Bent Valve

[SteG40]

I was down at Shakespeare raceway this weekend and it looks like I've bent a valve. I got the start all wrong and the revs went through the roof and it broke still did a 15.5 though. We've done a compression test there and cylinder 1 shows 0psi the others are fine. I'll take the head off sometime and have a look.

I'm going to do most of it myself so i'll probably be asking loads of questions when it comes to putting it back together 

[Max]

That's a pain in the arse mate, was 15.5 your best run of the day or did you get lower?

Hope you can get it sorted soon.

[SteG40]

No best was a 15.0@97mph. It was going quite well, reckon I could've gone faster too

[hayesey]

argh!

what do you reckon happened then, valve float or slipped cam belt or something else?  What's your rev limiter set at?

[SteG40]

Not sure whats happened, cambelts not slipped. Rev limits 8k but i never usually go above 7k apart from this time by accident. Once it's all sorted I want to try and get the rev limit lowered which I was thinking of doing anyway.

[Robin]

No best was a 15.0@97mph. It was going quite well, reckon I could've gone faster too

sounds like you were struggling for traction as you got a not bad terminal speed but slow 1/4 mile time.

i got 14.7 in my G when it was running only 150bhp with 175/50/13 tyres!

[SteG40]

Yeah thats Spot on Robin, I can't get the thing off the line. I need to get my diff fitted that should help.

[Andy]

I did a 14.0 @ 99mph running about 170bhp on 175/50 R13 tyres. Suspension (inc. geometry setup) and tyres can make a huge difference to your time.

Ste - I can edit your map to lower the rev limit if you want. It's something I did on mine when it was still running Digifant after Steve mapped it, went down to 7000rpm.

When you pull the head off, check the valve guides for wear. I had a big valve head that ate the guides in under 3,000 miles, wondering if your guides have done the same, culminating in mashing one a valve up as they rattle around at high rpm.

Having said that, wasn't your car breathing a lot of oil? May well be more bottom end related?

[SteG40]

That would be brilliant if you could do the rev limit Andy.

I'll check the guides once the heads off, it was breathing alot but i'm putting that down to a blocked breather were pretty sure it's a valve thats gone.