Re:The snapped cambelt saga

Not too long ago i decided to get a "summer car" - not a lot of choice in those in Finland. So i imported a "well-maintained" MG TF 160 (LHD)





You've guessed it, we're here about to unravel just how well maintained it was. It started with wheel bearings, rear links arms, some rubbers and steering bits at the front, replacement of way-too-old tires (winter at the front, summer at the back). Then she was finally ready for her import technical inspection - or so i thought.

Long story short - whilst idling on the driveway, the engine cut out. After inspection - Timing belt snapped. Could've been a lot worse if this would've happened somewhere on the road.

Decided not to sulk but take the productive route and opened her up. This topic will be used to write down whats done, and ask the experts for advice, im quite handy but have never performed a repair like this before.

So as it stands, it seems i have 4 bent exhaust valves, all others are ok. Seal tested overnight and no leaking on the other ports, no visible damage either.
Pistons seem ok as well.





Now to the shopping list with some future-proofing added:
-Cambelt set (VVC) with water pump (https://www.the-t-bar.com/forum/54-how-tos/22634-k-series-cam-belt-change-how-tovideo)
-Auxilliary belt (while we're there anyway) (https://www.the-t-bar.com/forum/22-cjjs-guides/30617-how-to-change-the-alternator-belt#30617)
-4x exhaust valve (

)
-Headgasket set MLS with uprated oil rail and headbolts
-Inlet, exhaust and cam cover gaskets
-Thermostat (https://www.the-t-bar.com/forum/54-how-tos/91134-changing-the-thermostat-how-to#140405)

Am i forgetting about something?

Also, i've never replaced a valve before. Is this something i can do myself or am i better of dropping the head at a machine shop to do it for me?

You're investing a lot of time & money on the car, by doing the head job yourself you're investing more time but less money. If you have the head done professionally, more money less time. Let's call the latter "investment " , the former " cheapskating". I'm a great cheapskater when it's appropriate but a great believer in investment when I don't want to be left at the side of the road.

Factual information on if and how a head rebuild can be done yourself would be more useful than a financial indicator :broon:

Replacing valves and "lapping in" is a DIY job but make sure the head is straight, Kseries heads are notorious for there shape (mainly after overheating, so yours may be ok" if in doubt get it professionally checked and skimmed at a machine shop and maybe "lap" all the valves at the same time, better saving time rather than money in this instance.

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Steve wrote:

Replacing valves and "lapping in" is a DIY job but make sure the head is straight, Kseries heads are notorious for there shape (mainly after overheating, so yours may be ok" if in doubt get it professionally checked and skimmed at a machine shop and maybe "lap" all the valves at the same time, better saving time rather than money in this instance.

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Thanks! I'll get the head over to a local mechanic with a straight edge to check for any deformation. Im quite interested in learning more about valve lapping and replacement so i might do it myself if the guides and ytube videos i see about it seem doable.

I've contacted the nearest machine shop and they quoted me the equivalent of the purchase of a replacement MG TF for a complete head rebuild and they dont want to do anything but a complete rebuild. I guess Finnish hourly wages are a bit too high for keeping older cars on the road. Ofcourse i can always take it with me abroad and have it done there, i'll keep this in mind as i regularly drive back and forth to Netherlands anyways. Dropping it off in Poland may be a good alternative.

You’re lucky the belt broke at idle speed and not at high RPM, the mechanical mayhem that would ensue would’ve done more damage than bent valves.

Cobber wrote:

You’re lucky the belt broke at idle speed and not at high RPM, the mechanical mayhem that would ensue would’ve done more damage than bent valves.

IMO, this is they key point. According to Roger Parker (see Page 104 of his book "MGF and TF Restoration Manual") when a valve contacts a piston and bends, the bending forces will pivot on the part of the valve stem where it emerges from the valve guide: (This makes perfect, logical sense to me} He goes on to show a picture of a head where bent valves have been removed, showing that the tips of the valve guides below the bent valves have clearly snapped-off. I suggest that you should check your valve guides on the bent-valve ports VERY carefully! If there is any sign of broken valve guide ends, a replacement, second-hand head or complete second-hand engine will be advisable.

Saint Roger also shows examples of pistons with subtle, but crucial damage to piston-ring gaps, below the impact zones where valves made contact. Harder to check this, and hopefully, the low revs and relative coolness of the pistons will have minimised and perhaps avoided this damage.

Roger's book is readily available on the net, and is a mine of useful information, so IMO, an excellent investment.

Good luck with the re-build. The one area I would disagree with the video on valve lapping is that a lower viscosity and (crucially) a lower surface-tension fluid like paraffin, white spirit or petrol is FAR more searching and better for checking valve seal quality than water. Also, probably obvious, but use lapping compound sparingly, and be VERY thorough when cleaning lapping compound off the seats and valves after the work. Lapping compound in valve guides is very bad news.

That is an excellent analysis & one to note. There will be a number on here who cut their teeth on A series engines, which were quite crude in comparison to the K & would be tolerant in the hands of less talented folk, but aside from a mechanics course that’s how you learned. Inlet & exhaust 1 would be beyond pier cylinder 2 nearly as good, by 4 exhaust the pub was calling loud & that might not have stood up to close examination. The last head I did was on a Ferguson T20 & it would take me two minutes to find my double sided paste pot (course one side, fine the other) & my sucker stick. To strip a K series & to get it to the point of valve lapping, that’s all sixteen valves perfectly prepared & rebuild it to close tolerance is I now consider a job for someone on the front line.
I thought you were a little dismissive of my original comments, most contributors on here enjoy the car on the open road, as I was yesterday & would advise the best way to achieve that, if your route is to end up in a puddle of oil & tears with very sore hands & a very poor recollection of the last valves ground in, so be it.
I wish you all success & look forward to you reporting on your first runs out & hope you derive the same amount of pleasure as I had yesterday as I cracked open the throttle & roamed the byways of the Lancashire & Yorkshire borderlands.

Alexbrz wrote:

Factual information on if and how a head rebuild can be done yourself would be more useful than a financial indicator :broon:

At the risk of mentioning finance as a factor, why dont you put a call out with the trusted suppliers people on the forum use to ask if they have a good usable 2nd hand 160 vvc head. I strongly suspect this will be significantly cheaper than getting your head rebuilt and these people will only sell you a good head that you can just bolt on and use.

So what did you decide or have you decided to leave us all permanently in suspense ?

With regards replacing the oil rail ,this ( IMO ) is an unnecessary expense and is causing more work . When I replaced my HG with the upgraded type , I left the original rail in place . After 25k miles there have been no problems 😊.

John