TomPengelly

I have a mk3 fiesta xr2i 16v (1.8 16v)

I want to do a 2.0 turbo conversion

Was going to use an st170 bottom end with a blacktop head.

What would the differences be between the 2 blocks? Would it be easier to fit different rods and pistons to a silvertop block and keep the silvertop head instead of a blacktop?

Cheers

CrOwSoN15

Your initial thought on a blacktop head on an ST170 bottom end is the way to go, Blacktops flow a little better as standard due to slightly bigger inlet (I think?) valves.

There's not huge amount of difference, the Blacktop with mechanical followers as apposed to the Silvertops hydraulic being the most notable I think.

I'm sure someone more clued up can give you the run down.

frsjon

the fitment is not as easy as the silvertop due to the rear alternator,you can use the mounts that your car already has but you cant swap the water pump on a blacktop like you would on a silvertop.you can get a bracket/pulley system to run a front mounted alternator but as i say silvertop fits in just as your 1.8 would

TomPengelly

Cheers for the replies. Would be nicer to stay silvertop, so i have less problems with things fitting and i can use most of the parts i already have. Il uprate the valve springs and use arp bolts ect, im only aining for 300-350bhp, on a budget, what pistons do people recommend? Or even if i kept my 1.8, i could pick a set of forged rods up, and heard that 1.8 20v audi tt or golf gti ect pistons fit the 1.8 zetec

Any comments on this? Cheers

bj928

the water pump can be change to one that flows the other way on a black top, but its only available from america i believe, some race engine uses a black top pump running backwards to normal,

Johnny Knoxville

My mate was the first person to engineer them Pistons to fit Zetec rods

There are two types of Pistons that will differ in compression. The ones from a BAM, APY, etc.will give you the lower compression 7.5:1 ish, AGU will make it higher at around 8:1 ish

Don't quote me on the compressions

TomPengelly

Cheers for comments. Any idea what standard silvertop rods are good for? Worth getting forged rods to go with the VAG pistons if i go down that route?

TomPengelly

Do the 20v turbo rods fit too?

If not, whats involved making the pistons fit the zetec rods? Are the bore sizes the same?

frsjon

standard rods and C20LET pistons up to around 280 is 'safe' they will do plenty more but for how long i dont know lol my last engine was fairly standard,C20let pistons,area six valve springs and on 470cc injectors and emerald ecu it did 277bhp/295 ftlbs of torque..ive since sold that to build a higher spec one.. if you can get a 2.0 block bored cheap enough and find some good/second hand pistons(little end of rod bored too) then your laughing

TomPengelly

Do i need the block bored for the let pistons to fit? And the rods machined for gudgeon pin?

But mabey st170 bottom end is the way forward and just make the altonator and water pump fit?

b11lkw

I was lucky that the silver top I picked up from a scrappy didn't need boring so a genuine set of WRC Pistons and FRS rods went in

TomPengelly

Will frs rods go in a silvertop? With standard crank?

Johnny Knoxville

As long as you use the frs pistons too