Hi guys, this is a mirror of a post I made over at CG. Just looking for some more insight and personal experiences. Thanks
http://www.corvette-guru.com/modules...post_id=117046

I saw Summit has these on sale:

http://www.summitracing.com/parts/SUM-G6938-16/

I need to pick up roller rockers for my build. Heads are 3/8 stud, non self aligning (has guideplates), centerbolt vcs. I can hardly find any information about them. Some guys claim they are made by scorpion, I can't verify that. Anyone running these or have any personal experience with them?

Matthew

 

I have used those. Not the BEST quality, but fine for light duty.
You may run into problems trying to run them with center-bolt VCs. I used them with perimeter bolt heads.
They are light in weight.
Be careful not to run them too far down on to the radiused area of the stud where they might touch.

 

Thanks for the reply. This will be in a daily driver street car. I have no problem paying for quality, but I want to make it a budget build as much as possible.

As far as the VCs, these are narrow bodied and I will be using aftermarket edelbrock covers. I don't remember if there are drip tabs, but if there are I will trim them off.

 

i have a set of brand new scorpion 1.5 for 3/8 stud for sale. If iterested, pm me.

 

Looks like Prime 1 Rockers.....those are great rockers...



if you want to screw up your engine that is.

They are not scorpions!

Here's more uglyness

http://forums.corral.net/forums/show....php?t=1037191

 

Thanks for the reply and link, TT. I like this guy's quote:
"OUCH! As a general statement from me and regardless of how this came to be, this is a good example of why when it comes to custom engine building we should not think strictly with our wallets but instead give the greatest priority to using quality components that are up to the job and application!"

As far as my build, my motor will never see 7000 rpms. It will be a ported SLP LTR setup. However, if spending an extra $75 gives me that much extra piece of mind, it's well worth it to me.

On that note, suggestions for narrow bodied, non self aligning 1.6 rrs?

 

Thanks for the offer, Ken, but I'm trying to go with 1.6 for my cam

Matthew

 

I understand. good luck.

 

those are just like the proform rockers.. the hardened material in those style rockers are HORRIFIC!! the set I had the bearings wore through the fulcrum the poly locks were chipping in less then a 1000 miles my engine at that time was flawless... all that nice material goes where OHHH yes inside your engine.. I would stay away form that style rocker!!! step up and get HD stainless or chrome moly!!! rockers at least proform was great.. I sent them in. they knew they were bad they changed there design they sent me a new pair I SOLD THEM

looking at the pic... of that rocker someone had a clearance problem.. or they were not adjusted correct

 

That pic is from a guy here that knows what he's doing, they were sold to him by a cam grinder as being scorpion rockers. There were no clearance issues, they exploded from the high spring pressures

 

TT While I feel your pain with your busted rockers, those are neither Summit brand or Scorpion rocker arms and are not evidence that either the Summit branded or Scorpion rocker are sub standard.

Reguardless..... it takes a lot of force/shock abuse to create the failure you experienced. Like valve float/crash.

I have not used the Summit branded narrow body rockers specifically but the conventional wide/full body aluminum roller rockers are top notch and if they are not actually made by Scorpion, are a dame good copy. Mine (plain/natural aluminum finish) look exactly like the Scorpions without the Iodizing colour finish. If these Summit rockers were a cheap piece of crap they would have gone back to Summit a long time ago.

 

Great technical analysis, they look great so they must be good...good luck with that

 

My experience with the Summit/Scorpion brand rockers goes way beyond appearance comparison. They have proven to be a top notch rocker in more than one race motor and marine race motor for me and my friends. If they were crap they would have come unglued or wore out a long time ago.
If it will stand up in a high rpm max performance marine motor, it's a dame good part.

 

Same as your technical analysis that summit rockers LOOK like that failed one.

 

point me to my tech analysis please, I would love to see where I point out the fact that they don't look nice and thus are not strong

 

Paraprashing, "they look like these, these are garbage". This implies based on looks that the summits are also garbage. Otherwise why even bring it up?

 

Whatever, stupid arguing of semantics. If you are such a brass knuckle racer and have been there done that you tell me what the run-out is on those things. They're either proform, procomp or prime 1 pieces most likely (leaning towards proform since they sell that a lot) and they'll have up to 10 times the run-out that a quality comp cam or crane rocker will have.

But since everyone here seems to like the cheap Chinese junk don't start pouting when your engine turns to shrapnel.

 

They do have a lot more run-out, which can become a big problem when the springs are no longer controlling the valve motion. Many things can go wrong in that situation, and a bargain rocker arm is not immune to such things.

If everything is set up right, they perform well in light duty applications.
If you intend to abuse the valvetrain with the combination of high revs and a camshaft with radical closing ramps, and/or possible over-revs, the best bet is to use the much heavier and more expensive steel rockers like Comp sells.

An over-rev situation can create clearance in the valvetrain and the pressures against the rocker will spike to levels of double or triple the pressure of the spring momentarily.

 

So how do you measure run-out for a roller rocker? What are acceptable numbers?

 

I'm leaning towards a set of CC roller rockers. Still not sure. This is the cam I'll be using - comments?

http://www.compcams.com/Cam_Specs/Ca...?csid=207&sb=0

08-465-8
RPM Range 1200-5200
Duration 260/270
Duration at .50 210/218
Valve lift (1/6 rr) .56/.555
LCA 113
Intake centerline 109

Thanks,

Matthew

 

You can measure runout in a rocker with a dial indicator, but an exact number is fairly meaningless. They are either loose or tight.
I have used both, actually many different types of roller rockers and never had a failure, so both are very usable.
Don't miss my point on having clearance in your valvetrain. If it develops clearance ANYWHERE during operation, you are likely to have some parts damage. With tight rockers, it is much less likely that the rocker will be what fails. Loose rockers will likely fail quickly in that situation.
If you don't generate clearance during operation, the loose rockers work fine in most cases.
Even a tight aluminum rocker can break due to clearance caused by whatever reason, be it an over-rev or a stud or posi-lock coming loose.

I have seen CC steel rollers with a lot of runout after heavy usage, but Comp offers a rebuilding service. Some other companies also offer this service.