mx5cartalk.com

Hey guys,

Long time lurker first time poster.. I have a 05 SE which has had an unfortunate mishap.. was driving the car st a low speed ~40kmh and all of a sudden the car stalled and could hear some clanking. Checked out the rocker cover and it had cracked.. opened it up to find the cam gear bolt had snapped off and the timing belt has come off.. some pics attached..

Questions being - I’ve been told the BP4 is a free standing/non interference engine.. is this true?

2nd question.. how tf do I fix this?! Does anyone know any good mechanics in the southeast of Sydney? MX5 Mania is abit too far for me!

3rd.. if the engine is gone, happy to buy another.. what are the chances of finding an SE longblock to fit in?

Cheers guys!

Matt

Help appreciated!

Just buy a cam cover and a cam.

Dann

Yes, non interference if factory spec.
What is that broken bit next to bolt? Camshaft position sensor?

Thanks guys.. yep it is factory spec internals. Only concern is it was abit boosted. Hopefully just the rocker cover, cam and camshaft position sensor is all I need to replace.. get it timed and be on my way..

I can think of two possible causes for this.

The first is that the cam bolt was never properly tightened in the first place and eventually the bolt weakened and sheared. In that case Dann is right and just replace the parts and you're good to go again.

The second is that for some reason there was excess load on a cam lobe. This could be either a seized/damaged valve or a valve hitting something solid inside a cylinder. I would check this by inspecting the valve gear you can see (springs, valve stems, buckets, etc) as well as looking for pieces of stray metal around the valve gear and then hand turning the damaged cam with a shifter to make sure nothing is stopping it. Then I'd put a scope down each plug hole to see that there's nothing nasty inside. If valves, pistons and cylinders are all good then go with Dann's rec, otherwise it's head off time to assess what to do next.

Excuse my ignorance, but if there are no other engine problems, why would the camshaft need replacing? You should be able to get the sheared off bolt out of the camshaft.
I would think the gear broke the cover, so probably damaged & need replacing.

How difficuilt is it to drill out those bolts?
Surely a pro probBly woulnt charge more than $100?

Even at 150 per hr and it takes 15 min.....thats like less than $40.00

I dont know what the going rate is foe mechanical work these days. I drilled out a seat bolt the other day a good drill bit...made reasonably easy work for it. Im sure the seat rail bolts are the same material

Sent from my SM-G935F using Tapatalk

I bought a pair of BP4W cams off this forum for $70. Heaps of people here have a pair sitting on a shelf. I would not trust a cam that had had the main bolt sheared off.

Don't spoil the ship for a ha'p'orth of tar.

manga_blue wrote:I can think of two possible causes for this.

The first is that the cam bolt was never properly tightened in the first place and eventually the bolt weakened and sheared. In that case Dann is right and just replace the parts and you're good to go again.

The second is that for some reason there was excess load on a cam lobe. This could be either a seized/damaged valve or a valve hitting something solid inside a cylinder. I would check this by inspecting the valve gear you can see (springs, valve stems, buckets, etc) as well as looking for pieces of stray metal around the valve gear and then hand turning the damaged cam with a shifter to make sure nothing is stopping it. Then I'd put a scope down each plug hole to see that there's nothing nasty inside. If valves, pistons and cylinders are all good then go with Dann's rec, otherwise it's head off time to assess what to do next.

Maybe it was over torqued at some point too.

True. Either way, too tight or too loose, the threads in the cam are most likely U/S.

manga_blue wrote:I bought a pair of BP4W cams off this forum for $70. Heaps of people here have a pair sitting on a shelf. I would not trust a cam that had had the main bolt sheared off.

Don't spoil the ship for a ha'p'orth of tar.

Thanks for the tips all.

In terms of the BP4W internals, what is the difference between the standard BP4W and the turbo? Is it just the pistons? Cams etc should be the same, correct?