300x melted a piston

[Mad300x]

Well my 300x decided it wanted to burn a hole in one of the pistons anything worth doing while it gets a rebuild? I was planning on a big bore throttle body and a lightened flywheel anything else that someone should do

[slowaction420]

1st I'd try hard to find out why it leaned out and go over the hole fuel system from the tank all the way to the injectors also bb throttle is great but adding more air with out adding more fuel is not a good idea will need some one to remap and tune or you will be rebuilding again real soon

[Mad300x]

Is there a chance it could have been caused by old fuel? I had around 10 gallons in the tank that was a little over a month old then added 10 more the only fuel I have available in my area is the ethanol mix

[slowaction420]

Tuff to say month not that long but if it turned to water yes it could have been a issue

[Go Time]

Did it actually burn a hole thru the piston dome?

[Mad300x]

Yes it's about the size of a quarter

[JPEROG]

Bad fuel sounds logical. Those motors were designed for (true 91+ oct. gasoline) not the alkajunk we are buying at the pumps today which has no shelf life.

Joe

[Go Time]

I think you have an ignition problem ....cdm could be multi firing....this happens often with the 3.0l

[capteliminator]

How would one go about determining if one of the cdm's are actually bad?

[Go Time]

Tests are provided in the service manuals. You maybe able to see it with a timing light. It could be also caused by the stator.

[Mad300x]

I will bring that up to the mechanic... thanks for the input

[R.grover]

Post a pic of piston please.
I'm no expert but have rebuild many 300x for play and race offshore/water ski, and you will find you need good stable fuel. Check fuel pressure as I have found with a remote gauge go for a good hard run and u'll see fuel pressure slowly drop away.
Cdms do fail/cross fire so I do replace them all at a rebuild.
Strip all the fuel system get the fuel injectors tested and strip clean the vst tank (fuel pump tank on side of motor)

What pistons are you putting back in it?
Make sure you check the reeds/reed block thoroughly don't be surprised if you have to replace a block/all of them.

If you are fitting a big throttle body id fit a remote fuel pump set up with adjustable fuel reg and bump up the fuel psi alittle.

Like I have said before I ant an expert but have done many this way and have not had any issues.

[Mad300x]

I will try to post a picture of the piston a little later....I was looking for any input on any aftermarket parts to make it better I don't see the point in cheaping out when in will be better in the long run

[MeCapnDave]

Well now that you have it apart you have a perfect opportunity to make a stroker out of it ! Talk to Chaz, he'll get you headed in the right direction !! Was it #6 piston? Get that injector flowed too.

[MeCapnDave]

Looking back through your posts, several months ago you thought you had a water in fuel issue. Could this possibly have been the result of your fuel/water issues as described a few posts ago?