BLACK BEAST BUILD Slicktop R-Spec

These holes were free?


MaxMax

 

Your heads are decked again making the cams lower than they should be right? And it keeps happening on the passenger side intake cam?

Maybe the belt is jumping off the passenger exhaust cam and putting a locked force on the passenger intake cam.

Just a thought.

 

any updates on failure??

 

There is not going to be a definite failure answer .
Have covered all possibilities.
The fact that it's happened on 2 different engines on different sides and no mechanical failures makes it hard to diagnose.


It's rotational force that's shearing the cams .

Both engines had 80lb springs and the heavy series 2 BDE gears .

I can only conclude that the extra force to rotate the cams with stronger valve springs coupled with the extra weight on the cam gears has the cams torsional strength at its limit .


Intake cams are weaker as well due to the oil gallery where they have snapped both times .

Currently looking at possibly machining and lightening the gears . Have also organised to get a new set exchanging my old set from BDE just in case it's gear related .



Pic of Where they snap at oil gallery

 

Would a (any) preventative weld to the weak spot of the Jun cam suffice ?

 

With any welding there is usually a heat affected zone along the periphery of the weld. If the cracking is propagating from the oil gallery, no amount of welding will help, unless going solid and removing VTC is an option.

 

Weighing the two, my bde S2's weighed just now are 4.3 kg

 

To put things into perspective.

stock exhaust gears are about 950grams

my BDE exhaust gears are only 585 grams

zano weighed ...S2 intake gears - 4.3 kgs

series 1 intake gears - about 500grams lighter. ...so 3.8kg

massive difference from exhaust to intake .

 

well yeah either lighter springs or lighter gears .....or both ......

I'm going to look at reducing the weight of the gears at machine shop .

don't want to touch the head setup.

would rather less rotational mass at the end of the cam.


.

 

Not like it can be anything but beneficial anyway...

 

Hey not being a smart arse or anything like that if it was rotational mass that's breaking them how come rb25 engines arnt breaking there intake cams witch use the same style cam caps and are no bigger in diameter and use bde intake cams aswell yet there a lot longer and pushing six spring instead of three I think you've got bigger problems than it being rotational force I don't think putting lighter springs and lightning the pulley will help

 

true but unless you can tell me what the bigger problem may be ...I have no real answers nor does anybody else ,just a logical process of elimination .

again its happened on 2 different engines with only thing in common being same valve spring pressure and Series 2 gears .

The 4 gear timing belt set up on a VG may create more force on the gears than the RB set up....it would be a combination of things


how many people here running double valve springs and series 2 BDE gears.

.

 

In staying on topic of the problem area, is an extended cam bolt of greater depth feasible ? A type of Helicoil ?

...Thus, relying on the *additional axis, & pitch too thread strength gain.



Annnnd if the OEM bolt were too greater diameter for the win, a helicoil approach none the less ?

As can be seen in the pics below,

-----What is the actual "OEM Bolt & Hole" depth like ...are we not quite in full proximity too the actual cam journals *integrity,
...considering weight support and etc ?

 

I have the s2 gears, but JWT HD single coil springs and JWT cams so much less pressure then you

 

I cant recall if my Ferrera's springs were doubles.
I can't find any ? ..springs in any of my history logs, which is strange.

I faintly remember Mitchell advising me not to go doubles as what i had at the time would have been sufficient. - Ahhhh, Now i remember,
...I initially had R5's with the JWT Springs fitted to the build....and swapped out the R5's for the Jun's, ...and retained the JWT Springs.
...I queried to completing with Ferrera Springs but were advised the JWT Spring pressures would be sufficent,
.....buuuuut, we used Fererra titanium retainers, ermmm ? yea
Anyways,

 

Not sure if you're referring to the hole in the top pic, but I believe that hole is for the passage of oil. So extending the bolt deeper into the cam would then disable VTC.

 

Buuut there would be a way around that as welllll ?
...I know too little on that gallery right now or Vtc operation, but are i/we on the write track for adding strength ?

It's dicey, but if an added length of bolt were added their just may be a chance, no ?

 

Sure, but if you were going to disable VTC, you wouldn't use the heavy BDE gears, which would likely solve the problem anyway (assuming weight is part of the problem).