Competition Who has cracked a 24V head?

[GO 4LO]

I've heard from a lot of 12V guys that 24V heads tend to crack more easily than the 12V head at higher power levels. Who has cracked a 24V head before, and at what power level? Are we talking like Kent Crowder's level here, or street trucks? Thanks.

Chris

 

[HoleshotHolset]

The 12-valve heads crack between the valves... the severity of the crack is what determines if the head is 'good' or 'bad'...



I have yet to see a head that wasn't prone to cracking in that area...



Matt

 

[2broke2smoke]

i thought the '01 and '02's got hardened valve seats to prevent cracks?

 

[mattymac]

Originally posted by 2broke2smoke

i thought the '01 and '02's got hardened valve seats to prevent cracks?

Well DC said that the 3rd gen (03 and up) got this as well? You would think by now that they should be bullet (or at least heat proof) by now.

 

[Bova]

I had 15 cracks in my head (24vl. ) I was at the 450 hp level and had some stout egt's at times! The heat is what does it, when I started building boost at an idle I knew it was time to grab my wallet.



More important than that, check/change your valve springs if you run any kind of boost. After 100k mine got weak enough to whack the pistons.

 

[Reb.B]

i had 21 cracks in mine. The 24v's crack toward the injector. the 01's and above are better. !2v's are better too, i still love the 12v head. need to put a common rail pump and injectors on a 12v!

 

[Hohn]

I've been told that most guys' 24V heads are cracked-- they just don't know it.



If I find a cracked head in my truck, then I know it's time for a full ported Marine head from Don M. The marine heads are supposed to be extra tough.



jh

 

[HoleshotHolset]

Jarhead/Bova/"Mo": Why am I not surprised that your head had 15 cracks in it?!! :-laf



Matt

 

[Bova]

Holeshot, there was way more than 15 cracks, but thats as high as I can count!

 

[HoleshotHolset]

:-laf

 

[GO 4LO]

Thanks, everyone. So has anyone had a failure due to a 24V head?

Chris

 

[snowracer69]

Just found out today that the exhaust housing of my turbo is cracked... . only thing that can cause that is high egts..... high egts and cracked exhaust housing would probably indicate cracked head... ... ... ... ... ... ... ... ... ... ... ... ... ... ... $2000 I was saving for more flight time this fall has probably just been re-allocated to a new head, exhaust housing, and head work... ... ... ... ... ... ... ... ... ... ... ..... living at 4000+ feet altitude and trying to run 450RWHP sucks... ... ... ... ... ... .

 

[Hohn]

B1 housing cracked? Hmmmm... .

 

[snowracer69]

Originally posted by Hohn

B1 housing cracked? Hmmmm... .

Yep... . turns out +1600*F will do that after probably 50+ times doing it.



Ken said to run it... not a problem even if it goes all the way through. I think differently, as does Dave who's doing some port/polish work on it for me and is who found the crack. Am first on the list for a single opening standard housing fit for my -2 wheel whenever Ken gets them in. Need something else for these temps though... . nitrous maybe?

 

[Snow man]

need twin for thsoe temps , i knocked about 400 degrees off my temps going form a large housing B1 to PDR twins.

 

[FFL8N]

Well, it looks like I outdid most of you guys with the cracks! I had 22 cracks in my head. I will try to get the picture into my readers rig picks. I do have a picture of my number 5 and what is left of my number 6 cylinders there now if you want to take a look at what the damage to the piston was.

 

[lmills]

ah man those pics make me sick. I can't stand looking at melted pistons.

 

[BillGotthelf]

We redid the head on my 99 in july-aug last year because of a crappy fire ring job. We pulled the valves as the piston tops had slight valve impressions from pushing the valves into there seats. We discovered dozens of fine cracks in the valve area radiating out from the valve seat area. This is a non hardened 99 head. We had a good machine shop deck the head to bring back to a flat deck and try to correct fire ring holes that were off by as much as . 018 inches from recommended depths. The machine shop recut the valve seats and pressed in hardened seats available for the 2001 and up heads. We then measured every every valve and had the hardened seat decked to allow . 030 shims under the valve springs. This now allows the valves to start opening with 85 lbs of pressure so we are hoping the max of 80 lbs of boost will allow the valves to close fully without the pistons help.

 

[sbentz]

I have seen 12 and 24 V heads crack, but has anyone seen it cause a problem? The cracks through the valve seat seems to not hurt much... . if anything.



Likewise, last inspection of the HP turbo on the dragster, the volute divide is cracked. 4 places. So what? Still runs. It was cracked 100 runs ago. Same places. Thermal expansion joints..... Right.

 

[lmills]

Likewise, last inspection of the HP turbo on the dragster, the volute divide is cracked. 4 places. So what? Still runs. It was cracked 100 runs ago. Same places. Thermal expansion joints..... Right

I mentioned this same thing to a turbo builder once before. He said it was very common for the casting to crack as it went through heat cycles and told me not to worry either.