I bought a 1800 zvh with supposed forged bottom. I pulled apart to find arp bolts but Mahle 84st74 m279a pistons which I think are standard. Nit dished out etc. Engine code suggest 2.0 ltr and pistons are 84.4/5 mm

It was supposed to ve running 15 psi but if they are STD pistons and it has no decomp plate how can it? The pistons at tdc sit about 1mm 1.5mm below deck? Is this STD or do they sit flush normally?

The gasket was multiple layer but only thin.

Not sure how to check compression it will running and safe boost without knowing?

Anybody know what STD pistons are and they sit flush else I presume it was running 10:1 compression and lucky it did not go bang. Never seen running only bought engine.

 

 

another

 

thats the normal piston height mate.

that piston code is for an N/A standard 2.0 piston

not clued up about ZVH's but they should definatly be dished pistons.

i think you've been sold a duff mate

looks like a standard 2.0 bottom end with ARP's

have you looked and the rods used?

 

somone has skimmed them ever so slightly, they should be flush to .5mm proud normally mate

 

cvh's will have a 48.8cc combustion chamber (including gasket) zetecs have a 50cc combustion chamber including gasket, using pieXd you can work out how much lower it will be with the 1.5mm off the piston crown, do it all in centemeters 8.45x3.14=26.53c squared x .15= 3.978 or 4cc more with the skim, so your combustion chamber is 52.8cc now on a 500 cc cylilnder, easy!

 

500cc divided by 52.8cc equals you compression ratio; 9.469:1 or 9.5:1

 

thanks chaps, i have measured the piston and it is 43 thou below block or 1.09mm, so if it should be 0.5mm proud 1.5 mm roughly shoudl be correct. although 9.5 seems high for turbo.

so if i use a zetec head at 50cc then it will be 53.978 / 500 = cop ratio 9.26. still seems high. Could i get a 1mm extra gasket or more so 500 / 56.632 = 8.8:1

what psi can run safely, going to MS with stainless inlet and t3. My target is 230-250bhp will it make and be reliable?

 

just checking calcs pie x r2 = 3.145 * (4.225 * 4.225) * 0.15 = 8.76cc so 57.97

499 /58.765 = 8.5:1

with extra 1mm gasket 8:1 i think??

 

I have done several zetec turbos with std pistons, broke one set too (ringland) then upgraded to wossner forged.
thw way i see it is you have two options (in my opinion) go with what you have and a single normal gasket (despite what you think 9.5 is not that high, my friend is currently running 14 psi in a v6 24valve golf at 10.8:1 compression ratio) the secret is all in the "tune".
The other option is to use an ALU decomp plate, but this will only move your torque curve and not allow you to run more/less boost as the pistons are still not any stronger. Decomp plates are very good if used correctly.