Valve spring pressures

[cortexx]

Have been requested by my engine builder for poncam b cams with their 9.15 mm lift . seems like the HKS spring rates are a bit light and he wants to double check them . It's possible they are meant for much hotter cams but HKS have been no use when i tried to contact them.

What on average are the spring rates uncompressed and conpressed ?

cheers

[xcye]

The poncam A or B is built with stock springs in mind. You should not have any problem to run them with healthy stock springs under 8000rpm no mention any HKS springs. What I found is people tend to run stiffer springs than needed, thinking that provides some sort of insurance. That is wrong. You should always choose the softest springs that is suitable to your CAMs. Any stiffer springs only puts unnecessary loads to every part of valve train and timing belt, which can lead premature failure of valves, valve seats, valve guides, cams, cam caps, cam cap bolts, cam gears, timing belt, tensioner, tensioner bolts etc, etc.

All in all, stay with the softest springs required by you cam and rpm.

[caliber676]

Agreed with xcye. A buddy of mine put bc dual springs into his b16 with a mild cam and he ended up wearing his lobes down to the point his car wouldn't idle lol. I would suggest sticking with the suggested springs from the manufacturer. And if anyone runs high lift cams to use the same companies recommended springs. As they have been r&d' to suit eachother

[cortexx]

good answers thanks ...

so what is the seat pressure and compressed pressure of the stock springs ?

cheers

[Skym]

If valve spring pressure is excessive it can cause problems as listed above.

Read last paragraph in this link, as they talk about the tradeoff when using higher spring pressures in racing applications -

http://www.kelford.co.nz/flat-tappet-cam-break-in

Also they recommend you buy new lifters when installing new cams.

I was told (with stock cams) if rev to where my car is reving now (500rpm into redline), upgrade valvesprings. If keep below redline, use stock valve springs. Start of redline is where stock valve springs are good to and I think max lift of stock valve springs is the max lift Tomei Poncams give. So it's not just lift, but revs as well that you have to take into account. This is for racetrack use.

If look at Tomei catalogue, they list what their valvesprings are good to with revs, lift, pressures, etc -

http://www.tomei-p.co.jp/_2003web-catalogue/efr_index.html

Also important info to know when using Tomei valve springs (what you mentioned about valve springs being initially light with pressures and how to solve this problem) -

http://www.tomei-p.co.jp/_2003web-catalogue/e095_valve_seet.html

If I was you, I would contact a cam specialist, like shown in link below and buy valve springs suited to your application -

http://www.kelford.co.nz/valve-springs/

They have a PDF in above link with different pressures, etc for the valve springs they sell. Also they can probably answer your stock valve spring question, as they probably have tested them.

[xcye]

According to the SM, the installation pressure is 24gk at 35mm length and free length is 45mm. Assuming it is a linear spring, then with 10mm lift (that's 25mm length), then the pressure is 48gk. So, I'd say at 10mm lift, the actually pressure should be somewhere between 50kg to 60kg.

good answers thanks ...

so what is the seat pressure and compressed pressure of the stock springs ?

cheers

[Dragon Humper]

The poncam A or B is built with stock springs in mind. You should not have any problem to run them with healthy stock springs under 8000rpm no mention any HKS springs. What I found is people tend to run stiffer springs than needed, thinking that provides some sort of insurance. That is wrong. You should always choose the softest springs that is suitable to your CAMs. Any stiffer springs only puts unnecessary loads to every part of valve train and timing belt, which can lead premature failure of valves, valve seats, valve guides, cams, cam caps, cam cap bolts, cam gears, timing belt, tensioner, tensioner bolts etc, etc.

All in all, stay with the softest springs required by you cam and rpm.

That is only good info if you are dealing with a pedestrian motor doing light duties and plodding along to the tune of 200k km. For a high performance engine that will live a good portion of it's life on the ragged edge you should always run 10% more spring than recommended if there is no specific spring available (especially on the seat pressure).

You will do FAR more damage with valve float than an overly stiff spring ever could.


Jon.

[caliber676]

Very true^ its always good to fork out the extra cash instead of chancing it with stock headwork.

[xcye]

Running stock spring with Type-B CAM in my own car, rev to 8000rpm constantly (even to 8500rpm every now and then) without an issue. One of my neighours ran dual springs and snapped the belt tensioner bolt. So, please do not say stiff springs can't ever cause more damage than a floating valve.

As most of us mainly use our cars for street, therefore I'd suggest to stay with recommended springs. Tomei developed the PONCAMs with stock springs. To build race engines is another story.

On the other hand, 10% more stiff does not matter too much either (Spring to Spring variation in the same package can be more than 10%) What I was trying to convey is that PLEASE DO NOT be carried away too much to buy much stiffer spring than needed. People need to be aware the drawbacks of stiffer springs when they are considering upgrade the valve springs. As far as I know, car manufactures try very hard to bring down valve spring rates and not the other way around.

Back to the original question, any HKS spring (I am not aware of any AM performance spring that is softer than the stock ones) should be sufficent for the PONCAM. So, get the softest ones.

That is only good info if you are dealing with a pedestrian motor doing light duties and plodding along to the tune of 200k km. For a high performance engine that will live a good portion of it's life on the ragged edge you should always run 10% more spring than recommended if there is no specific spring available (especially on the seat pressure).

You will do FAR more damage with valve float than an overly stiff spring ever could.


Jon.

[Dragon Humper]

Running stock spring with Type-B CAM in my own car, rev to 8000rpm constantly (even to 8500rpm every now and then) without an issue. One of my neighours ran dual springs and snapped the belt tensioner bolt. So, please do not say stiff springs can't ever cause more damage than a floating valve.

Springs do have a tendency to relax over time and you can loose about 10 to15% just to fatigue, normal fatigue. You start reving 500 to 1000 rpm past normal operating cycles and that happens faster. Now these engines with the solid OHC, lobe directly on bucket arrangement can cope with alot more than a "cam in block" setup with pushrods. So you can run much more spring than needed without any detrimental effects, other than you must be more gentle on the break-in period.

A busted belt tentioner bolt is hardly conclusive to a stiff spring package, there are far to many variables to take into account. Namely the batch of faultly Nissan tentioner bolts that were making the rounds, guys were shearing them with stock springs and Pon Cams. More people were tightening them up too much and running the belts too tight. If you had said that he wiped out some lobes or bucket faces I might buy it a little, but then, what oil was he using, were the clearences right, etc...?

In the end, I wouldn't worry too much, any aftermaket single spring should be fine on a cam with only 9.1mm lift. If you were at 11.5mm I would be very carefull.



Jon.

[Skym]

From what I understand, Poncams are just like reground stock cams (using new blanks, so can increase the lift). I gather that's why they work with stock camgears, etc.

Stock cams can be modified to have longer duration (reducing? base circle on lobes) -

http://www.camshafts.co.nz/Nissan.aspx

They used to weld onto cam lobes, regrind to increase the lift. But it's more reliable to use a new blank and grind with increased lift.