I am assembling my 7.3 using the Ford rebuild kit that came with the Mahle pistons. The stock piston being replaced measures 4.106 while the new pistons measure 4.103 which is below the service limit in the factory service manual. The bore measures 4.108. This leaves .005 clearance which is on the far end of acceptable. This seems real loose is there new specs for expansion with these pistons?
are you replacing the liners too or just the pistons? if not that could be some of the problem and possibly the expansion rate is different. kind of like a forged and a cast piston expand differently.
just my thoughts on it
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95 Ex. Cab 4x4 Auto, Lots of Oil, Lots of Fuel, Lots of Air=Broke Truck
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jacob_partridge</div><div class="ubbcode-body">are you replacing the liners too or just the pistons? </div></div>
No liner to replace in a PSD. [img]/forums/images/%%GRAEMLIN_URL%%/blush.gif[/img]
You can bore or sleeve the hole.
then why is cavitationa problem and what are you supposed to do when cavatation becomes bad enough it dumps coolant in the cylinder? you replace the liner just like a big wet sleeve engine. press fit or slip fit they are still a liner.
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95 Ex. Cab 4x4 Auto, Lots of Oil, Lots of Fuel, Lots of Air=Broke Truck
As far as the pistons go, I'd measure all of them, new and old, to see how much of a variance there is; and then I'd still call the factory and see if you got a bad batch of pistons.
Jacob,
Bill's correct, the T444E/PowerStroke is a parent bore engine, not a wet-sleeve engine. There are no sleeves in the engines from the factory, the cylinders are cast as part of the block. As far as I know, cavitation hasn't been much of an issue in the PSDs, unlike the IDIs. However, SCAs should still be maintained in the PowerStrokes. If cavitation does pose an issue, the cylinders have to be machined out and then a special sleeve is installed, it's a complicated job.
The Mahle is a forged piston so it's expansion rate would be greater than a cast piston. Do the pistons still have the steel or cast iron insert for the ring lands?
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Denny
'96 F-250 Reg. Cab 4X4 5-sp POWERSTROKE
294,000 mi & NO Problems, LUK Clutch, and the Cat is buried in the back yard!
ok well sorry bout that but i was almost certain they had a liner. It has been about 6 months since i had the head off a 99 and although i didnt pay that close of attention it looked like the top of a liner. i guess i just assumed.
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95 Ex. Cab 4x4 Auto, Lots of Oil, Lots of Fuel, Lots of Air=Broke Truck
After taking more time and measuring the bore it is actually 4.110 which is still well in spec. This is even worse, the new Mahle pistons won't even be in spec. As per the manual they should already be replaced.
The Ford rep is working on it. We'll see.
And no liners, I have been staring at the block for a couple of weeks now.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tjbeggs</div><div class="ubbcode-body">It was my understanding that Mahle are the stock pistons. who knows why the difference though. keep us posted. </div></div>
Did you have your block kiss-honed to put a new cross-hatch in the cylinders? Just because the bore measures in spec does not mean it's ok to just stick new pistons in an old bore. You should use .010 pistons and have the block honed.
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