I have an old 1275GT block which I am considering re-boring out to 1380cc. If I fit a stage 4 head and Kent 286 cam, would I need to upgrade the crankshft too?
Edited by Hughieboy, 07 August 2018 - 08:34 PM.
Posted 07 August 2018 - 08:19 PM
I have an old 1275GT block which I am considering re-boring out to 1380cc. If I fit a stage 4 head and Kent 286 cam, would I need to upgrade the crankshft too?
Edited by Hughieboy, 07 August 2018 - 08:34 PM.
Posted 07 August 2018 - 08:38 PM
No just make sure it is checked by an engineer for being straight and that the journals are good.
I would also consider 73mm to 1360 as it leaves another overbore, and the difference in output is nothing
to be honest a tuned 1330cc is plenty for the road
I think you mean a 286 cam...
The only performance related 186 I know was my uncles F1 stock car number, and another relatives Ministox number
Posted 07 August 2018 - 08:43 PM
Check too that the block has no hole above the centre main bearing, they are to be avoided.
Posted 07 August 2018 - 08:43 PM
No just make sure it is checked by an engineer for being straight and that the journals are good.
I would also consider 73mm to 1360 as it leaves another overbore, and the difference in output is nothing
to be honest a tuned 1330cc is plenty for the road
I think you mean a 286 cam...
The only performance related 186 I know was my uncles F1 stock car number, and another relatives Ministox number
Posted 07 August 2018 - 09:35 PM
Thanks all, appreciate your replies. Will definitely consider the 1330/1360 options.
Posted 08 August 2018 - 01:19 PM
If you are planning on hi horse power outputs and rpm I would get the crank tuffrided and a center main strap fitted to prevent crank flexing.at hi rpm.
Posted 08 August 2018 - 05:53 PM
A stock Crank as Retroman has suggested will be fine. About the only thing other than a balance is to consider having the Crank Wedged.
Posted 08 August 2018 - 06:49 PM
Why not start at 1293, get a really good head, decent cam, ignition system, exhaust system etc then a good rolling road set up.
Now you will have a really good setup, loads of life left in the block for rebores and potential.
The head, cam, fueling , ignition and exhaust system is where the power is at. Yes an increase in CC's will help with torque but not outright power.
Posted 08 August 2018 - 10:04 PM
Best advice, unless building a full-on competition car, is to always go to the next bore size up. Then, after you get to 1330 cc (+0.060" overbore) at the next re-build sleeve back to 1275 cc. That way there is no need for offset boring (= expensive) and no risk of scrapping the block.
Power and torque come more from accurate build and good gas flowing than simple increase of capacity.
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