Rocker DAQ

[Don W.]

My Vortec's have what you might call pedestal mound rockers. Non adjustable. When I built the motor last time I spent hours checking and double checking inj preload with a dial indicator and ordering custom push rods.

Just wondering if these heads are convertible to stud rockers or if there are any other rockers available for these heads. Unlikely I'll actually change anything, the motor ran fine, I'm just curious more than anything.

Thanks.

 

[Syclone#2960]

Re: Rocker DAQ

Yes they can be converted to fit reg rockers.
The only shaft mount rocker that "I" know of is the the 1.7 ratio from the LSX motors.
Turbo time has a custom cam to make it work for that ratio.

I have the same heads being built...going to try & run it with a 412 cam. Need to figure out the lift with this ratio first...to make sure its possible.

 

[Don W.]

Re: Rocker DAQ

I'm using a 412 cam with these heads/rockers and have no issue. IMHO You will have to spend some time setting lifter pre-load and, probably, ordering custom push rods.

 

[blk00z28]

Re: Rocker DAQ

The only shaft mount rocker that "I" know of is the the 1.7 ratio from the LSX motorsossible.

Actual shaft mount, or pedestal mount?

I have 1.6's and 1.7's for my bowties. But they are true shaft mount's.

 

[UR50SLO]

Re: Rocker DAQ

I'm running the Vortec's on the wife's truck and had my machiene shop re-tap the holes for the american studs like on SBC... I run a guidplate as well.
~Scott

 

[Don W.]

Re: Rocker DAQ

I'm running the Vortec's on the wife's truck and had my machiene shop re-tap the holes for the american studs like on SBC... I run a guidplate as well.
~Scott

Ah ha, I was wondering if that could be done. What rockers did you use?

 

[Windedv6]

Re: Rocker DAQ

Ah ha, I was wondering if that could be done. What rockers did you use?

My advice is to stick with what you have. I ran those stock ped mount rockers with a 412 cam into the the low 11s with my Typhoon. There need no adjustment once set up correctly. They also have a better pattern on the the valve tip which aids the cam in duration.

I ran 10.70-10.60s with with the same rockers setup with a slightly larger turbo and cam setup. Richard Burns at Flowtech convinced me back in 2002 to run those rockers as they will out perform a 1.60 roller tip rocker. Even with a well ported vortec head and changing to a 1.60 ratio from a 1.5 ratio you are only going to pick a few CFM at .500-.530 lift. On a forced induction motor a few cfm is not noticable. The duration setup is actually more critical. Changing 1.50 rockers to 1.60 only changes the duration a couple of points at best.

A typical aftermarket roller tip has a small dia surface that contacts the valve tip and opens and closes the valve very precisly (for even the high hp racing pros). For our low reving turbo motors those GM ped rockers work well as they have a low long sweeping curve where the rocker meets the valve tip which opens the valve quicker and runs the duration longer. It makes the cam seem bigger.

I was convinced of this back in 2002 and even feel better about it today as GM uses these in their LS motors. If you have Vortec heads with this setup you should think about keeping them.

John

 

[Don W.]

Re: Rocker DAQ

Interesting info. Like I said spent some time getting the pre-load correct. Motor is apart for other reasons, wear on rocker tips looks good. I was just wondering but think I'll leave well enough alone.

Thanks!

 

[Windedv6]

Re: Rocker DAQ

It's fairly easily to set the correct preload with these. Since there is no adjustment we have to set the preload with the push rod length. A simple way is to take the lifter preload allowance from the lifter spec sheet (typically .020 to .070 for comp and cranes lifters).

Using an adjustable pushrod find the zero lash with rocker torqued to spec. Find zero lash by adjusting the adjustable push rod until it barely spins freely (no preload). Add .030 to .060 to this length for your push rod length. With our low rpm motors .040 -.060 is a good preload. If you are running a high rpm setup then you should run a lessor preload such as .030 - .040.

There is "room to play" so if the preload number is not exactly a shelf part number go longer or shorter to the next standard size.

A nice thing about these rockers is once they are setup you can easily take them off, (if retorqing head bolts or changing head gaskets), and put them back on without having to readjust them.

John

 

[Don W.]

Re: Rocker DAQ

I did that originally. I rigged up a dial indicator to double check. All went well. And yes, I like the no readjustment "feature."