390 Cam Pedestals with Performer RPM cam

[Janus]

I will be running a Edelbrock Performer RPM cam in my 390. Some guys have told me that I need to look at changing the current aluminum pedestals to 427 style steel pedestals.

Apparently the rocker shafts take too much strain with the higher performance can and it wil break because of weak support at the ends!? Is this nonsense or not?!

Cheers
Janus

[BB427]

That is true, however, with the Performer RPM pkg. the camshaft is a pretty mild hydraulic stick. A solid camshaft or a roller would require good shafts and end stands but you should be ok with the factory stuff. You will need to get adj. rockers if yours are not. Avail on e-bay for about 100.00 or they are avail. new also.

[CJ428CJ]

Janus,

I think the stock aluminum pedestals are fine (that's what I'm running on my 428). It's hard for me to envision how they would break. After all, there's a bolt running right through them to secure them to the heads. Where would they break? BB427 is right about the adjustable rockers though. I'm running Isky adjustable rockers on mine. I got them through PAW.

Chris

[BB427]

I have not seen the aluminum pedistals break but I have seen the shafts crack or break on the outside of the stand. The ends of the shaft are not supported. The aftermarket bilett stands I run have supports all the way out on the end of the shafts. If you run a strong spring you can actually see the stock shafts move on the ends. The isky stuff is very nice for the money.

[ted]

The aluminum supports allow some deflection at the end bolts for the rocker shafts which over the long haul could allow the shafts to break at that point allowing the end rocker to fall off. You'll know it immediately by a popping sound back through the carburetor. Although the aluminum supports are more prone to breaking shafts when running higher than stock valve spring pressures, I've seen a several 360 and 390 pickups in the seventies and eighties with broken shafts due to the aluminum shaft supports. Age fatigue on the shafts more than likely contributes to breakage problems that are encountered while running stock valve spring pressures although the rocker bolts not being properly torqued can also contribute to the shaft breakage. Those thick washers that came from the factory under the heads of the rocker shaft bolts are also mandatory as they provide additional support or pressure to the top of the rocker stand.

The factory iron supports or aftermarket steel supports make the shafts more rigid thus cutting out more of the flex at the end rocker support bolts which will prolong the life of the shafts. The 406's and 427's came with the hefty iron rocker supports and still show up occaisionally as used parts for sale. There were two different widths available but that's easily worked around also. Although the Hi-Riser engines had a shorter support, they do not show up too often. Easily recognized if they do as they are considerably shorter than all the standard height units.

If you know someone in a machine shop, steel supports are quite easy to produce. Doing it yourself out of the appropriate width barstock could be performed with as little as drill press, bandsaw, dial calipers, and a reamer. The measurement from the bottom of the shaft to the hole would have to be maintained to a pretty close tolerance though to keep any additional flex out of the shaft when bolting them down.

Although expensive, end supported rocker shaft assemblies will cure the problem with all valve spring pressures.

[SCOBRAC]

I have aluminum pedestals.. See my gallery..

[Janus]

Thanks guys!

Who manufatures these aftermarket end supports? Maybe one could look at their design and make something custom. Are there some picures that one can look at? Remember that I am in South Africa and our resources on FE engines are very (capital V) limited. There are only a few guys that make life difficult for themselves (deducted that I am one of them)...

The problem that I was refering to was the breaking of the rocker shafts, due to the deflection in the pedestals and unsupported ends. The pedestals did not actually fail.

Cheers

[CJ428CJ]

Janus,

You can get the complete roller rocker assembly with the end supports from CompCams. Here's a link to that set up.

http://www.compcams.com/catalog/284.html

You can also get a pretty nice roller rocker set up from ErsonCams. Here's a link to that set up. http://www.mrgasket.com/pdf/Valvetrain.pdf

Both of these parts are available through Summit. I suspect Summit will ship internationally but I'm not sure. Both set ups are pricey. The Comp Cam set up is about $1000 and the Erson set up is about $600.

Chris