FE-FC Holden Discussion Forum

The new YellaTerra 12 port alloy head is very close to being on the market. Any discussion on the advantages of an alloy head over cast? They haven't been priced out yet but I imagine they won't be cheap.

I wasn't aware the 12 port alloys were going to be re-released so I don't know if it's the same product as was available previously or if it has been reworked. Alloy heads have the advantages of lighter weight, a quicker warmup and slightly less tendency to detonate, plus they have the big benefit of being easy to weld for the purposes of repairs or modification.
I have spent a lot of time playing with Holden 6 build ups, and there isn't a lot of good reliable information available. I tested some stock 12 port heads and also spent some time (too much!) modifying and testing a couple of 12 port EFI heads. From memory (and I'll drag my notes out to verify this later) the stock 12 port head flowed somewhere around 130cfm, and with a lot of work I ended up with about 160cfm from the VK one. All these flow figures are at 28"h2o and 0.45" lift by the way. So you can see that the scope for improvement with the 12 ports is nowhere near as big as what it is with the old 9 port heads. Mind you, the stock 9 port head is truly abysmal, and a typical 9 port YT head would be somewhere around 140-150 cfm. To put all this in perspective, I tested a (used and slightly crusty) stock standard EF Falcon head and got a smidgen over 200cfm. Yella Terra used to claim up to 35% better flow from their 12 port heads, so that would put them somewhere around 170 - 180 cfm. I gave up on the 12 port heads (and the Holden 6) eventually, the gains were getting smaller and smaller and the walls thinner and thinner. If you really are serious about getting the most from a Holden 6 - and to be honest they really are pathetic compared to modern engines - try talking to the guys that race Group NC. They are getting over 300hp from NA 9 port motors and if you must run a Holden motor they can point you in the right direction. You might also want to read these notes :http://www.bur.st/~oljohnno/holden.html ($2). If I can find my flow test notes on the 12 ports I'll post them up.

Thanks for the feedback OldJohnno, You are right, pathetic to say the least but you cant beat the nostalgia.

I feel bad about the "pathetic" remark actually, I was probably being overly harsh. For any "normal" use they are fine and I have to admit my stock 149 performs sweetly and is perfectly adequate. I guess I just didn't want anyone kidding themselves and wasting money trying to build something that would beat 2JZs, RB30s, LS1s or whatever and being disappointed when it didn't happen..

oldjohnno I crew for JZED on his FED and he has the National Record with a Holden six he took the title of a Rotary so much for Holden six's not performing .....7.7 at 168MPH must be slow or Pathetic ???????  .....FC427.......

I envy you FC427 being involved with that car.. I only wish I could build something equally slow and pathetic  :)

Ok for anyone interested these are the numbers for the 12 ports (at 0.4" lift and 28" suction):
Standard 202 black - 115 to 120cfm
Ported black w 1.74" intake - 165cfm

I don't have any 9 port heads handy but would expect to see about 90 cfm for a stocker depending on valve size.
By comparison - and I promise I won't use the "P" word this time  ;) - an EF Falc. flows about 205 and a 3 litre 2JZ Toyota does about 225cfm in bog stock form. FC427, do have any numbers for the JZED head? I imagine they would be pretty big...
The general rule of thumb is cfm/4 x no. of cylinders = horsepower potential. This is naturally aspirated of course, and on pump petrol. It usually works out to be fairly close for a reasonably well developed engine.

Oldjohnno can't remember what they flowed of the top of my head will get some flow figures of JZED and let you know  ......FC427....

Re..JZED Head the way they are sent out they flow around 400 HP but a tricky engine builder can make around 500HP but to make make that sort of HP the engine would have to turn over 10,000 RPM...JZED also does a roller cam and lifter kit as well as the heads .......FC427.......