What kind of difference valve lengths.. flathead briggs.

[Magice]

I was wondering how the length differences effect a Briggs flatty..

As you can see there are a few different lengths.

Will certain sizes only work with certain cams?

 

[Kenny_McCormic]

I think it has something to do with BIG cams that or setting lash.

 

[iwanttogofast]

the bigger the cam the heavier the springs.....

 

[jr dragster T]

the bigger the cam the heavier the springs.....

Not realy. When you plan out your motor you have to think your planned TOP rpm. Then build from there.

 

[iwanttogofast]

so it is ok to use a stock springs on some bigger cams? Does stiffer springs rob horsepower or torque.

 

[jr dragster T]

Stiffer springs robs HP and torque overal. But normally when you are putting a larger cam in a motor you plan to run more RPM anyways so valve springs are swapped out for heavier ones anyways.

 

[iwanttogofast]

but wat is the heavier spring for? to close faster since it is running a higher rpm?

 

[jr dragster T]

The heavier spring is to help stop valve floating. This is a indepth view of valve floating. I highly recomend you watch this. So basically valve float is when the valve never fully seals, so the engine spits pops and sputters.
http://www.youtube.com/watch?v=_REQ1PUM0rY

 

[iwanttogofast]

Very informative video but i guess my question was. Why does changing the cam make a difference on the valve springs if they are stock. Is it because there is higher combustion in the engine forcing air around the valve?

 

[jr dragster T]

No, Not realy. But normally stock valve springs are longer than a stiffer performance spring. So a big cam with stock springs is not good because you can run into a probelem called "Coil bind" Where the cam tries to compress the spring more than it can be compressed which causes damage. Normally a performance spring is shorter and has less "coils" For example here is a 18 LB spring VS a 26 LB spring.

http://www.affordablegokarts.com/mm...e=A&Product_Code=HON14751&Category_Code=GGPP5


http://www.affordablegokarts.com/mm...de=A&Product_Code=VS26LBS&Category_Code=GGPP5

 

[iwanttogofast]

Very nice that is what i was looking for thank you. Is there any charts that shows how to determine what springs you need according to your cam or desired rpm?

 

[Scout]

No, Not realy. But normally stock valve springs are longer than a stiffer performance spring. So a big cam with stock springs is not good because you can run into a probelem called "Coil bind" Where the cam tries to compress the spring more than it can be compressed which causes damage. Normally a performance spring is shorter and has less "coils" For example here is a 18 LB spring VS a 26 LB spring.

http://www.affordablegokarts.com/mm...e=A&Product_Code=HON14751&Category_Code=GGPP5


http://www.affordablegokarts.com/mm...de=A&Product_Code=VS26LBS&Category_Code=GGPP5

That and normally bigger cams make power at higher rpms, and depending on how fast you want to spin your motor stock springs may not be able to handle the extra speed. So you need stiffer springs.

 

[jr dragster T]

Just get 18 LB springs. As mod'd as a clone is it shouldnt rev past 6800 anyways. 18 LB springs will hold with ease at that RPM.