As some of you know, I swapped out my SLP 1.85 rocker arms for a set of Crane "Quick-Lift" 1.80 roller rockers. When we then dynoed my car, we discovered that my motor experienced a power dip at around 5900 rpm. Even with the dip and even though I lost around 10/1000ths in peak valve lift going from a ratio of 1.85 to 1.80, the dyno results were that my engine output with the Cranes nearly equaled that with the SLPs, 389 rwhp vs 392 rwhp.

Crane attributed the power dip to valvetrain harmonics caused by valve spring incompatibility and they suggested I use their dual valve springs with the Quick-Lift rockers.

Well, after this long, hard winter, Mike/Rapid Motorsports installed the Crane dual valve springs today and redynoed. The first thing we immediately noticed was that the new springs completely eliminated the dip in the graph. Second, my peak horsepower jumped from 389 rwhp to 402 rwhp and my peak torque went from 367 to 375!

I'm thoroughly impressed and pleased with the results.

 

Steve, as long as you've been on these boards I can't believe you would use anything other than a 1.70 rocker. Want more lift get a bigger cam, you know that better than I do.

 

nice results. do you have any of the graphs we can see?

why get a bigger cam when the right selection of parts will do better.
compcams 220/224 .581/.581 115 LSA with vinci/crane 1.7 accelerated lift rockers vs vinci 055 cam 216/224 .551/.551 (@ 1.7) 113 LSA with vinci/crane 1.8 accelerated lift rockers (.583/.583)

 

Actually, there are distinct advantages to these "Quick-Lift" roller rockers that can't be had with another cam swap.

 

It'll take me a few days to get the graph scanned in and posted up, but I'll get it in here.

 

thanks.

 

how did i know mr223 would be in this thread .

nice results steve, i posted some questions on ls2.

 

because of your innate psychic abilities.

either that or the near mention of crane or vinci excites me.

 

Hey trooper, glad to see you're still around, even after the "old days" lol. Now, could I use those crane "quick lifts" even with the thunder racing 224/224? Do they like the XER lobes?

Edit: okay, I checked their site, and they advise against it

 

Nice to here from you again. I have a couple of questions.

Do you have less valvetrain noise as advertised by swapping to the Cranes and using their prescribed preload adjustment?

Do you feel you made the correct cam choice for your Corvette?

 

Go big or stay home mrr23! Soon I will post what the crane parts do with a crane 242/248 .638/.638 112 lsa.

 

Thanks, Jerami! I'll get to them shortly.

 

Believe it or not, some people just would not be happy with a cam that big. Even those that LOVE them when first installed, sometimes tire of them in short order.

Good luck with your setup! You'll undoubtedly make MONSTER POWER!

 

The first question is an easy one. Yes, the valvetrain is noticeably quieter with the Crane "Quick-Lift" rockers. Mike and I both commented on this and he's since seen it happen on every other occasion that he's installed them on a motor.

Your second question is a bit tougher to answer for me. Yes, I love the XTrooper cam and its specs and I've no plans to swap it out anytime soon, but with the switch from 1.85 to 1.80 (really 1.82) ratio rockers, I wish I had a little more valve lift than I have now. Nothing crazy, but something in the .580's would be nice, though I really don't know how much I'd gain with another 20/1000ths of valve lift.

Not enough to make me want to run out and order another cam, that's for sure.

 

Sorry for the picture quality (I don't presently have a scanner so this is actually a photo), but here's the graph from our best run yesterday.

 

Steve, when you figure the outrageous expense of the rockers vs a new cam it obviates any potential benefits.

 

I was just joking around with mrr. I may very well hate it but I am going to drive it less now with the price of gas. The nissan 4 cyl is a whole lot cheaper to fill up. I hope it makes alot of power. I couldn't find too many h/c cars with huge cams on 346's posting on here. The price on the cam was too good to pass up, so I'll give a go.

 

what they recommend is not going to any 1.8 rocker. you could get the 1.7 accelerated lift rockers instead. that way, max lift will be about the same. but the whole 0 - .250 lift will be changed. on the tech and tuning page on vinci's site, it explains how stock rockers actually start of at 1.54 and gradually reach 1.7. the 1.7 accelerated lift rockers start off at 1.79. by about .350 lift, they decrease to about 1.72. the june issue of chevy high performance has an article about the rockers. it explains the same thing in there. next month, they will post the results of installing them in their test truck. and i know where the testing was done at.

 

swapping rockers requires no added parts. swapping a cam, needs alot of work and some other items. things like oil, antifreeze, gaskets, and lots more time. so, does it really cost more to have aftermarket rockers?

it's easier to swap rockers than it is a cam. the other benefit is only the valve is moving at the faster rate. not the lifters, pushrods, and rockers. there are times when people confuse valve float by blaming the springs for not controlling the valves. sometimes, it's the lifter bouncing off the cam from them being 'thrown' off the cam itself. then it comes slamming down on the cam. which just like a basketball being thrown to the ground, bounces right back up.

this is another one of those, 'we could go round and round' debates. i just keep going back to the graph and going hmmm.

 

Unless you are doing your own cam installation, the cost factor becomes much less of an issue. Almost anyone that can pick up a wrench can swap in a set of rockers in an hour or less with no muss or fuss. The same can't be said for a cam swap especially in a C5 which requires the removal of the rack & pinion assembly to get to the crank pulley.