valve springs

[kenny]

what is the difference noticed with 1mm oversize valves is it worth the buck. are they reliable.have stage 2 hotcam.rockers-sub rockers and springs all stock seems fine at this time.why should i harden them and replace sprinds.thanks

[cals400ex]

for a drop in cam like the stage 2, you don't want hardened rockers. however, with a higher revving cam like the stage 2, your springs may wear out over time. i am still using stock springs, but plan on getting new ones next year. i doubt you will notice much with the larger valves.

[slosh13]

with my own personal experience, you dont need them with a drop in cam BUT i would as a reassurance thing. B/c once you make something in your motor more powerful, that puts that much more stress on all the other parts inside the motor. But valve springs arent a neccessity, more like a reassurance with a drop in cam.:)

[Colby@C&DRacing]

As for the springs they are just added insurance that at high rpm the valves won't float. As for the hardened rockers do not ever put hardened rockers on a drop in cam you will ruin the cam..

[wilkin250r]

Just to explain the terminology for those that don't understand.

Picture your cam, rocker, and valve. When the cam pushes UP on the rocker, the rocker then pushed DOWN on the valve, opening it up. When the cam stops pushing up on the rocker, the valve spring causes the valve to close.

A "floating" valve happens when the engine is moving so fast that when the cam stops lifting the rocker, the valve springs don't close the valve fast enough. The result is a valve that is open when it is not supposed to be. This can be extremely bad. If the piston is moving upwards, and the valve is supposed to be closed, the piston can hit the valve, causing major damage.

Heavy-duty valve springs are stronger, so they close the valves faster at high RPMs, eliminating the problem of floating valves.

[Dunlap]

The reason you put stronger springs in is more seat pressure. The higher lift cams and the higher you rev the motor the more seat pressure you will need, otherwise when the valve slams down on the seat it will bounce and either wear the valve and seat faster or like in the old 250x it drops a valve because of harmonics. The 400ex,raptor and old 250 mojaves have this problem. On the 400ex you can shim the spring .040 more and help the stock springs.

[JD400exrider]

When I built my motor I was told by a couple builders with a drop in cam (HRC) I did not need to worry about heavier springs when I called to order them. Infact It was my understanding that a heavier spring could even wear the cam or rockers due to the added pressure. Is this true or what? After reading this thread now I wish I would have gone ahead and bought some. :confused:

[kenny]

does a drop in cam suck compared to a web.i know the price is alot different,and you have to send your cam to be worked.what is the difference between drop in,and what do you call its not drop in - requires hardened rockers. thanks for the education.mickey you say to shim stock .040 where might i find these and do you just add to the existing or do you replace with one shim .040 bigger than the stock shim.

[Dunlap]

There is all kinds of valve spring kit out there and you have to know what you are looking for thats why you need to match them to the kind of cam you are running. The stock shim can be doubled up to give you more seat pressure with out raising the nose pressure to high on a "drop in" cam that most cam people say you dont need.

[hotex]

Drop in cams, like a regrind of the stock cam, or a HRC, or a Hot Cam, are the same hardness as the stock cam. Which means you can use stock rocker arms without having the fear of mismatched metal harnesses in your valve train. These types of cams make modifying your engine to a higher level of performance less expensive when compared to a hardweld camshaft.

Hardwelds are as they imply, cams that are reground to a new specification after they have had the lobes welded up. While this is an acceptable method it also has it's draw backs. The new surface of the lobes is considerably harder than that of the rocker arms' wear pads. This makes for a mismatch in hardness and the camshaft will rapidly wear the rocker pads, which will eventually destroy both items.

I have seen a lot of people say that it is OK to use hardened rockers on a Hot Cam or HRC camshaft. That is simply not true. If you are a racer and change your engine oil after every race you could MAYBE get away with that combination. But for the average person where the oil change intervals are much longer, there is NO WAY for the rockers to survive. The lubrication would have to be perfect and with clean fresh oil for both items to survive. If the engine gets over heated or the oil film breaks down even the slightest amount, it's all over for the rockers and the cam.

Drop in cams provide excellent durability, (for the most part) a great value, and you don't have to pay a core charge in case the cam you sent is no good. As for performance, sure there can be more available because, the drop ins are limited by the amount of lift and duration that you can throw at it due to spring considerations and valve guide heights. So, they are not for everyone. They are designed with the high performance trail rider in mind. Or the occasional racer.

Hope that helps.

Tony

[kenny]

thanks

[RED121572]

Did I miss something or did we answer his question about larger valves yet??:)

[AlaskaSpeed]

:eek2:

[Out_Sider]

Originally posted by AlaskaSpeed
:eek2:

THOSE SMILIES AGAIN!! :p

When i was doin all this motor work on my 300, i thought it would be safer if i just went all out. so i did, and i dont regret any of it. ;)

[RED121572]

Originally posted by RED121572
Did I miss something or did we answer his question about larger valves yet??:)

Let me rephrase that..."Have we answered if 1mm bigger valves would be worth the expense?"

[kenny]

did you have something you would like to mention about the oversize valves.maybe you can also give your opinion about shortened guides.i have learned so much playing on this site.mickey has pointed out some obvious problems with my engine. it is apart now waiting for a new head gasket. im going to ck sleeve clearance at case.also i see the tight spots only 2 on mine from torquing head studs after bore. ifeel like i am learning more than i want at times.+ my wife is getting pist.

[hotex]

Big valves go with a good port job, from my understanding on this motor. I'm sure Mickey could better on this subject because he knows more about this specific engine than I do. From my understanding of this, the ports are the limiting factor in this head. They flow enough for the engine if it is under 420cc. More displacement than that requires porting and then bigger valves after that.

Shortened guides are not good from an engine durability standpoint. Rocker arms by their very nature put stress on the valve stems because they don't press stright down, they side load the stem. Shortened guides will have less area to keep the valves' movement in check and therefore will wear faster.

I hope Mickey will shed some more light on this. I really don't know enough about this engine to be the real expert unless it's about the effects a cam has on it.

Tony