My head rebuild - getting interesting...

[mcandmar]

I rang my machine shop this afternoon to find the head is finished, basically i gave them the head with just the valves, no cams etc. They have taken it all apart and cleaned it up, polished the intake and exhaust ports, and fitted new valve seals.

BUT, when they took it apart they found one bent valve and two broken valve springs!!! ..Now i've rebuilt a lot of broken engines in the part and never ever seen anything that serious without knowing all about it. Anybody else ever had any similar experiences?

Mark.

P.S. Collecting the head on sat morning, then the fun begins.,

[SteveH]

Never heard of broken valve springs on an S2

[A1QSHIP]

Broken Valve Spring

[QUOTE=SteveH]Never heard of broken valve springs on an S2 [/QUOT
Living here in the states, I have yet to see an actual S2. I do have some experience with a broken valve spring in a 20valve motor. After purchasing my 20vCoupe I noticed that it would not rev past 6400rpm. Also, there was a slight rattle from the valve cover area near the ignition distributor(7A motor). I was told that it was most likely the plastic gear on the distributor drive having excessive clearance. While waiting for the distributor to arrive, I made a spirited run down the Interstate. To my dismay, the low oil warning lamp came on . I was over two quarts low on engine oil!
Also, there was a new more ominous deeper sounding noise from the motor.
Turns out that the top-end rattle was a broken valve spring. The broken bits had worn away the top of an exhaust valve guide. The oil had been sucked past the guide and burned up in the catalytic convertor, so no tell-tale smoke trail. The weak link in the oiling system (#3 rod) had reared its ugly head, spinning the rod bearing. Luckily, the crankshaft was not hurt but I needed to find another 20v motor to find the rods to repair the motor in my car. The rods are not avaliable seprately but I got a great deal from a breaker (I love that phrase). And a factory header too. After the repair, the motor would now rev to the redline. Turns out the knock sensor interpreted the broken valve spring as low octane fuel detonation and a reason to retard the timing, thus no upper rpm range. There was no check engine warning lamp (49 states emissions control) so no warning from engine control module. Expensive lesson learned.

[Chris M]

Thats interesting. I'm also getting a engine rattle from the same area, posted a thread when i bought the car. I've got another inlet cam and distributor gear to fit to try solve the problem but as you have found it could be a broken valve spring. Cheers Tech48.


Chris

[mcandmar]

Now that is very interesting, First off my car is a CQ20v not an S2, Secondly ever since i bought the car its had an "abrupt" rev limiter at 5900-6000rpms, sounds really nasty when it calls a halt to the fun. At least now i know why, thanks

Mark.


[QUOTE=TECH48]

Never heard of broken valve springs on an S2 [/QUOT
Living here in the states, I have yet to see an actual S2. I do have some experience with a broken valve spring in a 20valve motor. After purchasing my 20vCoupe I noticed that it would not rev past 6400rpm. Also, there was a slight rattle from the valve cover area near the ignition distributor(7A motor). I was told that it was most likely the plastic gear on the distributor drive having excessive clearance. While waiting for the distributor to arrive, I made a spirited run down the Interstate. To my dismay, the low oil warning lamp came on . I was over two quarts low on engine oil!
Also, there was a new more ominous deeper sounding noise from the motor.
Turns out that the top-end rattle was a broken valve spring. The broken bits had worn away the top of an exhaust valve guide. The oil had been sucked past the guide and burned up in the catalytic convertor, so no tell-tale smoke trail. The weak link in the oiling system (#3 rod) had reared its ugly head, spinning the rod bearing. Luckily, the crankshaft was not hurt but I needed to find another 20v motor to find the rods to repair the motor in my car. The rods are not avaliable seprately but I got a great deal from a breaker (I love that phrase). And a factory header too. After the repair, the motor would now rev to the redline. Turns out the knock sensor interpreted the broken valve spring as low octane fuel detonation and a reason to retard the timing, thus no upper rpm range. There was no check engine warning lamp (49 states emissions control) so no warning from engine control module. Expensive lesson learned.