http://www.cranecams.com/?show=promo...1c258cd9bf4582

What's the scoop on these? i have a 232/236 .585/.585 cam with XE-R lobes. Not sure if this would be a bad thing or not. They seem like a good deal however the cariable thing has me wondering.

~Eddie

 

IMHO Iwouldn't push your luck because of your lift and your duration. This might be a good product but my feeling is if you want a bigger cam put in a bigger cam. Also I looked at the above link and question how 50+ HP can be gained from a lid, MAF ends and cat back. I call BS. I also have never heard of a LS1 engine starting at a 260+ RWHP baseline on a Dynojet, maybe on a Mustang dyno but not on a Dynojet.

 

They would give you a lift of .619. Yes, you'd definitely gain power.

Look here: https://ls1tech.com/forums/generation-iii-internal-engine/219558-gains-1-8-rockers.html

BTW, I'll be testing a set of these rocker arms very shortly.

 

.585 cam with 1.7 rockers is .613 at 1.78 (not .619) and as long as you don't have piston to valve clearance issues they should be fine since they progressively change to 1.7 after .300"lift.

 

PVC has little to do with lifts but more with duration and VE's.

 

I don't think it's the peak lift, it's the lift with the long duration and if any valve float takes place. Kaboom!!!

 

That is controled by your springs.

Crane rockers start at 1.89 and by .250 lifts go to 1.82 untill peak where they settle back to 1.89. They are not like a constant 1.89 ratio.

 

FWIW, The Crane rockers work great in my Tahoe. I don't understand why some of you are afraid of using Cranes accelerated lift rockers. You certainly aren't afraid of using "radical" lobe profiles. What difference does it make how the valve gets open as long as the opening rate is increasing the area under the curve? Isn't that what it's all about? The quick opening rate is just as the valve is coming off the seat and that is establishing airflow into the cylinder sooner. The only possible problem would be if you were running a very long duration cam (250* or more at .050) and a wide LSA and/or bigger diameter valves that would really cut down early lift PtoV clearance. That's certainly easy enough to check!

Some of the short circle track guys around here are running the new Crane shaft mounts for the SBC and they swear by them. They are running 13.5:1 with 268* at .050 and 1.75 ratios that come off the seat at 1.88 ; gross valve lift is in the .735 range and they aren't having any issues. I understand that they aren't LS1s , but they just took their Jesel 1.75s off and installed the Cranes and had no problems and said the drivers could feel the throttle response immediately. Take that only as anecdotal info;but I can't see why you would want to not try something new. I've raced for the best part of 30 years and one thing I've found for sure: If you do what every one else does you will be stuck in the middle of the pack. If you want to win, you have to try a combination that other people haven't discovered.

A slight correction Predetor; According to what Roger Vinci told me, the 1.7 advertised ratios come off the seat at 1.79 and come back to 1.72. The 1.8 advertised ratios start off the seat at 1.89 and come back to 1.82.

 

Corrected the typo. (I have big fingers)

 

Sorry. I had the 1.80s that I'll be testing on my brain.

.3441 lobe lift x 1.80 = .619

 

This is correct except that, according to Crane, the 1.7s come off the seat at 1.78 while, as you rightly state, the 1.8s start at 1.89.

 

I still don't get it if you want more lift and more duration get a bigger cam. A new cam is like $350, how much are thse new rockers. I'm also not clear about changes in valvetrain geometry either. Moving the pushrod down and closer to the fulcrum of the rocker puts greater stress on the system.

 

hey guado, i have the 1.89 accelerated lift rockers on the wife's 99 formula. here's some graphs showing the hp and tq gain. the tq peak is misleading on the graph as there was a spike at the beginning of the run.

 

Someone correct me if I'm wrong, but I don't think you can run 1.8 rockers with XE-R lobes.

To me, it doesn't seem like you can run either the 1.79's or 1.89's.

 

Why not if you have the piston-to-valve clearance? And the 1.78/1.89 numbers are the ratios as they start off. The rocker arm ratios at maximum valve lift are an advertised 1.70 and 1.80.

In the case of guadofreak's .585/.585 cam, this would give you a valve lift of .585 with the 1.7s and .619 with the 1.8s. There are lots of cams out there with higher valve lift numbers than that.

 

most people are concerned with their springs not being able to withstand the rapid accleration of cam and rockers together.

 

What these rockers will do for anyone is make any cam have a quicker opening rate early on and progressively "slow down" to a standard rate of opening as the lobe reaches, say mid lift. It isn't about just getting a bigger cam and/or one with more duration. These rockers can make a valve accelerate its opening rate much as a so called "bigger' cam would, without the penalty of the maximum lift going up to, say .650. I still am not happy with my explanation of this. Maybe someone else can simplify, say Predator or J-Rod.

 

Running standard 1.75 and 1.8 aftermarket rockers with cams having over .550 lifts (a little more for 1.75) is putting a lot more stress on the valvetrain geometry, and there for not recommended, as it changes the pressure angles at the rocker tip to valve contact point.
This is not true with Crane/VHP as they were designed to do that an maintain center point contacts on the valve.

 

Thanx for the info people. And for the ones just telling me to get a bigger cam...thanx for nothing.

There is a point to these rockers and you missed it three stops ago.

I will look into these some more. I do have XE-R lobes and the crane double springs. Not sure if that would make my springs cringed.

 

I just installed a set of the Gold Race 1.7 rollers on the Z06 this past Saturday...After my cam install, I had alot of tapping...I finally theorized that it was a lack of lifter preload...So, I went ahead and got a set of the fully adjustables...

The engine is as quite as a church mouse now...

As for running these with a bigger cam...My cam is somewhere around 234/238 .598/.602 114 lsa and no problems whatsoever...

Peace...Gman