Keep Breaking Jesel Rocker gear
 

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

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

No Lash caps, and not mushrooming top of valves

Thinking when i change all i will try Crower SS

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.

^^^^ 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:


http://33outlaw.zenfolio.com/img/s10...60690284-4.jpg

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.

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.

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.

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.

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"..

Just food for thought. Piston to valve, and or any "smiles" from float?

Couldn't he put a dial indicator on the cam and a degree wheel for one hole (intake & exhaust) and get the Gist of what the cam is. it wont get him all the info but he may be able to learn something. sounds like a radical cam with a blower (which isn't really needed)

I am no master engine builder but I do know the basics. right now I have to agree with what all of you are asking but until the OP can produce a cam card none of it matters. this cam could be .580 lift or .800 lift. with out knowing what the cam is the spring pressures, pushrods, etc, etc. are meaningless. I see he is in Australia so hopefully he can come back and figure out what he really has so that you guys can point him in the right direction.

Very good advice..and with the rest of the motor too.

Yup, it's like Marrying a girl before the beginning of your first date. All you really know is what she looks like clothed and have no idea what she act's like.

Huge chance she costs you a bunch of $$$$ and frustration.

Step back, get to know her every last detail and then when you are satisfied, lean into her like a pornstar on crack cocaine. :evilb:

Thanks for your feedback

I found cam specs

Valve setting Intake .020 Hot
Valve setting Exhaust .020 Hot

LIFT Intake @ cam 420 @ Valve 714
LIFT Exhaust @ cam 420 @ Valve 714

Rocker arm ratio 1.70


opens closes Advertised duration
Cam Timing @ .0205 Tappet lift Intake 44.0 BTDC 86.0 ABDC 310.0
opens closes
Exhaust 96.0 BBDC 42.0 ATDC 318.0




opens closes Max Lift Duration
Cam Timing @ .050 Tappet lift Intake 29.0 BTDC 69.0 ABDC 109 ATDC 278.0
opens closes
Exhaust 81.0 BBDC 25.0 ATDC 119 BTDC 286.0


spring requirments

part 96886

Loads closed 225 @ 2.000
open 658 @ 1.330

recomended RPM
Min 4400
Max 8400
float 9000


only thing i know we done was set the lash at 0 cold 77f ( this is what i was told was cold setting )

have never checked while hot

see what you guys make of this

anything else you think you need to know please ask

dont know piston to valve but there are no smiles
while we have the head off to repair we will be checking it

MrMalo
 

There is significant data regarding the well defined, finite levels of fatigue (and the specific cycle value) incurred using aluminum as a body material in a rocker arm construction. Durability testing (T & D) of shaft rocker systems has shown the point of failure of an aluminum rocker to be ~ 11 million cycles. That cycle rate, at an average RPM of 3500, is ~ 105 hours run time. That may not seem excessive, but to give a frame of reference, that is the cycle equivalent of running a Cup car 8500 RPM at Daytona for 43 hours. Lets emphasize here that is the point of first failure, not an average or sampling. As happened in your case, it is not uncommon to see closely sequenced batch failures when the arms are not cycled out at the end of their usable lifespan.

Fatigue is not necessarily a failure in design or manufacture; it is primarily inherent to the material property differences between Alum and steel. That figure represents the count the component reaches a cycle value that Alum becomes fatigued. The relatively low modulus (Ealum30.103 psi) of aluminum, in conjunction with the repeated cycling of the arm, through extension and compression of the spring, is the primary cause. From that point foreword potential failure becomes a possibility. There are a number of parameters that will influence the rate of degradation, but the rockers will, at some safe point, need to be cycled out or risk a failure.


What are the advantages of a steel rocker? First and most importantly are the stiffness advantage 4130 represents in comparison to aluminum. The elastic modulus of the materials is:

E steel 30.106 psi
E alum 30.103 psi

That 200% increase in stiffness is a huge advantage in minimizing deflection within the system. Any reduction in compliance nets a more accurate valve path, increasing lift at the valve while increasing the natural frequency of the rocker element of the system. I would also be wary of taking literally (and introducing into practice) the idea that compliance introduced into the system (by aluminum arms) is a valid way to damp unwanted “harmonics”.
What are the downsides to steel? There aren’t any. Steel does provide increase in mass due to the density of steel compared to Al. The good news is: with advance design and manufacturing capabilities it is possible to mitigate the mass penalty incurred using steel. A properly designed steel arm will incur only a small amount of mass increase over AL when properly executed. That increase is primarily at the pushrod side of the lever and therefore minimizes increases to the mass on the valve side. Any mass reduction on the valve side of the fulcrum, including valve diameter and mass of the spring itself pays far greater dividends than mass reduction on the PR, lifter system. The continued use of aluminum is driven largely to maintain a competitive price point in the market.

As far as value is concerned, it’s no contest. While steel has higher upfront costs, the perceived saving in aluminum is false economy. Steel has virtually infinite cycle value. With the exception of an occasional tip or bearing replacement steel will provide safe, reliable performance for the life of the engine. Aluminum will offer upfront cost reductions, however the renewal of the cycled parts will quickly eradicate the initial value.

Bob

Most solid rollers are set .015-.022" hot that I've seen. .020" super common.

Who told you O ?
Your cam card says .020 " lash hot.

The replacement schedule is probably why there are 14 pages of "good" used jesel rocker arms on eBay.

Unfortunately, I'm locked into the jesel shaft mount arms as my heads have been machined to accept the mounting apparatus for jesel stuff.

I rebuild a lot of Jesel rockers in my shop. The biggest point of failure I encounter is the bearing cages. They use a "loose" roller bearing and the cages have an extremely thin wall that doesn't offer much lateral support. They like to blow out the sides. They should always be disassembled and inspected during a rebuild. I have a grease pin that I pack them with before disassembly so the rollers stay in place for cage inspection. Often, you can feel when they are broken. They don't roll smooth.

The Torrington bearings I use when rebuilding them have the captured bearings and the ends of the cages are three times as thick as the originals.

So bob which are better to use, the jessel pro steel or crower SS shaft rockers..?

+ 1

Jesel steel @ $220 each rocker $ rails

Crower @ 1640 each motor complete with rails

Jesel get up ther in price, will be nera $8k to do this

unfortunately,your gonna have to pay to play.especially at the rpm's you want to run.

btw,what are you doing w/ this boat?

Jesel is very expensive. I've used their 3 piece pushrods on a 632" build with 14° chiefs. They were $70 each....the next time I just bought them from Manton, who incidentally, makes them for Jesel....and they were 1/2 the price.

we had a problem like this on a pr of sc 540s in our race boat . the push rod tip was incorect for the jessel system and would move the push rod out of the cup on the rocker , causing the valve to tag the piston slighty , breaking the valvehead off !, the fix to the problem was a pushrod change .

Some need 210° ball ends even if the length is correct. I've seen this many times.

I get asked this a lot
We just say " just go FAST ! "
We have a few boats that get out together, stop in the middle oth the lake, swim, eat lunch, then go fast to the other end of lake.
While it's going it just fantastic, and then we have these problems,
It's worth fixing just to get back out and do it all again
Cross my fingers to sort this issue out and get some hours up.
Over there you guys have many of these boats but here you can only imagine what people think of them
Love it !

you stated that you set your lash at zero correct....well i would first set them at the reccomended valve lash of the cam card you p[osted first and go from their..thase cams dont seem special ,,they look to be a 800~1000 sc cam,,i think..i have a box of them lol..

I have pulled engine apart and found a few things !

we had valve float for sure, i can see where pushrods have been bouncing out of the bucket in the lifter and ends of pushrods are peened over,exhaust must have still been open when the inlet colected in on the way closed , ride over !
the engine that broke only had 160 pound @ 1.950.the other engine had 200 @ 1.950.
head stud tention 70 ft on a 1/2 stud ??
the most we turned engines to was 5500 rpm.

The fix:

remove heads and strip
check guides
touch up seats and valves
valves are all new ( 4hrs old )
heli coil threads for Jesel mounting rail and blocks
check piston to valve ( 123# )
install new Crower lifters
New Isky Toolroom RAD springs ( 260pound @ 1.950 ) ( both Motors )
New delwest steel retainers ( both Motors )
New Jumbo collets ( both Motors )
New Jesel Pro steel Mowhawk rockers, New shafts, New ARP Bolts ( both motors )
New 3/8 pushrods ( i just cant get bigger in ) ( both motors ) ( yet to do geometry to check length )
retention heads to 90 ft
leak down cold average 8-9 %

Hoping this fixes valve train issues

if you think i should check anything else that may help please let me know

Ian.

Do you happen to know the spring part numbers that were used? Seat pressure is only a small story of the spring package. Over the nose pressures are just as important. You can have 1 spring with 160 on the seat, and 400 open, and another spring with 160 on the seat, and 500 open. Lofting the lifters after full lift is very likely and seat pressure doesn't control that.

What will your new springs be over the nose psi wise? 260 in the seat seems like a bit much for a lower rpm marine deal, but I don't recall your setup. Did you at least go with a heavy wall 3/8 pushrod ?

Ian,

At sub-6000 RPM there may be a better option than the 9988 RAD spring for what you are trying to accomplish, particularly in light of the fact you’re utilizing a tall deck application with a significantly longer pushrod

Your cam yields .694” at the valve, after lash, requiring a shorter spring to keep your stack value at .060” @ max lift. The key is to control the dynamic mass of the system while minimizing compliance in the pushrod. The additional PR length required in a tall deck application is a definite negative. Column width trumps wall thickness, however when you run out of real estate on diameter you can only move in toward wall thickness.

If exchanging the springs with your vendor is an option that would be helpful. When you calculate the spring force necessary to control the mass of a SS 2.300” intake and a 1.880” inconel exhaust, and the extended length pushrod, this may require a tapered pushrod if you’re maxed out at 3/8”.

What is your max WOT RPM?

Bob

Isky RAD 9988

I have not got pushrods yet as im going to check the geometry when the rockers arrive, and i was going to get heavy wall with tapered ends

I will check open pressure today

Max WOT 6500

I was going to get heavy wall tapered end pushrods

I will check pressure at full lift today

Open pressure @ 1.330 is 490 pound
I checked spring coil bind and it is @ 1.100

hope this helps

Thanks
Ian.

Your installed height is 1.950 and at full lift only at 1.330 with a 714 lift cam?

I re checked and spring compresses to 1.280 at full lift this gives me 520psi

table
 

Ian,
There appears to be a calibration issue with your spring measurement apparatus, or you have the incorrect spring for the part number RAD 9988.

Your measurements provided a height / force of:

1.330” @ 490# measured
This is;
1.330” @ 616# actual

1.280”@520# measured
This is;
1.280”@644# actual

Attached is a height/force table for the RAD 9988 to validate your springs in conjunction with.

Bob

Well i have got it all back together again

Both motors ended up getting:

Jesel Pro steel rockers with roller tips
New Crane lifters
New Manton push rods 3/8 - .145 wall
New 9988 RADS 250 psi closed
New steel Retainers and locks

I stuck with the 9988 RADS

Re heli coiled most threads in heads where rails bolt on

set tappet clearance to 8# cold

timing is at 32*

also found crack in my tailpipe right at the collector ? not sure if water was getting in with reverberation

going out on sunday so fingers crossed

Well i have taken the "Cannon" out for 4 runs now, 3 tanks of gas, Man does it like a drink, phew.

Been running pretty hard in the flat water up to 160-165 and 6500 rpm for a good 5-6 Mins at a time, also cruising at 125-130 for 15-20 mins

engines have been perfect, bit of an oil leak from 2 piece covers, even with new O rings.

Going to put some Billet "Noonan Race engineering" ones on ( very nice )

I know i had some mixed reaction to my spring choice but all seems to be ok.

I went with the manton push rods as recomended and they are a heavier wall than i had.

Jessel Pro steel are just a nice piece.

Now just learning to drive this Beast has been a blast, she is pretty happy at 150,at 160 im feeling a little uneasy making sure im running flat

I Had it out in some Big water and that was an eye opener, Launching 10-12 ft in the air, it was choppy crap water and was not that much fun

https://www.youtube.com/watch?v=BIXvKhiuDRQ

Please enjoy my little fly buy @ 150

I think i had the trim tabs set a little low pushing the nose down

I have had times where she just sits beutifull and smooth with no porpise

cheers

Ian.

thanks for the update.hope your problem free for a long time.