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Class Wrecker!!!
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Discussion Starter #1
Here is my collection of heads.


These next pictures are the first set that cracked between int/exh bowls up to the guide.






I bought a second revised set with more material in the problem area and they are cracking in the same spot and exact end on all 4 heads.





Is everyone else having problems and or are other brand heads doing the same? Thanks for any info or help.
 

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Damn !!!! Sorry to hear about your bad luck. Is Allpro helping you out on this problem ? I hope so !!!
 

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I like IceCream
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Can I buy one to hang on the wall in my shop!!! Help you recoop a little...........
 

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Well, just to clarify those heads are for an engine that I'm responsible for. This is a turbocharged, 2000 hp engine.... we have zero detonation, the plugs are very consistent from cylinder to cylinder, and I'm not yet convinced it's a cooling issue.

The latest head has the exact same end of the head with cracks in the ports. On the engine it is number 2, and number 7. Number 2 gets plenty of coolant being in the front right at the water pump entry.

I'm not looking to have this turn into a bash of any particular company, but I'd like to know if there are any other LS heads cracking like this under extreme conditions?

The latest heads with just 2 cracks have about 120 runs on them. As was mentioned more material was put between the ports on this last set, with about .120" of material. The previous pair, which had every port cracked, had approx 90 runs on them, and had .080 material between the ports...

As of right now, the 2nd set is going back on the engine.
 

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Another thought...
Seen this before on other heads, a lot has to do with the way the coolant is entering and exiting. Some heads need a fitting for a coolant passage in the middle of the head?

Maybe reverse cool it by pulling the cool water through the head first?
Just throwing some ideas out we've tried.
 

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Class Wrecker!!!
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Discussion Starter #10 (Edited)
Chris your statements on the latest heads are very generous and I do not want this as a bash thread.

I did forget to add about the latest set of heads that they are cracking from the spark plug hole to the intake seat.
 

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do you have a knock sensor on the motor ? curious how one can be 100% sure of no detontation ?? after all i have heard it being called the silent killer .

and i have to agree with the post about there not being enough material between the ports to support seats allowing them to move around .
 

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Maybe it has something to do with exhaust Temp in the port or system, was it run overly Rich??.....

Funny how they are cracked right next to the ehxaust port, and thicker material in that area helped

Do you think it is a casting strength issue or just the HP you are pushing

Wonder if Coated ports would help at all???
 

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2,000 hp from a LS style cylinder head, .. hummm, .. doesn't that seem like alot to ask?

I had the same issue with some Trick Flows, several sets just to get through a season, ..
so it's not the first time for this issue.

The fact that they are cracking so quickly, .. and not just between the seats tells me the
casting is flexing under the stress, .. .. Bob makes great stuff, .. but you might have reached
the limit of that casting. After all, it's JUST a casting.

I'd have to agree on the detonation though, .. almost every issue I've have with
a customer's blown or turbo combo has been from it, .. bent intake valves, cracked chambers,
seats coming loose, etc, ..

Curtis
 

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The Edelbrock Victors even have cracking issues. Curtis mentioned flexing, I tend to agree since you don't see the yates style heads cracking.
 

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This is common place on in line heads with turbos. I have fixed tons of these kind of cracks. Grind it ALL the way out then weld it up. Leave the wall thicker and be careful when you put the seats in because i have seen it want to crack when you drive the seat home.
 

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Bracket racer
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This makes me think....is there a billet LS head in the future?!
 

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I would grind out the cracks and start welding.

Although detonation could be the problem, Imagine the intake and exhaust pulses of an engine of that produces 2000+ HP??

Let us know the out come.

I don't consider that a fix. The area will not be as good as it was as a casting....

The only way to fix it correctly is to window the whole area, out, insert a piece of plate and weld that in.... re-machine all the seats, etc.

As for detonation, there has never been an indication of detonation on the plugs. I've seen plenty of severe detonation on engines, and it is easily seen on plugs.

To me it seems like every manufacturer I have seen for cylinder heads has had a cracking issue under certain circumstances....

This is why there is a big drive for billet heads today...

I believe the answer is that as has been mentioned there is not enough material between the ports, and between temps and pressure in the exhaust port it is degrading the aluminum over time.... the heat treat is certainly gone in that area.... all the way through.

Now all that is left is a porous soft .120 piece of aluminum supporting pressure, heat, dynamics of the valves etc...
 

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2,000 hp from a LS style cylinder head, .. hummm, .. doesn't that seem like alot to ask?

I had the same issue with some Trick Flows, several sets just to get through a season, ..
so it's not the first time for this issue.

The fact that they are cracking so quickly, .. and not just between the seats tells me the
casting is flexing under the stress, .. .. Bob makes great stuff, .. but you might have reached
the limit of that casting. After all, it's JUST a casting.

I'd have to agree on the detonation though, .. almost every issue I've have with
a customer's blown or turbo combo has been from it, .. bent intake valves, cracked chambers,
seats coming loose, etc, ..

Curtis
Well he doesn't have bending, or stretching valves. He don't have leaking head gaskets, or loose seats, and no indication on the plugs of detonation. The rods and pistons were unchanged in both sets of heads and the pins/bores did not show signs of detonation either.

I'm a pretty savvy plug reader and cylinder to cylinder distribution is not too bad in terms of fuel and temp in the plugs... The tune up in the engine is always safe.

Other than these cracking issues the engine has been maintenance free.

Edit: If there is detonation, it's not apparent, and if we are not seeing the detonation evident in the plugs, pin bores, rings, gaskets, I am not believing it is enough to rattle a head apart.
 
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