I have a new (~1000 miles) 400 SB in my '69. It's got 10-1 pistons, RPM aluminum heads, CC XE274 hydraulic cam and stock type long slot replacement rocker arms.

It ran great for a few hundred miles then I got this odd rattle/knock sound from one side. Turned out to be a rocker arm that was burned up.

I replaced it and all was well for another couple hundred miles. Now I'm hearing the same rattle/knock from the other side in what I'm learning sounds like the early stages of rocker arm death.

Has anyone else had problems with stock rocker arms? I noticed CHP just tested a new 406 and burned several stock rockers. They're replacing them with roller rockers - which I may end up doing as well. However, it doesn't make sense to me that stock rockers wouldn't hold up on the street. Any thoughts?

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Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
www.geocities.com/sdenning1 (http://www.geocities.com/sdenning1)

I read the same CHP article and it seemed to me that simply changing to roller rockers was a fix to the immediate problem (i.e., burnt rocker arms) but didn't address the underlying problem. I'm not sure what the underlying problem would be though.

If you go with rollers, price them at a GM dealership. The GM parts are made by Crane (the equivalent of their top of the line "gold" version) and the last time I checked were about $30 cheaper for the set than Summit or Jegs.

Thanks gheatly. I'm very curious about the root cause of this problem.

I'm only speculating, but maybe the aggressive ramps and stronger springs are too much for stamped steel rockers - particularly generic replacements. Maybe it causes them to deflect and therefore bind, increasing friction and leading to an early death????

Are the burned rockers from one of the middle cylinders (2,3,4 or 5)? Exaust side?
Alot of 400 blocks are missing 1/4" cooling holes just outside of the outer steam holes in the block. This area is the hottest area on a 400 because of the siam. cyl. and 2 exaust valves in the center. If these holes are absent, HP 400's will have problems in this area. Sometimes the valve seizes in the guides, especially with cast iron guides. You can use a felpro gasket as a template to drill these holes in the block. One hole per side. This might be your problem. I don't know if all the gaskets have these holes, but I can find the part number if you want it. As soon as I drilled these holes in mine, all the problems went away. BTW the temp guage did not show the problem. A sprint car racer brought this to my attention.

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67 Camaro 410sb 11.63 @117.6
67 Camaro 388 ET-???
website (http://www.geocities.com/lonnie67_1966)

The reason is because of too much spring pressure or rocker ratio. Stock rockers still use the old ball and socket pivot, which creates VERY high friction, and therefore high heat. When this area gets extremely hot, the oil burns, and no lubrication is provided. Usually these areas are blue in color, surrounded by burnt oil. SBC don't oil the rockers very well, so some people have resorted to grooved balls. I, however, don't completely agree with this, as it decreases the available friction surface area, and therefore increases the lbs/in^2 causing an increase in wear in the non-grooved areas. Some poeple have also tried valve covers with what are called "dripper" molded into them (usually cast aluminum valve covers), like the old Z-28 and Vette covers, and the NASCAR guys even pressure oil the top end with an integrated oiling system in the valve cover (although this is used primarily to keep the springs cool since they use roller rockers). Roller rockers will definitely solve your problem. Hope this helps. Take care.

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69 SSRS Frame-off Resto
81 Z-28 377ci Drag Car

69SSRS - I think you've identifed the problem and the solution! I do have the grooved pivot balls and I've noticed that when the rocker starts to go the wear pattern gets uneven and the pivot area is scorched. Time for roller rockers.

Lonnie - I have the steam holes - I drilled them myself but it's a good thought anyway.

Thanks for your help guys!

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Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
www.geocities.com/sdenning1 (http://www.geocities.com/sdenning1)