Doing some stupid shit to an old datsun head

[TK]

Ok, done 1 whole cylinder, took a little while to nut out the shapes I wanted, expecially on the exhaust side.
The exhausts on these things are the real problem, abrupt short turn & not much you can do. So rather than try to perform a miracle I instead concentrated on unloading the turn as much as possible - I threw away all the existing info & port designs & started from scratch with the focus being on getting the correct cross sections in the correct areas, getting the port to taper out as required & unloading the turn.
Intake is also a little different to what I've done in the past, the new chamber shape allows for a more aggressive short turn, which in turn allows for more flare after the miminum cross section just before the guide.
I've gone for a 40mm port at the min cross section, the port tapers down to 40mm (or 1.9^") from around 42mm at the head face, then flares back out.

[Roadsailing]

amazing work!

With a 4 valve pentroof head swirl is almost non-existant, if you can promote a little swirl it's a good thing.

getting a bit off topic but quick question: have you had much luck fitting one oversized inlet valve per cylinder to a 4 valve head to do this?

[Benonymous]

I still find it hard to believe that you do all of this work by hand TK. Its beautiful craftsmanship combined with science

[TK]

Never tried it!

Just CC'd the chamber - 39cc, won't be accurate coz I'm just using the dummy valves, but will be close.
That'd give 11.5:1 comp as it sits, going to have to mill it down a bit - which is a pity, I'd like to keep the valves as deep in the chamber as possible, but it is what it is.
As it sits the highest part of the intake seat is about 5mm below the surface of the head, I reckon I'll need to take about 2mm off the head, so I'll still have a minimum depth of 3mm - which is ok.

[MRMOPARMAN]

[dat2kman]

37cc chambers, in background 53cc chambers. Both heads at stock height.
Can take up to 4mm off but not using stock timing chain guides or tensioner.

[260BC]

With a 4 valve pentroof head swirl is almost non-existant, if you can promote a little swirl it's a good thing.
But we're talking inline 2V heads here, due to the intake valve sitting against the side of the bore there is always plenty of swirl, more than you want.
Better that energy is used to keep the charge following the piston down the bore, rather than swirling around at the top of the bore & impeding incoming charge.

That makes perfect sense, diverting energy away from getting air into the chamber makes no sense, love it.

[BigMuz]

That's awesome but you made the first one too good and now you can't cut any corners :D

Also holy fuck your photography has come a long way!

[Dogsballs]

Man those ports are opened up a metric fuckload. Was going to ask about the deep chamber and comp but you answered.

Fairly thick castings

[Billzilla]

getting a bit off topic but quick question: have you had much luck fitting one oversized inlet valve per cylinder to a 4 valve head to do this?

Never tried it!

FWIW Repco-Brabham tried all that in the late 60's. They found that the same size valves opening at the same time and rate worked best. Things may be a bit different now but I suspect not.
The David Vizard Polyquad is worth having a bit of a look at as well. http://www.motortecmagazine.net/article.asp?AID=1&AP=1

The pressure recovery thing is why other reason why I like the 7AFE heads over the 4AGE heads, as the chamber shape lets you do a bit of that and still keep reasonable squish areas.




BTW, TK, I did work out how to make lots of swirl in a 4V head, but it probably wouldn't work.
http://performanceforums.com/forums/...-it-won-t-work

[Ben Wilson]

FWIW Repco-Brabham tried all that in the late 60's. They found that the same size valves opening at the same time and rate worked best. Things may be a bit different now but I suspect not.

I was having a poke around a mate's B16 Civic motor and it looks like they stagger the inlet valves at low revs, then join them all together as the revs come up.

[sambrad]

Amazing! When doing it all by hand, how to go about making each of the chambers/ports the same?

[9triton]

WAA??? Swirl is bad??



So Suzuki twin swirl was all bullshit? Dissapoint....

hmm probably marketing hype misnomer- what that pic shows is 'tumble'- which 4 v lend themselves to .

[EJ DUDE]

Happy to admit I have no fucking idea what any of you guys are in about but that looks amazing TK
Shame such a beautiful piece of craftsmanship and science gets hidden and never seen.

[Lord_fahrquhar]

Jesus that looks better than a right fit tinder chick asking for a right banging


Actually maybe not but fuck it goes close