BLUE99T/A

iTrader: (2)

I'm considering a rocker swap on all stock internals, with a cam later on. I don't know what ratio to get. Any help would be appreciated.

4mula

save youre money for now and do a rocker swap at the same time as the cam

vettenuts

iTrader: (4)

The Cranes sold by Vinci seem to be a really good setup and appear to keep the valve train quiet. As for ratio, I would stick with 1.7 and use the cam to increase lift. Some cams are too aggressive a profile and won't work with 1.8's.

HAMRHEAD

iTrader: (8)

I agree don't get the 1.8's if you ever plan on doing a cam swap. Get the cam now and the rockers after. You won't see much if any gain from a rocker swap. Stock rockers work on many cams.

4mula

btw, i did 1.85 rockers and im getting rid of them now because im doing a cam swap.
i gained 9rwhp on the stock motor with those rockers

mrr23

iTrader: (3)

you can use the 1.8 and do a cam swap later if you so desire. you just have to choose a cam that'll best benefit with the rockers.

here's my dyno of the vinci/crane 1.8 accelerated lift rockers on the wife's 99 formula with stock cam

dyno 9 before
dyno 11 500 miles later
dyno 14 10 months later

mrr23

iTrader: (3)

now case in point of using 1.8 rockers with after market cams. this is a dyno of the PROJECT AFR 03 corvette vinci is doing. it compares a comp cam 224/224 .581/.581 LSA 115 with 1.7 accelerated lift rockers VS vinci 055 216/224 .551/.551 (1.7) LSA 113 with 1.8 accelerated lift rockers. this brings the total lift to .583/.583. less cam, more rocker ratio (brings total lift to the same on both cams) did better overall.

BLUE99T/A

iTrader: (2)

Is tuning required after a 1.8 swap?

mrr23

iTrader: (3)

nope. my dyno was without tuning on the before and after. i didn't tune the car until i put the vinci ported heads on.

QuietTahoe

Thanks for posting Robert! I would like someone out there to explain to me why they think ramp rates preclude the use of 1.8 ratio rockers. I prefer to use the rockers to supplement the cam lobe because what I am concerned about is what the valve is doing, not how the lobe is designed. The valve depends on the lobe and the rocker ratio and activation rate. I would like an expert on this site to explain this. I have only installed over 800 cams personnally(not counting over 3000 installed at my shop over 24 years) and I have never seen a case when power dropped off with higher ratio rockers. I have seen cases where power just didn't improve and I have found that the limit in all of those cases was port flow limitations. I have never seen a lobe wear out due to excessive rocker ratio. 1.8's can't be that bad or Chevrolet wouldn't use them on the LS7!! Most of my 33years experience in this area coincides perfectly with what Vinci has found. Personally, I think a lot of BS gets repeated on this site that has absolutely no basis in fact. If you use 1.8's you must watch P to V clearance and make sure the springs can take the lift. If I'm wrong, please set me straight; but don't try to BS me. I want to see documented facts, SAE publications, test results done to SAE standards or something. The total BS on this site is astounding!!! Please someone prove me wrong!! I would like to have a serious intellectual discussion on this!! Q/T

vettenuts

iTrader: (4)

If you are referring to my post above, I am simply quoting the guidance given by several vendors on cam selection. One quick look at Thunder Racing and you can see they don't advise the use of 1.8's on many of their cams. This is taken directly from their site: "Due to the fast ramp rate of this camshaft, the use of 1.8 rockers is not recommended."

mrr23

iTrader: (3)

might want to call them and ask why. is it because the valve springs they use not capable of controlling the valve? i don't think anyone has ever explained why other than fast ramp rates. i do not know why. maybe someone from TR will chime in and answer.

QuietTahoe

I've seen that on their site and I have never understood it. The only thing that I saw was that in many cases the 1.8 rockers would cause p to v issues. Rocker ratio doesn't affect the pressure angle on the lifter. It does increase initial inertia loads on the lobe. The only way that would be detrimental was if their cams were made out of an inferior grade of steel or didn't have the proper heat treat, case depth or some quality issue like that. If the case depth is adequate and the proper grade of steel is used their shouldn't be an issue. BBC hydraulic rollers run much higher spring loads than LSx engines and the inertia loads are much higher because of spring load, valve weight, etc. I really want someone to explain it to me. To my way of thinking it is just a marketing ploy to make people think " these lobes are so damn radical, man, that they are the ultimate and anything more aggresive will destroy your engine!!" I don't buy it! Someone is going to have to provide some definitive data to convince me!! I'm not saying I'm right, I have an open mind. If someone can convince me with data, I will be glad to say I am wrong. I've just had a lot of experience building a lot of engines with some badass cams and very high rocker ratios. I just think this "ramp rates are too aggressive" is ridiculous. Look at it this way, if these ramps are that aggressive, what are they going to sell to the guys with LS7's who have 1.8 rockers? I guess the performance world will come to a screeching halt! Just a thought!!!! Q/T

01TA

iTrader: (7)

I believe the issue would be with possible valveguide wear from the extra stress of the 1.8 ratio on top of the TR or XER cams already very fast ramps.

XTrooper

I'm using the Crane 1.80 Quick-Lift rockers in my motor. I had a custom grind cam specifically made to use with them. It's a Cam Motion cam that I supplied the specs for and obtained through Futral. As most know, the Futral/Cam Motion cams may not be the most aggressive available, but their ramp rates are definitely on the aggressive side.

This cam and the Crane 1.80 rockers work just fine together and this combination is yielding good power for me so I think the idea of fast ramp rates and higher ratio rockers not working together is based on opinion and not fact. Also, keep in mind that the new 500 hp, 7000 rpm redline, LS7 motor has a pretty stout cam and it comes with 1.80 rockers from the factory.

Here's a dyno graph from the last tune with the mods in my sig.

PREDATOR-Z

The only problem with the stock ones are the bearing issues.

Most if not all aftermarkets have had clearance issues or floating issues.
One of the solutions is to send your rockers to Nasty's and get them fitted with new trunions and c-clip kit from Harland. ~200 bucks.
It is much better to try to keep yor stock 1.7 ratio as much as possible.

The CRANE 1.7's are nice but mucho $$$ for the swap IMO. ~ $600+ That money could get a cam kit.

QuietTahoe

The rocker ratio is determined by the position of the pushrod seat, not the nosewheel arc, so that aspect can't affect guide wear if the rocker arm geometry is correct. Q/T

QuietTahoe

Please explain how most aftermarket rockers have floating issues. I just don't see it. As for dyno runs showing this, I submit that there are issues with more than one thing being changed at a time, improper preload, wrong pushrod length, too weak of pushrods, improper seat pressure, etc. I have yet to see conclusive proof of rockers causing valve float. I suggest that the number one problem with valve float on most LSx engines is flexing in the pushrod with inadequate lifter preload (less than 1/4 turn) which will definitely lead to valve train separation which lifter "pump-up" then tries to compensate for by movement of the inner plunger up to the snap ring. At that point, when the lifter returns to the basecircle the valve is held slightly off its seat leading to a slight vacuum leak and it doesn't fully seat again until it is forced shut during the compression stroke. But that is just a thought. Q/T

PREDATOR-Z

I mispunctuated I meant that:
"Most if not all aftermarkets have had clearance issues. Or some floating issues."

you are absolutely right on with regards to "no concrete proof of rockers causing float", but I've seen a few people switch to aftermarkets, have float, then switch back to stockers and float dissapears.

One thing that baffles me is that if aftermarkets were so necessary why can't anyone just make one roller tiped rocker, that just fits under the covers.
Most sponsors here just reuse the stockers on their motor build ups.

XTrooper

FWIW, I had no trouble whatsoever with my Crane 1.80 rockers. I simply removed the old rockers and swapped in the Cranes. The valve covers went right on and I didn't have any clearance problems. In fact, the only clearance problems I've heard about concerning the Cranes is with the '97 and '98 perimeter bolt heads.

As far as "most" reusing the stockers on their motor buildups, that is changing more and more everyday and all the motors I've seen built this year so far had one brand or another roller tip rockers on their heads. Even if you're going to stick with the stock ratio, it only makes sense to use roller tip rockers if you want to get the most out of your motor. I don't think anyone at this last date is going to argue that roller tip rockers don't make more power.