During my current search for an MX5, I have seen on flea-bay a car that is listed as a non-runner due the cam belt having gone (whilst in a traffic jam), and the garage that replaced it now advises that it’s got bent valves. I was under the impression that the MX5 engine had sufficient clearance that if the belt went you didn’t get bent valves. Or am I living a life of dillusion ?
As far as I’m aware the engine has non-interference valves. I thought that was one of the great things about the block design.
Could this suggest that there is something a little darker going on with this particular engine, therefore best to leave well alone???
Unless the engine had a lot of metal removed to up the compression ratio, then the engine is non interference. The garage are probably trying to cover something up—
I was informed by a mx5 garage that the valve to piston clearance tollerances are very tight and a broken belt gives a 50 /50 chance of bent valves. Apparently, if the engine was revving at over 4000 it increases the chance of bent valves due to “valve bounce” as the engine speed increases.
If the car was in a traffic jam as claimed when the belt went I’d be surprised that it would be revving ‘at over 4000’.
Even so, I’ve never heard of a problem with bent valves, whatever the revs, so suspect something else. What is the age of the car? Could it be more like the LWSC issue?
Sounds like they are pulling your chain to me and personally I would rather deal with someone who appears to be little bit more honest and/or clued up on these engines.
On a Mk1 £1K should cover the costs of sourcing and fitting a known good engine so if you really do want to pursue this particular car then bear these costs in mind, treat them to a little bit of their own contempt and offer them a ridiculously low price.
Where on earth did that come from?—
I was informed by a mx5 garage
From the mechanic at the garage above? - ‘Bill O’Knee’ (Say the name quickly! 
)
Apologies - that was awful 
I thought that “Valve Bounce” only happened at the very top of the rev range and now is very rare due to ECU control?
Old “A” series and “B” series engines suffered valve bounce when in any sort of mild tune. Caused by the weaknes in the valve springs and the tendancy of the old rockers to flex when the revs went up. I’ve suffered it many times, but never blew a motor—
We had a 1954 Morris Minor in the family from new until I managed to mate it with a renault 25 in 1979. Every now and again I would “clear it out” by running in 2nd gear until I hit valve bounce. The Minor owners club recommended this and I now believe it is known as an Italian tune up! Oh happy days!
<o:p></o:p>
I noted that someone last September managed to get their Mazda fixed after the cam belt broke. I have actually had exactly the same problem recently. I believed that it was a ‘non-interference’ engine. However, the cam belt broke while I was in traffic on the way to work. All the ‘so-called’ experts that I spoke to assured me that actually this was not the case. The garage that I managed to get the car too replaced the cam belt (which cost £230, plus £70 for the tow). Even worse they told me that it still would not start and that compression was low on the valves and that it would cost another £900 to fix. I phoned around having the belief that there could not be damage to the valves / engine because it was ‘non-interference’. Anyway I got exactly the same as other people on this site. A lot of people making you feel quite small because everywhere says (which obviously means their garage manual) the engine is ‘interference’ meaning there is likely to be costly damage. I was gutted, so I recently put the mazda on Ebay feeling that I had no option but to cut my losses. I really can’t afford that sort of money to repair the car. I found that I was inundated with messages from (often) mechanics that clearly know what they are talking about, advising that it is a ‘non-interference’ engine.<o:p></o:p>
So I stopped the auction before it sold and I am hoping that I can now get the car repaired for a sensible price. I am posting in the hope that someone may be able to point me in the direction of someone who can help me with this. I am in Epsom Surrey. Does anyone know a good mx-5 mechanic in this area?<o:p></o:p>
Many Thanks<o:p></o:p>
The best MX5 outfit within 35 miles of you is P5, here’s the contact details.—
Contact P5
| Telephone: | 0845 230 4505 |
| E-mail: | info@performance5.com |
| Mobile: | 07951 023341 |
| Mobile E-mail: | mobile@performance5.com (No attachments please). |
| Postal Address: |
PO Box 418 Pinner Middlesex HA5 9AA |
|
Workshop: (by prior appointment only) |
Gutteridge Farm A40 Western Avenue Hillingdon Middlesex UB10 9AP |
Timing? Belt out on the correct tooth alignment?
Many Thanks to both of you.
When I spoke to the garage I told them (through advise of others) that it was probably because they have not got the timing belt aligned correctly. They told me that there was no way that they could get this wrong because it was just a case of lining up the marks on the belt.