Rb25Det S2 Head Porting And Head Gasket Choice

[Gta51]

Hey guys

head gasket let go due to it overheating suddenly, so thought I would port the head while its off and upgrade to a metal head gasket. Would porting the head affect the cars current tune in it? I'm guessing it would but thought I would confirm. What metal head gaskets are good ?

Thanks

[NYTSKY]

If you are not resurfacing anything use a stock gasket. I would get the head checked for straightness though.

[GTSBoy]

Porting could well mean that you get more cylinder fill in a given rev range than you used to. If the timing map in particular does not have enough safety in it then you could get it to ping where it didn't used to. So, yes, it would pay to at least check the tune.

[Gta51]

Cheers guys! Is it worth porting the head in general? I'm making 305rwkw on 19 pound with a gtx3076 .82 rear

[GTSBoy]

Of course porting is always "worth it". For a given value of "worth it".

To do it properly takes many many hours. If you are paying someone to do it, that adds up to a fair amount of coin. On top of that, any decent porting guy will want to know exactly what you intend to use the car for, expected power goal (to within a few %, none of this 350 - 400rwkw bullshit you generally hear), what cams are being used, revs intended, swept capacity and so on. Without this stuff, what you are actually going to get is either a light clean up and de-dag, perhaps with a little reshaping of the guides and bowl, or something that is so severely hogged out that it won't work below 10000 rpm. Or anything in between those extremes. Whether that suits your purposes or not would come down to luck as much as anything.

Basically, unless you are doing a maximum effort engine build, there are probably better places to spend money. A decent exhaust manifold would come first, then cams, then probably a few other things, before considering porting to be the next thing you need to grub a bit more power out of it.

Don't get me wrong, a decently ported head can flow a massive amount of extra air and so make more power on less boost.....but it is like everything we do, there are compromises to be made. Big flow generally costs low rpm gas velocity which negatively affects torque at the bottom end. And of course that slows boost response. The engine might be much more powerful as a result, yet feel slower just because it is a little lazier at the bottom. For a race engine where you keep it spooled up, not an issue. For a street engine, it might not be as nice. So as I said, you really have to work off the usage model of the engine and the power goals to work out if it is "worth it".

[Gta51]

Thanks for the reply mate appreciate it, cleared that up right away. If you were in my position shooting for more hp down the track what head gasket would you go? I've heard the cometic brand a few times now.

[GTSBoy]

Cometic is a good enough choice. You'll get differing opinions on what's the best around here. I'd personally go with what my engine builder (brother-in-law!!) recommended (which he hasn't with regard to my RB. We haven't built anything for me since my Alfa, last century!!).