Rocker Arms discussion

[patmckinneyracing]

I've been pondering this for a while now since my engine is gonna be coming out for an inspection after that driveshaft snap. I was looking at doing a cam swap to a Lunati 60102. But then I started thinking that I like the summit .442/.460 cam I got now and haven't had any problems with it.

So what if I go with a set of aftermarket 1.6 ratio rockers, which will increase the lift and duration? I'm currently running OE stamped rockers for the valvetrain and 882 heads with 2.02/1.60 valves. What about going to roller rockers as well? What are the benefits and dangers of going with a 1.6 roller rocker vice the OE stamped steel rocker? Will I need to replace my pushrods? I am running the reinforced steel tip pushrods, the ones that have the steel ball the each tip instead of just a rod. Here are some of the rockers I've been looking at on eBay:

http://cgi.ebay.com/ebaymotors/Sbc-Smal ... 563a1706c3

http://cgi.ebay.com/ebaymotors/1-6-3-8- ... 27ae9cfd7a


What is the difference between self-aligning and non self-aligning rockers? Do I need stud girdles to run roller tip rockers? Thanks guys. 8)

 

[shotgun]

Going up to 1.6 ratio will add lift and minimal duration.

Your cam will end up as follows:

Int .442/1.5 X 1.6 = .474
Ext .460/1.5 X 1.6 = .491

Many things effect duration, but here is my "rule of thumb".

1.5 ratio base
1.55 add 1 degree to duration @ .050
1.60 add 2 degress of duration
1.65 add 3 degrees '
You see the pattern.

Rollers tend to be more accurate and do reduce a small amount of friction.

If you have guide plates you do not need self-aligning. If you remove the plates you do.

Spend money on good/large diameter pushrods. Even with the mild cam you are using replacemnt style deflect.

No girdle needed with your cam.

I am not familar with those heads so hopefully someone will tell you if the need to be clearanced for 1.6 rockers. I highly doubt it but would rather be sure.

Last press in or screw in studs?

 

[patmckinneyracing]

I am not sure about the studs. I'd have to check them next weekend when I go home for spring break. I know the 882 heads were commonly used in the 70's. Nothing special just regular iron heads.

What are guide plates? Is that the girdle?

 

[86Cutlass383SR]

Guide plates are commonly used with the screw in studs. If you have press in rocker studs you will not have guide plates. Guide plates hold the pushrods in better alignment between the rocker and the holes in the heads. You MUST run a hardened pushrod to run guide plates. I think the 882 heads have pressed in studs.

Pushrods will flex to an extint, more so as rpm's and valvespring pressures increase. As long as you're pushrods are giving the correct sweep across the valve tip, then increasing the rocker ratio won't require a longer/shorter pushrod. If the sweep across the tip isn't correct, then the increased ratio will only make it worse.

S-A rockers have either small *bumps* ( http://www.summitracing.com/parts/NAL-1 ... /?rtype=10 ) or small *washers*
( http://www.summitracing.com/parts/PRO-66914/?rtype=10 ) that hold the rockers in alignment with the valve tip.

You do not need to run a stud girdle to use roller rockers. Either run a good stamped rocker (without the roller) or a full roller rocker. The late John Lingenfelter stated that with the pressure of the valve spring on a roller tip, they won't roll anyway, even on a full roller rocker. The benefit of a full roller over a stamped rocker lies in the roller fulcrum as in reduced friction.

The opening in the head where the pushrod goes thru will determine if the heads need clearanced. The 1.6 rockers will position the pushrod closer to the outside slightly. You need to check to see how much clearance is there with the 1.5 to know if the heads will need clearanced or not. If you run a pushrod with a bigger diameter and a 1.6 ratio you *might* need to clearance them. They make a tool to increase the clearance in the pushrod slot called a *Louis Tool*.

 

[adumb]

i went to 1.6 roller rockers when i put on my dart iron eagle heads. i am still using stock length pushrods as according to what to look for in the comp cams book at work, the stock length are still working for me,