Focus Fanatics Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter #1
So my timing belt went out. After finally taking it apart the end result 10 bent valves, (all the exhaust valves an 2 intake valves). .
There are marks on the the pistons from were the valves hit.

My question is since the valve hit the pistons like that do the pistons need to be replaced?

An if not what kinda damage should i look for in the cylinders?

Here are some pics.

Another question is the ring at the top of each cylinder wall supposed to be there or not?
 

Attachments

·
Registered
Joined
·
3,080 Posts
Pistons are fine. Just polish the high spots from the valves hitting off. Yes the ring at the top of the bores are fine. Just check with a finger nail if you have a step. That line is from the fact that the top piston ring stops at that point in its stroke.
 

·
Registered
Joined
·
3,080 Posts
On a side not i hope you marked the cam gears before you took them out. It's not the end of the world but it makes it a lot easier to line back up. And I see you did the snap an ear off the cam bit. Just makes it a tad bit harder to line up.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #4
What do you mean mark the gears ? And yeah i broke that ear when attempting to but the new belt on before we realized it was an interference motor
 

·
Registered
Joined
·
18 Posts
Discussion Starter #5
An thank you i was so afraid that the block would have damage an i would have to give up on the car ,but i noticed to, i broke one of the little plastic lines that went to the injectors
 

·
Registered
Joined
·
321 Posts
You seem to be one lucky guy - visually I can't see any serious damage to the piston crown surfaces so I say you are good to go. Just make sure no debris gets lodged between the piston and the cylinder liner - use a vacuum to clean it up and smear a little bit of grease on the outer edge of the piston to prevent metal fragments from falling in when polishing the top. Wipe the grease off once finished.

As for the valves, I recommend changing all of them and the stem seals as well - these are usually included if you buy a head gasket kit.
 

·
Registered
Joined
·
321 Posts
I worked on a friend's Focus that suffered the same fate as yours but had more damage on the piston crowns. We made a judgement call and repaired it instead of replacing the engine. We filed down the dents on the pistons as much as possible and since in theory at least, this would have slightly changed the compression ratio, we took extra care to install all new valves 100% leak proof. Be patient and take your time to lap the valves and seat them properly. While we're at it, we also replaced the coolant pump and the injector O'rings. We used an Elring head gasket set which also included the stem seals and the valve cover gasket.

Months down the road, the car still runs 100% and has more pull than it did before the incident at 125k km.

Good luck.
 

·
Registered
Joined
·
360 Posts
Engines are tough. Years ago I had a 78 Kawasaki 650 and one day one of the rings flew up into the number 1 piston and got crunched into pieces. The inside of the head on that cylinder looked like it had been shot-peened with broken glass. Amazingly the valve seats and valves were still intact on the head.

All I did was take the top end apart, replace the pistons and cylinder walls, reassemble everything and bolted on the original head, and the engine ran for years afterwards.
 

·
Registered
Joined
·
321 Posts
@tmittelstaedt "Engines are tough" - So true. I remember the more we researched the Internet, the less our confidence that the pistons with the damaged top would work. I'm not saying that issues with hot spots, etc. aren't real but at the end of the day, one has to calculate the risks and make a call. In our case it worked perfectly and I see no reason why wadew1 shouldn't have a similar outcome.
 

·
Registered
Joined
·
17,175 Posts
Every valve mismatched must then be reground and lapped in and the valve clearance at tappet rechecked and reset.

Use the head with the most good parts and save yourself mucho grief. Of course if you don't have the cams that ran with that head you will be resetting all clearances anyway. Gotta be done.
 

·
Registered
Joined
·
321 Posts
You shouldn't unless you really have to. If you plan to use any of its parts on the original, you will need to recalibrate the valve train for correct clearances. Tappets have different thickness and should maintain the same valve location. Replacing cams, bearing caps, etc. has even tighter tolerances due to their machining properties but other members on this forum can provide you with better advice on this.

The way I see it is that if you are going to remove the head, you might as well renew what's needed. A set of new valves and stem seals aren't that expensive when compared to the time and effort and the rest of the items will need to be replaced anyway (bolts, gaskets, etc.)
 

·
Registered
Joined
·
17,175 Posts
Somebody has not been pricing valves lately............

The cam caps CANNOT swap, they are matched to the head as they were machined as a set together.
 

·
Registered
Joined
·
321 Posts
@amc49 - Over here you can get a complete set of quality valves for $200, sales tax included. Probably they're even cheaper in the States !
 

·
Registered
Joined
·
17,175 Posts
At one of our cheaper sources which should be cheaper SVT exhausts are $20 each, could not quickly find intakes......which should be cheaper. I haven't done one, just used to the usual norm of 16V engines or $300+ to do an engine.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #18
Ok guys thanks for all the help. Yall reallly are great..ok so im kinda strapped for cash at the moment. just found out the ole lady and I are gonna call it quits. So i have the other head but it looks ok to me but with my lack of experience im not sure but its complete except for the vct solenoid so and the deck surface has some scratches can they be machined? And its missing a bolt for one of the cam caps.an the cam caps were out of order come to think about it but werent tightened down all the way
 

·
Registered
Joined
·
17,175 Posts
A light deck cut will clean up the scratches. Put the cam caps back in order and look CLOSE to make sure each cap seems to match the machine cut on the head itself. What if someone simply pulled caps off another motor to stick them on that head? That would be a serious issue.

Caps and head have the cam bore done at the same time and then those caps are matched to head and why they are numbered or lettered. Each cap must match the head like at the bore hole like they were matched before, if they overhang or otherwise do not match, a problem.

No sense in using that head unless the valves have a valve job. That will require competent machinist to allow for cutting without having to change the tappets up for clearance again. Look into lapping valves only, that may remove little enough you can still use all/most of old tappets. The tappet clearance can be set up with head off engine, in fact the easiest way to do it.
 
1 - 20 of 22 Posts
Top