Ok. This is my 3rd new post. I did a compression test and cylinders #4,6,8, and #3 have no compression!

I originally bought the truck from a guy who had the timing chain break. It has 189k miles.

I'm tearing down the engine and am getting ready to pull the intake/plenum (correct?), And then the two heads. I removed the #2-8 cylinder valve cover on the passenger side and saw nothing visibly wrong.

What would cause compression to be lost in #4,6,8 on the same side? Cracked block? Bad head gasket? Bad plenum? Exhaust manifold loose?

I've done work on 4 cylinder ohv engines before but not a V8. I'm no engine expert by any means.

What should I look for? Broken valves? Cracks in the head/block?

I want to do an easy rebuild for as cheap as possible. I was going to pull the plenum/intake because I'm pretty sure that has to come off first.

Then pull both heads and see if the valves are broken. Once the heads are off, visually inspect the Pistons.

If the pistons are not damaged, should I replace the rings? Should I replace the Pistons anyways? Can I use stock piston size?

I should know more when I remove the heads as to any damage I see.

I'm not sure what all should be replaced on the engine when I rebuild it. Do I need to do anything else besides gaskets and head bolts? If I replace the valves, is there anything else i need to replace with the valves? Valve stem seals? Do I need to change main bearings? Cam bearings? Connecting rod bearings? Shou

Do I have to take the heads to a machine shop?

I'd buy new heads but they're $630 for the set.

I need step by step detailed instructions please!

 

If the timing chain broke, most likely the valves got bent and are no longer sealing. You should consider just picking up a used replacement from a junk yard. Just check it out in advance, doesn't make a whole lot of sense rebuilding if you can find one in good shape you can drop in over the weekend and be back on the road.

 

The firing order is 1/8436/572, all of your bad cylinders are together, suggesting contact between the piston and valves. Your cheapest fix will be to find a low mileage junk yard engine and swap them. Otherwise tear them apart and look at the valves and pistons. How does the cross hatching in the cylinders look? Is there a tall ridge on top of the cylinder? A cylinder leak down test before disassembly would show how bad the leakage is, and where it's leaking. Take pictures so we can look at it too.

 

That's not a bad idea. I could go to the pick n pull. You think that's better than just replacing the valves on all 8 cylinders? Also the #3 cylinder on the other side.

 

Passenger side valve cover removed.


Almost got the exhaust manifold off.


Where the AC compressor was.


The hole in the middle bottom is where I found the (temp sensor?) broken.
A leakdown test on the 4 cylinders with compression? Can I do a leakdown test on a cylinder with no compression? And leakdown meaning put a cap full of oil in the cylinder and then test the compression again?

I'd hate to swap an engine and then just have it break down on me again.

I'll know more when I take off the heads I hope. I should be able to pull them both off on Monday. I'll take pictures. Heres a few I took earlier today.

 

Leakdown test requires a specific set of gauges, and an air compressor. The gauge set has two gauges, one that shows input pressure, and another that shows cylinder pressure. I usually run input pressure at 100PSI, to make the math easy. If your cylinder maintains 70%, you have 30% leakdown. Etc. (anything less than 25% is considered 'good', but, I don't tend to be that generous.)

Best thing about the test is you can HEAR where the air is exiting the cylinder. Gives you a really good idea of where the problem is. Of course, with four dead cylinders, I am thinkin a replacement engine will end up being the cheaper/easier/faster fix.

 

Yeah, but you are not just replacing valves. Gaskets, bolts, machine shop fees... and you know you'll probably find a couple surprises while you're at it. Price out used vs parts/fees for repair, see what you think. People can't give 5.2s away around here, they are dirt cheap.

 

Not to mention what encountering valves does to pistons.......

 

Hey you, Heyyou! You found me, huh?

Well, to be honest, I've been really wanting to practice rebuilding an engine. Maybe, when I pull the heads, if there is no piston damage, I'll just get two junk yard heads. I worry about junkyard engines because most of the cars have nice bodies, and I think to myself, "why is the vehicle here?", And then I figure that the engine quit working.

I have an air compressor at my mom's I plan on getting, but I won't have that until tues and wanted to pull the heads tomorrow. Does autozAutrent the leakdown guage? I'm not sure how to do it.

What if I pull the heads and see no visible damage?

Do I have to use a machine shop? Is that to get the heads dye tested or magnafluxed for cracks? To get it resurfaced? Are they supposed to install the valves?

 

Gaskets and bolts are cheap. Valves are cheap. Pistons are probably cheap.

I was considering spending $100-200 on a rebuild kit. Maybe clean the Pistons, hone the cylinders. Replace the valves and valve seals. Redo the head gaskets. And redo the plenum gasket since those tend to leak oil anyways. It's got a brand new water pump it looks like. Brand New timing chain. New tps and iac. New distributor cap and rotor. I know I can easily swap all that besides the water pump. I wonder if the engine overheated since the previous owner installed a water pump.

Plus, I'm a little nervous about doing an engine swap and remembering where every stinking hose and connector goes.

That's y u see the white marks in the pic, I was using white out to mark places to remind me, lol.