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Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt

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12 hours ago, ajg193 said:

Surface finish on reground cams - how smooth should they be?

The one I just got ground looks like it has a pretty rough surface, especially around the base circle - even some voids in the casting.

Will the cam polish itself up as it gets bedded in?

They should be smooth, shiny almost polished finish off the grinder, like ~15RA surface roughness. If they are rough then they will eat the lifter for sure. Have you got any photos? Sounds like maybe the grinder operator didn't do a very nice finishing dress on the wheel. 

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12 hours ago, BobbyBreeze said:

They should be smooth, shiny almost polished finish off the grinder, like ~15RA surface roughness. If they are rough then they will eat the lifter for sure. Have you got any photos? Sounds like maybe the grinder operator didn't do a very nice finishing dress on the wheel. 

RTH0TCt.jpg

 

 

You can see the lines that go all the way around the lobe, it feels like a pretty roughly turned surface.

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Yeah that looks quite bad. Definitely shouldn't have been let out the door imo. Might be okay but I personally probably wouldn't run it. 

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Had a yarn with the grinder while getting some pistons, he reckons the rough surface is intentional on their cams.

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A balance between being too rough and too fine, he says if the wheel is dressed to give a perfect finish it burns the surfaces and causes micro cracks. Says it will all smooth out perfectly when run in with some moly grease applied to lobes and lifter faces

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1 hour ago, ajg193 said:

Yep, Kennelly Cams

Have had quite a bit of work done by him. Never had one of his cams fail. Good engine assembly lube and good oil when breaking it in and you’ll be fine. 

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Coating the cam lobes and lifters in moly grease on their advice. Will do assembly lube on all other surfaces

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Run a high zinc oil too.  

I've heard many good things about kennelly. I'll use him next time. I'll never use kelfords again. 

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On 14/08/2020 at 16:34, ajg193 said:

A balance between being too rough and too fine, he says if the wheel is dressed to give a perfect finish it burns the surfaces and causes micro cracks. Says it will all smooth out perfectly when run in with some moly grease applied to lobes and lifter faces

Well I guess I respectfully disagree there. Good to know what their take on it is though...

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3 minutes ago, tortron said:

Must have worked on the blmc production line back in the day?

 

Ford kent :pukeright: BMC have fancy steel cams!

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2 hours ago, ajg193 said:

I have a big bottle of penrite running in oil

What was wrong with Kelfords?

Everytime I've dealt with them they rub me up the wrong way. Their customer service is rubbish. 

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Why do new cambelts make a chirping sound? Book sed to tighten it after the 1st 1000 kms and no it’s doing it agearn 

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The square edges of the belt trap air in the pulley as the belt spins around it, as the belt wears the edges off the air can escape easier and doesn't make as much noise.

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@BobbyBreeze any idea what sort of vacuum I should be getting at idle with a pretty mild cam? The fresh engine is sitting at about 65 kPa absolute at idle (10 " mercury pulled), with stock cam I was at about 35 kPa (19 " mercury pulled)

 

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