Cutting Valve Springs

[soggycrashed]

Has anyone here had experience cutting valve springs to fit an engine? I'm not sure if people even do this... xtreme yard karts said he did this with Briggs Flathead springs for a Tecumseh.

Anyway, I bought clone springs because I thought that the install height was the same, but they were taller. I used a dremel to cut them down and a belt sander to get the end I cut flat. It installs fine and it flat/aligned. Is this safe? Thanks.

 

[porsche930dude]

Well youll find out when you get valve float. If youre looking for an improvement you should have left them long. If youre going for high rpm youll want them stronger. Why not just buy the right springs for youre engine? If they dont make stronger aftermarket springs for youre engine you can go to a hardware store and find some that fit inside the others to give them more strength

 

[soggycrashed]

Well youll find out when you get valve float. If youre looking for an improvement you should have left them long. If youre going for high rpm youll want them stronger. Why not just buy the right springs for youre engine? If they dont make stronger aftermarket springs for youre engine you can go to a hardware store and find some that fit inside the others to give them more strength

They are 18lb springs.

If I left them long they would not have fit inside the head. Now they are the same length as the original. I'm not sure if cutting them has compromised them at all... I don't think it did?

 

[Poboy kartman]

If I left them long they would not have fit inside the head. Now they are the same length as the original. I'm not sure if cutting them has compromised them at all... I don't think it did?

You have lost me there.....the height of the springs installed is determined by the seats the valve stem length and the keepers.....that's why they make valve spring compressors.....

 

[soggycrashed]

You have lost me there.....the height of the springs installed is determined by the seats the valve stem length and the keepers.....that's why they make valve spring compressors.....

What does that have to do with the physical height of the springs

I made this video demonstrating the 3 springs. First is factory Tecumseh, installs fine. Second is the Clone springs, cannot get this spring on. Third is the cut Clone spring which installs fine.

https://www.youtube.com/watch?v=U8-lEOJs-Ls&feature=youtu.be

Not sure if you guys don't understand me... or maybe I'm just a simpleton.

 

[ML-TOYS]

Are you just basing this on trying to put the retainer on with just your fingers

 

[soggycrashed]

Are you just basing this on trying to put the retainer on with just your fingers

Elaborate?


I have gotten the other springs on when I wasn't holding a camera with difficulty, and the valves were nearly impossible to open with them on. The rocker arms would snap with the clone springs if I left them like that.

 

[fowler]

Hahaha

Google valve spring compressors

U shouldnt be able to just push it on with a few fingers

If u can assemble the whole thing with one hand then the springs are way too soft

Once the spring are on it should take both hands pushing down on it to open

Dont forget that 18lb springs means they crack at 18lbs
Or 8 kgs
When your pushing down on a tiny point like that 18 lb is alot

 

[soggycrashed]

Hahaha

Google valve spring compressors

U shouldnt be able to just push it on with a few fingers

If u can assemble the whole thing with one hand then the springs are way too soft

Once the spring are on it should take both hands pushing down on it to open

Dont forget that 18lb springs means they crack at 18lbs
Or 8 kgs
When your pushing down on a tiny point like that 18 lb is alot

So lets say we have a Predator 212 and the stock spring is 1inch in height, would an 18lb replacement be the same height or taller?

 

[Poboy kartman]

So lets say we have a Predator 212 and the stock spring is 1inch in height, would an 18lb replacement be the same height or taller?

They could be....or not....I haven't personally done the swap...(perhaps someone here that has can say)....

But....to get a stiffer spring...there's only a few practical ways to accomplish that: make the coils thicker....(the wire they're made from), put more coils in....(make the wire they're made from longer).....or increase the space between those coils....(make the spring taller) .....or make the spring larger in diameter....

Now.....I'm not saying you aren't correct that the springs might not have been unusable the way they were, and I'm not a spring manufacturer or engineer, but , the only real test of whether they work or not is to install them...rotate the engine...and check for coil bind.....because thicker wire or longer wire may eventually compress to the point that no space remains and the valvetrain is trying to open the valve....and there's no room left ....so it's solid metal and the engine locks....


This is the reason HP automotive have inner springs at certain point....

So....while I can't answer your question as phrased...at this point....you should understand why "wouldn't fit in the head"....is probably a misstated notion....

EDIT: Automotive springs are designed with an "installed" height...(naturally associated with one paticular engine) ....but...(somebody stop me if I'm wrong here)....but is when the spring is rated...(in this case...18lbs..)...so that means a small engine spring is going to have to be compressed some to get there.....

And: BTW....You can't judge any of this with finger pressure....and it takes a lot to break a rocker arm.....

 

[d340b]

I wouldn't run a cut spring for cutting in reasons above. But if you are gonna try it , run a steel shim between the cut end and cyl. head.
And Po'boy is right about the coil bind thing.

 

[Louie The Lot Lizard]

Maybe I've missed something here, if so please ignore the ranting of a senile old man.

Think of a coil spring as a torsion bar wound round and round. If you straighten a coil spring, you will have a torsion bar. If you cut a coil spring you are shortening the torsion bar. This serves to make it stiffer, not weaker. Adding coils weakens springs with a given static height, increasing the wire diameter stiffens, increasing the coil diameter weakens given the same static height. Increasing the height with the same pitch weakens.

Sounds to me that cutting a spring will make it stiffer. It is also true that the retainer can be damaged.

I can tell a story on myself; as the chassis guy on a Modified team, I was needing a certain height spring at a specific weight to adjust handling. The only spring in my inventory that fit the bill was not made to be used with our upper spring cup on that car. Specifically the cup did not have a pocket to accept the pigtail of the spring, it was meant for a spring with one flat coil at the top. We decided that we would try it for a 25 lap race, what the heck! We won that race, but the last 5 laps the handling was in the toilet. Upon post race inspection we found that the pigtail had poked a hole in the upper spring cup and had threaded itself through the hole. In just 20 laps! We had to cut the spring cup from the spring to get it apart. Just think how many spring cycles there are in a running engine in a matter of minutes.

That's my nickel's worth.

 

[Poboy kartman]

You have missed something......I guess in one way you might think removing coils makes a spring stiffer....but you are ignoring the fact that both springs will be installed in a set height in this instance.....

In a chassis set up...."stiffer" ....actually refers to less travel not amount of force required to compress.....the reason cutting coils off a car lowers it is not because it increases the height of the spring....but the ability of those springs to resist the weight of the car....

And like I said....I'm not an engineer...and thinking about it now...a larger spring diameter would reduce the force required to compress it....my bad....

 

[Denny]

Cutting valve springs is bad if for no other reason it changes the harmonics (frequency) in which the spring resonates. Use the proper springs for the cam/rpm. That is all I have to say in this matter.

Denny

 

[Desertduler]

Exactly!
Watch this!
https://www.youtube.com/watch?v=_REQ1PUM0rY

 

[Louie The Lot Lizard]

God Bless Texas! You are right Po'boy, the spring height is an important factor on how much seat pressure you will have and I should have clarified that. The fact remains that the RATE of the spring per a given amount of compression will increase if it is cut.

I'm no engineer, I am a REVERSE engineer! LOL.

 

[Poboy kartman]

God Bless Texas! You are right Po'boy, the spring height is an important factor on how much seat pressure you will have and I should have clarified that. The fact remains that the RATE of the spring per a given amount of compression will increase if it is cut.

I'm no engineer, I am a REVERSE engineer! LOL.

On that we can agree.....which is why it works on chassis, the key being spring rate...the more a spring compresses the more force is required to keep compressing it....so a shorter spring will compress faster given the same amount of travel...

 

[OzFab]

I haven't read this entire thread, the heading was enough & my opinion is this is one of the dumbest ideas I've ever heard! Sorry, I'm not usually that blunt but, what can I say...

There are a number of factors that make up the spring rating, one of them being length; if you alter the length of a spring, you immediately & automatically alter the spring rate...

About a decade ago, around here, young drivers of middle eastern origin would cut their suspension springs in an effort to lower their car, making it look more sporty; the only thing they achieved was ruining their whole suspension & steering system & earning them a defect notice... this practice very quickly earned the nickname of "a lebanese lowering kit"

 

[fowler]

https://2ecffd01e1ab3e9383f0-07db7b...x800/f3827942-18a9-49b4-8539-457b0d0ee776.jpg

Holden gemini lowering kit

Fabroman know what i mean

U dont even have to remove them from the car to do it
Just drive the car on a few bricks and cut the springs in half

Then cut the unrequired bit in half again and u have a sweet ride sitting about 2 inches off the ground
Then all ya mates jump in and your draging

But thats ok because then the muffler gets ripped off and u have a swwet new exhaust

 

[soggycrashed]

Jeez guys, don't berate me for asking a simple question. Point taken.
This is the PM I got which "inspired" me to attempt to cut them. Did I take this message completely out of context then?