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Grass Roots Tech => Grass Roots Cylinder Heads => Topic started by: gresse on June 04, 2018, 03:40:08 am

Title: Broken valvespring
Post by: gresse on June 04, 2018, 03:40:08 am
Hello. Yesterday I started my car after sitting about 6 month. It started up fine and I took a ride around the block. Suddenly I heard a ticking sound and I pulled the valvecovers. It was a valvespring that have broken in two places.
Is this a common problem springs that break?
I have CompCams 999-16

Can I get one spring and change it or do I have to buy 16 new?


Title: Re: Broken valvespring
Post by: TKFD on July 21, 2018, 03:36:07 am
Sorry to hijack thread, but I also just had a PAC Beehive spring break - #4 cyl exhaust on a TFS 11R 190 head. Luckily no collateral damage. Not sure what caused it. PAC dealer says these springs are designed for high RPM and anything lower than 3K causes issues, as they are not in optimal frequency like driving around town normally or highway cruising. Im kinda not buying it.

Im replacing them with full new set.

Beehive theory is great (lower weight, better spring design) The one thing that spooks me with them is if ones breaks nothing to prevent valve dropping in like a dual can (still limited I know, but there is a safety net there).

I was thinking would there be anyway to slide on a brass or copper collar 1-1.5mm above guides, to act as a stopper on the valve going into chamber if the spring does fail. Obviously loss of power and a bit of a racket from floppy spring, but these could be the tell-tale signs to shut down. Most (if not all) collateral damage is from that darn valve dropping into chamber.

Putting it on might prove to be problematic, as obviously go to be done when valve in head, but something like a soft brass or copper or alloy sleeve, with low resistance (ie, easily slide over valve shaft and easily removed).  


Title: Re: Broken valvespring
Post by: gresse on July 27, 2018, 05:25:21 am
I got ahold of one new spring and changed it.
Took the car for a spin and about 6k it felt weak like valvefloat so I ordered a Moroso in car springtester.
Seat pressure should be about 245# but all was in the 180# range except the new one.
So it´s time to buy some new ones.
Anyone know how excact the Moroso tester is?
The new spring read about 210# but should be around 245#


Title: Re: Broken valvespring
Post by: dennis112 on July 27, 2018, 06:53:41 pm
None of the on car spring testers are truly 100% accurate.  Their real purpose is that they allow you to compare future readings to the original readings that you measured (using the same tool) when the springs were checked the first time.   There are also some consistency issues if you do not do not mount the tool the same place on the head of the valve or the rocker arm.  The rocker arm type mount must be pulled absolutely straight in the direction that the rocker pivots.

That being said you should first have the new spring (and one of your old springs) checked on an accurate bench mounted spring checker.  You must know the spring height to achieve the desired pressure (which would be in the comp specs.)  Then you install the new spring on your head (at the same spring height) and then check it with your overhead tool.  That will give you an accurate baseline of YOUR tool. Then you can move onto the other used springs and check their pressures.  Compare the readings to the ones you found on the new spring (and even to the used old spring you had bench checked.)

Title: Re: Broken valvespring
Post by: dennis112 on July 27, 2018, 07:01:07 pm
Part of my reply disappeared in the process????

Anyways the difference in pressure of the new valve that you found could be due to not having the same installed height as Comp specifies.  If the height is taller, the pressure will be less.  As far as comparing the new spring to the old springs, used springs will often test 10-15#'s less than they were originally setup after the springs have been worked some.  This is considered normal for the most typical springs on the market.  You want to look for more extreme differences of 25lbs or more.