the heavier oil produced.
It was on the next drive that things went pear shaped.
It seems unlikely that straight 50 did any harm. More likely the low pressure was indicating the impending failure.
Hit 10,000 miles in 00072 today. Bloody hot out, but he thunders on.
Picture of intact plug noted by Franco. This plug didn’t get removed for rodding during the overhaul, but early testing shows good flow through the rear main shell.
|07-20-2019 04:16 PM|
Originally Posted by DPeterson3 View Post
It might be worth the extra expense to replace the other five pressure plate bolts and why you are in there the flywheel and guibo bolts...
|07-20-2019 11:31 AM|
I don't want to distract you right now from getting the 2nd engine running. Feel free to ignore my questions -- either completely or until you have more time to analyze and/or comment on the failure -- I'm sure the post-mortem will become a very interesting (but unfortunately, for you, also frustrating part) of this thread.
Could you also tell us what oil you were using? I the past, I got the impression that synthetic 20W50 oil resulted in less pressure at operating temperature than 20W50 mineral oil -- i.e. that the viscosity was not the same despite what the label said.
Did you intend to use a different oil for the break-in period than for regular use? I heard from engine builders that they use a thinner oil for the first 20-50 hours of operation to let the rings get seated.
|07-20-2019 06:25 AM|
The bearings were new manufacture, and now I’m thinking they came from CA.
This is a no-oil problem. But that’s about all I’m sure about.
When first started, pressure would go to about 60%. Typical Alfa. After oil temp came up, pressure at 3000-5000 about 35%-40%. Not acceptable. I checked and cleaned the pressure release valve, and added a washer under the spring. Pressure at start (cold) went to about 75%, showing that the unshimmed spring had been correctly controlling high pressure. Pressure when warm, still about 35%-40% at 3000-5000.
So, I’m not expecting release valve is the problem. I just wish it was.
I’ll post a pic of the bearing shells later, but the mods may yank the post for being gratuitously horrific.
After I get a new compressor (tank died), I’ll do more flow checks on galleys. It is pure conjecture, but it’s as though there would be a little flow at startup, but then something loose would block at a critical point, shutting down flow.
I’m expecting new head gasket(s) Monday. Replacement engine complete Tuesday. Maybe installed also.
|07-20-2019 05:51 AM|
OKP probably supplied you with newly manufactured bearings -as opposed to NOS bearings. If not, I recall long ago that there was a problem experienced by users of NOS bearings, after long term storage. When manufactured, the bearings were covered at the factory with beeswax wrap. Apparently sulfur from the beeswax wrap attacked the soft metal and caused inter-granular corrosion, ruining the NOS bearings.
I am sorry for your loss but I must say that I admire you for your 'truth in reporting' and putting it all out there for us -no fake news here!
In rebuilding the Duetto's 1600 cc engine for the second time in 35 years, a local engine builder/club member 'Ernie' has 'saved my bacon' on 3 or 4 occasions, already!
|07-19-2019 11:38 PM|
It is clear that this story of low pressure when the engine is hot is a serious track.
The blocked valve seems a good hypothesis.
When hot, how was the pressure behaving when going up into the rpm ?
|07-19-2019 10:46 PM|
Originally Posted by PSk View Post
The only gasket sealer I use for the cam covers is at the very rear at the joint between the gasket and large rubber ring.
|07-19-2019 09:32 PM|
Hmmm, a stuck pressure relief valve makes sense to me.
What I don't understand is I thought this engine had run for quite a long time by now, with tuning and small test drives, so I'm suspicious of what was changed when the cams were played with ... did something get dropped down the timing chain chest and cause issues below?
Gasket sealer for the cam cover drop off and end up clogging oil pick up ... ?
|07-19-2019 05:32 PM|
You"ll get it.... I think a stuck open relief valve would not lead to your kind of starvation.
.002 - .00250 maybe even .003 oil clearance on a round journal works. Like you said this ain't your first rodeo.
That video of your other spider with the engine sounding like NO other iron 2.0, that I ever ran across, is assurance you'll get to the root in short order. Thanks for sharing!!
|07-19-2019 04:00 PM|
I had also problems with low oil pressure in my "rebuilt " engine
the problem was a forgotten plug.............
in the iron cast ( see picture )
|07-19-2019 03:35 PM|
Originally Posted by ballough510 View Post
No, I do not believe I blocked off anything. I dismantled the engine slowly, looking for anomalies. The gasket punch-out was never a problem, although I noticed it during disassembly. I’m not even sure it was pre-punched. It may have become sort of embossed by covering an open hole with the aluminum plate pressing on it.
This morning, bright and sunny, I spotted the suction pick-up hole for the oil pump, and suddenly wondered if that was where the gasket punch out had been? When I found the punch out in the trash, I quickly matched it to the hole in the front of the engine, and that closed that line of inquiry.
My line of inquiry, when I get back to it, will be the oil pressure release valve. The engine made good pressure from start up, but it wasn’t until I drove it more than around the block that I saw the loss of pressure once the oil warmed.
By the way, a comment above notes how a bad crank grind can cause this, but no clarity on what the writer was thinking.
I accept final responsibility for my rebuilds, so I measure everything as I assemble. Not just the journal ODs, but also ovality, taper, radius, etc, then I platigauge to confirm it’s all ok and has the right clearance.
There are some cranks that might require rechamfering the oil holes, or rehardening the surface, but that’s not a factor with our 102s.
My replacement engine has one of Myron’s spin-on adapters. Don’t know yet if that’s good or bad.
|07-19-2019 02:50 PM|
Holly smoke Don..... Make sure you get to church early this Sunday. Broken bolt like that?
So do you think you may have blocked off a main galley with a gasket?
|07-19-2019 01:31 PM|
|Jim G||A crankshaft that wasn't turned correctly will do the same thing that has happened in your engine.|
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