are the much more quiet then OEM rockers?
Any one make 1.7 ratio with rollers?

 

They have the potential to be quieter, but there are lots of other variables that contribute to valvetrain noise (e.g., preload, springs). I have Harlan Sharp 1.7 roller rockers in my LS2 402.

 

Crane rockers are quiet and have the quick lift technology. Since they are adjustable, if you do the install correctly, they have the correct preload and you dont need to mess with pushrod length.

They come in 1.7 and 1.8 designs. I have used both. I currently use the crane 1.7's with a 228/232 xer cam with no issues.

 

I have [edit] Comp 1.85 roller rockers and they are slightly quieter than the stock valvetrain.

 

Thanks for the info!
One more question:
would using 1.8's on a stock cam slightly increase overlap and potentially lose low end torque by a decrease in DCR?

 

There is a slight increase in duration 1.5 degrees but it isnt significant. The rockers increase low end TQ.

 

Crane doesnt make a 1.85....I think you mean comp cams magnum rockers....good product too.

 

Where are you guys getting the 1.8 Crane Roller Rocker Kits from. My tuner agrees the low end torque should be better and the RWHP gain should be in the previous mentions ranges with the upgrade. Not trying to highjack the thread just trying to find the product. I have fould several places that sell the SLP'S but they are not the roller type.

 

low end is what I would want but what are the trade offs? Aside from $$ I am thinking the higher lift means more spring wear--anything else?

 

well I answered my question about the trade offs after doing some reading:

Valve guide wear if push rods are not properly adjusted

Need for stiffer springs with higher bind

Spring wear

Also the lit I read was that low end suffers with increased ratios. Peak numbers are up though.

See: www.lmengines.com/rocker_arm_changes.htm the chart there is an example of many narratives I have read.

Where am jacked up on this? Maybe I was reading what I wanted to see?

 

I would do a comparo with the Harland Sharp rockers before jumping on the Cranes, IMHO.

 

Yes I meant comp. Sorry :o

If you do rockers, it is essential to do hardened pushrods and dual springs at the same time. Going with shaft rockers is also preferrable. All in all, they will cost about the same as a cam ($1,500 or so), but they avoid smog issues altogether and you keep your torque down low. All in all a good mod. Cams give better stated Hp/buck, but they will cost you torque on the low end.

 

Vinci High Perfomance, Crane or Summit.

 

show me a dyno sheet where a cammed car didnt produce higher low end TQ than stock?

here is my reply from the other thread

 

will someone comment on my hyper link above. It kind of makes my point that installing a bigger(even mild cam) will decrease DCR and effect low end performance. Installing higher rocker arm ratios make your cam bigger and the same caveat applies

 

First, not all "bigger" cams will decrease DCR, it depends on the grind. Some reverse split grinds could increase DCR. Also, even if the increased overlap of a bigger cam does decrease the DCR, the resultant power losses could be offset by the gains from the increased flow.

Second, a "bigger" cam can mean that it has more duration, or more lift, or both. A cam that has the same duration but increased lift will not decrease DCR. However, if the flow characteristics of the heads will not complement the increased lift, low end performance could still suffer.

Third, higher rocker arm ratios primarily increase the cam's lift, with only a negligible increase in the duration. So long as the heads can handle the increased lift, low end performance should improve slightly.

 

Thanks Hitman,

So lets say I like the stock cam, then adding some 1.8:1 roller rockers can only make it better throughout the RPM range? Is that a safe comment to make? Is it even more applicable to say this with AFR 205 heads as well?

 

ttt

 

Shawn, I am not going to argue with you to prove a point. After very careful consideration, discussion with several vendors, and price comparisons, I chose the roller rocker route. I am very happy with it and I still believe it was the best choice for me. Incidentally, I am making 427RWHP without touching the heads or the cam.

But I will clarify a few technical points.

First, any increase in overlap, be it via increased lift, narrower LSA, or added duration, decreases DCR and impacts torque. The least impactful is increased lift. The more compression you have, the more torque you have, all things being relative. It's that simple. If you go from a .525/.525 204/217 116LSA cam to a .596/.596 220/230 114LSA cam with no advance in timing or increasing static compression, you WILL lose torque below 3500. I would challenge you to show me a cam-only before/after dyno where that did not occur.

Valve lift is valve lift. Whether you increase it by changing the rocker arm fulcrum or changing the cam, the net effect is the same. Either route definitely requires stronger pushrods and springs.

You mention valvetrain instability. That is another word for valve float and that is caused by weak springs. A sure way to induce instability or float is to not replace springs when you increase valve lift. Unstable valvetrains are not a characteristic of high-lift rockers. They are a characteristic of the stock LS2 valvetrain after 6K and they are a characteristic of a poorly executed cam/rocker swap (i.e. failing to change to stronger springs).

Another problem is valve angle deflection, again a by-product of increased valve lift. Roller rockers specifically cure this issue in addition to reducing friction. Roller rockers should be part of any mod that increases valve-lift, be it high ratio rockers or a high lift camshaft.

Finally, regarding weight: bigger or dual springs increase static weight, but you cannot include them in calculating moving parts inertia. In fact, aftermarket rockers are typically lighter than the stamped steel stockers, and Ti retainers futher reduces the weight. In the end, your valvetrain inertia is reduced where it counts.

Most of your negative comments seem directed at the SLP product, and I agree with you if such is the case. The SLP product is inferior IMO because it uses single beehive springs with a history of failure, and it is a non-roller design. Plus their customer service sucks. But it is not fair to place excellent rocker offerings by Jesel, Crane, Comp, and Harland-Sharp in the same boat, because they are a totally different animal.

Are rockers the best way to add power/$? No. But neither is a cam. If you want BANG for your buck, Nitrous is where its at. And doing a cam without heads is leaving quite a bit of power on the table. There are many posts on this topic by others who know more than me and it os late, so I'll stop here.

 

if you're happy with your gains and it has been a trouble free mod, no argument here. 427rwhp without a cam is very nice. if you want to read more of the opposing views, go here

http://forums.corvetteforum.com/show....php?t=1615200