peter/jedi

quick question i am just starting to rebuild my cossie engine and want to check if i need to have a rebore and pistons as it slapped quite bad when cold the bore messures at 90.80 and the pistons at 90.60 its a 200 block with 2wd pistons i am aiming for 500 brake the spec of the engine is 7.4.2.1 cr ported polished head 25mm inlet 24 mm exhaust bd14 inlet bd10 exhaust isky valve springs long studded etc running a t4 and 83lb siemens do i need to change the spec and are the pistons ok to reuse?

COLEYST200

iTrader: (3)

i dont no about the sizes mate . But you will need to have the pistons pocketed its about £100 to have done

mechanic28

iTrader: (5)

its the offset of the gudgen pin on 2wd rods that causes the slap!4x4 rods needed chap!

COLEYST200

iTrader: (3)

iv got 2wd rods with 4x4 pistons on them with pockits in them ????????

liam-rst

iTrader: (1)

surely the rods would be the same but gudgeon pin off set in piston? or am i just bein thick lol

mechanic28

iTrader: (5)

yes your indeed correct!my mistake !like my english teacher said as long as i know what i ment that is all that matters lol"

liam-rst

iTrader: (1)

lol i tell myself that all the time, i kno wot im on about but when i try to explain it, it all goes tits up lol

RickyLee53

Yes, that will slap like mad.

You did measure the pistons the the skirt though? Not at the crown?

peter/jedi

when you say the skirt do mean below the rings if so yes mate and it slapped like fuck but the more you raped it the quiter it got

CossieRich

iTrader: (1)

Straight gudgeon pin in the 2wd piston is the cause of slap. 4wd piston uses an offset pin so eliminates slap somewhat. If piston to bore clerances are too large then it will still slap. Not sure on the effect of your bore clearances on the slap side of things.

I would ditch the BD10 exhaust cam and use a standard one though. Your lowering the comp so off boost driveability will be slightly worse than normal and made even worse with the BD10 exhaust cam. That cam is generally regarded as useless in a cossie engine due to it making the engine feel somewhat lifeless at the lower end of the rev range, no matter if its inlet or in your case exhuast. Standard exhaust cam is good for 550bhp anyway

peter/jedi

love the wheels mate got same on mine but in anthrecite best looks mod so far another question mate you've ready seen the head spec but i've just been offered another 1 with 27mm inlets and 26mm exhaust also has leary cams i'm told equivilent to bd16s wat would i be better off with my head with a std ex cam or the 1 ive just mebtioned obviously i'm looking for big power but want to keep some mid range driverbility