oil pressure issue, pics of teardown, what was the cause?
08-18-2013, 08:17 PM
#42
If you're asking if I solved the problem of the engine damage, then the answer is yes. I rebuilt the engine. Found a decent shop to turn the crank 0.010, turn the rod ends 0.002, ordered the correct main/rod bearings, and after 3 tries, finally got a set of durabond CHP-23 cam bearings that fit perfectly (the other cam bearings being the wrong fit was what took me so long). Also went with a melling high flow pump.
It's been back in the car and running for about 3 weeks now. With the 5-30 oil and assembly lube still inside there, I see about 55psi pressure on a hot engine from 2500rpm up, and about 30psi at idle. Still a bit less than I expect with the melling pump and the high pressure spring, BUT it might go up when I switch to 10-30 synthetic after break in.
IF you're asking if I ever found out the "why" behind the original failure, the answer is no. I found no metal missing from any parts of the engine and I can't really figure out how anything could get in there. I guess the most likely answer is that I shot myself in the foot when I powdercoated the external parts, and maybe some leftover blast media was in that stupid vent chamber in the one valve cover, in spite of me thoroughly blowing it out afterward. That's really the only way I can think of that anything could have got into the engine and circulated through the oil.
It's been back in the car and running for about 3 weeks now. With the 5-30 oil and assembly lube still inside there, I see about 55psi pressure on a hot engine from 2500rpm up, and about 30psi at idle. Still a bit less than I expect with the melling pump and the high pressure spring, BUT it might go up when I switch to 10-30 synthetic after break in.
IF you're asking if I ever found out the "why" behind the original failure, the answer is no. I found no metal missing from any parts of the engine and I can't really figure out how anything could get in there. I guess the most likely answer is that I shot myself in the foot when I powdercoated the external parts, and maybe some leftover blast media was in that stupid vent chamber in the one valve cover, in spite of me thoroughly blowing it out afterward. That's really the only way I can think of that anything could have got into the engine and circulated through the oil.
08-18-2013, 09:15 PM
#43
I guess since this thread is back up and since I already have the pics hosted, I'll post some pics of the teardown and rebuild.
here's the block completely torn down.
Some clearer shots of the original cam bearings.
I found this in two of the cam bearing bores.
I lightly ground them down.
Comparison pic of the new crosshatch I put in the cylinder with a 240 grit ball hone.
Cleaned up the block after honing all the bores, scotchbriting all the mating surfaces, and rinsing off in the mineral spirits tank.
here's the block completely torn down.
Some clearer shots of the original cam bearings.
I found this in two of the cam bearing bores.
I lightly ground them down.
Comparison pic of the new crosshatch I put in the cylinder with a 240 grit ball hone.
Cleaned up the block after honing all the bores, scotchbriting all the mating surfaces, and rinsing off in the mineral spirits tank.
08-18-2013, 09:53 PM
#45
I bought a set of cam bearings, and a tool to press them in and out.
Turns out the tool is not designed to be used in a press, you're just supposed to smack it with a hammer to remove and install the bearings. But the bearings seemed to sustain a little bit of scratching and burrs when you did this, so I didn't really like that.
Also I found out that all except the middle 3 cam bearing were the wrong size for the block, so I took it back out. Turns out my block is an 04 which doesn't use the same bearings as all the other gen III engines, 04 was a crossover year for the blocks as they had almost all gen III parts except cam bearings and possibly head bolts could be different...and mine was one of the different ones.
So then I ordered more cam bearings, two sets in case the tool messed up the first set and I needed spares. This time they sent me clevite cam bearings. These are a bit wider than the durabonds.
At this point I got a spare shaft and modified it in two parts to allow me to press the cam bearings in without striking them with a hammer, which I thought would give me more control and be less likely to damage them.
So as I pressed in each bearing, the tool's mandrel was hard to get back out of the bearing. I would have to tap it out with the butt end of the hammer to get it out. Then I would check with the cam and it would also be quite tight. So I pressed it back out and saw a high spot beside each drilled oil hole, and at 12 oclock.
So then I tried some fine steel wool rubbing on those areas and pressing the bearings in, checking with the cam, rubbing again, etc. until the high spots seemed minimized.
This went on for quite some time, since I only got one or two hours per week to work on it. When all was said and done, I had tried and modified both sets of clevite cam bearings and even after massaging them for hours, the cam still felt kind of tight and did not have sufficient clearance when checked. I was frustrated and pressed all of them back out and tossed them in the trash.
Turns out the tool is not designed to be used in a press, you're just supposed to smack it with a hammer to remove and install the bearings. But the bearings seemed to sustain a little bit of scratching and burrs when you did this, so I didn't really like that.
Also I found out that all except the middle 3 cam bearing were the wrong size for the block, so I took it back out. Turns out my block is an 04 which doesn't use the same bearings as all the other gen III engines, 04 was a crossover year for the blocks as they had almost all gen III parts except cam bearings and possibly head bolts could be different...and mine was one of the different ones.
So then I ordered more cam bearings, two sets in case the tool messed up the first set and I needed spares. This time they sent me clevite cam bearings. These are a bit wider than the durabonds.
At this point I got a spare shaft and modified it in two parts to allow me to press the cam bearings in without striking them with a hammer, which I thought would give me more control and be less likely to damage them.
So as I pressed in each bearing, the tool's mandrel was hard to get back out of the bearing. I would have to tap it out with the butt end of the hammer to get it out. Then I would check with the cam and it would also be quite tight. So I pressed it back out and saw a high spot beside each drilled oil hole, and at 12 oclock.
So then I tried some fine steel wool rubbing on those areas and pressing the bearings in, checking with the cam, rubbing again, etc. until the high spots seemed minimized.
This went on for quite some time, since I only got one or two hours per week to work on it. When all was said and done, I had tried and modified both sets of clevite cam bearings and even after massaging them for hours, the cam still felt kind of tight and did not have sufficient clearance when checked. I was frustrated and pressed all of them back out and tossed them in the trash.
08-18-2013, 10:28 PM
#47
I ordered a new set of durabond CHP-23 coated cam bearings.
I also sent my tool's mandrel to another forum member after reading his rebuild thread in which he made his own tool, which seemed to be superior to mine in terms of safety to the cam bearings. I had him modify mine to match his. This would prevent metal to metal contact between the tool and bearings under almost all circumstances.
I pressed in the durabond cam bearings with ZERO issues, and the cam fit perfectly and had proper clearance immediately. I could tell that it was finally right at this point.
I guess the clevite bearings just have terrible quality control or perhaps they were still not the correct ones for my block.
So at that point I resumed the build and taking pics. Here are the main and rod bearings.
My engine had previously been rebuilt. It is an LS6 that is supposed to have the coated piston skirts. The engine had sustained damage to two pistons when it died in the original corvette before ever being rebuilt, and apparently the machine shop had replaced those two pistons with uncoated LS1 pistons. I didn't really like that so I tracked down some replacement LS6 pistons so they would all match properly.
Then I sent the rods and pistons out to resize the rod ends 0.002 to suit the ARP rod bolts. Here they are after coming back.
Also got my crank back from being turned 0.010. I started to test fit the bearings and plastigauge them all prior to assembly.
All the mains gauged out perfectly right at 0.015 which seemed perfect from the factory specs and everything else I had read, so I was happy with that. The rods gauged between 0.015 and 0.018 which still seemed well within spec and most of the recommendations I'd read online. So all of that seemed set.
Then I started assembly. I used permatex ultra slick assembly lube on all the bearings.
I used some of this quick-seat powder on the cylinder bores after reading about it online. Of course, I guess I have no way to know how well it actually "works" since I have not built any other LS engines prior to this one. As advertised, it did turn the bore a little bit green after application, which is supposed to let you know that the bores are clean of all loose metal etc.
New rings.
Piston/rod/bearings install.
Cam goes in...
I also sent my tool's mandrel to another forum member after reading his rebuild thread in which he made his own tool, which seemed to be superior to mine in terms of safety to the cam bearings. I had him modify mine to match his. This would prevent metal to metal contact between the tool and bearings under almost all circumstances.
I pressed in the durabond cam bearings with ZERO issues, and the cam fit perfectly and had proper clearance immediately. I could tell that it was finally right at this point.
I guess the clevite bearings just have terrible quality control or perhaps they were still not the correct ones for my block.
So at that point I resumed the build and taking pics. Here are the main and rod bearings.
My engine had previously been rebuilt. It is an LS6 that is supposed to have the coated piston skirts. The engine had sustained damage to two pistons when it died in the original corvette before ever being rebuilt, and apparently the machine shop had replaced those two pistons with uncoated LS1 pistons. I didn't really like that so I tracked down some replacement LS6 pistons so they would all match properly.
Then I sent the rods and pistons out to resize the rod ends 0.002 to suit the ARP rod bolts. Here they are after coming back.
Also got my crank back from being turned 0.010. I started to test fit the bearings and plastigauge them all prior to assembly.
All the mains gauged out perfectly right at 0.015 which seemed perfect from the factory specs and everything else I had read, so I was happy with that. The rods gauged between 0.015 and 0.018 which still seemed well within spec and most of the recommendations I'd read online. So all of that seemed set.
Then I started assembly. I used permatex ultra slick assembly lube on all the bearings.
I used some of this quick-seat powder on the cylinder bores after reading about it online. Of course, I guess I have no way to know how well it actually "works" since I have not built any other LS engines prior to this one. As advertised, it did turn the bore a little bit green after application, which is supposed to let you know that the bores are clean of all loose metal etc.
New rings.
Piston/rod/bearings install.
Cam goes in...
08-18-2013, 10:41 PM
#48
Cylinder heads were not milled this time (had been milled 0.030 in the previous rebuild) but just cleaned with scotchbrite.
ARP head bolts.
Cylinder head install...
Other cylinder head install...
You can see some remaining damage from the previous rebuild/engine failure when the engine was originally a Z06 corvette with a blower that damaged cylinders 5 and 7...
Valley cover etc.
08-18-2013, 11:04 PM
#51
The only thing I did to the last set of durabond's was to take a razor knife and chamfer/shave material from the edges and the drilled holes, as they seemed o be left a little rough to me.
08-18-2013, 11:09 PM
#52
One other odd thing. After I had cleaned the block really well and was about to paint it, I discovered that three of the castings on the outside of the block for the head bolts were actually cracked. I guess someone in the past had done a head install without cleaning out the threads and cracked them when they torqued down the head bolts.
Since I knew it was this way the entire time I've owned it, and they did not leak at all, I went ahead and left them alone, after cleaning the threads out well with home-made taps I made from the old head bolts.
Since I knew it was this way the entire time I've owned it, and they did not leak at all, I went ahead and left them alone, after cleaning the threads out well with home-made taps I made from the old head bolts.
