rocklord":1rtgy19y said:
I need some specifications for my AU 4.0 engine to calculate the static compression ratio if I install a Tickford 94DT head. I've been told that the Tickford 94DT head has a chamber volume of 60cc, whereas the AU head is 65cc.
I will cc the Tickford head after machine work to be sure. I want to keep the CR below 10.0 to be able to still use 93 Octane unleaded. I don't want to pull the current AU head until I have everything ready to install.
What is the stock compression height (CH) of the AU 4.0 piston?
What is the recess volume of the stock AU piston?
I've seen websites stating compression heights of 1.208", 1.215", and 1.2165".
Very confusing.
The other question I have is the stock AU block, or deck height.
Doing a search of other forums I came up with a post stating that the deck height is "somewhere" around 9.2-inches. Another website stated the deck height as 9.22-inches.
I don't have access to local (Australian) reference material so I can't look it up.
So I'm wondering what the stock deck height of the AU block is?
Any help is appreciated.
I'm not, nor ever will be, and OHC man. The metics, they screw you over....But
9.22 " for sure.
To get more piston choice from German pistons from Mahale (simlar to why pistons from from Subaru, Chev's GM 4200, and Cologne 2.8/2.9 V6's ran sub 3.736" pistons sizes). So they are 48 thou under 250 pistons. Or 104 thou under 305/229 Chev pistons.
If you over bore, you can then use pistons like the similar CH 3.3 or 3.7 Mopar pistons, they are 1.22 or 1.26 from your past info, and 6" Chevy rods are what I'd use.
The websites list egg head numbers, which need converting with a "Divide by 25.4" to get PROPER UNITS.
And Liters, um LitREs.
British Gallons rather than proper US Gals.
https://www.zazzle.co.nz/a_metre_is_3_2 ... 6869393890
And Aluminum, um AluminIum.
And KM/H which they call Kpa, drongos,, i'll never forgive um forit.
I like and have gotten used to metrics, the FRENCH ARE COOL, but its just another smack over for the grey matter, and its never nice having to do the change overs. Same with cc's,
DIN kW
DIN Nm
and torque tightening conversions, and the boron head pre AU 2 cylinder bolt stud issues and replacement Mahale pistons, CP parts and piston rings variances since Repco listed ACL as a sold off company has made the information gathering a proper SH!+.
Historic changes before AU.
Pistons varied. PRE el 2 Rods were generally 5.88 +/- .005, but the last EL's were EL2 Intech Half breads with AU internals, long rod 6.060" engines with the 1.205 clearance target to get a zero deck.
For a zero deck, and the blanket old 250'S 3.91 crank stroke they used till the day of the 4.0 I6 death, the idealised piston with 5.88" rods would be 1.385", and 1.205 with 6.06's.
The pistons and valve gear changed throughout the course of SOHC life, and the heads were reprofiled many times,
Just like the X-flow, had about 9 different head castings with "no two alike" machining, the SOHC had the same variances.
NB//
Now I haven't looked/checked my bookes, because today I've been working the last 12 hours after 8 hours of truck driving...
but , IIRC, I can't remember, but the 5.6 T3 stock bore "347" has the same piston deck register as the AU to BF/ FG, something like 1.163" pstons, a 42 thou shortfall to the dry deck block.
CP pistons forged are the ideal compression height becasue these engines like to rev, and the block and cranks do flex a little.
For the AU, they changed the rocker arm ratio too, from 2.0:1 to 1.8. There were pictures on the net here by Magnus, showing the head casting changes, but I won't be able to find that since I'm bussy again....
I probably won't be back for a L-O-N-G time.
You'll get the answers you seek. Join and go find and hassle Aussies on there forums if you are eligable, and keep asking them. They are salt of the earth, and there knowledge is encylopedic. My knowledge base is from the ardour of the Australian Information highway. Rupert Murdock and Kerry Packer have trained the smartest "journo's", but they don't ask "Hod Rod" tech questions. Kevin Bartlett at ACP Mens "Street Machine" is the man for tech info.
Don't worry about forum hazing, Aussies play Oz Rules and Cricket is there national game, and for non Aussies, like (Kiws and Yanks and Canucks), we've just gotta undestand the culture. Its just the ignorance that comes from unabashed love for there Geelong In Line Sixes!
Kiwi culture and Aussie culture is largley the same, but there are some really ingorant Kiwis around and the Kiwi media is unhelpfull.