Rebuild or Replace

[FreeBeeTony]

Wasn't the outdrive or hydrolock............the intake vale in the #3 cylinder was shatered.......

First sign was the plug.

Then the condition of the #3 piston.

Then the missing pcs of the intake valve on the #3 cylinder.

Then pcs of the valve in the #2 & #8 cylinders..........

What are the opinions? remove/bore/replace pistons? or buy a short block and have the heads machined?

What would cause this to happen? Just a valve failure?

 

[bomar76]

Re: Rebuild or Replace

GM Crate long block .....
I would never trust that head, the cylinders ought to be really scored up beyond 30 over, wouldn't doubt there is a bent rod too. By the time you try to clean it up, buy a rotating assembly, new heads, pay the machine shop bill, etc, you are way past a GM Crate $ wise.

 

[Haut Medoc]

Re: Rebuild or Replace

Well that sucks.....
I agree with Bomar, (what happened to your avatar? )
I would just start off fresh with a new motor, unless you know someone in the biz.....
I'd think that you would get a plastic hernia from the machine shop bill....​

 

[FreeBeeTony]

Re: Rebuild or Replace

Would this be called "sucking a valve"?

Really don't know what to do here?

Haven't even turned it over by hand..........if it isn't scored too much should I bore it out and fix the heads?

Why did this even happen?

 

[bomar76]

Re: Rebuild or Replace

Would this be called "sucking a valve"?

if it isn't scored too much should I bore it out and fix the heads?

Well, so much for the advice we have offered.....

 

[FreeBeeTony]

Re: Rebuild or Replace

Don't be an ***** bomar...........looking for alternatives here!

If that's all you've got...............move on.

 

[bomar76]

Re: Rebuild or Replace

Well that sucks.....
I agree with Bomar, (what happened to your avatar? )
​

I fixed it again.....I have uploaded it a couple times, and it mysteriously dissapears after a few days. Think someone is not too pleased w/ it.

 

[bomar76]

Re: Rebuild or Replace

Don't be an ***** bomar...........looking for alternatives here!

If that's all you've got...............move on.

Not a problem!
Don't ever expect any help from me....

 

[Bondo]

Re: Rebuild or Replace

Why did this even happen?

Ayuh,.........
It looks like it might have gone Lean,+ had a Detonation Melt-down.......

 

[FreeBeeTony]

Re: Rebuild or Replace

bondo, can you expand on that?..........can this happen all of a sudden?

would you think i can have the heads reworked? and have the block bored out?

 

[FreeBeeTony]

Re: Rebuild or Replace

Been giving this some more thought........as I said I haven't even tried to turn it over by hand yet.

Going to try and get the pcs out of the cylinders and turn it over to inspect the cylinder walls...........is it at all possible that the walls will be ok and I can just replace that piston and have the head(s) reworked?

Still don't understand why this happened? bondo sugests "going lean and melting down"........don't quite understand that.

 

[John_S]

Re: Rebuild or Replace

Tony,

Can you post a close-up of that intake valve? It kinda looks like it broke into many little pieces, vs meltdown. How about a pic of the good head?

On that valve, was the rocker arm stud pulled out or other damage? Was this the same valve that had the lifter replaced?

As far as rebuild vs replace, you will have to do the complete teardown and inspection first. New longblock may be the best and most economical way to proceed.

 

[rodbolt]

Re: Rebuild or Replace

freebee
which motor is this? is it the inline six you made freshwater cooled? and do you have a trusted machine shop near you.
here I dont it all has to go 2 hours away from me.

 

[Bondo]

Re: Rebuild or Replace

There's a resent thread about Burnt Intake valves,.....
It's usually caused by Detonation,+/ or a Lean condition,.....
O'course,.... The Lean condition can bring on Massive Detonation all by itself......
The Fuel System might show Cause,......

In some of your pictures,... I think I can see some erosion or pitting in some of the piston edges,....
That points to Detonation.......
The Intake Valves are cooled by the head while they're seated,+ by the flow of Gas when they're open......
A Lean condition causes the valve to overheat,+ the Detonation that's caused By the Lean condition just adds to the Meltdown,......
Maybe Disintegration is a better word than Meltdown.......

I Agree with the above,...... A Teardown is Required before a Battle Plan can be devoloped........
Either break out the micrometers,+ calipers,..... Or get friendly witha local Machinest,.....

 

[KaGee]

Re: Rebuild or Replace

With the checkered past of that motor, I would replace it if it were mine.
Re-manned or crate is up to you and your wallet.
Rapido will not ask for your core is you get a re-man long block from them.
A truck crate motor if you want new.

 

[FreeBeeTony]

Re: Rebuild or Replace

How much more of a tear down can I do?

I am thinking those spots on the pistons are from pcs of the disintegrated valve.

My timing was set at 8* BTDC.............all seemed well....

WOT was 4400RPM............seemed strong. Could this just be a valve failure? The pcs in the cylinder were big.

 

[ziggy]

Re: Rebuild or Replace

since the question is rebuild or replace. i'm with bomar and kagee. R&R it with whatever suits ya. ya might even get back on the water in time for the strippers that way.....that engine treated ya poorly from square one. right up to disintegratein at 3K. nows yer chance to get something in there that ya will not wonder (hopefully) weather it'll hose ya out at sea.......

 

[Destin]

Re: Rebuild or Replace

From what I have read, standard Chevy heads need a maximum 32 degrees of timing advance, and Vortec heads need 28 degrees max. When I replaced my 1991 5.0LX engine with a 1998 Vortec marine base engine, I swapped the Thunderbolt IV onto the new engine and set the initial timing at 4 degrees BTDC instead of 8 degrees BTDC to move the max advance back 4 degrees, but I have never checked maximum advance with a timing light. My original module had a total advance of 32 degrees.

 

[Buttanic]

Re: Rebuild or Replace

I tend to agree with Bondo, looks like some detonation. The real issue, no matter if you rebuild or replace, something other than the block and heads is responsible for causing the detonation and until you find out what and why it is happening it could/will happen again.
In the picture of the plug is the ground electrode bent to the side or is it melted to the center electrode and broken from the shell, I can't quite tell in the picture.

 

[John_S]

Re: Rebuild or Replace

I thought Tony had a Thunderbolt V with knock detector.