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Old 05-28-2011, 03:46 PM
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Rocker Arm ????

Here is a few pics of a rocker arm off my 400/408 in my camaro, I first thought it might be the cam going south on me but when i pulled this off and looked at the bottom side i think different now,
Just wanting your opinions on this if you look at the pics you can see where the rocker is worn, now these are not high dollar rockers they are pro form but i have to say they have been on this engine for over 5 yrs now without any trouble. Tell me if you think this rocker is the culprit causing me problems i am getting ready to order some Harlan Sharp 1.6s to replace these pro form rockers. just need some opinions about this much appreciated. i don't want to order them if something else may be the problem. Hope you can see the wear pattern in my pics.




Cole
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Old 05-28-2011, 04:34 PM
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Best I can see Cole the rocker is making contact and that`s not good. This is why anytime I`ve used full rollers on builds I`ve did for others I always check
to make sure the rocker isn`t making contact. Sometimes you have to get a little creative and do some trimming with a carbide cutter. When rockers make contact they can create the rocker to not lift smoothly which accelerates valve guide wear due to it pushing in another direction and no directly down. When you get your new rockers I would check the rocker arm geometry and make sure you check it high and low for signs of contact.
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Old 05-28-2011, 04:37 PM
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Thank's DV, When i get the new rockers i will do that, i will check the geometry and i really appreciate your thought's on this.



Cole
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Old 05-28-2011, 04:47 PM
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Quote:
Originally Posted by eloc431962
Here is a few pics of a rocker arm off my 400/408 in my camaro, I first thought it might be the cam going south on me but when i pulled this off and looked at the bottom side i think different now,
Just wanting your opinions on this if you look at the pics you can see where the rocker is worn, now these are not high dollar rockers they are pro form but i have to say they have been on this engine for over 5 yrs now without any trouble. Tell me if you think this rocker is the culprit causing me problems i am getting ready to order some Harlan Sharp 1.6s to replace these pro form rockers. just need some opinions about this much appreciated. i don't want to order them if something else may be the problem. Hope you can see the wear pattern in my pics.




Cole
The circular cut where the retainer would hit might have been put there by the 'factory', but that's unclear to me- I'm sure you can tell in person if it was a machining op or actual damage from contact w/the retainer. Some rockers need clearanced in that area for larger than stock retainers, but most good quality rockers are made to clear most retainers, or will say what they WILL clear, diameter-wise, but not every case can be accounted for.

The other wear looks like the rocker was all the way down on the stud and making contact w/the shank/hex part of a screw in stud, as if the stud boss were too high. The stud boss being too high can be caused by not enough height being removed for installing guide plates and/or screw in studs, or contact can be made there if the pushrod or valve stem is shorter than usual.

What heads are you using on this bad boy?
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Old 05-28-2011, 04:57 PM
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Is it only one that looks like that?

I've seen improper machining of the rocker stud pads on the head(left too tall) cause the problem you have with the base of the rocker fouling the radius at the base of the screw-in stud...but it would be more than one rocker if that was the case.

Looks as if pushrod cup side would be sitting too low( indicating pushrod short/damaged or cam lobe/lifter wear problem). If the roller fulcrum still feels good, not completely sloppy worn out or failed - then the problem isn't the rocker arm it is somewhere else
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Old 05-28-2011, 05:22 PM
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Quote:
Originally Posted by cobalt327
What heads are you using on this bad boy?

Hi mark and Eric, This is the heads i have , Dart Iron Eagle 230 heads 64cc
208 intake valve
160 exhaust valve
K-Motion springs
I haven't removed any of the other rockers yet, but it seems to run just fine no popping through the carb or rough running or anything, just this one rocker kept getting a slight tick in it and when i would adjust it out it would come right back in no time. but i will pull the rest and have a look though got to come off anyway for the new rockers.


Cole
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Old 05-28-2011, 06:00 PM
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Quote:
Originally Posted by ericnova72
base of the rocker fouling the radius at the base of the screw-in stud...
Some manufacturers, such as ARP, will leave a large radius on the stud, claiming that it strengthens the stud and offers greater resistance to flex. That makes sense, but it means that you have to triple check everything on trial assembly of the parts and maybe do a little parts changing or a little surgery.
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Old 05-28-2011, 06:51 PM
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One more thing - you did check rocker geometry at initial assembly?? The Dart 215 and 230cc heads usually require a +.100 longer valve, which means a longer than stock pushrod will typically be needed.

If you find more than one rocker with the wear pattern from contacting the stud radius I would look closely at pushrod length being incorrect.
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Old 05-28-2011, 07:17 PM
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I pulled the rest and they are all just like the one in the pic, and i will re-check the push-rod length for proper geometry also while i'm at it. do you know off the top of your head what the stock length push-rod would be 7.800"?
originally i was suppose to have push-rods +.100 in length but i just pulled a tape on the push-rods i have and from the tape they measure 7 3/4 inch long. so that sounds to me like i have the wrong push-rods correct ?





Cole

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Old 05-28-2011, 08:15 PM
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Quote:
Originally Posted by eloc431962
I pulled the rest and they are all just like the one in the pic, and i will re-check the push-rod length for proper geometry also while i'm at it. do you know off the top of your head what the stock length push-rod would be 7.800"?
originally i was suppose to have push-rods +.100 in length but i just pulled a tape on the push-rods i have and from the tape they measure 7 3/4 inch long. so that sounds to me like i have the wrong push-rods correct ?





Cole
That could be a 0.050" shorter than stock or a stock length of 7.8", depending on how the pushrod was measured, how much wear to the pushrod, and the accuracy of the measurement itself.

Overall or "actual" length doesn't always equate to the pushrod length as specified by the manufacturer, odd as this sounds. The difference is in whether the pushrod was measured by overall or actual length (longest measurement of the three), "theoretical" length (about 0.020" longer than actual length) or "gauge" length (longest of the three).

The theoretical length is longer than the overall length as measured w/calipers, etc. because it takes the oil holes out of the measurement and instead treats it as though the ends of the pushrods were round, w/o an oil hole.

The gauge length is what Comp Cams (as an example) uses. This is measured as how the pushrod sits in the rocker arm and lifter seats. In the Comp Cams diagram below, 8" is just used as an example:



But the pushrods you have still could be the right length for giving you the correct geometry. The acid test is what the geometry looks like. To accurately judge the geometry, the hydraulic lifter either needs to be pumped up, or made solid, or a solid lifter w/the same seat height substituted to judge the geometry.

A page on checking geometry- http://www.lunatipower.com/Tech/Valv...nGeometry.aspx

Last edited by cobalt327; 05-28-2011 at 08:34 PM. Reason: Add link.
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Old 05-28-2011, 09:44 PM
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Thank's Mark, i measured mine with the tape at theoretical length, and i will check the geometry like Lunati shows to see exactly what i have and will need to be correct.



Cole
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Old 05-28-2011, 11:43 PM
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I really didn`t say anything helpful Cole, so perhaps I shouldn`t have answered, My apologies if not. I was thinking some days ago, when I took the 4.3 V6 out of my truck for the rebuild, I reused the swirl port heads, however I did do a bowl clean up, purchased necked down SS fearra valves for it with a back cut done to help flow a bit. I would have went the Vortec route, but wasn`t up to spending the dough to get it tuned on a dyno to work with a TBI. Anyways, I took the heads to the machine shop with the block, The engine, I was told when I got the truck was "rebuilt" which was a lie I found when I stripped it and it had all GM pieces. The bores were 4.009 and two were 4.011, but it had 267,000 miles on it. I asked the machinist to replace the guides as I was sure they were shot. He checked them and they checked good, so he didn`t replace them. I was honestly shocked.
Now since I added a new isky roller cam, crane roller lifters, comp hardened pushrods and roller tip rockers I noticed about 5 thousand miles back it`s developed a light smoke when first started cold which is telling me the guides have started to wear. I didn`t check the valve train geometry as well as I should have being I was in stall for time as I had to get the truck back running ASAP. Now I wish I had checked it better as it`s only going to get worse being it`s obviously got some not lifting directly down so the valve guide wear is occuring quickly, as it only has about 20,000 miles on it since the build. Too many times it seems when something I neglect to check as well as I should have I get bite in return, but that`s the way the game rolls, I never get lucky.
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Old 05-28-2011, 11:59 PM
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Just a note...when checking geometry - a narrow sweep pattern is far more important than the pattern being right in the center of the stem. If the pattern is wide that means the rocker is trying to move the stem back and forth in the guide more than a narrow pattern and this increases wear. It doesn't so much matter where on the stem the rocker is contacting it(as long as it isn't dangerously close to the edge, or running off the edge), as long as you minimixe the back and forth motion.

The Miller Mid-Lift web site used to give the best instruction on how to completely and accurately set pushrod length, but now that it has been sold it looks like you now have to pay for what was once free info(and the only truly correct info).
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Old 05-29-2011, 12:40 AM
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Quote:
Originally Posted by eloc431962
Thank's Mark, i measured mine with the tape at theoretical length, and i will check the geometry like Lunati shows to see exactly what i have and will need to be correct.



Cole
Cole, I'm sure you're aware that Comp and others sell tools that replace the rocker arm to determine the right length pushrod. Another option is to make yourself (or buy) an adjustable pushrod to use for getting the correct length for the right geometry.

But a short pushrod will cause interference between the retainer and rocker in some cases. Obviously, the whole valve train should be checked over for proper clearances, etc.

HERE is a list of valve train points to check.

Good luck and keep us posted.
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Old 05-29-2011, 01:29 AM
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Link to the Miller Mid-Lift and rocker geometry article in the AERA(Automotive Engine Rebuilders Association) quarterly magazine named Engine Professional- http://www.aera.org/ep/downloads/ep1...2010_20-30.pdf

This is the only correct way to set rocker geometry, what Comp Cams, Crane, Lunati and others have on there web sites is not correct. This article explains where the original error that keeps getting repeated came from (when Harland Sharpe made the first aluminum rockers) that everyone else has erroneously copied through the years.
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