My on going 8.1L saga

[brain55]

A couple of months ago I posted about changing the intake gaskets on my 8.1L in my 2001 GMC Sierra K3500 dually.

intake-gaskets-2001-gmc-k3500

Well, things slowed down enough for the winter that I decided to go ahead and pull the engine out, because the 2 quarts of oil every 350 miles was getting to me, and making the truck nearly useless. I also pulled the Allison transmission because it had started to act up shifting into 4th gear, that is a saga by its own right. Anyway the machinist found a problem with the heads, the #7 and #8 intake guides had broken right above the spring seats, definitely a source of oil consumption. Tonight he called to let me know that the cam had a bad lobe and that a new cam was on the way. I had stripped it down to the heads and short block, so he wanted to see the lifters. A few minutes later he called back to tell me that he was ordering new pistons too, apparently the second ring grooves had closed up on almost all of the pistons, enough to bind the rings. I'm glad that we found problems so we weren't putting the engine back together without fixing something, but I sure wish we hadn't found so many problems. I'm hoping when I get it back together this time I won't have all of the problems.

Brian

 

[mbrule]

Hi Brian,

Does this engine have a lot of miles on it?

 

[Diamondpilot]

Brian, with the way you use your truck I would get it back together and make it someone elses problem. You need a diesel buddy.

Chris

 

[Ryan03]

Does your 8100 use a hyd roller or a hyd flat tappet camshaft ? If it is a flat tappet, I would attribute the flat lobe to either improper breakin, or the low amount of zinc and phosphate in todays engine oil. If it is a hyd roller, most times wiping a lobe is a result of to much lash, weak or broken springs leading to valve float, or a bearing failure in the roller portion of the lifter.

I have seen a couple cracked guides on bb chevs before, normaly this is a rocker geometry issue or coil bind caused by mismatching a cam and valve spring.

I have raced and built BB chevy's for 13 years, I blew lots of them up before I got them figured out LOL.

 

[FlaDon]

Does your 8100 use a hyd roller or a hyd flat tappet camshaft ? If it is a flat tappet, I would attribute the flat lobe to either improper breakin, or the low amount of zinc and phosphate in todays engine oil. If it is a hyd roller, most times wiping a lobe is a result of to much lash, weak or broken springs leading to valve float, or a bearing failure in the roller portion of the lifter.

I have seen a couple cracked guides on bb chevs before, normaly this is a rocker geometry issue or coil bind caused by mismatching a cam and valve spring.

I have raced and built BB chevy's for 13 years, I blew lots of them up before I got them figured out LOL.

Should be hydraulic rollers as his is the same age as mine. Oil use in mine has always been 1 qt every 1000 to 1500 miles unless running straight weight SAE 30 oil. 0W-30 or 5W-30 are no different to it than 10W-30 in usage.

 

[Ryan03]

I was not sure in Brain55's case because in the intake gasket thread he linked to in his first post, he talks about having a custom ground crower cam installed, and the first cam having the wrong firing order, which tells me that he ended up using a new cam and not a regrind. He also went on to state that he had custom pushrods installed as well, which implies to me that he either A. had the cylinder heads and or block deck surface milled, B. used a aftermarket performance lifter, which sometimes are taller to allow for the use of a rev kit and require a shorter pushrod, or C. the aftermarket performance cam was ground on a smaller base circle than the stock one to allow for more lift [taller lobes that will still slip through the cam bearing bores].

I think a little more combination specific info is needed from the OP for us to effectively troubleshoot this ,since the intake gasket thread implies that this is a fresh engine with many things changed from the stock configuration. Nothing wrong with that, but it is important to know exactly what was done, if anything to give him good sound advice. It would realy be nice if we could help him get this thing sorted out since he depends on it to make a living.

 

[brain55]

The cam is a roller. The problem with the cam was a bad core, there was a chunk missing out of the center of one of the lobes. As far as the geometry, the reason the pushrods were changed is because this engine does not have adjustable rockers. The cost to go to full roller rockers and adjustable valve train was too much. I would have had to have had custom valve covers made to clear the rocker nuts or spacers, since there is nothing off the shelf to fit this metric pig. The springs were matched to the cam and all of the clearances were correct. This isn't my first time to the rodeo either, nor is it my machinists. At this point it looks like detonation was the problem. The second and oil ring lands were pinched on most of the pistons. I had a cat plug up not long after it was rebuilt and I rattled it pretty good with a load on it. That might have been what did it. The upper halves of the rod bearing were a little beat too. I might be dropping another $2K on cats if I'm not happy when I stick my video borescope down the pipes and check the cats before I put it back together. I also ordered new knock sensors.

Brian

 

[Ryan03]

At this point it looks like detonation was the problem. The second and oil ring lands were pinched on most of the pistons. I had a cat plug up not long after it was rebuilt and I rattled it pretty good with a load on it. That might have been what did it. The upper halves of the rod bearing were a little beat too. I might be dropping another $2K on cats if I'm not happy when I stick my video borescope down the pipes and check the cats before I put it back together. I also ordered new knock sensors.

Brian

That is a bummer . Have you compared the cost of a reman long block with the cost to go through your current engine again ?

 

[Ford tractor]

That is a bummer . Have you compared the cost of a reman long block with the cost to go through your current engine again ?

Or a low mile engine from a junk yard?

 

[brain55]

That is a bummer . Have you compared the cost of a reman long block with the cost to go through your current engine again ?

Fortunately for me, this is not costing me anything substantial. My machinist has known from the first few thousand miles I put on this engine that something wasn't right. The way we both remember it, I had put about 15,000 miles on it when the cat came apart, so the oil consumption was happening before that. It burned 4 quarts of oil in the first 3000 miles. Maybe it was detonating and I couldn't hear it. But either way he has taken responsibility and is making good on it. My job is to make sure it doesn't happen again. As far as a crate motor they are $9000 and a junk yard motor is a rare find, not to mention when we were looking for a rebuildable core we got 3 motors that all needed significantly more work than rebuilding mine.

Brian