Weisco / eagle kit | head rebuild

[xXaTaXx]

confused!
http://cgi.ebay.com/ebaymotors/NEON-TURBO-EAGLE
-RODS-WISECO-PISTONS-ECLIPSE-420A-53_W0QQitemZ260096566107
QQcategoryZ33623QQrdZ1QQcmdZViewItem

It seems there is now an influx of 420a kits/parts on ebay and other such sites. I'm not nessecarily saying i'm buying this kit (if i were. i'd call first to get more details) but, its still strange. could it be true?

ANYWAYS.......

I'm starting to rebuild a head, and I don't completely understand spring rates, lift and everything... If I were planning to run 272's in the future, what exactly do I need to upgrade (aside from machine shop fun)? I know I want to get new springs/retainers/followers(?) but what else? and what are some reputable names?

NOTE: This head is going to be used on a turbocharged 420a block (eventually, if that helps). So just in foresight, I'm not building a 4gxx series engine/head(for all the people who are members of team crankwalk ;D). Oh, also, I do not want to sell my GS for a GST/GSX, but thanks!

<-- 0wn3d
Chris

 

[Locke]

Since I am good and bored, I will go ahead and let you know some stuff about camshafts. Ahem, here goes.....

-Lift:
Valve lift and Lobe lift are two separate things. Valve lift is how far the valve moves from fully closed to fully open when pressed on by the rockers and cam, it is measured in inches. Lobe lift is the distance from the base, to the peak of a lobe, on a cam, also measured in inches. The cam hits the rocker in the center, the rocker pushes down on the valve on one end, and pivots on the other end. This will multiply (rocker ratio) the lift of the lobe, giving you valve lift.

-Spring Rate:
Spring rate is the amount of weight need to compress a spring one inch. It is measured in lbs/in. The higher the spring rate, the more quickly it will be able to attempt a return to its natural state. Higher spring rates are needed to keep the rockers and springs against the cam as it moves past the nose.

-Duration:
Duration is how long a valve will be open, as measured in degrees. Advertised duration is just that, an advertising gimmick, and could be largely ignored. It is often measured at its lowest point, where next to nothing is happening. The fun starts to happen at around 0.050" of lift. This is the number you want to pay attention to. The longer a valve is open, the more time there is for air to go in, or out. Less duration makes power in lower rpm range, more duration makes power in higher rpm range.

-Lobe Separation Angle (LSA):
Lobe separation is a measurement between the lobe centerlines of the intake and exhaust, in degrees. Smaller lobe separation will make peakier power, usually earlier, while wider lobe separations will spread the power out. Separation, along with accompanying overlap, effect the vacuum and drivability of a camshaft.

-Valve Overlap:
Overlap is how long, in degrees, both the intake and exhaust valve are open at the same time. This can be good, or bad, depending on what you are doing. More duration will increase overlap, less LSA will increase overlap, more lift will increase overlap. The effects of overlap are known, but their uses are debatable. Start a new thread if you would care for me to preach my thoughts on overlap. Generally, what you want to keep in mind is, more is good for high end power, less helps with low end grunt.

-Modern profile vs. old school profile (Aggressive vs. Symmetric):
Most cams you can buy anymore have a modern "aggressive" lobe profile. Back in the day, the lobe of a cam was symmetric, ramp angles were the same as it raised and lowered the valve. This worked just fine. Nowadays, the profile is "aggressive", meaning it is an asymmetrical lobe profile. The lobe's peak has been moved forward of the lobe's centerline, and usually incorporates a wider nose. This creates a very steep incline, and a more graded out decline. The valve will snap open, stay open, shut more slowly, and gently seat. If you were to plot valve action against a cam's lobe on a graph, it would be the rough shape of the lobe itself. On newer cams, this will give you more area under the curve, which means more potential flow. On some mild cam grinds, the trailing ramp will begin before the lobe centerline. They do this so you can run bigger cams (than stock) without the need for higher spring rates (or with old, worn, stock 100,000 mile springs). You won't find these with huge lift, as stock springs will bind.


Hmmm how much did I leave out? Does it matter to you?


What do you NEED to upgrade to run big bumpsticks in our cars? High rate springs that will follow both ramps of an aggressive cam profile at high rpms, while not binding under big lift. Thats all.

-Valve Float:
When springs cannot keep with the ramps of a lobe, it is called valve float. The valves don't shut completely before opening again. This isn't physically harmful to the valvetrain, but you tend to lose a lot of engine power. Power will seem to almost shut-off at around a certain high rpm.

-Coil Bind:
When springs bind under lift, it is usually because the spring wire is too thick, meaning it cannot compress far enough to accommodate the camshaft. When a spring binds, often things break.

Taller springs, with cut down spring seats will allow more lift. Double wound springs, usually with an enlarged spring seat, and matching retainers, will allow thinner wires (more lift) and very high spring rates. There is also just a sturdier steel, which can have smaller wire, and higher spring rate. If you don't want your head machined to accept springs, our friend is the sturdier, drop in spring. Crane and Crower both make good springs (and cams, and other valvetrain goodies) for us.

You don't need new retainers unless yours are cracked, worn, bent, etc.. You can go with the titanium retainers (lightweight), for a more lively valve train, but I don't suspect anybody really notices the difference when using them, and IMO not worth the money.

We dont actually have "followers", per se, on our cars. Our rocker arms follow the camshaft directly, which pivots off of the lash adjuster. While you don't have to, you can "upgrade" to the rocker arms from a PT Cruiser. Get the lash adjusters for the PT also. Both drop in replacements for our stuff.

Ok, fingers need a break now, hope that was helpful to you.

edit: and maybe tomorrow i will make this easier to read.
edit: is it easier to read yet?

 

[dsmclipse97]

thats good stuff.