mrmalo32

we keep breaking Jesel rocker gear after about an hour of use, 3-4hrs 3 blow ups

1st time we run with Methanol injection hooked up and plugs seemed to run lean and hot on the tips rpm up around 5500-6000
2nd time we run No Methanol and 93 octane and plugs were perfect 5000-5500


done it 3 times now on fresh engines and a differant cylinder head and motor each time, thought i might put it out there for any feedback.

im thinking rockers may be old and have had a life and im happy to put a new set on each engine, but for them all to start beaking within 3-4hrs still makes me nervous to just go put all new stuff on

we think it breaks the Exhast rocker first right at the nose where the pin goes through, that then turns it into a perfect collet removing tool, so then out pop the collets and the valve drops into the bore piston bends valve and hits it back up the guide and thats where it stays.

then somehow it punches the inlet rail off the head ripping out the threads and crating massive tappet clearance

end result is bent valve jammed in guide, collets and broken rocker laying in top of cylinder head, bent rail holding inlet rockers flapping around

engines:
610ci 1205HP @ 6300
PSI blower 10PSI boost
timing 32 btdc
Dart pro2 heads
Jesel rockers
3/8 push rods
tappet clearance "0" cold
valve spring pressure 200 pound on the seat

what i have checked and found to be ok:
no coil bind
wipe across the valve is perfect
tention and locktite all bolts
collets are correct fit
rocker geomitry
adjusters are running nice and short ( not all the way out )

what i dont know:

cam lift or specs
How old the rocker are ? ( we have not broken a new one yet only old ones )
why and if valves are trying to open against any pressure after ex rocker breaks

Thanks in advance !
any new thoughts will be much apreciated

FIXX

iTrader: (2)

sre you running lash caps?? we use to run jessels because of beakge and switched to t&d rockers..no more issues..

mrmalo32

No Lash caps, and not mushrooming top of valves

Thinking when i change all i will try Crower SS

rev.ronnie

Hi,
I have a few observations and suggestions.

First, you need to validate the open pressure on the valve springs. If the cam is "lofting" the valves, the rockers will pound the valve, essentially, getting a run at it, much like an impact hammer. You want the springs to be between .050" and .070" from coil bind at max lift. This keeps the coils from "surging" and causing undue harmonics. The rule of thumb is 100# per .100" lift. I also add extra pressure to compensate for boost. At 10psi, you really only have 190# on the seat. I would like to see that at 240. Use a good quality, surface enhanced spring like PAC, Isky Endurance or Tool Room springs.

As far as valves go, I don't know if you're running 11/32" or 3/8", but I have no problem using 3/8" on our marine builds. I like REV or Manley super duty type intakes and inconel exhausts. A 3/8" valve has 18% more diametrical area than a 11/32". The weight is a small price to pay for the additional strength. Obviously, if the budget allows, 11/32" titanium valves with a DLC coating is primo. You would want beryllium copper seats as well.

In regards to the cam, if you don't have a cam card, it's hard to really know how aggressive the lobes are. If you have an exhaust valve that is opening too soon, it's fighting the cylinder pressure that is still driving the piston downward on the power stroke. Opening the valve too soon before BDC is usually a real power killer on a normally aspirated engine. It causes too much blow down and subsequent pumping losses. This would be masked by having forced induction though, from a horsepower standpoint...but the extreme pressures would still take their toll on the parts. On most high boost applications I deal with, I use stainless exhaust rockers. Crowers are excellent. T&D are my first choice.

My last concern, is the pushrods. In my opinion, there is not a 3/8" pushrod made that is up for the job you are asking. Pushrod flex is a huge issue when it comes to valve train harmonics. I would use a 1/2" to 7/16" dual taper pushrod with a .188" wall thickness. The dual taper helps with cancelling harmful harmonic frequencies, as well as reducing flex. If you saw what a 3/8" pushrod looked like on a Spintron at 6200 rpm, you would faint. If you have clearance issues, a 7/16" pushrod is the next best thing.
Personally, for non tapered, I prefer Manton series 5, .168" wall 3 piece pushrods. I could go on and on, but just call them yourself and talk to a technician. You will probably never run swedged end pushrod again. A swedged end cannot be made with the precision of a machined end. The material is not as good either because it's only as good as the tube.

Anyway, I hope you get it figured out.

ICDEDPPL

iTrader: (1)

^^^^ excellent post!
Agree with everything especially the pushod size and wall thickness. My set up was 160# seat pressure, It is now 230#

I know you may be out of ideas but heres a long shot. My valvetrain destroyed itself very quickly due to the same effect in paragraph #3 .. incorrect length spark plugs (too short) caused the timing to be retarded quite a bit .... the exhaust valve was fighting the cylinder pressure still burning off.. Result was high egts, and self destruction of most of the valvetrain.

original plugs in my motors:

MILD THUNDER

iTrader: (3)

I think a lot of people only look at seat pressure, and ignore the open pressure. Theres more to a valve spring than just ''Seat pressure''. Lets say you want 200psi on the seat and 550 open. You need the correct RATE spring for the application, and also the proper install dimensions, installed height, coil bind, etc. if you are lacking enough pressure over the nose, you may very well be lofting the lifters off the cam. You can have 200lbs on the seat, and only 400 lbs open, with the incorrect spring. Or severe pushrod flex like Ronnie said. Sounds like your valvetrain setup is not up to the task. A lot of times people blame parts failure, when its really improper setup breaking things. The exhaust valve sees a tremendous strain, esp on a blown deal.

SB

iTrader: (1)

Did we measure how much exhaust valve clearance we have ?
I ask for 2 reasons;
- You don't know what cam is in there. Exhaust valve opens when piston is going up to TDC. Thus, exhaust valve is usually what get's smacked out of the two valves.
- Obviously, it's the ehaust valve and/or rocker you are having problems with

Do you know your exhaust valve guide clearance. Maybe you are sticking the valves and thus breaking schit.

My mind is questioning alot as it sounds you have used some used parts and some unkowns.

rev.ronnie

Correct on exhaust valve hitting, but the piston is actually chasing the exhaust valve before TDC while it's closing. The exh. valve opens ATDC on the power stroke, and the piston chases it up the hole as it's closing, The intake valve starts to open BTDC and chases the piston as it continues past TDC. If there is an open spring pressure deficiency or a harmonic issue, the piston can hit the valves, or each other at split overlap.

A lofting exhaust valve will get pushed closed by the piston in real bad cases.

SB

iTrader: (1)

Thanks for proof reading my mess RR. Thought/typed too fast. My bad. Hope didn't mess anyone up.

Yes, going towards TDC for overlap the intake valve is opening and the exhaust closing.

However, the exhaust valve is more likely to git hit...if there is clearance issues.

This should always get checked when the engine is being assembled. Also, valve pockets in pistons vs valves too.

rev.ronnie

Yes, the intake really can't "open too fast" so to speak, but the exhaust is always a problem child. I had an engine in her once that we were upgrading and on inspection, it had .020" piston to valve on the intakes! Funny thing was, they didn't hit! I couldn't believe it. It was the result of the wrong valve reliefs and severely advanced timing, apparently the original builder though that advancing the cam till it had the highest cranking compression was the way to "dial it in"..