Benefits Of 4k With 3k Bigport Head?

[Nostalgia]

I've done a search, but I can't find an answer for why.

FAQ says they're not actually that good, but why do people do it then? Is there power gain? Surely a 3k head wouldn't be stronger?

 

Any info or links much appreciated!

 

cheers, toby

[Evan G]

short cut to high compression, IMO don't use 3k heads there old and more worn than your 4k head.

 

if you want high compression shave your 4k head! and give it a headjob!

[Nostalgia]

So more power from higher compression, but most likely worn and outdated? What if it's a reconditioned cylinder head?

 

And yay headjobs!

[philbey]

If it's recoed yeh fine, but the point is that it's the OLDEST of all the heads out there. For 150 bucks I had my ports matched to my manifold on a 5K head and that ended up bigger than a 3KBP anyway. And the head is half the age of the 3K ones.

[Nostalgia]

So if you're not thrashing the car, it should hold up fine?

No real dramas?

[Clapped out]

Yeah mate, you'll be right. Thrashing or not, if its going to break, it'll break. if you do decide on running the 3k bigport, in my opinion, piss off the old valve's, valve guides and seats and replace them with a 4k setup, far better oil seal setup. When i got my bp head reco'd they modified and shortened the guides for better flow, maybe that could be something else to look at,

 

cheers phatke30!

Edited July 10, 2010 by phatke30

[Nostalgia]

It's just, I'm looking at a car that HAS this already done. Outside the house the car was at there was a sign saying "Machinist" so i'm guessing it would be properly done. It's the only thing I'm worried about in the whole car. Plus I'd rather a wagon (ke26) rather than the coupe/sedan, but beggers can't always be chosers! haha

[Clapped out]

personally go for it, you can't really lose out, if the head has been changed over, you should be able to see the top of one of the guides just by taking the oil cap off, see if its 4k setup or not,

 

cheers phatke30!

[Nostalgia]

Thanks phatke30, but can you elaborate? How can I tell it's a 4k setup after removing the oil cap?

[Taz_Rx]

Thanks phatke30, but can you elaborate? How can I tell it's a 4k setup after removing the oil cap?

 

Couple of different ways:

 

3kbp's have an o-ring around the top of the valve stem as a stem seal. 4k's have a much nicer seal which clips onto the top of the valve stem guide.

 

Also the top valve retainers are the easiest way to pick them. The 3kbp ones curl around the top of the spring a bit and down the sides slightly as seen in below pic (bottom head). You can't see the 4k ones all that well but the top retainer is flat and doesn't curl around the side of the spring.

 

[Nostalgia]

So a 4k with a 3kbp head will have the head with the o-ring seals? But the valve springs from the 4k head?

 

Sorry, I'm just starting to learn about porting etc!