2.8 crd valve pics

pulsenpal · **Joined:** Sun Aug 05, 2018 9:53 am **Posts:** 42

from a head subject to catastrophic failure

I put together valve spring compressor with higher applied force required to allow twisted
valve removal--pics of tool soon

these valves. intake and exhaust, will take an enormous degree of abuse before head separates from stem

https://postimg.cc/gallery/3gpry4pvc/

GordnadoCRD · **Posted:** Tue Aug 21, 2018 3:46 am

Wow,

I wonder what damage they did to the guides :?:

geordi · **Posted:** Tue Aug 21, 2018 12:46 pm

They SHOULD be able to take an enormous amount of abuse before separation... But for some reason when the alloy gets to around 300 billion cycles, it just lets go. Even under normal operation stress which should only be spring tension. I am at a loss to explain why, but the evidence is there. What happened on this engine to bend up those valves?

pulsenpal · **Joined:** Sun Aug 05, 2018 9:53 am **Posts:** 42

geordi

this was a California crd--113,000 mi seemed to have proper care, lube change, etc

hard to tell if it was a rocker failure or valve separation which ignited the failure sequence

I think you are on track with your analysis--the dimensions of crd valves is same as 18 hp briggs garden tractor --as I ready components of new engine for install I wonder if the initial design should not have been 3 valve cylinder---two intake with one larger exhaust?
any thoughts?

geordi · **Posted:** Wed Aug 22, 2018 7:11 pm

I am inclined to think that the intake valve could be a single since boosted air will always force itself into a cylinder, when combusted air may need to be pushed out and at a lower pressure. But that is irrelevant speculation in our case. What isn't speculation is the strength of the alloy - It should be more. There is no good reason for the valves to be failing like this, other than poor manufacturing.

2.8 crd valve pics

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