imprezagaz

iTrader: (2)

Il be removing my engine soon to fit a 2.1 block. I have standard low milage big port heads but I'm unsure if I'm worth uprating the valve springs and or valves? I have a sc46 so il be planning on maxing this out power wise. Would standard big port heads be okay boost wise and to cope with 500ish?

Any advice would be great.

Thanks

bustaMOVEs

iTrader: (31)

Standard big port heads.
What do you mean by that? As in what heads actually are they, are they jdm heads, avcs, or been ported.

imprezagaz

iTrader: (2)

Jdm avcs big port heads👍

bustaMOVEs

iTrader: (31)

Ok, well yes they can cope with your requirments easy, but seen as you gonna take them apart, may aswell fit with new stuff etc, pressure test them if you can afford to and replace everything for peace of mind and future proof you for more power in future.
Apparently I think these can cope with upto 650hp iirc.

bustaMOVEs

iTrader: (31)

But just FYI I never replaced anything, it all looked good so didn't bother as build was chewing my funds up

imprezagaz

iTrader: (2)

Thanks. Yeah I know what you mean about the funds. I've got a quote for the valve, Spring kit and its abit more than I thought. A minimum I'd skim and new valve seals.

bustaMOVEs

iTrader: (31)

And pressure test.
Yeah that's good.
Tbh my heads were near mint anyway, no cracks near plugs whatsoever

imprezagaz

iTrader: (2)

Yeah I only fitted these end of last year and they was all well then.

tom-r33

iTrader: (2)

lap the valves in so you get a nice constant thickness mating surface on the seat, after that dummy build them and check cam - follower clearances and adjust valve stem length to suit. if you ahve spare followers then you might get away with using different thickness one to compensate. also worth looking closely at the valves and cleaning them up as they do suffer from burning out so swap out the thin ones
doing some minor porting wouldnt hurt either, and its as simple as running some sand paper over the rough bits to blend them in, not much point in polishing, especially the inlet which needs to be left a little rough
skim them after the other bits otherwise be very careful not to mark the surface
clean up all the gasket faces prior to final clean & assembly so none of the crap drops down the ports when built. after cleaning tape up ports to be 100% sure nothing goes in when building
doing all the above makes a nice set of heads and isnt too much work even using basic tools
just be 100% sure they arnt cracked before you start as it can waste time, effort and money. some cracks are tiny when the heads are cold and normally covered with a layer of carbon, so use a magnifying glass and clean thoroughly around the plug hole before doing anything else. also check the cam bearing surfaces as this can right off a set of heads
as for the stem seals, depends which year as to the colour, different colour for in and ex too, cant remember off top of my head though sorry, supplier may know though
Hope this helps!

imprezagaz

iTrader: (2)

That's great thanks. The last thing I want to do is cut corners so it has to come back out again. Is it worth fitting nitrided valves over the standard ones?

tom-r33

iTrader: (2)

i didnt bother upgrading any of the valve train in my 500bhp 2.5 (sc46) build, from what i understand you dont want to run much more than 1.5 bar otherwise the turbo life reduces dramatically, full boost and max torque should be around 3.5-4k so no need to rev it any higher than stanadrd limit so springs should be fine too
if you want to future proof then its a different story....