The V8 Owners Forum -

heard back from V8D regarding the parts GULP.

looking at around 2K for custom forged pistons from Diamond pistons in the USA,
offset grind the crank to 86mm,
light weght steel chevy H beam 6.0" rods,
full bottom end balance,

have also been asked if I want the crank tuffrided too............

then theres new cam and lifters to go on top of this and gaskets etc.

What is actually damaged ?

What actually needs replaced ?

If you're getting custom pistons made ( and I assume that quoted price is for everything, not just the pistons ), can you not just retain your crank and rods and get pistons made to suit ?

It would reduce costs a fair amount

Hi Stevie,
damage:
well the block needs the faces machining as we know, but still not sure if the liners are going to move again,
Pistons yup they need the cast ones replaced with at least forged ones,

I contacted a few of the v8 suppliers as would not have a clue what to order if I wanted to have a set of one off pistons made, just being honest,
None of them stock a 94mm forged piston for the 4.6 rod or bore,
they all seem to stock/use a 96mm forged piston,

rods been told by a select few from this forum/facebook the 4.6 rods are weak as well as using cast pistons with a charger and need replacing with the 6" chevy rods, only going by what I have been told.

that price I was quoted was for everything listed excluding the cam bits etc,
Rob said the pistons may work out £400 cheaper if I get them collected and shipped from a house address and not the courier Diamond pistons use.

I used the 4.6 for some time in my car, and never had an issue. It was a totally standard bottom end with the low compression pistons

I did eventually melt a piston, but that was my fault, nothing else. The OEM 4.6 pistons whilst obviously cast, are a decent design, but yes forged pistons would be better.

Rods....if you arent running a lot of rpm over std I probably wouldnt be too concerned....but the chevy rods are cheap if you can get uprated ones to fit.
How many people have broken a rod or had one fail ? and in what build ?

IMO given budgets...I'd be more than content to run with the standard crank and rods, maybe just uprate bolts.

I would be concerned about the block/liners though. Have all 8 dropped the same amount ? Were you getting any signs of losing head gasket integrity ? ie pushing water, air locks in the cooling system, excessive pressure etc etc ?

Has whoever installed the liners into the block offered you any answers or solutions ? IMO that is something that shouldnt happen, and you would have to question the work. On a RV8 platform, that sort of thing shouldnt be experimental at all. They've either done them before and they know it works...or there should be answers as to why it didnt.
If they insist the work is up to scratch, the the droppage would have to be a soft block or something ( less likely ) in which case it's bound to happen again.

As for pistons, if you need custom pistons give Dave at Performance Unlimited a shout. Obviously if you can find an off the shelf piston to suit, all the better.
But if retaining std crank/rods, you could simply send him a piston to measure up.

What exactly was the damage to the pistons ? pics ?

Have some guys not used Ford or Chevy pistons before ? Maybe with a different bushing in the small end of the rod ?

With all that said...if you could buy a decent quality rotating assembly it would be a lot easier than piecing things together yourself. The block would concern me most though...if you build everything around that and it isnt a solid platform, it'll all come apart again and sourcing/replacing the block is a ballix.

All 8 pistons (had started cleaning them at this point)
http://i3.photobucket.com/albums/y93/th ... istons.jpg

The only broken piston, Cyl 2.
http://i3.photobucket.com/albums/y93/th ... nbroke.jpg

Not a lot of detail, but they do seem to be in good order.

Typically that sort of damage shouts detonation, but some weak pistons can break in similar fashion even without, or with even very mild detonation, if there is such a thing. The crowns and even top ring land of the damaged piston look to be in good order though. No pitting or marks that would suggest detonation

You'd almost never see a forged piston break like that, so forged pistons would make sense this time around.

Any hi res pics of the combustion chamber ?

Cheapest repair option if re-using the block, send Dave one of your pistons and ask him to have a set of forged made in same fitment and supply rings more appropriate to boost.

Sorry for late reply, been busy trying to sort out the forum loading fault with the hosts in USA,
picture of which chambers mate?
pistons or heads???

Coops wrote:Sorry for late reply, been busy trying to sort out the forum loading fault with the hosts in USA,
picture of which chambers mate?
pistons or heads???

All chambers ( heads ), just to see if there are any signs of detonation there.

Not a big deal anyway

will do that today as have the heads here still,
they have been cleaned up though to remove the oil deposits etc,
didn't see none when cleaning but will take pics anyways,

Coops wrote:will do that today as have the heads here still,
they have been cleaned up though to remove the oil deposits etc,
didn't see none when cleaning but will take pics anyways,

Although no detail in pistons pics, they did seem ok other than the fact one is broken, so there probably hasnt been

Always handy to keep good photos anyway for reference at a later date and sanity checks lol

I think when rob looked at the pistons as sent them with the engine , he said didn't see any signs of det,