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Discussion Starter · #1 ·
Hey guys I was wondering if you all could explain rockers for me or others who dont know about the different kinds??? Like 1.5 or 1.7 etc... Diferent sizes. Why you should use certain ones and the benefits.
 

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Hey guys I was wondering if you all could explain rockers for me or others who dont know about the different kinds??? Like 1.5 or 1.7 etc... Diferent sizes. Why you should use certain ones and the benefits.
Hey guys I was wondering if you all could explain different types of camshafts for me and others to reference. Like whats best for certain applications. Different sizes cams, different lifts, LSA, Durations. Why we would use one cam over another and benefits.

Wow, these are a taller order than you yet realize, these are book learning size question rather than blog site questions. I'd recommend you start with this book.

How to Build and Modify Chevrolet Small-Block V-8 Camshafts and Valves by David Vizard

David has many other books and there are many other excellent authors writing about engines and their components.

Mr. Vizard gives you very straight up info as to what is used, when it's used, how it's used, why it's used, and what to expect from its use. His reads are content accurate though sometimes a bit deeper understanding of the subject by the reader is assumed so you get to do more digging as you gain enough knowledge to realize that what is said assumes you have this deeper understanding in some cases. This book is specific to Chevrolet, but in terms of concepts it transfers to engines in general. Anybody's and everybody's engine that you will ever look at is a physical design response to natural physical laws that govern everybody playing in this game. So while you as designer can push certain aspects of the design around to fit available space, materials and cost constraints in the end no matter who you are, you've got to make Mother Nature happy or fold up and go home.

It's not that we can't nor won't talk about this stuff, but these are subjects that get really deep, really fast and are not without their positional arguments as I'm sure you'll see in the responses you get.

Bogie
 

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RED FLAG: 1.5 or 1.7? Mixing up engine "families". What engine are we talking about? Small block Chevy? They use 1.5 or 1.6:1 rockers (multiply "lobe lift" by rocker ratio to attain actual "lift at the valve"). Big blocks use 1.73:1. Small Fords are 1.6 or 1.7. Pontiacs are 1.5 or 1.65... Of course there ARE variations, but these are the "common" ones.

Like Bogie says, a LOT more here than meets the eye.

Jim
 

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Discussion Starter · #6 · (Edited)
AWWWWW, ok I didnt know all that, but I was talking about chevy small block. I didnt know it was that complex. Sorry guys. So if I am using a .420INT and a .442EXH Lift cam with 1.6:1 rockers its actual lift is what????? I cam up with .672INT and .707EXH. That dont seem right. Also what is dual and single pattern
 

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AWWWWW, ok I didnt know all that, but I was talking about chevy small block. I didnt know it was that complex. Sorry guys. So if I am using a .420INT and a .442EXH Lift cam with 1.6:1 rockers its actual lift is what????? I cam up with .672INT and .707EXH. That dont seem right. Also what is dual and single pattern
Yeah it gets complicate fast, don't be sorry we all started out from less than we know now, how did that song line go,,,"I wish I didn't know now, what I didn't know then."

The math for rocker ratios is ratio your going to divided by the ratio your coming from in this case 1.6/1.5 equals 1.0667. That answer times the known valve lift for a 1.5 ratio rocker will yield the lift at the valve for the 1.6 rocker. So .420 times 1.0667 is .448 on the intake and the exhaust is .442 times 1.0667 which nets .478. Also the lift event happens faster with the increasing ratio as does the loading on all the components, no free lunches allowed.

Springs are fun in a not very funny way, get this wrong and you ruin a lot of expensive parts.

- Typically a single spring is just that a simple winding of a piece of really good wire.

- A single spring with damper is the addition of a flat cross section wire wound into a spring that rides against the inner coils of a single spring to absorb (dampen) the natural harmonics of the single wire that would cause it to continue bouncing once excited (just like the shocks on you car's suspension in purpose).

- A single spring may also come with variable distances between windings which tends to dampen harmonics without a seperate damper, they may be made from wire that is not round you will see the term "ovate" and in more modern designs we see a variable diameter of the winding in what's called the beehive. Beehives have a lot of advantages in being more self damping and will tolerate more RPMs before loosing control with less spring rate and pressure. A lot of this is due to using a smaller thus lighter retainer.

- Dual wound is actually two springs a smaller nested inside a larger. They are wound in opposite directions to gain damping of harmonic responses in either but the main attraction is increasing spring rate and pressure without increasing diameter, lenght or wire size.

- Tripple wound is more of the same as dual with one more nested spring.

I highly recommend that you use the camshaft manufacturer's recommended springs and retainers if not lifters and valves as well if these are specified. They have the equipment like a Spintron that lets them do the testing to determine whether a selected spring actually performs the task of keeping the valve train tracking the cam. Loss of control quickly leads to broken parts in some cases even the loss of the engine. While a major player in keeping control of the valve train can be found in spring rate and pressure, the harmonic respose of the spring, also, needs to be studied and included into the spring design This is more complex to calculate and needs to be studied for actual events compared to calculated to be proofed by test that the spring doesn't get out of control harmonically somewhere in the RPM range.

Bogie
 

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Discussion Starter · #9 ·
WOW Thats amazing. I have some dual springs I kept off of some 84 vette heads I think they were 293's but do you know if they would be good to hold onto. Also I have a cam I installed in my truck with the following specs::

IntakeExhaustAdvertised Duration262°272°Duration @ .050"204°214°Valve Lift w/ 1.5 Rocker Arms0.4200.442Valve Lift @ Cam0.2800.295Max Lift Angle107°117°Lobe Separation112°Cam Timing @ .050" - Opens-5° ATDC44° BBDCCam Timing @ .050" - Closes29° ABDC-10° BTDC

Would it be safe to install 1.6 rockers later down the road to improve torque. I have the 193 heads which I know they are desingned for low end torque and fuel mileage and not so much for performance. But Could I squeeze a little more towing potential out of my chevy pickup by doing this.
 

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You may not know this, but you can't just swap out 1.5 rockers with 1.6 and not check the pushrod length to ensure proper pattern on the end of the valves. If the contact pattern is off from the wrong length pushrod and a higher ratio rocker it can cause damage to the end of the valve at the least, and possibly worse things if a keeper comes off or something else fails.
 

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Information on Rockers

They made me a new set of 1.61 Hi Lifts for my engine and moounted them on a new shaft and also towers. I ahd to rearrange a few on the shaft to get it right but they work like a charm. Remember there are different length Chevrolet Push Rods too and bet sure to get that right too. These folks have been doing this since I was racing at LADS in the LA area years ago. When "the Snake" was running big block Ford V-8's they were doing this then.
Normbc9
 

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Do you take the tool and act like your doing a valve adjustment until you get the right length
No. You install rockers on one cylinder with the adjustable pushrod. Then you use machinist dye or a colored marker to the end of the valve stems. You crank or roll the engine over with the valve adjusted and adjust the pushrod until the pattern shows contact on the center of the valve stem. Then remove the rocker and check the length against the stock pushrod to see how much difference is needed. Lots of various lengths available in pushrods to get close to what your measurement shows.
 

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No. You install rockers on one cylinder with the adjustable pushrod. Then you use machinist dye or a colored marker to the end of the valve stems. You crank or roll the engine over with the valve adjusted and adjust the pushrod until the pattern shows contact on the center of the valve stem. Then remove the rocker and check the length against the stock pushrod to see how much difference is needed. Lots of various lengths available in pushrods to get close to what your measurement shows.
One needs to add that you need to watch the push rod for clearace where it passes through the holes in the head which in older heads will also be the push rod guide, there is a tool sold specifially to open these holes when 1.6 rockers are used or high lift cam is used to provide clearance such that the push rod does not bind where it passes through the head from the valley to the rocker box. If you're using seperate guides that fasten under screw in rocker studs, these also need to be checked for push rod binding and relieved as necessary. Another couple possible contact ponts are the push rod against that side of the rocker and the slot if this is a ball and socket style rocker needs to be checked to insure the slot is long enough not to bind on the stud.

You also need to check for valve spring coil bind, needed .050 inch minimum between each coil. Clearance between the spring retainer and valve guide including the guide oil seal needs to be checked this also should not be less than .050, preferably more.

When you start getting toward .5 inch lift at the valve it's also time to check the clearance between the open valve and piston. Here .080 inch on the intake and .100 inch on the exhaust is considered safe.

If you need them lash caps that fit on the end of the valve stem are available to increase stem length if this becomes necessary to put the contact pattern in the correct place. It's not a bad idea to keep a set around when checking to see if more stem length provides better angles and patterns.

Bogie
 

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Yes, clearances can be an issue, especially if you have guide plates, and if you don't have guide plates and screw in studs, then you should upgrade to them! Also be sure to order hardened pushrods when you get new ones, as standard pushrods can wear on guideplates and break.
Buying 1.6 rockers sounds like cheap HP upgrade, but it causes a trickle effect, and can lead to some work, and a fair amount of money to make them work. Be sure you've got valve to piston clearance for the higher lift too, as Bogie mentioned.
 

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Generally speaking, it's better to spec the cam for 1.5 rockers from the get-go. There are reasons one might need to use 1.6 rockers, like in the case of the SBC roller engine that doesn't play well w/cam lobe lifts higher than 0.354". Higher ratio rockers is one way around that to get more lift w/o causing the dog bone to lose contact w/the roller lifter. Maybe not the best way, but it is an option that costs less than the better aftermarket roller lifters.

The valve train has a few places that you can get into trouble when adding lift, like spring coil bind, retainer to seal or guide boss interference, etc. Most things like this are covered in the Points to check link above.
 
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