I realize this subject has had alot of coverage, but I need to know what the effect would be on switching to the 1.6 on a dual pattern cam. Should I use the 1.6 on just the intakes? or is it just on the exhaust valves. or.. just run all 1.6 on both valves? I run the XE262 cam & World iron heads 2.02/1.60 & 1.52 Comp Mag roller tips

On the XE262 with the rocker change from the 1.52:1 to the 1.6:1,,,you would gain 0.025" of lift on the intake and exhaust.. hardly worth the effort for the $ as both would still be .500 or below.

What about combining the rockers with longer push rods? Any problems there?

With longer pushrods you'll only throw your valve train geometry out of whack. It won't do anything for performance...unless you already need longer pushrods...

edit if you up the rocker ratio you MAY need a longer pushrod

[This message has been edited by Acal57 (edited August 16, 2005).]

With that small of a cam it is highly doubtfull that the added 0.025" of lift is going to change geometry, adding some funky brand of rocker 'might'.
Johnny, you need to think about what is going on with the valve train. The lifter rises ONLY as much as the cam lobe lifts it. The top of the pushrod is still only going to rise only as much as the lifter. The pushrod being longer does nothing but change the angle of the rocker. Tappet lift, rocker ratio and valve lift does not change because you STILL have to have the same lash / preload. For all practical purposes unless you change heads that have a raised rocker position, or run a cam with .6+ lift, or if the rocker manufacturer says you MUST use longer pushrods,, you should leave things alone there. The stock length pushrods are 'close enough' for most all motors with stock heads and mild hydraulic cams/rockers with lift under .550"

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Yea Marv, I am being a dumdass lol...I forgot that part about lifter preload on hydraulic lifters....ok, heres my trane of thought.....................................I have the pesky noisy dual pattern cam & the magnum rockers which are said to be noisy too. I was thinking of changing to a full roller rocker hoping for a bit more silence, as well as maybe boosting performance a little. You say my cam is small, but it sure acts like a big one.lol. The specs are .462-I .469-E Duration @ .050 .218-I .224-E LS/110*

So....adding .025 to both the I & E would look like this: .487-I & .494-E were getting close to .500 I would think there would be a noticeable gain there, no??

big is relative Johnny, just ask,,,, well never mind.

We just got a cam doctor report back for a cam I was going to run in my big inch small block,,, 28x / 29x @ 0.050" (yes @ 0.050!) .8xx, .79x lift (sorry exact spec are classified) So when I say that cam is SMALL, you get the comparison http://www.nastyz28.com/ubb/wink.gif

Myself I don't think your going to see or feel much (if anything) from the small gain in lift. The difference between the 1.52's your running now, and 1.6's will still be .025" Yes the closer you get to .50 you get the better. But I don't think the Butt-o-meter is going to feel anything significant.

I always heard the stock rockers are not very consistant and fluctuate as low as 1.43:1 that would mean a .500 lift cam is .476! and it may be different on every cyclinder so if you can spare the cash its not a bad investment just because of the tighter tolerances the aftermarket rocks have.

I regularly use 1.6 rockers on my small blocks, depending on the cam. Nowadays many manufacturers grind some pretty aggressive profiles into the cam and it may get a little hairy with 1.6 rockers (for instance the XE268 in my Malibu with 1.6 rockers is a clicky-clacky annoyance, even though it works the valves just fine). Lots of the older, less aggressive lobe designs can take a higher ratio rocker with absolutely no downside whatsoever. I like the idea of a slightly less aggressive lobe design with a more aggressive (higher ratio) rocker a lot more than a more aggressive lobe design with a less aggressive rocker. It's not just about more lift, it's also about getting more EFFECTIVE duration from the cam without increasing it's actual duration. That's why you will often see a rocker swap add 15-20 HP or more to a modest street performance engine. It's not just the extra lift that gets that for you, it's the increase in effective duration.

FYI- Big blocks have used 1.7:1 ratio rockers from day one. Just stamped steel pieces of junk like a small block uses, nothing really high tech, but they work just fine. The latest LS-1/2/6 engines also come from the factory with 1.7 ratio rockers, although their design is more advanced than earlier engines. In racing applications (always a dangerous comparison to street-driven engines) you will see rocker ratios as high as 2.1! So, when engineers have the opportunity they always seem to go for higher ratio rockers. I do too.

[QUOTE]Originally posted by Mwilson:
[B]I always heard the stock rockers are not very consistant and fluctuate as low as 1.43:1 that would mean a .500 lift cam is .476! and it may be different on every cyclinder so if you can spare the cash its not a bad investment just because of the tighter tolerances the aftermarket rocks have.

I already have the Comp Magnums, not stockers. theyre 1.52 ratio roller tips.

Damon, I run the XE262 cam & its already noisy...to me...so does the 1.6 mean more noise?? I was attempting to get less noise actually, thinking a full roller might be quieter cause of the fulcrum action being smoother.....plus some gain in performance from the extra lift.

I've said this before...
If you think you want higher ratio rockers you actually want more cam.

<font face="Arial,Verdana" size="2">Originally posted by Lowend:
I've said this before...
If you think you want higher ratio rockers you actually want more cam. </font>

Why?

Snapping the valve open both quicker and more distance will only help, regardless if the duration is increased or not. That's why cams like the Xtreme Energy series do so well.

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350CID, Vortec 062 heads, Magnum 280, Performer Intake, Holley 650 DP, 3.42 rear w/ Auburn posi, 2600 Stall/TC
"Things are more like they are now than they ever were before."
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If you already have comp 1.52 RT's I wouldn't waste the money unless I had it to spend.

Not true - the valve WILL bounce off the seat if the acceleration rates are too high.
The cam manufacturers build their cams for use with a specific rocker ratio in mind. Do you really think you know more about valvetrain acceleration/deceleration rates than say Ed Iskiderian or Bruce Crower

Jeeze. Is someone a little touchy? http://www.nastyz28.com/ubb/rolleyes.gif

First off, I never said anything about valve bounce because you didn't. Will increasing lift by using higher ratio rockers cause valve bounce? It's possible if the proper spring rate and seat pressure isn't used.

And cam companies don't design cams with any ratio in mind. They simply give their lift specs using the more commonly used 1.5 ratios for the general public to understand.

They may use 1.5 for other specs, such as how much valve spring pressure to use at a given lift, coil bind, retainer-to-seal clearance, etc., but that doesn't mean someone can't use higher ratio rocker arms with any particular cam. The user just has to adjust or change the rest of the valve train accordingly.

And why do you think I claim to know more than Ed Iskiderian or Bruce Crower? Where did I say that?

Am I speaking with either of those two gentlemen? Not that I know of.

Did I mention either of their names? No. You did.

Did you claim that either of those two said "If you think you want higher ratio rockers you actually want more cam."?

No. You posted "I've said this before...", referring to yourself.

Am I claiming to know more than you? Not in the least bit.

You made a generic, general statement that isn’t necessarily true. I simply corrected you.

[This message has been edited by AJ_72 (edited August 18, 2005).]

Johnny- yeah, chances are it'll be noisier with higher ratio rockers. My experience, anyway. Lotsa people have reported "worrisome" levels of valvetrain noise with the XE cams. Not everyone, but many people. Most end up with no problems becuase of this, just annoying valvetrain noise.

<font face="Arial,Verdana" size="2">Originally posted by Damon:
Johnny- yeah, chances are it'll be noisier with higher ratio rockers. My experience, anyway. Lotsa people have reported "worrisome" levels of valvetrain noise with the XE cams. Not everyone, but many people. Most end up with no problems becuase of this, just annoying valvetrain noise.

Thats where I,m at right now, not woorisome, just annoying....even after 2 years. I'm getting bored I guess. Its time to "change" something.... http://www.nastyz28.com/ubb/smile.gif I guess the next step would be to go to an AFR 195 head & another cam swap....does it ever end?

</font>

Smokey Yunick machined small block heads to use the 1.7:1 ratio big block rockers way back in the late 60s. The Idea was to move the valves off their seat in a hurry to improve air flow through the cylinder head. It also increases the total lift available at any point in the operating cycle. He also used big block springs because he found the small block springs would not last long with the 1.7:1 ratio rockers. I found that the small block springs dont last long with the 1.6:1 rockers either. Bigger springs will increase cam lobe wear also. Just a thought.
Bob

Everyone is in love with the LS1 motors, what's the rocker ratio on them? http://www.nastyz28.com/ubb/wink.gif

it ain't 1.5, or 1.6...

<font face="Arial,Verdana" size="2">Originally posted by jakeshoe:
Everyone is in love with the LS1 motors, what's the rocker ratio on them? http://www.nastyz28.com/ubb/wink.gif

it ain't 1.5, or 1.6...</font>

Apples to oranges?

<font face="Arial,Verdana" size="2">Originally posted by BonzoHansen:
Apples to oranges?</font>


Actually it's not apples to oranges IMO,
You are dealing with valvetrain design, obviously every variation has it's application, but if LS1's, BBC's, Ford FE's, and other engine designs can run a 1.7 ratio or higher, why would a classic SBC be limited to a 1.5 ratio?

I'm sure when GM designed the LS1, there wasn't some engineer there telling the others, if you need 1.7 ratio rockers you need a bigger cam...

There are alot of reasons for a greater rocker ratio,
faster valve motion for a given cam ramp, less valve spring pressure required for a given cam ramp.. think about how the rocker ratio multiplies the valve spring pressure on the lifter..

Is a 1.6 ratio rocker the answer for every combo, obviously not, but making a generalized statement that you need a bigger cam because you think you need more ratio is foolish.

We all know very well that a cams opening rate ( and therefore valve's) is limited by the mechanical limitations of whatever type of tappet you use. i.e. the cam cannot accelerate the lifter too fast or it runs off the face of a flat tappet, or beyond the angle a roller can safely tolerate..

The way around this is to increase rocker ratio. With the same tappet opening rate you can increase the valve's by quite a bit.

If it wasn't a valid piece of valvetrain engineering, would the LS1's be designed that way?

More efficiency = more power.

The LS1's are one of the most efficient pushrod engines designed and mass produced, doesn't require a genius to figure out that borrowing from GM's modern technology can make old technology work...


[This message has been edited by jakeshoe (edited August 20, 2005).]

Maybe not apples and oranges Jake, BUT,, with the LS1 we are talking a difference between a small efficient roller lobe, lifter, rocker, spring rate and valve that was DESIGNED with a 1.7 ratio from the get go.
I'm not going to say swaping in a 1.6 or 1.7 rocker ratios is mindless and doesn't have it's practical use. BUT no one has brought up the fact that what you do by increasing lift on one side of the rocker, you do by 1.6 times on the other side of that 'lever' as well. The ratio forces exerting more pressure on the pushrod and lifter can be a good thing to help keep the flat tappet hydraulic following the cam lobe. But IS that a good thing??? If the cam designer wanted the increased spring pressure on the lobe and lifter why would he not have used a stiffer spring in the first place??? Will a 30-35 pound of effective spring pressure on the pushrod cause the hydraulics to collapse? will it wipe the oil film off the lobe of the cam???? Heck I don't know! and that's the point! Cam design really is close to rocket science these days.

I think here is the one single point of what I'm getting at. Cam manufacturers spec a spring specific for that cam to control the valve AND the lifter and not wipe the oil film off the lobe. That spec assumes a 'normal' rocker ratio of 1.5:1, a 'normal' valve/retainer weight. The lobe is designed to offer valve train movement within specific limits. IF you start monkeying with rocker ratios, you make changes to both sides of the rocker. My thoughts are that if you changed to a higher rocker ratio AND changed to a lighter springs to put the same effective pressure on the pushrod,,,, you would NOT have sufficient spring pressure to control the valve. If you leave springs alone and increase the load on the pushrod,, what is that going to do to the hydraulics in the lifter and the oil film on the cam. You can't have your cake and eat it too! You ARE going to change the dynamics of how it all was designed to work together.

With that said,,, the cam manufacturers know well that there are tons of aftermarket rockers out there and that we are going to try everything possible to squeeze a few more ponies out of our motors. How much 'comfort factor' have they allowed in their lobe design and spring spec???? I don't know. But I do know the mass produced cams go out the door designed for a specific spring pressure (stated on the cam card) and typically they show valve lift expressed with 1.5:1 rocker ratios. They know the lobe will survive, and valve / lifter control will be satisfactory with those pressures.

I know your a member over at teamChevelle and Harold frequents that site. What does he have to say about it all? I know I made this argument once before and I was jumped on by a few saying that thinking is OLD SCHOOL!! Todays cams are much more sophisticated than I'm giving them credit for. But I also know when you fill out a cam tech card to have a cam spec'd for you,, one of the questions is "rocker ratio"....... WHY??????

Just some food for thought.

<font face="Arial,Verdana" size="2">Originally posted by AJ_72:
[B
And cam companies don't design cams with any ratio in mind. They simply give their lift specs using the more commonly used 1.5 ratios for the general public to understand.
[B]</font>

If you read through the descriptions of characteristics from most cam manufacturers, Crower or Erson for example, they will specifically say whether the cam was designed for or "likes" specific rocker ratios. I've also seen several cams despriptions that specify 1.5 ratio only.

There is a reason the cam design is called a science.

IMO,
Between the car mags where they "have" to write about "something" each month, and the proliferation of computer dyno programs, everyone thinks that they can instantly become cam designers and second guess what professionals spend tons of research on.
Again, just my opinion.

Go roller Johnny! http://www.nastyz28.com/ubb/wink.gif Seriously, you can keep similar duration and go over .500 lift. That would put those heads in their sweet spot.

Marv,
I don't talk to Harold much, but have discussed a solid flat tappet/1.8 rocker BBC setup as opposed to a roller cam/1.7.

He said the solid cam 1.8 would mimic the roller, not quite the same, but it can be made to work extemely well.

We all know the deal with solid roller reliability on the street, etc..
I initially bought a solid flat tappet and 1.8 rockers for the 505, and then had a change of heart and bought the Crower lifters, roller cam. I spoke to him around thaty time frame.

Obviously there will be pros/cons to the alternate rocker ratio. It isn't all pro, and that is why I said that different applications will vary.

I think the biggest reason a 1.6 isn't very effective on a typical street SBC is that the heads don't necessarily support more valve lift.

It still never hurts to get the valve off the seat quicker with a higher ratio... but we all know what you do on the other end of the lobe matters ALOT too.

But a blanket statement against using a 1.6 rocker is silly IMO..

Lots of good info here even through the disagreement & differences of opinion. So, now the original question for me was basically, if in deed the switch to 1.6 full roller rockers would be worth the gain. I see there would be gain, but will it be noticeable enough for the $200. I spend. The swap is easy enough to do, so theres not really a concern there.

Now that a can of worms is opened, I guess the best bang for the buck may be to get away from the dual pattern cam profiles, go back to a single profile cam, aluminum heads, & some 1.6 full rollers.

My cam choice would probably be like the .480/.480 Magnum series duration is 230*

Comp makes a 1.65 rocker, so if you DO decide to swap rockers, go for the max! Hell, 5.0 Fords can go 1.7-1.72!

<font face="Arial,Verdana" size="2">Originally posted by HEAVYchev:
If you read through the descriptions of characteristics from most cam manufacturers, Crower or Erson for example, they will specifically say whether the cam was designed for or "likes" specific rocker ratios. I've also seen several cams despriptions that specify 1.5 ratio only.

There is a reason the cam design is called a science.

IMO,
Between the car mags where they "have" to write about "something" each month, and the proliferation of computer dyno programs, everyone thinks that they can instantly become cam designers and second guess what professionals spend tons of research on.
Again, just my opinion.

</font>

Just to clarify a few things,
I've probably read most of the cam companies literature before it was on the internet. I've been studying alot of this for years, and have probably several hundred SBC builds of some sort behind me..
I deal directly with a custom cam grinder, ordered a custom grind YESTERDAY.

So although I do read some tech articles in the car rags, most are for a "refresher" if they are decent articles.

I don't claim to be a valvetrain "expert" but I am familiar with all the basics.
If I have a question that is a little more complex, I call my cam company and ask.

Although I've built hundreds of motors, some peopel will still know more about certain aspects than I do. Marv knows probably 10 times what I do about FAST SBC's.. mostly because I've been playing with BBC's for the last 10 yrs and not as up to date on the SBC stuff.

However,
It is always a wise thing to look at what the OEM's and modern high end racers are doing, if they are running high ratio rockers, it might be soemthing worth looking at.

You can always call up a grinder and tell them, I'm going to run a 1.7 rocker on my 355 cube SBC, what do you recommend for a grind, they may have a design to fit, that will make a more efficient package.
Higher ratio rockers aren't for every package..

To answer the original question..
I wouldn't run a 1.6 rocker on a modern aggressive flat tappet. They are already moving (closing) the valve pretty fast.
However if you are running an older design cam ( say a Summit, Edelbrock RPM, or similar) then you might see some gains without any issue with a too fast closing.

If you have a cam that fits the rpm range of your motor duration wise, but isn't terribly aggressive, AND the gross lift could be more to fit the head package you have, a higher ratio rocker may be worthwhile.

And there you go...
hi-ratio rockers are not ALWAYS a bad idea, but it takes more homework than just simply slapping a set on a motor.
I'm not trying to offend anyone, I'm just trying to make a point.

In general I state that lift is the least important factor in selecting a cam. Get the proper valve timing events, the lift will follow suit. You can learn a lot more about how a cam is going to act in comparision to another by comparing Duration @050 and Duration@seat than by comparing gross lift

For the record I did design/build a small block with 1.6 intake rockers and 1.7 exhaust rockers once; only after directly discussing the cam masters and acceleration rates with Dave Crower .

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1971 Camaro
383 stroker ~500HP
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16x10" Wheels
Autocross competitive
Engine Designer - The Speed Merchant, San Jose, CA
http://www.speedmerchant.com/

Answer me this??

Why are the OLD 4- and 6-bangers and the old 348/409/427 "W" motors 1.75 ratio??

pdq67

Engines and cams are specifically designed for their rocker ratios. If I wanted to put say a 1.97 rocker ratio on the W motors we would be having the same conversation.

Ferrai doesn't use rocker arms at all... does that mean the we should do the same on Small Blocks?? Of course not, there is more at work here than meets the eye

<font face="Arial,Verdana" size="2">Originally posted by Lowend:
Ferrai doesn't use rocker arms at all... does that mean the we should do the same on Small Blocks?? Of course not, there is more at work here than meets the eye </font>

WTF does Ferrari have to do with this?

Is there anything else that you'd like to bring up that's totally irrelevant to the conversation?

The point is that just because another engine uses something doesn't mean it will work well in this one.
Engines are designed, not thrown together

Right, that's why I like to read the 6 or 7 different corporate BB motor magazine build-ups b/c of all the different head designs AND port volumes as well as lengths and rocker ratios!

AND they still put out darn near the same power if built the same, imho!!

AND I too have talked to Harold about a 1.8 ratio BB solid cam like Jake mentioned that would mimic the good old CC 288 solid street roller!! HE said yes, almost!!

AND I am NOT going to use a solid roller b/c of eating lifters!! BUT I want the extra power I am leaving on the table b/c I won't use one!! So go figure.... Can you say, "Catch-22!!"...

pdq67