60thou oversized pistons?? good or bad??

[bazeng]

Hi Guys,

I'm currently running 40thou over pistons in my block, and I'm considering using 60thou over pistons due to some bore damaged...

Is this a bad thing?
Will the block be ok?

does 20 thou make a difference?

Anybody know what the thickness of a standard cylinder wall is?

Thanks guys..

 

[Brianawd]

BAD! You are really getting the cylinder walls thin. I would never go over .040

 

[3rdstrikedsm]

Yea trash that block, I have seen the cyl walls crack on a 40thou motor.

 

[bustedsm]

My motor did well at .060 but then again, the motor died from the harmonic dampner coming loose /ubbthreads/images/graemlins/frown.gif

 

[3rdstrikedsm]

It will work but put any power to it and forget it.

 

how long have u been running the motor? just wondering y u have had to bore so much, if buy choice the first time now by need due to wall damage.

 

[JNR]

I'm surprised you guys use 'standard' measurements on that and not metric /ubbthreads/images/graemlins/grin.gif

Depends on the block (I don't know how much meat is available and it's layout with respect to coolant passages); some you can get away with it, and others it's not a good idea to go much more than .030". Personally, I would see about getting a new block, but least they're iron, I suppose.

 

[Dialcaliper]

If you can locate a new block, that's probably the best option, but the engine will be fine at .060 (1.5mm) over as long as you're not blowing huge amounts of boost into it expecting it to last. There's enough wall thickness in some 6-bolt 4G63 blocks that some of the drag racers run .080 over pistons. I can't speak for the 7-bolt though, I think the water passage is laid out a little differently to match the head.

The problem you'll have is that the OEM Mitsu MLS gasket is made for .040 over (or less) - you'll have to get a special Cometic or Fel-Pro gasket to do more than that.

The 4G64 block doesn't have much extra wall thickness since it starts out 1.5mm over already - .040 over is the most you'd ever want to go on one.

 

[bazeng]

The only reason I'm planning to build a 60thou over motor is because I ordered some pistons for my 2.4L build and they need to be bigger..

60thou over is the std 2.4L size..
Anyway, fingers crossed!!

I'll be half filling the block with grout also to assist with block rigidity...

I'm aiming for about 400hp - 450hp at the front wheels...

Thanks for the comments guys!

 

[Terry Posten]

Your "rock-titeing" a 4G to only make 450whp?

 

[H05TYL]

he must mean 400-450hp at EACH front wheel. . . /ubbthreads/images/graemlins/rofl.gif

 

The engine in my talon is .060 over, no problems yet. It was already in the car when I bought it. I figured I can't use it for another build so I might as well see how long it lasts.

 

[bazeng]

The AMG will be getting my old setup which made 550hp at all wheels, so I'm playing it safe on the AMG and keeping it on low boost..

It will be a GT3040 setup running about 20 psi..
(I ran 30psi on my vr4)..

The AMG will be a cruiser, we are not looking to make big power!

I'm hard filling the block (lower part just below the freeze plugs) just for a bit of insurance.
I believe it doesn't affect cooling whatsoever from other peoples experiences here...

The thing is, I know I'll be tempted to boost it back up to 30 psi and make 600+hp at the front wheels which I'm sure it'll be capable of. It'll be running a VR4 RS gearbox with a kaaz front lsd.. Hopefully 11's is on the cards with full leather / sound / street spec...

 

[Dialcaliper]

It shouldn't affect cooling for a DD or drag car, but if you flog it hard on a long drive or road race, you might have issues when the cylinder walls start heat soaking.