queen1874 wrote:
what do you guys think about the 4g54 engine performance normally aspirated?
it depends on what you wont them to do - I have run the 2.6 engine in NA form for hill climb and sprints and the car have done a few state race rounds circuit racing
and a NA engine it has made 119.5 Kw atw @ 6100 rpm but will easy spin past that
if you wont to make a 2.6 spin up and make good HP one of the biggest things is get as much weight out of the spinning mass
heres a few things to start you thinking
flywheel I made my own from 4140 steel under 5 kg that has most of the outer edges milled away to reduce the moment of inertia
I also run a light clutch
the crank has 2 kg machined off with knife edging
the front pulley is and under drive aluminium pully
the balance shafts were binned ( a real weekness in design for high revs )
the rods although are factory have been polished and peened with arp bolts
a crank scraper was made and fitted
along with a custom sump
the head started life on a magna it was ported the guides bulleted and the valves back cut
and has 3.5 mm removed from the face to up the comp
it runs quite a large cam with 300 deg duration on the inlet and 310 deg on the ex
cant remember the lift
the cam is dailed in using a redrilled cam gear
twin 45 mm webers with custom 41 mm chokes ( these are realy to small and will be replaced with a set of 50 mm quad tbs )
as you see theres not a lot left untouched in the engine and being a track car ( 1979 GE sigma ) it gets spun to 7200 a lot
very few things have gone wrong with the engines over a 10 year period
I run 1 bearing early on ( it was a 4g52 and found to have a fauty pump )
I've burnt a hole in a piston twice - not and engine fault more a tuning fault
as you can see I think a lot of these engines - if you do build one they are a very simple engine to work on
getting machining shops to do what you wont is the hardest thing
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