4.7 piston de volume

[DaviesDJ]

Hi guys

Contemplating the final skim to my heads (they will need a certain minimum)

However trying to calculate a provisional final compression ratio I am attempting to ascertain the dome volume of the CP 4.7 pistons I have for the 93mm bore.

Trying to measure these is difficult

Nothing is written on the box or spec sadly.

Does anybody know the dome/dish volume of these pistons at all???

The actual dome looks very similar to 4.5 standard squeeze cast pistons.

Any answers gaterfully received

Best wishes

Dave

[MoonMonkey]

I don’t know the volume of the 4.7 piston dome, but I would normally measure it.

For domed pistons you can create an imprint in plaster of paris or something similar, and measure the imprint when dry. For dished pistons/imprint you can place a piece of clear Perspex with 2 holes drilled in it over the dish and fill the dish with liquid from a burrette until the meniscus just touches the Perspex

[DaviesDJ]

Going to use the bore and water method I think. Many thanks

Any example compression ratio ballpark guidesout there - with the 4.7 piston and 1mm skim?? As long as less than 12.8:1 Ish:-)

[gruffalo]

mine is a 4.7 with a 1mm skim, 11:1 comp ratio.

[FarmyardPants]

gruffalo said:

mine is a 4.7 with a 1mm skim, 11:1 comp ratio.

How are you finding the 4.7 and how much power does it make?

[gruffalo]

Love it, loads more torque than the 4.5.

Not stuck it on a rolling road since it has loosened up but last time still really quite a tight engine it was 400RWBHP.

Must take her down to Surrey Rolling Road some time.

Edited by gruffalo on Monday 6th November 17:29

[DaviesDJ]

Measured the dome now at 7cc - think I need a minimum of 1mm skim to clean up - I thought his lead to greater than 11:1 CR ???? What’s the standard CR at a 1mm skim for 4.7???

How far can you skim until you hit timing cover and injector fitting problems??

[NuddyRap]

A 1mm skim (40thou) for my 4.7 is where things are heading at the moment, with mine being built at Power. It should be an 11:1 CR.