I had found the video about using the pressure/vacuum gauge and that is what we were trying. We never could get reading one way or another as we pulled through the cycle. Reminder I can't get any compression on #8. I will try with a long straw or something to visually see the rise and fall of the #8.

Would tapping the intake or exhaust valves with a soft hammer reseat a sticky valve?

 

Ah, somehow I missed the no pressure thing.. But, since you have the valve cover off, you should be able to see when the cam lobes are not opening the valves, then just use the long screwdriver trick (or whatever long stick you have laying around) and find where the piston is at TDC when the valves are supposed to be closed, this would be TDC on the compression stroke or power stroke as some call it, and this is the condition you need in order to perform a leak down test.

 

Following this thread as I have the same symptoms on my #3.

 

With at least 100 to 200 pounds of valve spring pressure being applied to the valves, your hammer tap isn't going to make any impact.

>>>>>>>>>>>Action

 

Checked for the 3rd time on #8 just to make sure before I started tearing into this thing. Still lots of leakage when the intake valve is supposed to be closed. Verified with both the cam lobes, and a 1/4" extension in the spark plug hole to find TDC. After I tried that, I found TDC on #1 really easy with the vacuum/pressure gauge. I never did a leakage test, but I did figure out how the vacuum/pressure gauge works to find TDC. I pulled the radiator, and fan this afternoon before family got me distracted... Even loosened the crankshaft bolt. I'm going to do a leakage test on #1-4 tomorrow just to see what that side looks like as I have gotten a few #1 misfires. I figure I might be redoing 1-4 anyway as I'm going to tear the other half down, so why not do both...

The bigger question is, do I look for manufactured heads, or rebuild these?

The plan for tomorrow is to pull the intake off, and get the cam timing figured out. I'm debating if I should pull the exhaust with the head, or take the exhaust out first?

 

Depends on what the issue is. You never know if you have a crack in the head or not. Remove the head with the exhaust manifold on, it's a royal pain in the *** to remove the exhaust manifold as it's so cramped in there, so it's way easier to remove that once you have the head on a bench. Good idea to verify the other side, would be really annoying to fix half the engine and then find out you have an issue with the other half as well.

Although not necessary, I would suggest that you replace the timing components as well, chains, guides, tensioners. They're coming off anyway, so might as well do it..

 

Today, I finally had most of the day to work on the truck. Got the intake manifold off. Big issue I had with this was the heater coil line that goes to the firewall and the manifold. I couldn't pull it off the manifold, so I had to disconnect it both on the block and at the firewall. Kind of a pain, but doable. Prior to pulling the intake manifold, I took the hood off finally. Much more room to work with!

Once I got the intake manifold off, it was fairly easy to get to the right side valve cover. A few of the plastic pins holding the wiring harness gave me some grief, but more due to the location (near #4) than anything else. Once I pulled the valve cover, I removed the front engine cover. I never had to disconnect the power steering pump, but the 3rd bolt was blocked by the power steering line. I used a racket wrench to get that one. After pulling all 19 bolts from the front cover it popped off easy. I doubled checked TDC on #1 before I pulled the timing chains. According to the book, one side of the time chain was marked (for easier install), but I went ahead and made multiple marks with a sharpie.

My biggest pain today was getting the bolts that hold the exhaust manifold to the exhaust pipe off. Heated, sprayed with penetrating oil, heat again...repeat. Finally, I borrowed my FIL's impact wrench set, and I was able to finally break free the rusty bolts with the impact socket. A big 1/2" breaker bar was the key. I ended up using the same set up for getting the head bolts loose as well. Tomorrow the plan is to finally pull the head!

I'm still debating if I should pull the other head off as well. I'm going to ask the machine shops when I call around and get quotes.

 

Before you start machining and overhauling the head you remove, verify what the problem is. Best case, it's just a bad valve, or valve seating. Worst case, there's a crack in the head. A crack means you need to buy a reman head. It's 450 to 700 dollars depending where you buy it, with a 125 dollar core. If you're gonna do both heads, I would try to find out if PI heads would fit on a '98 4.6, that's an improved version of the heads.

 

It's my first time doing anything like this before, but once you pull the heads don't you have to get them resurfaced anyway? I can see the value in pulling the valves to double check before I send it in, but is replacing/pulling the valves something that I could do?

I called around and got quote for rebuilding the heads; the closest place wanted $600 for the pair with about a week turn around. A place about 50 miles away gave me a quote at $325 for the pair with a 2 week turn around.

 

Typically a remanufacturer or rebuilder will re-surface the head in the process of the over haul. And the point Skauber is making is before the work is done do inspect! You want to know what caused the issue and what is the issue. The first may not be so evident. The second is a must. If the head is cracked, that has to be addressed before any machine work is done. The crack may not be repairable or may be repairable however with major effort.


$325 a pair is very inexpensive. So much so I would be skeptical. Not saying it isn't possible and I would be asking questions about anything less than $400 a pair.


>>>>>>>Action

 

You don't ALWAYS have to machine the heads, depends if they're warped or not. If they're not warped or have any issues with the surface, then there's no need of machining them. When you pull the head, you need to find the problem before you start putting money into rebuilding the heads. If there's a crack, any work you put into that head is wasted as you're not gonna be able to use the core.

 

Okay thanks for explaining this. I will pull the cam shaft off, and inspect the valves, springs, etc.

Any suggestions for looking for cracks? I know that I was having leakage out the intake valve so I will pull that spring and valve first.

 

I wouldn't pull the valves out before finding the problem. There are several ways of finding cracks, but if there was leaking air from the intake, I would start by applying some air pressure to the intake port with the valve closed, and see if you can find the leak. Do the same with the exhaust as well.

 

Pulled the valve from #8 and #7 to compare each other. #8 valve is bent.. Also #8 spring measures 2.030". Spec according to the book is 1.951" #7 isn't as bad at 2.015" but not anywhere close to the book. Haven't finished cleaning the head to see f any cracks are present, but a bent valve isn't a good thing..

Didn't see your reply about apply air to the valve to check for leaks in the head before I pulled the valve.

 

[QUOTE=ctown2;16191682] Haven't finished cleaning the head to see f any cracks are present, but a bent valve isn't a good thing..

{/QUOTE]

I hate to even read this I can only imagine what you feel like.

The valve guide from the bent valve is likely to have issues if not a crack. I believe you have found your stuck valve.

Many re-builders will magna-flux to check for cracks before re-building. Exchanging heads may be a good option at this point.

>>>>>>>>Action