need piston advice quickly....

[neal1980]

Im looking at getting some forged pistons for My Chimera 400. Ive found some in the states can anyone give me the size in inches for my pistons, the compression height and the piston weight.

Cheers

[hughesieII]

If you're going this route have a word with Paul at Austec - I've just had short skirted dished/forged pistons fitted to my 500 - he has them made specifically for the car so it would probably be best speaking to the man that knows, its makes the car sound very different, from cold it sounds like its about to throw a conrod out the side and takes a while to get used too, if you go the dished route you'll also need a remap to get extra fuel in there !!

[brummiewedge]

Just out of curio, why bother?

[neal1980]

cause mines gonna have a sodding big turbo bolted to it...

[brummiewedge]

Ahaa..it all makes sense now!! What fuel system will you use?

[GreenV8S]

I think the only way to be safe is to take one out and measure it. Be a shame to spend thousands on pistons and then find yours was the one car that TVR fitted with a 3.9 lump instead of a 4.0, or something like that ...

[Boosted LS1]

You should start by measuring your existing piston to head clearance. Working out required volume in the bowl. At the same time you can check bore condition and rebore if need be. Once you know all this you will be able to order correct pistons. Don't forget you will need a rebalance of the crankshaft.

Boosted.

[v8 racing]

your bore size is 3.702 and your comp height is 1.76 this will take it to the top of the block and not 40 thou down as they are standard, like boosted said though check your cr out as you may either have 29 or 34 cc heads.

[Boosted LS1]

v8 racing said:

your bore size is 3.702 and your comp height is 1.76 this will take it to the top of the block and not 40 thou down as they are standard, like boosted said though check your cr out as you may either have 29 or 34 cc heads.

If you have bore wear you can rebore. Once that's done you can order your pistons to suit the bore size you have minus .006" Piece of cake. Has your block been decked in the past? This is why you need to be patient and check what you have otherwise you could waste about £1200.

Boosted.

[pupp]

I'm assuming Hughsie's comments about piston slap are to do with the more tapered shape of forged pistons compared with cast, rather than any increased rocking moments associated with shorter skirts... ? I remember when I first ran up my old Kawa GPz motor on Cossie forged pistons I wondered what I had done. Soon got used to it, and then it got drowned out by the hairy cams and flat-slide Mikunis

[hughesieII]

pupp said:

I'm assuming Hughsie's comments about piston slap are to do with the more tapered shape of forged pistons compared with cast, rather than any increased rocking moments associated with shorter skirts... ? I remember when I first ran up my old Kawa GPz motor on Cossie forged pistons I wondered what I had done. Soon got used to it, and then it got drowned out by the hairy cams and flat-slide Mikunis

Kind of, it was explained to me as follows -

Std had 2 thou of clearance

The forged ones have 4 thou of clearance, this makes it sound weird when pushing on - obviously not from cold though

I'm still getting used to mine, and am still waiting for the engine to fall apart, but Paul assures me all is fine with it !!

[Boosted LS1]

I've built a few engines with forged pistons and they don't rattle. Quiet as a mouse in fact. Guess it depends on the manufacturer's specs.

Boosted.