-TheBandit-

iTrader: (1)

Please let me know what you think of this:

-Cold engine on a stand, fully assembled intake to pan, 63k mile LY6
-Harbor Freight two gauge leakdown tester, adjust second gauge to zero before connecting to cylinder-Bring cylinder to TDC on compression stroke using finger over spark plug hole method and flashlight to see piston top
-Connect gauge and read leakdown percentage
-Listen with ear close to dipstick opening in pan, intake @ TB, and exhaust ports

Here are the results I got. I retested the two worst. Update in blue, another retest the next day with the same tester. Update in red, another test the third day with a Snap On tester and a small amount of tranny fluid in the cylinders.

1:40 intake & pan, retest 22 intake only, 15, 0
3:60 intake, retest 30 intake, 48 intake, 38 intake, 45 intake
5:15, 11, 2
7:15, 8, 2
2:28 pan, 8, 15 pan
4:10, 10, 1
6:25 intake & pan, 15 intake, 1
8:33 intake & pan, 20 pan, 5 intake

I am going to retest all these cylinders, but I want to make sure I'm doing this right since I got widely varying results on 1 & 3 after testing. Is there something different about the LSX that I should know about? I'm sure my HF leakdown cheaker isn't the best, but I can clearly hear some air escaping through the intake on the noted cylinders. I know a slight noise from the pan is normal (indicating air going past the rings), but I did have noticeably more noise from the noted cylinders above.

For the ones that made noise past the intake valve, I tried tapping the top of the valve with a rubber mallet with no improvement. In fact they seemed to get worse.

One thing I really don't like about this leakdown checker is it only seems to hit 15psi on the first gauge to get the second gage at zero. I would prefer to do a leakdown check at higher pressure since it seems like that would have a better chance at seating the rings. I'm thinking I may replace the second gage with a standard zero to 150 gage and check this at higher pressure.

Any input is appreciated!

1SLwLS1

iTrader: (6)

FWIW, I have only ever performed a few leak down tests, and have always borrowed expensive gauges from friends that have the $$$ for quality tools. I always did the tests with the engine warm, making sure everything has expanded to running tolerances. I see you are on a stand, not sure if you have provisions to start it while on the stand. I read, somewhere(?), to rock the crank back and forth to give a better chance of seating the rings. I cannot remember where I read that, as it was a few years ago when I learning how to, it was a SBC though.

I would also prefer to have more than 15-20# and that may be the problem there, but I am not experienced enough to know the minimum pressures to seat the rings and seal it up.

1SLwLS1

iTrader: (6)

Also, I would be careful doing this on a stand. Make sure you can lock down the engine, because if you do get some serious pressure in the cylinder, and it can move, it will.

-TheBandit-

iTrader: (1)

Thanks for the reply. Unfortunately with the engine on a stand I don't have any way to get it to operating temp. I trust the HF leakdown gauge about as far as I can throw it, but just the same time I can clearly hear the air excaping through the intake on a few cylinders. My guess would be the valves either haven't seated very well or they are just plain leaking.

Rocking the crank back and forth a little seems like a good idea for seating the rings, but I'm afraid the engine would crank over on its own and take my arm on a 180 degree ride from TDC to BDC.

I'd like to get a flexplate & starter on the engine and run a compression test. I'm not sure if I'll be able to do that with it on the stand (not sure if there's enough room to install the flexplate).

1SLwLS1

iTrader: (6)

Hmm, if the intake is your problem, which it definitely seems to be, I am not sure how much heat as well as pressure would affect the results, however accurate or inaccurate they may be.

nysbadmk8

HF tools are horrifically inaccurate just a little PSA for ya.

-TheBandit-

iTrader: (1)

Yes, I am well aware. I am borrowing a better leak tester today and I'll give this another shot tonight to see if results are more consistent.

Leak tester aside, hearing air from the intake is probably not a good sign.

-TheBandit-

iTrader: (1)

Tested again tonight with the HF leak down tester again, results in blue:

1:40 intake & pan, retest 22 intake only, 15
3:60 intake, retest 30 intake, 48 intake, 38 intake
5:15, 11
7:15, 8
2:28 pan, 8
4:10, 10
6:25 intake & pan, 15 intake
8:33 intake & pan, 20 pan

It seems like #3 is a problem cylinder, or more specifically has a problem intake valve. I also noticed on a few rotations (by hand with a breaker bar on the crank) there was a difficult spot rotating the crank near #3 TDC. Sometimes I would rotate through it with just a slight increase in resistance in that area and other times I would rotate and it would seem to bind up right as that piston went to TDC. It was every 360 degrees of the crank, so any time the piston neared #3 TDC regardless of stroke.

I am going to call the salvage yard I got this motor from and see what they can do for me. This has a 6 month exchange warranty and I'm about two weeks into it.

Also after testing, I took apart the HF tester and it does in fact have an orrifice in between the gauges. It's much larger than 0.040in (the standard), but there is one there.

I also tried putting 100psi regulated straight from the compressor into that cylinder. The engine didn't spin over and I could still clearly hear a lot of air excaping through the intake. I tried tapping the valve a few times and it didn't seem to help.

1SLwLS1

iTrader: (6)

Seems like a wise choice to just swap it for another. Although, does this thing still retain the factory VVT or was it removed by yourself or the original seller?

-TheBandit-

iTrader: (1)

This has the factory VVT. The engine is a complete pull from an '07 2500 pickup and it ran fine before it was pulled. I was specifically looking for an LY6 becuase I want to play with the VVT. I don't think the yard will have another LY6 as they are a bit more difficult to come by. I would prefer to find the problem and fix it. The salvage yard is not local.

My plan is to swap a cam, phaser restrictor, springs, and pushods in this. Based on the leakdown results, I may end up pulling the heads and doing valves too. I wonder if there's just something in there keeping the valve from closing like a carbon deposit or something that resulted from the enginee sitting a few months.

1SLwLS1

iTrader: (6)

Hmm. I am not too familiar with VVT, but I think GM uses hydraulic pressure(oil?) to control the cam phasing. I would think that would throw a wrench in the mix being shut off, not sure though.

Also, since this is VVT, are you sure you are @ TDC on the compression stroke of each cylinder you are testing? Thats the only reason I can think of why the intake would be leaking aside from being damaged in some way.

-TheBandit-

iTrader: (1)

I am finding TDC by putting a finger over the spark plug hole while rotating the engine. On the compression stroke, air is forced out the hole until the piston reaches TDC. If you continue rotating past TDC, it starts pulling air back in on the expansion/power stroke. This can easily be felt with a finger over the plug hole. Neither valves are being opened by the cam near TDC, VVT or not.

The VVT system uses a hydraulic phaser/actuator to adjust cam timing, but it can only mechancially operate over a range of about 50 degrees. Even if the cam timing were fully retared or advanced, the valves wouldn't be near their openings at TDC on the compression stroke.

1SLwLS1

iTrader: (6)

Right. So, there must be something wrong with the intake valve sealing, no?

-TheBandit-

iTrader: (1)

Yes I think that's the logical conclusion. Now to find out why it isn't sealing. Bent valve, burnt valve, carbon deposit, valvetrain geometry keeping it open for some reason - any ideas?

1SLwLS1

iTrader: (6)

Hmm, I wouldn't think a bent valve unless there was contact with the piston. If the engine has ran hot for extended periods of time, a burnt valve could be the case. I assume you are going to pull it apart, if that doesn't void the warranty in place?. Post up your results if you do tear it down.

nysbadmk8

Talk with the parts supplier, See what they say... cause I know if you pull the head off and you find damage.. they wont do a dam thing for you then.

Logical next step if you dont care about the above is to pull the covers, inspect.. watch valve geometry. Pull the heads, inspect pistons, piston walls, combustion cambers and valves and valve seats, valve seals.

-TheBandit-

iTrader: (1)

I called the salvage yard and talked at length with the owner. This is the first time I've talked to the owner, but having dealt with their sales rep already I was not surprised to find he was responsive, willing to work with me, and genuinely wanted to help. I was very methodical in choosing a place to buy this engine from in case something should go wrong or missing. So far I am happy with my choice. He told me he would still honor his warranty if I want to remove the intake and look into things further. He recommended I add a squirt of transmission fluid into the cylinder to see if it frees up the bind and said he'd prefer the engine run at speed with proper lubrication . He said he'd continue to honor the warranty past the expiration if it takes me time to get the engine into the car.

My plan now is to get the intake off, repeat the test with a better tester (borrowed a snap-on tester today), and inspect things to see where they're at.

I'm also going to order a flexplate so I can do a compression check and see if the valve decides to seat at faster closing rates. The engine had been on a crate in their warehouse for about 6 months, so I'm not sure what I should do about lube other than a few shots in the cylinders and maybe some squirts on top of the valves. I dropped the pan last night and looked at everything - it looks like a brand new engine in there. The cylinder honing marks are still there, no noticeable wear in the bores (looking from underneath) and the pan had nothing but a few pools of clean oil in it.

1SLwLS1

iTrader: (6)

Sounds like everything ought to work out great. Post up the results with the SO tester and compression readings when you get em'.

-TheBandit-

iTrader: (1)

In case I wasn't beating a dead horse hard enough, here are the results in red using the Snap On tester. The only difference with this test is I squirted a small (<10ccs) amount of transmission fluid through the spark plug holes before testing. It didn't make an audible difference to the leakages

1:40 intake & pan, retest 22 intake only, 15, 0
3:60 intake, retest 30 intake, 48 intake, 38 intake, 45 intake
5:15, 11, 2
7:15, 8, 2
2:28 pan, 8, 15 pan
4:10, 10, 1
6:25 intake & pan, 15 intake, 1
8:33 intake & pan, 20 pan, 5 intake

I found it interesting that the Snap On tester showed lower numbers overall, but that may have to do with the tranny fluid helping to seal the rings. The only result that's consistent is the #3 leaking significantly past the intake valve. The Snap On tester runs at 100psi.

During this test I pulled the intake manifold and inspected as carefully as I could, but didn't see anything visually wrong with what I could see of the #3 intake valve. It looked like all the other cylinders - just leaked a lot. I verified I could push down the lifter side of the rocker arm and the plunger would move down, indicating to me there was still plenty of "lash" and the valve was not being held open by the cam. I rotated the engine and inspected with the valve slightly open. The seating surfaces looked fine.

I think I'll continue with my plan to do a compression check at starter driven speed to see if anything blows out of the cylinder and whether or not the increased speed makes any difference. Is there any reason put the pickup in oil during a compression check or is cranking without lube ok? This engine has set in a warehouse for a while so it's had a lot of time for the oil to drain.

Anyone have an idea on what a machine shop would charge to grind & lap the valves & seats? Did this myself a long time ago on my small block, but I don't have a source for borrowing the equipment anymore.

nysbadmk8

Dont spin it dry.