I've completed my HG change, thanks for the tips to questions in previous posts. I've taken it out for a spin and it's running better than ever, including fixing a long standing irregular idle issue (the very early signs of HG going perhaps?). Thought I might post a few bits and bobs I've learned as a conversion point, mostly to see if others agree or if there are any other suggestions or tips:
- If changing valve stem seals, rebuild the head before taking it for a skim. Sounds obvious, but I didn't know if it could be skimmed with the valves in place. That way you don't have to worry about damaging the freshly skimmed surface putting the valves back in. Putting in my last valve I managed to scratch the matting surface, fortunately is was only around a head bolt hole. The guys who did the skim said it would probably be fine.
- A magnet for taking the collets out would have been handy.
- When fitting and compressing the valves again, most of the time I got a bigger gap at one end of the spring cap. Don't stuff the first collet down there, because it'll be a bugger to get the next collet in. Always fill the side with the smaller gap first.
- When putting valves back in don't cover in copious amounts of oil. When you try and mount the head back on the block, oil will simply pour out of the holes in the head and foul the matting surface.
- Refit the cam when the head is on the car. I found torquing up the head bolts with the cam out is significantly easier and doesn't require any use of extension bars. Plus you can fill each of the valve spring chambers/bearings with oil before fitting the cam follower/shims, without worry of it pouring out. I also found it easier working on the came when the head was securely attached to the engine. Maybe this is easier on a 8v non-interference engine, where TDC is marked on the cam.
- On the Punto you have to remove one of the engine mounts that attaches to the head before you can remove the head. It's well worth reattaching this before attempting to unscrew the head bolts to counter the rotational force. My first head bolt I put some serious twist on the engine with relatively little physical effort by me (I was using a 60cm breaker bar, no doubt significantly increasing the small amount of force I was applying). There's no warning about this in the Haynes manual.
- If you're going to leave your engine supported underneath on bricks for a couple of days (as mentioned above I had to remove an engine mount). Jack up the engine a few cm and support at that level. After I removed the engine mount, about 10 minutes in I noticed the engine was sitting funny. There was a good 2-3cm clearance from the support I had put in. Guess I'd removed the load from that side, so the suspension raised a little. Sounds obvious now.
- This is my personal favourite. No matter how freezing cold, wet and hungry you are, don't just put the head back on the block and torque up if you're not absolutely 100% happy with it. Because next morning you'll be pissed off as f**k with yourself. I did this not once but twice, costing me £30 in new HGs and a new set of bolts.
- After disturbing the cam, finding perfect TDC isn't quite as simple as I thought. If I hadn't marked both the sprockets and the timing belt, I could have easily been a tooth out. I guess this is less of an issue when just doing a timing belt change, as you're less likely to disturb the cam. I guess if I needed to change the timing belt while doing the HG, I'd mark and retain the original. Put this on first to get the teeth aligned and then put on the new belt.
- Always get a head skim. Not sure about this one, seems to be a difference of opinions. But if the car didn't over heat is it likely to require a skim? Seems the general opinion is, if it's off it only costs £20-30 therefore you may as well just in case there are any issues.
- On rare occasions some sections in the Haynes manual tell you to do steps you don't need to do for the task in hand as they cover a more general job. The instructions for dismantling the head instruct you to remove the cam sprocket. I dutifully completed this step, then removed the bearing caps. Only then did I discover that the cam could simply lift straight out and didn't need the sprocket removed. Not a major issue except I was using a bodged tool to hold the sprocket, making the job a bit of a faff.
Regards,
Tim