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#101 _oldjohnno_

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Posted 02 September 2014 - 09:45 PM

BUT....i....LIVE....OVEREXCITED!!!

 

Dammit you've been on the red cordial again haven't you? Now we'll never get you to sleep...



#102 _Bomber Watson_

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Posted 02 September 2014 - 09:57 PM

Fireengines....Red cordial + better. 



#103 _Bluejinx202_

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Posted 03 September 2014 - 11:19 AM

I took the broken camshaft in to a local cam grinder to look at. He's first comment was that not relieving the cam of those raised sections is not good practice and was more than likely the reason for the failure. Upon close inspection he pointed out that the tips of the lobes were pitting and he suspected the life of the cam was not going to be a long one even if it didn't snap. I am going to get a new cam ground locally, I was shown some grinds that weren't usually offered as their intensity is more than average. I'm also looking at the options in regards to nitriding etc

#104 EunUCh

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Posted 03 September 2014 - 11:45 AM

brand new one would be better,get a decent base circle at least?

http://tighecams.com.au/



#105 _oldjohnno_

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Posted 03 September 2014 - 01:12 PM

brand new one would be better,get a decent base circle at least?

http://tighecams.com.au/

 

Enlarging the base circle isn't an option, or at least it isn't without also reducing the lift.

Max. base circle dia. =  journal diameter less the lobe lift.



#106 _oldjohnno_

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Posted 03 September 2014 - 02:24 PM

Enlarging the base circle isn't an option, or at least it isn't without also reducing the lift.

Max. base circle dia. =  journal diameter less the lobe lift.

 

Derrrrrr.. that should have been

 

Max base circle dia = journal dia less (lobe lift x 2)



#107 N/A-PWR

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Posted 03 September 2014 - 05:11 PM

We knew what you meant Oldjohnno,

 

which made me put some images up for others to see,

 

and so the Images are numbered for reference.

 

 

The 1st image shows how an edge of a lifter travels up the Camshaft lobe,

 

and the roller has a better contact compared to a rounded edge normal lifter,

 

so the greater the lift, the more strain:-

 

Image 1

0308pon_bump03_z.jpg

 

Image 2

69370camattribj_00000027829.jpg

 

Image 3

154_9901_06_o+154_9901_jeep_bumpstick_ba

 

Image 4

camanatamy.jpg

 

Image 5

Nockenwelle_ani.gif

 

Image 6

bcr_fig2.jpg


Edited by GASPOWER, 03 September 2014 - 05:25 PM.


#108 EunUCh

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Posted 03 September 2014 - 05:27 PM

I probably should have said that if a new one is used that you could 'maximize" the base circle for lift which would result in less wasting away between lobes if any and maybe knock a bit out of the springing,never really understood why such a heavy rate would be needed?,just considering a v63800 with a roller and they will go over 6 with the limiter fixed or so i am told,the springs on them don't seem too stiff.


Edited by EunUCh, 03 September 2014 - 05:27 PM.


#109 _Bomber Watson_

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Posted 03 September 2014 - 06:43 PM

Were talking 7500+ not 6+.

#110 warrenm

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Posted 03 September 2014 - 11:49 PM

The V6 will rev easily to 6500 with the limiter bumped.



#111 _tryhard_

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Posted 07 September 2014 - 10:20 PM

I just got a new cam and paid $100.00 extra and got it nitrided to help life at high revs speedway



#112 _Ned Loh_

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Posted 09 October 2014 - 12:49 PM

Hi James,

 

Apart from the obvious busted cam, interesting you were having or about to have lobe issues ( I think I may be able to just make out the start of the lobe going on the busted cam in a couple of the photos).  I went though this over a number of engines a few years ago.  At my worst I started to wipe a lobe (on a nitrided cam) at 500 comp km.  The whole zinc thing didn't make much difference either and I now suspect that as long as there is enough, lots of zinc doesn't make any difference, except for the marketing.

 

Sad to say I'm not really sure I ever really got it fully sorted, and accepted that camshafts are to an extent a wear item. If I was spending the money now I was back then I'd just go straight to roller, no questions.  I was part way down that path...

 

I'm not sure where you are up to on the rebuild, but my best suggestion is to run the cam in on the lightest spring you can find that gives you the valve lift you need, then fit your intended spring.

 

I can't remember the exact numbers but I formed the view at the time that just removing the inners (as many people do) didn't drop enough pressure.

 

Oh, and make 110% sure there is nothing hitting or binding (or very near to hitting/binding) at full lift.

 

Cheers.

 

 

 

 



#113 _Ned Loh_

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Posted 09 October 2014 - 01:28 PM

Nearly forgot, on the advice of comp cams tech people, I grooved the lifter bores on the last one.  I think it probably helped significantly, but haven't really proven that beyond doubt.



#114 _Bluejinx202_

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Posted 09 October 2014 - 05:58 PM

Hi James,

Apart from the obvious busted cam, interesting you were having or about to have lobe issues ( I think I may be able to just make out the start of the lobe going on the busted cam in a couple of the photos). I went though this over a number of engines a few years ago. At my worst I started to wipe a lobe (on a nitrided cam) at 500 comp km. The whole zinc thing didn't make much difference either and I now suspect that as long as there is enough, lots of zinc doesn't make any difference, except for the marketing.

Sad to say I'm not really sure I ever really got it fully sorted, and accepted that camshafts are to an extent a wear item. If I was spending the money now I was back then I'd just go straight to roller, no questions. I was part way down that path...

I'm not sure where you are up to on the rebuild, but my best suggestion is to run the cam in on the lightest spring you can find that gives you the valve lift you need, then fit your intended spring.

I can't remember the exact numbers but I formed the view at the time that just removing the inners (as many people do) didn't drop enough pressure.

Oh, and make 110% sure there is nothing hitting or binding (or very near to hitting/binding) at full lift.

Cheers.

As far as putting the engine back together, I picked up a new cam from Clive yesterday. I showed him the broken one and explained that the profile worked well and would prefer to keep it similar, he showed me some profiles I hadent seen before and were indeed similar in lift, duration and intencity. He explained the reason why the old cam failed and having the steps in the cast of the billet was poor design. The new one is nitrited and machined differently so hopefully a bit stronger and harder so we will see how we go. I agree that it sounds as if camshafts of this nature, and used in competition engines are indeed a disposable item. A roller is definatly on the shopping list for the new engine.
I am getting the cam machined to take a dry sump drive this week and then will install it and check for spring coil bind etc as the new profile is a little more lift (369l/lift). After that I can only be bothered with taking out the inner springs and running it in, but I heed your warning and know you are probably right about it still being too much spring. I'll let you kon how it all goes after the melb cup weekend

#115 _Ned Loh_

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Posted 14 October 2014 - 01:42 PM

Hi James,

 

Wow, dry sump!  Pics when it happens please.

 

I haven't been checking the forum much lately, but will keep an eye out for how you go. Should go like a rocket, good luck!

 

Cheers.






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