Machining Pistons

chodjinn · Post by **chodjinn** » Tue Jul 01, 2008 2:02 pm

Just spoke to Cosworth regarding a replacement piston to complete the set I've just bought, but it's not looking good at the moment! Since I have more than a full set of high comp pistons, I was wondering whether it would be possible to machine a high comp forged piston to reduce the comp ratio to match that of the low comp? Or is that just a really daft idea?!

chodjinn · Post by **chodjinn** » Tue Jul 01, 2008 3:42 pm

Cosworth just got back to me, and as I feared they don't have any of the pistons I have left in stock. They are willing, however, to recast a set for me, at a cost of £130 per piston, and a minimum order of 48!

So, I guess I have 7 spanky Cosworth paper weights for the time being until the unlikely event of a matching piston turning up! At least they only cost me £50!

jrv8 · Post by **jrv8** » Tue Jul 01, 2008 5:35 pm

Hi,
I've a full set of Cosworth pistons here that came in a job lot of engine spares. These are supposed to have been fitted to a supercharged RV8 engine, so are most likely low compression ones.
Do you have a picture of your pistons, or even the part number.?

Jim

chodjinn · Post by **chodjinn** » Tue Jul 01, 2008 5:46 pm

Hey Jim!

Cheers for the reply. The part number is PA 0470/1.

On the inside of the piston is COSWORTH * and also 18615 DTD 731

What size engine did they come out of? The ones I have are for a 3.5 litre block, and standard grudgeon pin size i believe (needs confirming).

thanks

jrv8 · Post by **jrv8** » Tue Jul 01, 2008 8:49 pm

Hi,

Number on these is PM 0209 cast into the inside of the piston , below the name Cosworth.
Other number is PA 0936/1
They're fitted to 3.5/3.9 HRC rods, and have deep cut outs on the crown.
If you PM me your email address , I'll send you a pic of them.

Jim

stevieturbo · Post by **stevieturbo** » Tue Jul 01, 2008 10:35 pm

Failing that...

How thick are the piston crowns ? It wouldnt be the first time Ive whacked a bit of the top for a blown engine

Forget £130 a piston though. Any of the US suppliers would make you a set for a fraction of that price.

I think my custom JE set were about £680 all in for 8 forged pistons, and that was from a UK supplier.

If you went direct to the likes of Ross, they would undoubtedly be cheaper.

kokkolanpoika · Post by **kokkolanpoika** » Wed Jul 02, 2008 7:02 am

stevieturbo wrote:Failing that...

How thick are the piston crowns ? It wouldnt be the first time Ive whacked a bit of the top for a blown engine

Forget £130 a piston though. Any of the US suppliers would make you a set for a fraction of that price.

I think my custom JE set were about £680 all in for 8 forged pistons, and that was from a UK supplier.

If you went direct to the likes of Ross, they would undoubtedly be cheaper.

I bought last year 4 ross custom pistons for my 5.2 and they cost about 400£ inc vat and taxes and carriage to Finland also it will inc set of new rings for 8 pistons.
And i bouht them for my local suplier. Direckt from ross they cost about 340USD + rings dont remember maybe 150USD + carriage + vat. Witch is almoust same what i buy..

chodjinn · Post by **chodjinn** » Wed Jul 02, 2008 8:00 am

Jim,

what size are the pistons? 3.5 or 3.9? I'm after 3.5 ones as I'm planning on using a 3.5 block.

cheers

olly