oohogwash1

Just pulled my YB pistons out. Never pulled a YB apart before, done lots of bikes etc.
I have some scoring vertically in the bore on the outside edges of the bore. This sides closest to the outside edges of block which I guess is where the pressure from crank movement comes into play.

How much is normal on YBs - none, some ... Is this something you fix with a light hone ?
What do I do to minimize this from occurring ?

There is no lip at the top of the bore. What measurements should I take to see what acceptable wear is on the pistons, if I need new ones.. same applies for rings and bearings. What are tolerances.

Any help appreciated.
Gavan

porksword69

Were the pistons put in the right way round

oohogwash1

Good question, having never dismantled a YB I don't know the right way.
However the arrow on the top of the piston points to the front (radiator end) of the engine. And the small moon shape cutout on the bottom of the piston on one side is to the rear.

In bikes I normall see the arrow as pointing to the front, so I am assuming they are in correctly till you guys tell me otherwise

Regards
Gavan

oohogwash1

I took in the wost piston to an engine place... as I suspected it is borderline so I am going to replace them and probably do all the bearings and rings / gudgeon pins... which sucks. It appears whoever had the engine before hand accumulated a ton of gunk in there which has let go and scored the pistons...
It fits with luck I have had so far... :-(

TurboShed

Well, I think it's safe to say you should replace rings and bearings if you're rebuilding your engine, it's not like they cost anything.

I've heard plenty of people say that you normally need new pistons when rebuilding a YB, something to do with them being slighly compressed by the forced induction? I might be wrong! But I know my engine had new pistons, Ł700 quids worth ouch, when it was rebuilt recently.

LHD220Turbo

iTrader: (4)

if you've got the motor apart you may as well replace the pistons and rings for peace of mind.

as your in OZ i cant recommend anyone do check the bores on the block; but you may get away with a hone or it might be a rebore. the rods will probably be OK; just get the checked for straightness

just get someone decent to do it for you

are you rebuilding to standard spec or are you going for more power?

i have a few manuals i can send you if you give me your email address? it will certainly help with the rebuild

oohogwash1

The near new 200 block was originally supposed to be good for 500 hp. I am going to take your advise and rebuild the bottom end. I just had to let the wife know that the house is further in debt and realise that yet again, a good plan went south :-(

It seems Mahle pistons are good. Not sure on what to use for rings, bearings etc... where should I go, where can I get specs to give to an engine builder (rather than hoping he knows where to get it as YB knowledge is limited here)

I know this is a little off the wall but I want to get a CR of around 8.5:1 up from the standard 8:1. Don't flame me, there are reasons for this. Are there pistons that help on this?, I only see 8.0 and 7.2 on web. Also I would like to get pistons that will take a high lift cam without paying for extra machining.

Thanks for your help guys.

LHD220Turbo

iTrader: (4)

standard mahle pistons are forged and good for circa 450-500hp IMO; if you are going for 500hp i would consider getting the 200 block long studded (fit and forget!); you can use standard rings no problem

all of these parts are available through lots of traders in the UK - Matt Lewis or woodford garage would be your best bet (tried and tested)

matt lewis comes on here so maybe send him a PM

i would advise getting the valve pocketed to avoid piston to valve contact; and if you are going for 500hp and want the engine to rev high; maybe get ISKY double valve springs

the CR can be whatever you want; just get the pistons machined to suit; personally i have no experience of the CR you want

you can always ask any questions on here - there's lots of far more experienced people than me on here

i assume the crank is on standard size? the sheels will be stamped with a size if not, normally .25 or .5

LHD220Turbo

iTrader: (4)

here you go; here's some manuals to help

http://www.cannell.co.uk/Manuals.htm ( 2/3 of the way down Ford, the manual titled "RS Cosworth Sierra and Escort Workshop Manual" will def help you with the rebuild)

oohogwash1

I have dealt with Matt before, he is a top trader...