SR Rockers; installed and tuned; data inside! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

Reply
 
 
 
Thread Tools Search this Thread
Old 06-18-2007, 07:17 PM   #1
Senior Member
Posts like a Corvette
Thread Starter
 
Join Date: Jan 2007
Location: San Diego, CA
Posts: 1,451
Thanks: 0
Thanked 0 Times in 0 Posts
agrazela is on a distinguished road
Default SR Rockers; installed and tuned; data inside!

Bought some SR ("split ratio"; first generation of ZZP'* current "ER") rockers used from ClubGP for $150 a few months ago:


These are 1.85 intake / 1.80 exhaust, modified stock rockers.

Finally got them installed (on stock springs/retainers; all shift points < 6000 rpm) and tuned over the past week; here'* the VE data in the continuing mod saga:


The rockers show an increase in calculated VE across the entire range from 2800 rpm up. I was hoping for more at the high end (more on that later); however, I was pleasantly surprised by the large positive impact even at 3600 rpm and below. The car pulls strong and steady from a dead stop, and I'm quite pleased.

Looking at the peak VE value, it seems that torque peak may have shifted up somewhat, perhaps by about 200 rpm; but I will still base my calc'* on a 4200 rpm torque peak / 5200 rpm hp peak for now.

So here'* the new incremental calculated improvements vs mod levels:

Mod Level---Torque (@4200rpm)---HP (@5200 rpm)
Stock-----------+0 ft-lb--------------------+0 hp
PLIM------------+10 ft-lb-------------------+8 hp
PEM-------------+6 ft-lb--------------------+5 hp
L67TB----------+16 ft-lb--------------------+17 hp
SRR-------------+4 ft-lb---------------------+9 hp

For a total of about +36 ft-lb @4200 rpm and +39 hp @5200 rpm over stock.

Having bought alot of hard parts used, I'm about $350 into parts/gaskets with what'* listed above. That'* less than $10/hp (if my calculations are close), so not too shabby.

(As always, these are calculated estimates only, not yet backed up by actual dynos...)

I think that I could get more out of these rockers with upgraded valvesprings; I believe I have--and have long had--some valvefloat issues at the high rpms. Plus, my calculated hp curve is telling me to start thinking about shift points beyond 6000 rpm, for which I would need better springs. Furthermore, I think I'll get ALOT more out of these rockers (and all the mods, for that matter) once I port out the spare heads:
http://www.bonnevilleclub.com/forum/...ic.php?t=77163

Heads and springs will likely be a Fall-Winter project, as the rest of my Summer car money is now earmarked for tires, brakes, and maybe struts. Unless I come up with some really low-cost ideas, I'm probably set performance-wise for the next few months.
agrazela is offline   Reply With Quote
Old 06-18-2007, 08:24 PM   #2
Senior Member
Posts like a Camaro
 
Join Date: Oct 2006
Location: montreal canada NEBF07 ONBF07
Posts: 987
Thanks: 0
Thanked 0 Times in 0 Posts
firebuick is on a distinguished road
Default

andrew is the a big difference between those and the ER rockers .what i have heard is that the ER has a bit more top end .but for 150 that a good deal
firebuick is offline   Reply With Quote
Old 06-18-2007, 09:32 PM   #3
Senior Member
Posts like a Corvette
Thread Starter
 
Join Date: Jan 2007
Location: San Diego, CA
Posts: 1,451
Thanks: 0
Thanked 0 Times in 0 Posts
agrazela is on a distinguished road
Default

Quote:
Originally Posted by firebuick
andrew is the a big difference between those and the ER rockers .what i have heard is that the ER has a bit more top end .but for 150 that a good deal
I have heard that ER'* are 1.84 / 1.81, though the actual ratios are a closely guarded secret.

zzp mods these stock rockers by filling in the original hole or "cup" the pushrod end fits into, then re-grinding the "cup" a little closer to the pivot point. You can see in the photo above that the bottom row has the re-ground cups a little closer to the pivot...these are the 1.85'*, the top row is the 1.8'*.

Between a measured manufacturing tolerance of +/- 0.03" from rocker-to-rocker on the location of the re-ground cups, plus the likelihood of unpredictable amounts of deflection from piece-to-piece on what are at heart stock rockers of unknown mileage and unknown mileage consistency (did all the cores come from the same original engine? I dunno!), I wouldn't dare try to quote an actual lift number with any more than about +/- 0.05" precision. And I certainly wouldn't expect any major difference between SR'* and ER'* :P

These things do go up used on ClubGP quite often for about that price...I feel lucky that the ones I got were extremely clean and in such good condition.

Note that the pedestals are modified too...the U-shaped cut-outs that guide the pushrods are ground deeper, because the pushrod geometry is changed. If you buy used, make sure the modded pedestals are included.
agrazela is offline   Reply With Quote
Old 06-19-2007, 07:00 PM   #4
Senior Member
Posts like a Camaro
 
Join Date: Oct 2006
Location: montreal canada NEBF07 ONBF07
Posts: 987
Thanks: 0
Thanked 0 Times in 0 Posts
firebuick is on a distinguished road
Default

if the ratio is 1.84 and 1.81 and i have to buy new one would the extra cost of true roller 1.8 rocker be better .i think there 100$ more butt the have a roller tip and they don't flex and the ratio should be more acurate
firebuick is offline   Reply With Quote
Old 06-19-2007, 08:26 PM   #5
Senior Member
Posts like a Corvette
Thread Starter
 
Join Date: Jan 2007
Location: San Diego, CA
Posts: 1,451
Thanks: 0
Thanked 0 Times in 0 Posts
agrazela is on a distinguished road
Default

My personal opinion is that roller rockers are an unnecessary extravagance for our applications. But if you've got the dough, go for it!

EDIT: Let me add: even if the stock rockers deflect by as much as 0.040" (number from zzp website), the SR'* or ER'* still give a intake lift on the stock cam of just over 25% of the valve diameter (and even more than 25% with a deflected 1.8 on the exhaust). According to engine theory, there is little or nothing to be gained by increasing lift more than 25% of valve diameter, as the area of the imaginary cylinder between the stock valve margin and the valveseat equals the area of the valveseat opening at this lift.

A 1.8 with no deflection will give ever-so-slightly more lift than a 1.85 with 0.040" deflection on the intake, and significantly more than a deflected 1.8 on the exhaust; since you already have all the lift you need on the SR'* or ER'* (assuming you have stock valve diameters), the fact that the roller rockers don't deflect (as much) is not, theoretically, an issue.

The rollers will reduce side-to-side motion of the valvestem, and should reduce valveguide wear...but that'* more of an issue in a race-built or strip-only car. For our 90%+ street cars, I don't see it as worth the extra money.
agrazela is offline   Reply With Quote
Old 06-19-2007, 11:24 PM   #6
Senior Member
Posts like a Camaro
 
Join Date: Oct 2006
Location: montreal canada NEBF07 ONBF07
Posts: 987
Thanks: 0
Thanked 0 Times in 0 Posts
firebuick is on a distinguished road
Default

ok thank you andrew i was sure you had a good opinion on that .so it will be ER or SR rockers .im getting a high flow cat install tommorow after i wil get into the engine soon
firebuick is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Series 1 roller rockers vs Series 2 roller rockers xtremerevolution Performance, Brainstorming & Tuning 7 06-04-2010 07:52 PM
Rockers installed, computer learning issue? (PROBLEM SOLVED) chadow427 Performance, Brainstorming & Tuning 28 07-08-2006 10:53 AM
Rockers are installed....vrooom! PontiacDad Performance, Brainstorming & Tuning 24 08-18-2004 11:23 PM
Rockers installed, two calfs delivered smellbird Performance, Brainstorming & Tuning 8 06-30-2004 01:10 AM
INTENSE 3rd Generation Rockers Installed Rogue General GM Chat 6 01-08-2004 11:37 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 08:38 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.