pitjardas

Hi all
I bought wossner forged pistons 80.5 mm. I've made a measurement volume of my head and it Gave me about 39cc for one cylinder.
My head gasket is cometic 0070 "(1.78 mm)
how much do I have to rectify the piston for 7,8:1
How do I calculate it?

project rs

i'd double check that head measurement as standard head cc is 60 so for you to be down to 39 there's some meat missing of your head which will effect how it performes

Canada1

The standard head volume is 55cc.
39 cc might be the lean burn chamber. This will be high compression.
One could not mill a hemi chamber 55cc head to 39cc's - there would be no deck thickness left.

Double check your combustion chamber volume. Is it a hemi chamber? Maybe take a picture and post it.

pitjardas

The head is a stage 3 efi (fiesta rs turbo) but skim sometimes. The volume is measured without the head gasket.

my calculations to get a compression ratio 7,86:1 but skim 2mm top piston

39cc head

head gasket 9,63cc´s (3,1416 x 41,5^2 = 5,41cc per mm 5,41 x 1,78mm =9,63 cc's)

the volume displacemtent is 1618 / 4 = 404,5 cc per cylinder 404,5+ (9,63+39) / (9,63+39) = 9,3:1 CR

skim piston 3,1416 x 40,5^2 = 5,15cc per mm skim x 2mm= 10,3 cc

then 404,5 + (9,63 + 39 + 10,3) / 58,93= 7,86 CR

my calculations this correct?

many thanks

pitjardas

7,8:1 is good to run 25psi boost?

Ben26

im running standard C.R with 25 psi so yes

Canada1

How are you measuring combustion chamber volume?
Standard round combustion chamber cvh is 55cc
If volume is 39cc I would not use that head - it has been skimmed far too much!

2mm skim from a piston top is also not recommended - definitely not recommended at 25 psi boost!

For a 25 psi boost engine - get a cylinder head that has not been skimmed (or very, very little)

pitjardas

Hi
measured with a syringe. I have another head with approximately 55cc of a fiesta XR2i efi but stock.
so is replacing the valves? (N / A to turbo valves)
And big valves of burton power (INLET VALVE 43mm/1.693" 214N 1.6 CVH 134.75mm LONG and EXHAUST VALVE 37.85mm/1.49" 214N 1.6 CVH 131.75mm LONG) what is needed to fit the head XR2i? size is equal?

thanks for reply's

project rs

the heads are the same the only difference is your other one has been ported but for what your after you could just bolt it on and away you go and what turbo are you going to be running at 25psi

pitjardas

my full spec to safe 25 psi run

FRST crank and flywheel balance
ap racing 4padle clutch
THS Performance H-Beam con rod
wossner 80,5
Cometic 0,70"
arp head stud kit
stage 3 head (back to buy burton)
new man double valve springs 200 poundage
new man valve retainers with double valves
new man camshaft
new man solid lifters
bailey water tank and oil breather
motorcraft 071 spark plugs
autospecialist tubular manifold
stage 3 t3 turbo
mongoose 2,5 exhaust
OFAB efi conversion but another conversion MEGASQUIRT MS2
Bosch 440cc injectors
Coswort 091 fuel pump
Gaz coilovers
front and rear brakes cosworth 2wd


head is to delay the project

12_Second_rst

iTrader: (1)

id use a genuine ford headgasket and bolts