fisherjohn Posted April 23, 2003 Share Posted April 23, 2003 Anyone know the piston to bore clearance on a Mk 4 when reboring the block. Rgds Quote Link to comment Share on other sites More sharing options...
Adam W Posted April 23, 2003 Share Posted April 23, 2003 What pistons are you using, what oversize are they? Your piston supplier should tell you. Quote Link to comment Share on other sites More sharing options...
fisherjohn Posted April 23, 2003 Author Share Posted April 23, 2003 Using HKS 87.0 mm so 1 mm over bore size Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted April 23, 2003 Share Posted April 23, 2003 There is no piston to cylinder wall clearance spec in the great book of words. The only spec for the cylinder diameter is 86.000 to 86.013mm and maximum of 86.02mm. There is no information on overboring the cylinders. Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 23, 2003 Share Posted April 23, 2003 The skirt profile on the piston will be turned to a complex shape as well - i.e. it won't be a perfect cylinder so the clearance will vary ever so slightly up and down the piston. Carrying over the bore limits from the basic engine and adding 1mm oversize is a starting point, but really the piston manufacturer should recommend the bore finishing dimensions, tolerances and surface finish for a given application. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted April 23, 2003 Share Posted April 23, 2003 Originally posted by fisherjohn Using HKS 87.0 mm so 1 mm over bore size Most modern forged pistons are sized according to the BORE they are designed to fit in, so I would expect they should go into an exact 87.00 mm bore. Quote Link to comment Share on other sites More sharing options...
Rich J Posted April 24, 2003 Share Posted April 24, 2003 Originally posted by Chris Wilson Most modern forged pistons are sized according to the BORE they are designed to fit in, so I would expect they should go into an exact 87.00 mm bore. Definately what I have seen, the pistons I am putting into the Integra (Civic Type R pistons which should produce a CR of around 12.5:1) are sold as +.25mm oversized, they are infact +.22mm oversized which make them just right to fit in the +.25mm bore. That said I have managed to get the piston cylinder clearance for the Type R engine which is 0.01-0.04mm so the pistons are nicely in spec. Quote Link to comment Share on other sites More sharing options...
Adam W Posted April 24, 2003 Share Posted April 24, 2003 Rich - I have to say I find it rather amusing that you gave up on Supras cos they were too powerful, and now you're spending a fortune on trying to squeeze more bhp out of the ITR! Quote Link to comment Share on other sites More sharing options...
Rich J Posted April 24, 2003 Share Posted April 24, 2003 Originally posted by Adam Wootten Rich - I have to say I find it rather amusing that you gave up on Supras cos they were too powerful, and now you're spending a fortune on trying to squeeze more bhp out of the ITR! Nah, not because of the power it was the combo of RWD and my big booted right foot that put me off. After trashing one I couldn't be sure I would learn by my mistakes. The Teg suits my all out driving style much better. The Teg will be nowhere near the Supra TT power 210 whp tops, although that will make quite a quick car (accel. not top speed mind) as it's only 1100kg. After it's all set up I have been lookign into changing the gear ratios to make best effect of the 9500rpm rev limiter. Quote Link to comment Share on other sites More sharing options...
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