KM Steel Rockers? Lester Owen rocker failure.

[kbmb02]

13 hours ago, TobyB said:

I run standard 1.5mm Reinz head gaskets.  They compress to (wait for it) 1.5mm

 

Another data point: I use 0.057" as head gasket thickness for compression ratio calculation.

 

7 hours ago, tzei said:

Went to KM rockers (old cast, heavy version), made em lighter. Not a single problem since. 

 

Got a photo of those you'd like to share, @tzei ? (or, send in a PM)

 

On 9/7/2020 at 8:27 AM, kuroneko said:

For this 336 cam 90# closed and probably 275-300#  open (the closer side of 300#) is in the ballpark. The last M10 head I did 3 or so years ago I know it was 90# closed and 260# open.  That was max lift heights for a 316 cam and IE springs.  Seem right? 

 

Did you use the Schrick 080/043 springs with the 336?

[kuroneko]

1 hour ago, kbmb02 said:

Did you use the Schrick 080/043 springs with the 336?

 

No, this head was built originally Terry Tinney.  I did an engine refresh a couple years ago including breaking down the head with basic "valve" job (new stem seals, check guides, lap valves, new caps/retainers - Crower).  I'm pretty sure they were either IE springs or the same thing sourced elsewhere.  But I don't know for sure because I don't know what the Schrick look like and I thinks dimensional specs are same as far as I know (which isn't much).   I simply checked them for consistency of pressure at some random height, nothing beyond that.    

Edited September 8, 2020 by kuroneko

[tzei]

On 9/8/2020 at 6:52 PM, kbmb02 said:

Got a photo

Only one atm. 123g a piece. Heavy i know but didn't have stomach to grind further.

[kuroneko]

On 9/6/2020 at 10:47 PM, Preyupy said:

I know VAC is selling CatCams but I have been dealing directly with CATCams. 

 

My car is back together thanks to the good folks at Korman selling me a single rocker and cometic gasket.  Ready to race the ELVF at Road America this weekend.  Korman shared the failure with Lester Owen and I guess is was a first.

 

I have a set of KM rockers showing up at my door today.   Not sure what I'll do with them but they are cheap and having something as an emergency backup in my spares box appeals to me.  

 

The Cat Cams rockers are $120/each plus shipping.   $1,040.30 USD delivered to the U.S.   In talking them, they seem interesting.  I think I will use them on a 121 head building for a friend this winter. To purchase simply email them.  Nice people. 

 

I've had this car for 4 years now and but still new to learning the little details of how to make an m10 race motor work.  But I love the M10 for it's simplicity, it ain't rocket science!   ho can't love an engine where the entirety of the nuts and bolts to put it together can fit in your cargo shorts!  I also love the engineering brilliance of Weber DCOE carbs in particular.  As well as the mechanicals, I've fallen in love with "B Sedan" racing with this 2002.   I wish there were more 2002 racing folks in the Midwest. They are scarce.  In 15 years I still hope to be doing this with a greater knowledge base to pass on.  

 

 

Edited September 14, 2020 by kuroneko

[evil02]

On 9/6/2020 at 8:48 PM, Preyupy said:

That’s a new one,  I probably have 15 race engines out there with Owen rockers and have never seen this.  I have not used the KM rockers but have used the new CatCam rockers on a Gp2 CSL race car for the last 2 seasons and so far I’m impressed 

 

I have been using a set too and they are very nice!

[Tommy]

13 hours ago, kuroneko said:

But I love the M10 for it's simplicity, it ain't rocket science!

 

But some rocker science ?

[EvilEmpire]

So broke a stock Febi/Bilstein rocker exhaust number 1 at this weekends endurance race - have CatCams 310 with dual valve springs. Rev limit at 7200 and ran it to there all the time. Engine could run higher 7500-7800 with that cam. 

 

I'm trying to find best replacement plan - contacted CatCams - their rockers are out of stock and will not have more till mid fall. 

sent emails to VAC and KM to check availability.  

 

[Tommy]

7200 is usually on the safe side, but running to the limiter all the time is not the best practice. IMO would be better to set limiter 7500 and avoid going there.

KM gets the best feedback but I think you would be good with Ireland HD's too.

[Preyupy]

8 hours ago, EvilEmpire said:

So broke a stock Febi/Bilstein rocker exhaust number 1 at this weekends endurance race - have CatCams 310 with dual valve springs. Rev limit at 7200 and ran it to there all the time. Engine could run higher 7500-7800 with that cam. 

 

What valve springs are you running?  The stock/replacement rockers are barely good enough for a stock engine (stock cam, stock valve springs AND stock REDLINE!!)  Any valve float at all and you risk braking a rocker.  If you were part way through an endurance race the heat build up in the valve springs could have easily dropped 30-40lbs from the spring rate.  If you were close to float with cold springs this could have caused the problem.  The reasonable $$$ option are the IE race rockers for a cam that mild and <7500 rpm revlimit.  

[EvilEmpire]

I have the IE dual valve springs.

[kbmb02]

12 hours ago, EvilEmpire said:

I have the IE dual valve springs.

 

Some version(s) of the IE dual springs are h-e-a-v-y ... did you measure them?

 

15 hours ago, Preyupy said:

If you were part way through an endurance race the heat build up in the valve springs could have easily dropped 30-40lbs from the spring rate.  If you were close to float with cold springs this could have caused the problem.

 

Listen and learn from @Preyupy ...  -KB

[EvilEmpire]

What should the target spring rate be for the double valve springs?

[tzei]

Well it depends... n/a or forced induction...

And you are actually interested in seat (installed) pressures. For example Schrick singles (090) has about 30kg at about 38.5 mm height and 10mm compression gives about 880kg. (used oe s/p is around 19- 20kg). These can be shimmed to have 50kg s/p without coil bind. Forced induction needs generally more s/p so could go as high as 90kg. Obviously one wants as low as possible compressed pressure.

[TobyB]

Nose pressures matter, too. 

Too little, and the intake valve comes off the top of the 

lobe when the cam ramp accelerates to its closing velocity,

but the valve isn't keeping up. 

As they say, it's the landing that kills you, and that's what breaks rockers.

Too much nose pressure, and the leading edge of the lobe galls.

 

So the BEST numbers are those that keep the valve on the

cam at redline when you lift off the throttle, plus about 25 lbs for safety.

 

Which means?

 

hellifiknow.

 

Depends on your rocker mass, your valve mass, retainer mass,

half the spring mass, valve area and ram effect of the intake.

And valve lift.  The higher the lift, the higher the nose pressure.

Oh, and don't forget the cam shape, as it affects the acceleration delta...

And valve guide and rocker friction too, I suppose...

 

#300 on the nose sounds a bit high, BUT I use aluminum rockers

and keep revs under 8000.  So a heavier rocker wants more

spring.

 

I too have found what IE has sold as doubles to be quite heavy.

I have an old BMP dual set that is lighter than stock.

I have at least a half dozen broken rockers, too.

 

There is a LOT of data on (Chrysler?) springs that have good dimensions

for the M10 head.  Maybe it's AMC, I forget.  But the short version is

that if you measure a stock spring, there are mainstream race springs

made by good manufacturers that will fit our engines.

It takes mix-and-match to get inners and outers, but there are options.

And shimming and cutting the head surface are viable measures, too, 

once you find something that really works well.

 

I could never spring for Lester's rockers, and all the other options happened 

after I figured out the aluminum ones.  Maybe someyear I'll try steel...

 

t

breaks other things these days...

 

Edited August 11, 2021 by TobyB

[EvilEmpire]

Thanks Toby - the "hellifiknow" is probably the best answer yet.  So it's RACECAR right - you break stuff. 

 

If I can get the folks at KM to respond I'll try their rockers - if not guess I can go back to IE or VAC.

 

Thanks for all the help.