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 Post Posted: Thu Jun 24, 2010 7:45 pm 
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shrinker wrote:
With that many beach lines it likely it failed over time, so toss the whole lot out.


So do you not have an opinion on the spring pressure issue? O:) What say you? ;-)

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 Post Posted: Thu Jun 24, 2010 7:55 pm 
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Ken0069 wrote:
BarryW wrote:
Ken, I suppose you are talking shaft rockers? I remember a couple of years ago,one of our local dirt trackers who runs high dollar store bought engines was breaking Crower shaft rockers.He finally took the engine back to the builder & they put a whole new set on & they are fine. He said Crower told his builder they had a bad batch & made them good. I wonder if you're luck is as good as mine..........


BarryW this set was purchased back in the spring of 2007? Does that time frame match the incident you are speaking of?

I've got a set of their stud mounts on my 23* engine that were bought back in 1991 and they are still in use today, which along with Kowalsky's experience is the reason I went with them again.


Ken, I built a couple of cheap =; engines for this guy about the time he had his rocker issues so I went back & looked at my notebook for those and it was 4-18-07.


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 Post Posted: Thu Jun 24, 2010 8:46 pm 
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Thanks, I may just give them a call.

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 Post Posted: Fri Jun 25, 2010 12:43 am 
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Ok think through the spring pressure issue. You were told that the low spring pressure broke the rocker. So to do that one would assume that the lifter is being lofted across the nose and slamming down on the closing ramp. Now when ever I've seen that, the part that breaks is the roller or the lifter not the rocker. So make your choice on the logic of that. Anytime the lifter leaves the ramp, when it recontacts it, the spring is in a lower load state so why would it break the rocker? On a closing all the rocker is doing is pushing the lifter and pushrod, its not struggling to fight the spring pressure. I doubt that the rocker broke from not enough spring pressure.

Now we come to the tricky bit. If your breaking exhaust rockers (which the first one was, you havent said about the last time) one reason for that is there is too much cylinder pressure when your trying to open the valve. I proved that to a respected engine builder once, he kept breaking them on a blown engine, he did what i said to do to the tune and it stopped breaking them. :-$


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 Post Posted: Fri Jun 25, 2010 3:05 am 
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Here's some more logic for ya. Each beach mark is a fracture cycle. This is what happens in a running engine, as the RPM's rise the load on the rocker to open the valve increases, simply because the speed your trying to open it at gets higher. Ok got that? So now you can count the beach marks and discover how many failure cycles it took to reach breaking point of the remainder of the rocker. Its simple crack propagation. So say there are 8 beach marks for example, that means it reached the failure load 8 times before it broke, so if you do the same peak RPM points each run down the strip then it would only have to do 8 runs to failure. Ill bet it did a lot more runs than that. So now you have to find another cause of load increase, and one can reasonably say that maybe the tune wasn't right 8 times, and that might be over a long time period to do that. certainly far more erratic than a regular RPM per run. So just for fun do some maths and figure out what pressure has to be exerted on the valve tip to overcome the spring seat pressure plus the cylinder pressure at EVO on the valve area. And thats what broke the rocker. Each time the burn was too slow and cylinder pressure was peaking too late it beach marked the rocker fracture.


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 Post Posted: Fri Jun 25, 2010 8:11 am 
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The last one that broke was an intake rocker. 1.6 ratio with a .550 offset. The exhaust rockers are also 1.6 but only .250 offset. I got Manton .120 wall pushrods and Crower offset HIPPO lifters in it too.

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 Post Posted: Fri Jun 25, 2010 7:54 pm 
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Well there junk.


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 Post Posted: Sat Jun 26, 2010 10:22 am 
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I started the Camaro engine last night without the mufflers on it and you should see that O2 graph?? O:) Man, that thing was all over the place! I see what others talked about now with the open header thingie pulling air back up the collector during the overlap.

Heh, I expect my neighbors really appreciated it too as it was around 10pm when I ran it. =; It was a Friday night though. ;-)

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 Post Posted: Wed Jul 21, 2010 11:32 pm 
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Ken, what I was getting at is, If your breaking rockers, I can't see 25LBs more spring pressure, or .012" closer to coil bind curing the problem.
Something else is causing it.

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