Tractorsport Flowbench Forum Archive

Posted: **Sun Sep 13, 2009 9:05 am**

Saying all that about the divider not making much difference, the proper 12 port head made more power on engines where we were allowed to use it, the alloy YT head was even better again, I don't know if they still make them?

I used a 2.8 blue head on an engine for a modified production speedway engine, it was 235 cu in. We ran 14.5:1 on mechanical methanol injected into an efi manifold. The nozzles were in the side squirting straight into the port and it ran 2 throttle bodies. It was very fast but hard to keep head gaskets on.

Posted: **Sun Sep 13, 2009 9:36 am**

Johno, how do you calculate for runner length when the runner ends at the head port entry? Do you factor in the extra distance to the valve seat or just measure to the end where the divided manifold port ends? Pipemax takes the calculation lengths all the way to the valve seat I believe. Just amazed that it works so well. Thanks for sharing. (tom c)

Posted: **Sun Sep 13, 2009 4:15 pm**

Yes the 12 port heads did flow better but few people really knew why! Iv studied them in detail and realised that, aside from the obvious valve size increase and tall ports, the factory heavily revised both the port shape and form along with the guide boss and a 30* back-cut on the intake valve only! Yella Terra are in the process of producing more 12 port alloy heads atm for $2300 AUS. When I measure the intake tract length on any induction set-up I always measure from the closed valve out and although it is a large siamesed port I still average the runner length as though it were a normal 'unshared' port, ie; measure roof and floor and divide by two then add half Diameter of carby ram tubes! I spent HEAPS of time making sure little things like this were spot-on! Iv always believed that its the extra little things you do, that ordinary people don't, that make a truly extra-ordinary engine!

Posted: **Sun Sep 13, 2009 5:13 pm**

I read every one of the responses to the initial post. Some interesting information in there.

FWIW, if a guy handed me that head and said "see if you can make this better" I would try this.

It's interesting that the divider installation didn't seem to make a difference in lap times. But then again, that's lap times and that doesn't tell the whole story. No more than a dyno tells the whole story.

I would effectively try to make that port like a typical 4 valve port divider except I would not fill in the floor. Adding aluminum / epoxy only to the roof, between the two intake valves and back as far as I could get it. Taper it and try to generate more velocity in the roof. Raise it as well. Also taper those guide bosses and guides down.

Similar to a typical valve guide runner boss but in between the two valves ... Some clay and a little time on the flowbench would be interesting..

The other thing I see is it looks like the chamber wall might be shrowding the valves pretty badly on the one side.

What size valves do these motors run?

Have you run this motor through PipeMax or any other application to see what you may require for airflow?

It just looks to me like there's a bunch of improvements that could be tried.

Larry C

Edited By larrycavan on 1252878051

Posted: **Sun Sep 13, 2009 8:10 pm**

Your idea of treating the port like a 4 valve per cylinder set-up sounds very applicable Larry! I know the guide bosses can be thinnned quite a bit (i have yet to try my new guide-tappering tool on these!!) and the roof lifted more but i have exhausted the available deshrouding room in the chambers (they are cut right out to the fire-ring of head gasket)! These engines were only ever fitted with 1.68"in & 1.44"ex oversize valves, when the 12 port version had 1.74"in & 1.55"ex oversize valves! I believed the valve sizes were the major reason for the 12 port flowing better, so i harassed my engine machine shop and they came up with a 9 port Yella Terra head fitted with 12 port head oversize valves! The stage 3 yt heads flowed around 80cfm (bare/no radiused guide) & came with 1.68"in / 1.44"ex valves, but i fit 1.74"in / 1.55"ex valves, removed the 'intake port head-bolt boss', blended the new seats and added a 30* back-cut to all valves, they flowed 105.7cfm (bare/no radiused guide). When i fitted 4 barrel manifold flow dropped a little to 103.6cfm, but the triple webber set-up flowed 115.7cfm! No prizes for guessing which one i went with!

Posted: **Sun Sep 13, 2009 8:22 pm**

Sorry Larry i have not run the set-up through pipemax or anything similar but i based my engine build on the final set-up they used in the Bathurst winning, V8 killing, 6cyl XU-1 toranas. I figured if i start my engine developement where they finished theirs, i would do well, but it turned out better than well, freakish is a more applicable word for it! P.S. all flow figures quoted above were taken on a Superflow-110 @ 10".

Posted: **Mon Sep 14, 2009 12:11 am**

Larry, in regards to the construction of a flow-seperating, hump on the port roof; Would you want it to be like a fish-hook shaped mound, rising from the front of the port mouth centre, running back along the roof ending at the SSR-floor area? Or a mirror image of the floor shape?

Posted: **Mon Sep 14, 2009 7:25 am**

Posted: **Mon Sep 14, 2009 4:35 pm**

I havent flowed it without the valve in the head, but i will, should give me an indication of where any remaining restrictions may lay in either the port or valve area. The throats have been reamed to about 86% of the valve size but, im waiting for my 'junk' head to be cleaned up so i can section it and see how close the water jackets are in this area. If youve seen the sectioned V8 pics i posted (i'l post some for chev too) you'll know this area can be surprisingly thin in most heads, so until i know for sure what mine looks like i'm reluctant to open the throat any more.

Posted: **Tue Sep 15, 2009 12:30 am**

I managed to find an original, untouched 9 port head recently and had intended (wrecker said it was poked!!) to section it up for study, but after the reconditioners said it was 'good to go', i decided to start from scratch and rebuild the head using the new flow-bench! Here are pics of standard ports, valve-seats & chambers before i start! I will post stock flow figures of "this head" in next few days! :;):

Posted: **Tue Sep 15, 2009 12:32 am**

Sorry, couldnt link both pics together!!

Posted: **Tue Sep 15, 2009 6:13 pm**

Individual runners this time I see. How thick is that dividing wall? Is it hollow and full of water?

If you can post the required engine data, I'll run it through PipeMax and another app for you. Let's see what comes out.

Edited By larrycavan on 1253052905

Posted: **Tue Sep 15, 2009 9:33 pm**

No, they are not individual runners, this is the same head, stock standard, before any modification!! Compare directly to my pic at top of this page!! :p

Posted: **Tue Sep 15, 2009 10:42 pm**

You still have more to go.

12 ports make about 275hp, The small CSA restricts it for racing
9 ports make 300+hp but at a higher rpm and are faster in Group Nc

I wouldn't use that head, go for a "H" closed chamber head.
Get it cracked tested before you start, they sometimes crack through the exh.

This is the serious head for Holdens

claims of 400hp

Posted: **Wed Sep 16, 2009 2:41 am**

I like that head much better then the one you just got clean.
More then the intake chamber, you can tell the intake valve from the exhaust. Intake is Much bigger.

Not that i really know any thing, just :O

Tractorsport Flowbench Forum Archive

Holden red6 siamese-port head