forged bottom end

6th August 2011, 11:29

hi

Looking to do a big spec throttle bodied vts build

know what ima do head wise jenveys,jp4,ph4 .. but dont know much bout the bottom end side :/

know i want to use forgded conrods ,hi-comp pistons 79.5 mm or 80mm does anyone which will be best a give the most bhp or better performance ?
also what would i need to replace internally in order to get ruffly 180 bhp ?
thanks

6th August 2011, 16:54

AlexB has some brand new 80mm wossner high compression pistons for a good price.

Is a hard shout as to which is better, as 80mm will increase the displacement, but then the wall in-between the cylinders is smaller.

I'd probably go with the 80mm ones if I was building an engine up

6th August 2011, 18:24

thanks mate

would it make much diffence if i left the other bottom end internals the same Bearings, crankshaft ect.. ?

6th August 2011, 19:41

Normally the crankshaft and bearings stay oem.

You can get acl race bearings if need be. Can go for forged rods if want it bulletproof

6th August 2011, 20:22

dont really have to do much

180bhp pretty easily obtained, you wont have to rev it past 8k.

stock crank be fine. we take these to 9. they require minimal work, bit of balancing etc. steel flywheel be recommended.

stock pug bearings are good, but as mentioned ACLs are good. if your going forged rods and psitons these coem with good bolts anyway, although ARP bolts are available for stock rods.. but if your regularly gona pull over 8k then forged are recommended.

head.. inlet side is pretty sorted on the JP4 but they scream for exhaust work!!! larger ex ports and ex valves easily pick up 10bhp

try the catcam 850. with a small exhaust these can make up to 190bhp, with power from 3k up to 8k.. or with larger exhaust can make few bhp more but will have narrower power abnd, 4k to 8k.

850 worth looking at though, still very street drivable, hard to beat. this is a solid follower camshaft.

check our onlien shop for the larger valves and catcams.

- colin.

7th August 2011, 14:35

If on a budget the proven method of pistons + catcam 734/newans ph4 is a good choice.

Sandy brown could build you an engine (one of the more experienced tu na tuners around still tbh), he does also have his own spec cam profiles he recommends too.

IMO only point of spending the extra and going solid grind is if you are wanting a more competition focussed engine, road use the hydro grind ones do very well for better value for money.