A little help?
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Lead Driver
Joined: Mar 2008
Posts: 7,177
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From: Near Los Angeles
A little help?
Hey guys. I started taking apart engine #1. I did all the rebuild two years ago, and started losing oil psi within 1k miles. Now I would like to find out exactly what happened, and was hoping for some guidance in case I over look something.
I thought I would run the crank and block into the shop, have the block magnafluxed for cracks. I'll double ck the rod and mains with plastigauge first. I'll then go over the rods with a magnifying glass.
Thanks.
There was an issue with one cam journal on assembly. We couldn't get the cam in journal #2 and had to sand the bearing with #600 w/d.
You can dig up the old thread 390 to 300 swap for reference.
Is there anything else I should ck.?
I thought I would run the crank and block into the shop, have the block magnafluxed for cracks. I'll double ck the rod and mains with plastigauge first. I'll then go over the rods with a magnifying glass.
Thanks.
There was an issue with one cam journal on assembly. We couldn't get the cam in journal #2 and had to sand the bearing with #600 w/d.
You can dig up the old thread 390 to 300 swap for reference.
Is there anything else I should ck.?
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
Likes: 4
I've always wondered if the cam break-in grease could cause the engine's oil pressure to drop if the pickup tube was clogged with grease and metal shavings?
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Lead Driver
Joined: Mar 2008
Posts: 7,177
Likes: 377
From: Near Los Angeles
So, I changed the mains and rod bearings. Psi continued to drop. I changed the oil pump to a h.v. and checked all the connections on the p/u and screen. Continued to drop. The only thing I did not ck was the first o.filter to know what had gone through the oil. And when the psi started dropping I changed gauges too, manual, from SunPro to Autometer. It still dropped.
I think I was down to 3psi at hot idle, in gear, when I pulled it. The only precaution I did not take was to have the block magnfluxed. There has to be a crack in the lifter passage, or the lifter bore(s). Oh, I did pull the cam and all the bearings are cherry.
I really just want to solve the mystery because it still keeps me up at night sometimes.
Elder User
Joined: Oct 2008
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I'm not sure how glass beads from the carburetor could get into the oil. Polishing compound up in the valve cover could probably wipe a bearing, but why would your cam bearings stay cherry if that were the case. I'm sure you put some lubriplate 105 or some other type of grease on the crank bearings during final assembly, but did you prime the oil system before initial start up? Maybe the bearings suffered some damage before the oil pump primed the whole system. I think most likely though is a crack like you say. I think the crank bearing just wiped because of lack of adequate oiling pressure and the cam bearings survived just because they aren't stressed like rods and mains are.
Maybe you could make an oil pump primer from an old distributor and drive the oil pump with a drill while you have the lifter cover off and see if you can see oil pressure escaping from a crack between lifter bores or something. I would probably just disassemble it and look everywhere very carefully for cracks.
Maybe you could make an oil pump primer from an old distributor and drive the oil pump with a drill while you have the lifter cover off and see if you can see oil pressure escaping from a crack between lifter bores or something. I would probably just disassemble it and look everywhere very carefully for cracks.
FTE Legend
Joined: May 2008
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From: In my own world
I had originally thought that your carb was leaking gas and it was washing into the oil thinning it until it wasn't lubricating any more. Smell everything that you open up, and see if it has a gas smell to it.
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Lead Driver
Joined: Mar 2008
Posts: 7,177
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From: Near Los Angeles
Maybe you could make an oil pump primer from an old distributor and drive the oil pump with a drill while you have the lifter cover off and see if you can see oil pressure escaping from a crack between lifter bores or something. I would probably just disassemble it and look everywhere very carefully for cracks.[/quote]
I always prime the system with a drill motor. Yeps, assembly lube was used on all bearings. Lol, you're right with the glass beads! I think that is a great idea with the drill and looking in lifter cover. I know this is a perplexing mystery, especially with the cam bearings being good. We got quite a surprise when we opened it up and saw how good the c. bearings looked!
It's just a two year old mystery that I hope to get to the bottom of. I will also put a light into each lifter bore to detect cracks. It is a shame to waste all that good machine work if the block is cracked. Looking at the bearings it makes me wonder if the crank was cut correctly.
Dusty: Yes, I did have a problem with a new fuel pump that malfunctioned and thinned the oil, but it was not much before I caught it and replaced it.
Thanks.
Rod bearing with under 1k miles:
All rod bearings:
And the mains:
Two things happened: something went through the oil, and since the psi continued to drop after bearings, pump change, then there must be a crack somewhere. But if that is the case, why would it hold psi high for a week or so, and then start to drop.
I always prime the system with a drill motor. Yeps, assembly lube was used on all bearings. Lol, you're right with the glass beads! I think that is a great idea with the drill and looking in lifter cover. I know this is a perplexing mystery, especially with the cam bearings being good. We got quite a surprise when we opened it up and saw how good the c. bearings looked!
It's just a two year old mystery that I hope to get to the bottom of. I will also put a light into each lifter bore to detect cracks. It is a shame to waste all that good machine work if the block is cracked. Looking at the bearings it makes me wonder if the crank was cut correctly.
Dusty: Yes, I did have a problem with a new fuel pump that malfunctioned and thinned the oil, but it was not much before I caught it and replaced it.
Thanks.
Rod bearing with under 1k miles:
All rod bearings:
And the mains:
Two things happened: something went through the oil, and since the psi continued to drop after bearings, pump change, then there must be a crack somewhere. But if that is the case, why would it hold psi high for a week or so, and then start to drop.
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