Piston/valve interface
Turbo Mini Forums

Does anyone know if the valves and pistons tangle if the cam chain snaps ?

Mine has - dont ask.

So pissed off that I cant be arsed to take everything apart to find out -I,d rather just chuck the spare engine in.

Yes based on valve lift and crown height in the squish area on mine. I can't think many piston designs would avoid it. I suppose if they were flat top with no squish and the cam lift was low they might miss... but the engine would be crap!

The cam can also munch on the con rods :(

If it's any conselation I bent 14 out of 16 valves on my Cossie when the belt stripped a few teeth (stripping teeth is worse than it just breaking as the drive picks up again and runs many degrees out until everything is destroyed.)

I cried for a while but just got over it and fitted a second hand head.

The pistons had surpringly little damage so I left them alone.



You can see most of the valve hits in this photo



The belt was well less than 30k (that's the service life) and was the first time I used a "competition" belt instead of the standard Ford one.

Never again, learn and move on.

Edited by Rod S on 31st Mar, 2011.

Schrödinger's cat - so which one am I ???

Thanks for that Rod, but I have spent so much time (and money) on this engine I wonder where its all going to end.

Ironically, the spare engine, which I took out because it was losing oil and it turned out to be a loose oil filter.was going pretty well up till then.

Seems I went a bridge too far in my quest to make the fastest road going A35 -which was always a stupid idea anyway.

I think we have all felt like this about a car at some point. Drop the other engine in and rebuild the damaged one when funds enthusiasm allows!

I know I felt like this last year when my engine munched itself!

One has to ask.....how on earth did the chain snap ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Bad times. As others have said, drop the other engine in along with the GT17 and have some fun in the early summer. Then come back bigger and better next time.

David,

We've all been there (and for those who say they haven't, your time is yet to come).

Cry for a while then start again.

Having a quest to do something different is really positive - especially for us older ones - and I haven't even got mine on the road yet.

Pull it apart ASAP to find out why the chain broke and take it from there (pulling it apart is free...)

BTW the only time I have known a chain to break is many, many years ago when I stopped to help........ I won't go into the story, it's too long.... but an early 850 which doesn't have cam bearings and had overheated (bypass tube failed) and the cam had siezed in the block. But that shouldn't happen on a 1275, so get it apart and find out why.

Schrödinger's cat - so which one am I ???

Stevie and Rod - yes why the hell did it snap ?

Mind you I,m not sure that it has yet, but the engine will turn over and the valves dont move so its pretty certain.
Early start tomorrow as I have to do a hospital visit in the afternoon and I want to know a bit more by then.

shame about this, i'm yet to manage it myself yet, try not to get to down, put your other engine in and enjoy it while the weathers good. and strip this engine down, might give you some inspriation for the next stage.

could be the cam gear spinning on the crank,

I agree with Joe C...probably a bad key on the gear....pretty hard to break a chain. Either way....sorry....

Most of us have had a huge failure at some point. Even my non-turbo car ate all the teeth off a laygear that was only 500 miles since it's rebuild. For what it's worth, I love your car and would hate to see you get frustrated and lose interest in it.

Eric
my pics.... http://www.fototime.com/inv/7AAF37CF3EFA956

Chin up Dave.

We've all been there at some point. Mine was certainly a surprise when I blew No 4 piston but it's all sorted now and going well.

I'd wager that the cam pulley woodruff key has probably sheared as Joe says.

I think you said you were up against it to have the car ready to go north so getting the spare in sounds the best idea and then you can strip the failed unit down when the panic's over. Don't lose hope my friend. You'll get your wish mate. Your A35 Turbo is spectacular and deserves your endless enthusiasm and energy to see it through to completion. It's just a raincheck moment matey.

Very best of luck.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Agreed Dave. Don't give up on it

Setbacks happen just like me and Andy nuking the van's first turbo engine.

If something is worth doing, it's worth doing half of.

Just chuck it all in the bin. I have a handily sized A35 bin just inside my garage!

As above diagnosis is free.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

blimey what a saga ! hope its not too serious david .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

In the workshop by 6.30 this morning and got the timing cover off - correct diagnosis -broken chain.

The culprit -me is the short answer, as one of the countersunk screws behind the crank sprocket had come loose and eventually tangled with the chain.


Got the screw out, as you can see, and was beginning to think that maybe just a new chain as the sprockets look OK.Cover is completely unmarked !!

Engine turns freely but when I same to turn the cam to align the dots before removing the cam sprocket it jammed.
Bent cam ? Bent pushrods ?

Cant get the head off without taking the engine out (bad design, I know) so its engine out, maybe later this morning, and have a proper look then.

Yes Robert it is turning into a saga and its not reflecting very well on my engine building ability. I,ve put together dozens of A series and never had these sort of probs so I must be getting senile, I guess.

Many thanks to everyone offering encouragement - I need it right now.

Jings Crivvens an help ma boab!! First time I have seen that.

I can somewhat understand your frustrations, and I hope its not more serious as just a set of push rods and valves

Well Colin, thanks to the dish on your pistons and the standard valves, it seems they missed each other !

Just got in from taking the engine out and removing the head. Cam now turns freely, so I must have just felt the spring pressure from a valve and was not prepared to force anything, given the circumstances.
Ordered new timing gear, head gasket etc from Minispares a moment ago and looks like I,ll be putting the engine back in next week. Bit fed up of this in and out business -four times in the last three weeks.
Got to clean up and change now - visiting my brother in hospital after radical cancer surgery.

Tomorrow I shall be riding my BMW 1150GS in company with some like minded people for at least 200 high speed miles - possibly around the Cotswolds,so if you live there give me a wave -with all four fingers, please.

You popping the sump off to make sure there is no damage to the rods/cam?

If something is worth doing, it's worth doing half of.

I dont see how rods and cam can touch each other.

It happened to joe when his timing belt snapped.

If something is worth doing, it's worth doing half of.

Is the bottom end now rotating OK?