Forged Piston to Bore Clearance - Rover V8

[debaron]

Round to getting the Rover V8 finish honed for forged Icon pistons - 2618 Alloy

https://www.uempistons.com/index.php?main_page=ind...

- Manufacturer calls for 3.5 thou piston to bore clearance boosted - 4.5 thou NA

- Local Skyline engine builder agrees around 3.5 thou although may rattle a bit when cold

- TVR Power recommend 2 thou max

Anyone with experience of 2618 Alloy in Rover V8 know an ideal clearance or concur with one of the above?

Thanks

[Boosted LS1]

I'd stick with the manufacturer's specs even though they're going to be OTT totally safe for worst case conditions. Also you'll only ever be on boost for short periods so .0035" wouldn't be unreasonable imo even for boost. As for rattle, I doubt you'd notice any.

[macdeb]

From experience, manufacturers quote 'safe' clearances (safe for them) I'd close them up a tad.

[Boosted LS1]

^ Exactly. They don't car if you're burning oil just as long as you don't sieze a piston.

[phazed]

I'm fairly sure Rob quoted 2 thou for my Diamond forged pistons.

[SamR380]

debaron said:

- Manufacturer calls for 3.5 thou piston to bore clearance boosted - 4.5 thou NA

Why would they allow less clearance for the potentially hotter boosted application? (Genuine question)

[Pupp]

And perhaps more to the point, where is to be measured (anyone who has ever measured cold forged pistons across ring lands and skirts will know why I query this)?

[debaron]

Pupp said:

And perhaps more to the point, where is to be measured (anyone who has ever measured cold forged pistons across ring lands and skirts will know why I query this)?

Manufacturer had told me that a while back

"At the dial point (.500” from bottom of skirt up and at 70F)"

[debaron]

phazed said:

I'm fairly sure Rob quoted 2 thou for my Diamond forged pistons.

Excellent thanks Peter.

Is yours boosted or NA?

[ChilliWhizz]

debaron said:

phazed said:

I'm fairly sure Rob quoted 2 thou for my Diamond forged pistons.

Excellent thanks Peter.

Is yours boosted or NA?

Hi debaron, interesting thread... I've included Peter's post in my reply as I also have Diamond forged pistons, (engine) also built by Rob, but I have no idea what the bore clearance is......

I can say that it is one noisy top end, particularly when cold.. but, like Peter, I have an ACT CF plenum, (we're both NA unless Peter is keeping secrets ) and the CF plenum allows valve train (and piston noise) to be heard much more (louder) than the standard LR plenum does.... I'm told

So, not much of a contribution from me, but very interesting subject...

Cheers,
Chilli

[Matthew Poxon]

ChilliWhizz said:

I can say that it is one noisy top end, particularly when cold.. but, like Peter, I have an ACT CF plenum, (we're both NA unless Peter is keeping secrets ) and the CF plenum allows valve train (and piston noise) to be heard much more (louder) than the standard LR plenum does.... I'm told

I was quite surprised when I fitted mine how much more chatter you could hear from the top of the engine with the CF vs the OEM plenum. Of course you only really notice it at idle.

[phazed]

NA