AustenW

There is alot of internet talk that Black tops are stronger than Silver top blocks.

Why is this?

Where is the proof?

I suspect this is someones opinion rather than actual fact.

Just because it looks chunkier it doesn't mean its stronger.

I personally think the silver tops have a stronger bottom end as the main caps are alot thicker.

Approx 10mm thicker.

The Black top CGI WRC blocks are supposed to warp under the first few heat cycles which can cause imediate engine failure.

I know someone personally who this has happened to and know of one other person who suffered the same fate too.

I wonder if this is a common fault with these?

Supposedly the Ford WRC team moved back to using the standard block after several failures with the CGI block, not sure how true that is though.


Has anyone ever had a block failure on a zetec engine?

Avinitlarge

Ive got a zetec turbo blacktop, The std bottom end had 14 psi of boost and never faulted, I know of a couple of silvertop zetec turbo's that have failed a few times, Either Ive been lucky or the blacktop is a good strong engine

AustenW

Please explain further about the failures with the silvertops you heard of?

Garage19

Austen,

Intresting to hear about the WRC blocks.

I have always thought that the silver top block was the strongest. I too had noticed the larger main caps.

As a side note, and not very relevant as you will be changing the rods, but the silver top actually runs 1mm bigger diameter big end bolts as well.

It would be interesting to cut up a couple of blocks and measure things like bore thickness. Don't suppose you have access to an x ray machine???

The last engine we built that we are hoping for 400+bhp we used a silver top block mated to a black top head (New Focus RS casting ported by CNC heads)

I can highly recomend the work done by CNC heads.

As you can see from the data they have collected
( http://www.cncheads.co.uk/products.html ) , the ST170 flows vastly more than any other zetec head and is the one to have.

If i had to build another ZT it would be a silver top block with a ST170 head ported by CNC.

AustenW

Read my mind

Avinitlarge

Non have been block failures a such

I had one that knocked a crank out for no reason

1 friend had one knock a crank out

another friend had 1 that melted 2 pistons

Someone on MEG had one melt a piston, These are all just off the top of my head.

AustenW

Cant see what block strength has to do with melted pistons

What other issues surrounded the crank failure you had?
Was it due to a melted piston or over reving?

Upto now one can explain to me why this myth of the black top block being stronger than the silver top block exists.

Another case of Passion Ford Whispers if you ask me.

JesseT

How can one knock a crank out?

AustenW

Too many revs, loads of power or a piston melt down which can cause the piston to stick to the bore which puts all the force on the rod and crank to name but a few.

Avinitlarge

Not sure about the melted pistons but the knocked out bottom ends were unexplained, Both on number 3 too

AustenW

Has anyone had a block failure?

Avinitlarge

This is a silvertop cap(huge pic), Looking at that though, Its the same as a blacktop one(small pic)