Lamborghini Talk banner

1 - 17 of 17 Posts

·
Registered
Joined
·
630 Posts
Do you have the P-250 Workshop Manual ?

The information is covered in there...

On the P-300 motors with JE (not Borgo or AP) pistons, we ran piston to cylinder wall clearances of 0.0635 mm

Paul
 

·
Registered
Joined
·
630 Posts
Mark,

What are you trying to do...? The old 1970's piston material used by both Borgo and AP expanded quite a bit more than the new alloys. That is why we could run the very tight clearances with JE...

Lamborghini would recommend replacement of both the piston and the sleeve...very expensive and pointless !

We found you could bore the sleeve .5 mm without problems.

Paul
 

·
Registered
Joined
·
299 Posts
Discussion Starter #6
Hello Paul, maybe i took the pistons for spare, but i am not sure that they are from a p250, so i need the measures from a original p250 piston....
 

·
Registered
Joined
·
630 Posts
Mark,

I am not anywhere near my Lambo parts, but this is not a P-300 piston...the P-200 piston is circa 75 mm...so by a process of elimination it is (a green; weight/balance marked) P-250 item.

The only thing I am not sure of is the 49.22 mm dimension

Paul
 

·
Registered
Joined
·
210 Posts
Hei, I have my garage 45 minutes away from Frankfurt and have several P250 pistons here. If you like you can visit me and have a look at the items.

The pistons above are from a P300, not from a P250. The P250 pistons have no spacer for the valves. The bore of 86mm is identical at the p250 and P300. The P300 has more stroke.

Send me a private message.

The picture with the two pistons is the current technology by CPS, the piston with the valve-tattoo is a vintage P250 item.

Talk soon, Martin.
 

Attachments

·
Registered
Joined
·
630 Posts
Martin is correct so your sample is likely a P-300...the P-250 does not have hemi-combustion chamber type valve reliefs.

The other measurements are similar to yours...except the diameter of my sample is 85.77 mm...so more worn...this motor had about 45,000 km on it !

Paul
 

·
Registered
Joined
·
630 Posts
Martin,

I am not familiar with CSP...but it appears you have pitting on the dome of the piston!

We had a motor with 11:25 compression JE pistons and after 10,500km... any carbon on the dome just washed off with solvent...and no pitting or hot-spots whatsoever.

I would roll back timing or use a higher octane fuel :)

Paul
 

·
Registered
Joined
·
210 Posts
Thanks. It's no pitting. It's some particles ash from the valves. I always fill 100 or 102 octane. Unfortunately I have a 11.5 compression ratio because of a dumb engine mechanic... ignition is 18 at idle and up to 30 degrees as the handbook recommends. Talk soon, Martin
 
1 - 17 of 17 Posts
Top