2000 Honda Civic with 186k
Original D16Y8
Timing belt broke, was replaced (along with water pump and other necessities)
Fired up again afterward and here's a video of how it runs:
http://www.youtube.com/watch?v=9TzTSlDGF-g

Low compression in 3rd cylinder (~60psi)

Can I just machine the head or do I need an entire engine swap?

 

Any ideas?

 

probably bent the valves and damaged a piston. wont know anything until you atleast remove the cylinder head.

 

Its going to take more than machining to fix that. More than likely you have internals that need to be replaced. Mainly valves.

Since the motor has 186k on it already I would just swap it. D series' are a dime a dozen anyways so no big deal.

 

Yes I would say that you bent some some valves. Honda doesn't relieve the pistons to clear the valves so the best case scenario is you just bent a valve or two but you will have to pull the head and inspect everything. I think I remember one case on here awhile back where someone's belt broke and they turned the car off right away and replaced the belt and it ran fine after that.

 

definatly bent some valves... take the head off and bring to machine shop they can figure out what valves are bent... if u go this route make sure when u but head back on u adjust the valves to spec

or buy some valves online and put on urself easy to do and save some money

 

Had a mazda that sounded like that and it ended up being the timing belt tensioner. Did you replace it when you did the belt? If not that could be your problem. Hope this helps.

Did not read the low compression part sorry but sounds internal.

 

Took the head off and everything looks fine. Even took it to get machined and the guy there said there's nothing wrong with it.

What could it be?

 

Did you check for piston/cylinder/block damage?

Before you removed the head, you should have done a cylinder leak down test to know where compression was lost.

I suspect that one of the valves is slightly bent, though other possibilities are bad rings in one of the pistons or even a blown head gasket.

 

Take the head to another shop and have it inspected. There is likely a bent valve or cracked guide. A bent valve is hard to see with the naked eye. I had a bent valve when I had my engine rebuilt and the shop showed it to me the only way you could tell was the valve seating surface was worn a little funny. Cost was $13 for a new valve.

Hopefully you didn't bust a piston skirt or anything. Pistons don't like to smack into anything while hammering away thousands of times a minute.

There is an awesome tool I saw at costco yesterday:

http://www.whistlergroup.com/WIC-3509P-spec.html

Can you imagine being able to look inside your assembled combustion chamber, under the intake manifold or up into your oil pan through the drain plug opening?

Well worth $150. It would pay for itself quickly.

Found this as well:

http://inspectioncameras.net/

 

Did you have a shop do it? They did not inspect before doing it?

Have you tried to drive it?

I am curious was it an original belt? or it was changed before?

 

I tore down a Toyota 3.0 V6 once (broken and/or melted valve) and the timing belt had about a 1/4 inch tear in one side. Non-interference engine though...

The valve had a little bite taken out of the lip (0 compression that cylinder). Didn't find any debris in the cylinder, all I can think is the chunk of valve was blown out right when it broke or it just melted away. The spark plug/cylinder was oil soaked probably due to failure of the guide/seal.

The cause was preignition/detonation because the previous mechanic had pinched the knock sensor wire between the intake manifold and cylinder head when reassembling.

Another reason I do all my own work now.

Also, take the head to a reputable shop. The shop I had repair/resurface these heads chipped the sealing surface all around the oil ports pretty much eliminating the possibility of the head gasket sealing there...

Thats what I got for going with the lowest bidder.

</ramble>

 

Forgot to mention..

The headgasket was surprisingly in bad shape after I removed the head (chunks were missing at one area around cylinder 3)

And there was also a HUGE split in the exhaust header.

 

Elaborate on said "chunks". There is a rubber gasket that will seperate during removal, but if it's MLS, it shouldnt be missing chunks...
better yet, take pics of the head at a near flush angle and pics of each cylinder. From the sounds of the video, your mechanical timing sounds off by a tooth or two.