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Yella Terra 12 port Aluminium head for Holden straight 6 motors

Started by _BW Yella Terra_ , May 27 2014 04:41 PM

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#1 _BW Yella Terra_

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Posted 27 May 2014 - 04:41 PM

Hi Everybody,

This is a rundown on the YT head for the straight 6.

I know some of you are going to ask questions for which I don't have answers, but I will do my best.

Yella Product Release

NEW HOLDEN 6 ALLOY HEAD

Suitable: BLUE/BLACK and RED ENGINE 6

YELLA TERRAS LEGENDARY ALLOY 12 PORT HEAD IS BACK !!!

The Yella Terra Legendary alloy 12 port head to suit the Holden Straight 6 has been re introduced into the Australian Market. Revised port designs that flow over 30% better than that of the factory 12 port heads with potential for much higher flow figures when professionally ported. This dramatic improvement is due to the development of the taller, wider ports, improved “short turn radius”, larger valve throats and bowls as well as streamlined valve guides, giving huge increases in port volume and airflow efficiency. Half the weight of as cast iron head, these heads are fitted with 2% nickel iron inlet and hard nickel alloy exhaust valve seats.

The lightweight alloy casting features re-designed water jackets for much improved head cooling. And is available with a choice of 56cc combustion chambers or CNC profiled 72cc low compression chambers for forced induction

This new performance product will transform your vehicle with more free revving power, improved performance and reliability with the following features:

• Excellent Flow figures:..240HP potential out of the box

• Average of .250” port wall thickness for custom porting

• Over 60% lighter than factor Iron Heads

• Flow over 30% better than the standard Heads

• Holden exterior design with totally revised ports and water jackets for improved cooling, reliability and performance.

• Both Standard Compression and Turbo Versions

TECHNICAL SPECIFICATIONS

BARE HEADS

Material 356 Alloy Heat treated to T6

Chamber Volumes Standard Head- 56cc Turbo Head 72cc

Inner Runner 82cc

Exhaust Runner 71cc

Intake Valve 1.740”

Exhaust Valve 1,480”

Valve Guides K Liners

Valve Seats

Inlet Cast Iron 1.812”x .250”

Exhaust Nickel Chromalloy 1.625” x .250”

Spark Plugs Tapered Seats

Deck Thickness 0.450”

Installed Height with Std Valves and .060” Valve Spring Insets/Shims 1.520”

Spring Seat OD. 1.250

There are a few options for rockers on these heads, stud mount street terra shaft type and our platinum range.

ACH 33C74

Bare head

List $ 1705

Trade (requires abn) $ 1619.75

ACHA 33C56

Assembled head

$ 2310

$ 2194.50

ACHA 33C56R

Assembled head with street terra

Roller rockers

Hydraulic $ 2585

Adjustable $ 2695

List and trade same price, already discounted as much as we can!

Platinum race rockers

Variety of ratios

$ 1101.05

$ 935.90

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Sorry the table of prices didn't work quite right lol

Edited by BW Yella Terra, 27 May 2014 - 04:43 PM.

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#2 _BW Yella Terra_

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Posted 27 May 2014 - 05:04 PM

Also, the prices listed here are our trade and list prices,

So if you were too ring one of our distributors like Rocket, Precision international, Nasons or VPW and quote these part numbers, you may find you can save a bit more on whats quoted here

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#3 _Bomber Watson_

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Posted 27 May 2014 - 05:05 PM

THanks for that.

Do you have an air flow curve for the inlet you could post up?

Are there any plans in the future to make one with a closed chamber around the 46cc mark to make them suitable for a hot aspirated engine?

Cheers.

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#4 warrenm

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Posted 28 May 2014 - 12:04 AM

You beat me to it Bomber, I was going to ask the same question. Being alloy, you could always weld the chambers up, but that would add some expense.

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#5 _Bomber Watson_

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Posted 28 May 2014 - 12:22 AM

Grumpy Humpy runs one with welded up chambers, but yeah from what i gather by the time they were done welding, re machinging the chambers, new valve inserts, new valve guides, and porting to acutally make it work the price was not far off a JZed, and its not hard to work out which you would choose out of those two.

Cheers.

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#6 warrenm

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Posted 28 May 2014 - 12:33 AM

Is the inlet valve in the same location as the Holden heads?

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#7 looznugtr

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Posted 28 May 2014 - 06:46 AM

You beat me to it Bomber, I was going to ask the same question. Being alloy, you could always weld the chambers up, but that would add some expense.

yella terra once apon a time did make a closed chamber head and they are out thier if you look. I have 2 of them

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#8 _Bomber Watson_

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Posted 28 May 2014 - 07:36 AM

Yes but we want new ones.

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#9 warrenm

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Posted 28 May 2014 - 07:36 AM

yella terra once apon a time did make a closed chamber head and they are out thier if you look. I have 2 of them

Bragger.

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#10 _BW Yella Terra_

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Posted 28 May 2014 - 08:13 AM

THanks for that.

Do you have an air flow curve for the inlet you could post up?

Are there any plans in the future to make one with a closed chamber around the 46cc mark to make them suitable for a hot aspirated engine?

Cheers.

I will have a dig around in the files, but at this stage no I don't. I don't even have flow figures at .5 or anything. I should have some soon though, as we have a head being ported by Eddie Woods just to see how far the revised design can go. So after that is finished I will have before and after flow figures.

So far as CC goes, they are supplied at 56 in an assembled head, 72cc in an assembled low comp version or 74cc as a bare head.

There is room to skim more off and decrease the chamber size.

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#11 looznugtr

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Posted 28 May 2014 - 08:14 AM

Bragger.

Yeah I know. I got lucky.

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#12 _BW Yella Terra_

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Posted 28 May 2014 - 08:14 AM

Is the inlet valve in the same location as the Holden heads?

Yes, all stock locations.

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#13 _Bomber Watson_

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Posted 28 May 2014 - 09:43 AM

So far as CC goes, they are supplied at 56 in an assembled head, 72cc in an assembled low comp version or 74cc as a bare head.
There is room to skim more off and decrease the chamber size.

That wasnt the question.

The question was if you are looking ti make one with a closed chamber around the 45-46cc mark out of the box.

The open chamber 56cc head you offer is unsuitable for a high performance aspirated engine without spending thousands of dollars on welding and re machining.

I would not be confident milling the head down that far, and the closed chamber seems to perform better anyway.

Cheers.

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#14 _BW Yella Terra_

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Posted 28 May 2014 - 04:58 PM

That wasnt the question.

The question was if you are looking ti make one with a closed chamber around the 45-46cc mark out of the box.

The open chamber 56cc head you offer is unsuitable for a high performance aspirated engine without spending thousands of dollars on welding and re machining.

I would not be confident milling the head down that far, and the closed chamber seems to perform better anyway.

Cheers.

No we wouldn't offer that small of a chamber. And you are right, machining that much off would be too much, we do leave a bit on there though.

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#15 _BW Yella Terra_

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Posted 28 May 2014 - 05:03 PM

There is a possibility that in the next run/batch of heads that we will be looking at reintroducing the closed chamber design, as we can always machine it out for the bigger chambers.

But this is just whispers around the engineering department atm, no promises.

49cc is the smallest you can go with the current design on machining alone

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#16 _Skapinad_

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Posted 28 May 2014 - 05:11 PM

You will make a couple of new friends if you do it

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#17 _Bomber Watson_

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Posted 28 May 2014 - 07:06 PM

YOu would also want to do a bloody big run of them as they will sell like hot cakes.

Cheers.

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#18 N/A-PWR

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Posted 28 May 2014 - 07:16 PM

This is going to be an Interesting Read,

I agree with DJ, we need 44cc Chambers

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#19 _BW Yella Terra_

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Posted 29 May 2014 - 08:46 AM

Ok, well I will flag it too them, the current design is still selling like hot cakes, so management will take some convincing.

Maybe when it get closer I will get everyone that is willing to purchase one to e mail me, and I will use that as the driving point for the project

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#20 _Ned Loh_

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Posted 29 May 2014 - 11:49 AM

Hi Brenton,

Just out of curiosity how many heads would it take for YT to be interested? Anyway, put me down for one if the 'GMH-T closed chamber head group buy' gets off the ground.

Very interested to know where Eddie ends up on the maxed out head. Flow figures and pics would be brilliant. What application is the engine being used for?

Have the YT platinum rockers design been fixed to give a better/proper wipe pattern on your alloy heads?

& BTW decking heaps off the head isn't a great way to increase compression on these engines as you can run into valve to block issues (depending on the combo).

Apologies for all the questions. Enough out of me. Back to the salt mine...

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#21 _Bomber Watson_

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Posted 29 May 2014 - 12:28 PM

Yep i would certainly grab one with the small chambers, maybe two depending on spare cash at the time.

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#22 _BW Yella Terra_

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Posted 30 May 2014 - 04:52 PM

Good to hear. Will put it too them. Hopefully will get the ball rolling. We only just finished a batch though, so will may be a while.

I don't where the end application for the ported head is, not even sure what stage it is at with it all ATM. Will ask and let you all know monday.

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#23 _BW Yella Terra_

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Posted 30 May 2014 - 04:58 PM

Have the YT platinum rockers design been fixed to give a better/proper wipe pattern on your alloy heads?

Good question, this has only really been an issue with the 1.7 ratio set, which has been put on hiatus until its sorted. I believe people don't have an issue with the 1.7 on longer valve applications?

As for the other ratios, (1.5, 1.6 & 1.65) I have not had any negative feed back, unless people are keeping quiet.

So yes, the 1.7 is under review.

No date on when it will be done

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#24 N/A-PWR

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Posted 01 June 2014 - 10:38 AM

Hi Brenten,

Will Yella-Terra make another 9 Port Head, or is there no need.

It was just that the original 9 port heads allowed port porting before the water jackets became an issue compared to the 12 ports.

I also see that the new YT 12 port design that you have stated, have 250 thou walls.

The 9 Port HQ head I have, has been ported 12mm wider ( 2 x 250 thou ) than standard, and 4mm higher ( 165 thou ),

which makes any standard motor a Race engine with a big cam and holley.

Edited by TORYPOWER, 01 June 2014 - 10:41 AM.

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#25 _oldjohnno_

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Posted 01 June 2014 - 11:19 AM

The 9 Port HQ head I have, has been ported 12mm wider ( 2 x 250 thou ) than standard, and 4mm higher ( 165 thou ),

which makes any standard motor a Race engine with a big cam and holley.

I don't know if that's the dumbest thing I've ever read but it's certainly up there...