mk1trb

hi guys, i have been told that using a 1.8 zetec bottom end with the cvh head lowers compression on the zvh to the correct 8.2 or something, how much truth is in that? also other than the obvious water pump and front breather mods what else is needed to build the zvh lump?

xr2wishy

iTrader: (2)

won't be that without the pistons being skimmed and still won't be that low i don't think.
can't remember the exact CR of my engine i've taken out, but think it was 8.5:1 with a 1.8 zetec bottom end with the pistons skimmed a little.

series_one_rst

I've read somewhere the 1.8 pistons are safer for skimming as the crowns are thicker. is this true?

bezo

if your wanting to build a zvh use a 2.0 bottom with FRS pistons and rods, i picked my last set up off ebay for Ł150.

or you can use ST170 pistons and rods.

chaffe

It will be low enough for a turbo conversion, i think the combustion chamber size of a cvh is 47cc with the gasket thickness, so an 1800cc bottom end with flat and level pistons at tdc (same as an rst) will be 9.5:1. A thicker gasket could get it nearer 9:1, or as you say 1.5mm off the pistons would drop it further. What is the exact setup you plan on running? boost? power? managment?

mk1trb

i want 220bhp, always use optimax anyway, managment no idea yet,

Matt carter

you will get 220 on mfi.

my zvh is the st170 standard bottom end. P+P head + inlet 285 cam big intercooler T34 turbo.
And the good old 5th injector 250 chip ECU at 1.2 bar of boots. 248 BHP

chaffe

Thats not my point, the point with the management is that if you go programmable the compression ratio doesnt matter soo much as you can map it to suit. For example my car is turbocharged and about 10:1 comp ratio, no probs on programmable efi, but i think you would struggle when using a management setup tunned for a lower compression ratio.

chaffe

If you are going to use programmable then fully consider full 1800 zetec turbo, if using k-jet then ZVH is easier, i would consider a decomp plate rather than skimming the pistons (to keep the strength and weight in the pistons) use a ferriday aluminium plate, way better than a steel one.

Matt carter

a mate of mine did the ferriday plate and it works well.

mk1trb

thanks for the advice peeps, have considered full zetec t too and if things go as planned i will hopfully go that way

series_one_rst

i`ve thought about a full zetec turbo but in two minds as to sacrifice half original looks for a more up to date engine.

mk1trb

well i goin to use to to do alot of miles so modernising is the only way really and im sick of the tappy cvh heads

xr2wishy

iTrader: (2)

i've been using a 1.8 silvertop block with skimmed pistons, 4wd cossie turbo, efi, ported head etc. and ran it at 23psi without any issues to mention, very strong indeed.
the 2.0 pistons have thinner crowns and are weaker to begin with, early 1.8 pistons have much thicker crowns and are safer to skim.
although i'm building a full zetec turbo engine and selling off the zvh.

mk1trb

i have a rs1800 engine from a k plate, that early enough

xr2wishy

iTrader: (2)

if it's a series one zetec engine then yes.
basically would need to have the silver alloy rocker cover as far as i know.

mk1trb

i have jsut found a very very cheap st170 lump, its said above this would be well suited but what sort of comp ratio will this have? will i need a spacer plate etc???

chaffe

ive never broke crowns, just ring land on the 2 litre and 1.8 pistons

Matt carter

http://sitechracing.co.uk/default.asp

no spacer plate mate.

tomS2-Rst

iTrader: (1)

I think decomp plate is cheapest way, there good for 1bar boost if I remember correctly.

I built a zvh recently, 2.0block had it bored to 86mm used early vauxhall C20XE mahle forged pistons cost me Ł55 from ebay, had pistons machined for rods ect.

this is best and strongest way to build ZVH on a budget, with 86mm bore makes engine a 2.1 with correct comp, for Zetec turbo people seem to do the same but use C20LET pistons.

Maxwell

why or how did you have the "pistons machined for the rods"???? the gudgeon pins on the c20 pistons are bigger, therefore needing the "small end bearings" on the zetec rods bored/machined to take the c20 gudgeon pins!

chaffe

getting a block bored and then getting new rings and then the rods machined surley isnt the cheapest way of doing it? a set of forged pistons with new rings is only 500 quid NEW, plus im not a fan of making the already thin wall section between cylinders even thinner

Canada1

Chaffe is correct.
The Ford zetec block has very thin cylinder walls.
Boring more than .5mm can be risky. Unless you have sonic checked the block.
Forged pistons for Zetecs are plentiful - using a Zetec head or CVH head.
Makes no sense to "save" money on cheap pistons.