Two engines down - Time for an engine swap!

[stagnetti]

Same here - having just sold a Roadster with 150,000 miles on the clock and running like a dream and knowing of 6 roadster engines that have passed 200,000 miles without rebuild, makes me wonder what level of bad luck, or neglect, was involved to kill two engines?

More bad luck than neglect. I've had it overserviced if anything! Especially after the first engine issue!!

First one had the water pump give up the ghost and casued a valve to burn out scoring cylinder wall. Pump was only installed 3 months prior to this by a recommended Smart specialist and car was driven on mostly weekends. Car had done 56k at that point. New engine purchased and installed by local garage - just so happens to be another Smart lover. I had him install OEM new valves, tappets, rollers, springs and camshaft to be on the safe side along with new accessories. Ran like a charm right up until another valve burnt out! luckily block is still usable this time hence my dilemma in doing the rebuild or commiting to a conversion.

Whats worse is a friend of mine absolutely abuses his 451, hardly services and foot to the floor as often as possible and its still going strong at about 76k

Completley understand the magnitude cost impact of the conversion, im certainly not looking to have it back on the road quickly. If it needs two years to complete I'm happy to commit. I feel like there's so much potential to this car and a decent engine / gearbox combo will help fulfill that.

[tolsen]

How can a water pump burn a valve I wonder?

[stagnetti]

Car was running fine until it pissed all over the floor, next time i started it up (with another pump installed) it sounded like a tractor. Did a compression test and saw a cylinder had none so pulled the cylinder head off and saw that half the exhuast valve and come off and decided to bounce around the cylinder. With one happening right after the other, I can only assume that there was a connection.

[pinger]

Late/slow combustion leaving too much heat in the exhaust stream (IMO) is the most common cause of burnt exhaust valves.
Too low octane fuel (causing the ECU to retard ignition timing) or defective ignition components is where I'd look first.
Was the it the same cylinder affected on both engines?

[tolsen]

Their heads may come off if you keep on driving with burnt valves for too long. Surely, burnt valves will be noticed by reduced power and uneven idle. Nothing wrong measuring compression from time to time, especially after overheating, reduction in power, bad idle etc.

[tolsen]

As for converting to different make engine and transmission, it is essential that engine is fitted right way around so you do not end up with five or six reverse gears and only one forward.

[stagnetti]

It did have an issue where at 70mph it would judder slightly. Above and below this perfectly smooth. It was like that from purchase.
Took it into a garage for a check over and coudlnt see any reasons as to why this was happening. They concluded that the ECU may be having some issues reading the sensors and over/undercompensating with the air/fuel mix. So replaced the 02 sensors and fuel sensors and had the OEM map reflashed to the ECU to be on the safe side... no effect at all. There was never a loss power though and the idle was smooth as butter. Just meant if i wanted a comfy ride i had to sit above 70

[stagnetti]

As for converting to different make engine and transmission, it is essential that engine is fitted right way around so you do not end up with five or six reverse gears and only one forward.

Isn't that the standard setup in France?

[stagnetti]

Late/slow combustion leaving too much heat in the exhaust stream (IMO) is the most common cause of burnt exhaust valves.
Too low octane fuel (causing the ECU to retard ignition timing) or defective ignition components is where I'd look first.
Was the it the same cylinder affected on both engines?

I always ran either BP Premium 95 or BP ultimate 99 whenever i could find it so hoping its not an octane issue as I'll be needing to by race fuel to get any higher! Cylinder 1 on the first and 3 on the second.

I never got round to changing the ignition packs unfortunately but on removal of the engine the second time i saw that they had become pretty corroded. They were fine when they were swapped on from the first engine though, so perhaps water ingress caused an electrical short or something the second time round, i have no idea :/

[pinger]

It did have an issue where at 70mph it would judder slightly. Above and below this perfectly smooth. It was like that from purchase.
Took it into a garage for a check over and coudlnt see any reasons as to why this was happening. They concluded that the ECU may be having some issues reading the sensors and over/undercompensating with the air/fuel mix. So replaced the 02 sensors and fuel sensors and had the OEM map reflashed to the ECU to be on the safe side... no effect at all. There was never a loss power though and the idle was smooth as butter. Just meant if i wanted a comfy ride i had to sit above 70

Re the 70mph 'judder' - definitely from the engine?

On Maniacs a while back there was someone switching to ethanol and doing a lot of work to adapt his engine to it which required that he dig deep into the programming of the ECU. He found that at a predetermined rpm there is a shift from open to closed loop fueling (or vice-versa). From memory it was at around the rpm you are probably at at 70mph.

That different cylinders have been affected suggests (perhaps) less a cooling (water pump) issue as I'd expect one cylinder to be repeatedly vulnerable. It doesn't highlight one particular ignition coil (and associated leads) either though a fault could be present on more than one (or coils interchanged between cylinders).

Dirty abrasive air is something else that will punish valves - air filtration in good order?