New Zealand Datsun Club

classicdat wrote:Oh Wow, don't think that will buff out. Was the cam the chicken or the Egg?

Oh wise one you ask all the right questions it looks like the head fell off the valve first so the cam was the egg.Now you look at the pics and till me how I came to that?

Ohh that's nasty!

gman wrote:

broke wrote:Did you remove and refit the cam towers?

No the spring rate had to be so high because the ramp on the cam is so harsh.So looks like I am going to have to make a chromoly cam?

What is the cam profile and what were your open & closed spring loads? I'd be happy to look into this a bit for you as I have never seen an L smash a cam to bits like this! Could be a harmonic issue.. Ramp acceleration doesn't change spring requirement much, it is more the negative acceleration over the nose that does. High opening acceleration however does tend to increase the Fourier content of the profile which can excite valve springs in a bad way.

volodkovich wrote:

gman wrote:

broke wrote:Did you remove and refit the cam towers?

No the spring rate had to be so high because the ramp on the cam is so harsh.So looks like I am going to have to make a chromoly cam?

What is the cam profile and what were your open & closed spring loads? I'd be happy to look into this a bit for you as I have never seen an L smash a cam to bits like this! Could be a harmonic issue.. Ramp acceleration doesn't change spring requirement much, it is more the negative acceleration over the nose that does. High opening acceleration however does tend to increase the Fourier content of the profile which can excite valve springs in a bad way.

Thanks Man I had to go up 10% on the springs last rebuild because I was getting sign of spring flutter and it looks like it pulled the head off the valve and the pistons have come up and hit the valves and that's broken the cam.

volodkovich wrote:

gman wrote:

broke wrote:Did you remove and refit the cam towers?

No the spring rate had to be so high because the ramp on the cam is so harsh.So looks like I am going to have to make a chromoly cam?

What is the cam profile and what were your open & closed spring loads? I'd be happy to look into this a bit for you as I have never seen an L smash a cam to bits like this! Could be a harmonic issue.. Ramp acceleration doesn't change spring requirement much, it is more the negative acceleration over the nose that does. High opening acceleration however does tend to increase the Fourier content of the profile which can excite valve springs in a bad way.

So basically this is what I heard in my head when I read this!
https://www.youtube.com/watch?v=vHk40Vv ... tu.be&t=59" onclick="window.open(this.href);return false;

Haha that video is awesome

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Only one word required.

Bugger!

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Do you have a replacement cylinder head? I know where there's an.old l26 that might have a good head.

Bartman wrote:Do you have a replacement cylinder head? I know where there's an.old l26 that might have a good head.

Thanks Bart always looking for heads. well now its time to work out what to do I think I will get the little women a new handbag and me some more HP?