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Calculating BHP and cc
Posted: Mon Sep 08, 2014 11:32 am
by bazit
Hi
After having a re bore to + 1.5 (gt 380 1973) and having the head skimmed 20 thou I would like to calculate the cc ,has any one a formula ?
Re: Calculating BHP and cc
Posted: Mon Sep 08, 2014 1:16 pm
by tz375
bore squared/4 x Pi x stroke x number of cylinders = capacity.
20thou off changes compression ratio but not capacity.
Re: Calculating BHP and cc
Posted: Mon Sep 08, 2014 3:29 pm
by Craig380
Suzi made a special version of the GT380 for the Italian market, which had 55mm bores as standard compared with the stock 54mm cylinders. This was 384cc compared with the stock 371cc.
At 1.5mm oversize, yours will be approximately 390cc, as TZ says the 20thou head skim will reduce combustion chamber volume by a cc or two but will not affect overall 'swept volume' (i.e. capacity) very much at all.
I have sometimes wondered how a full 400cc 'GT380' (56mm pistons, which were available for the Italian market) would feel and go compared with a stocker. Maybe about 7.8% better
A guy on this forum, Rocco Garzone, had one, he said it went very well indeed
