Tickford 6 they are fantastic pictures and detailed information. Much appreciated.

Love this thread, so much information. Thanks to you guys contributing.

Autospeed did an article on porting and compared an EB head to an AU head - i think they said that the AU head had the better potential for porting or something along those lines. Probably because the ports are supposedly smaller in the AU head, you have a better base to start from with regards to shaping and opening up areas of the ports as there would be a little bit more alloy to work with from the get go. With the earlier heads the ports are fairly large already, so there isn't as much alloy to work with, but there is still room for improvement. By the way the 91AA head is just a std EB2-early ED head, not XR spec

The way i see it, it doesn't really matter which head you start with. If heads are going to be ported the port shaping/sizing will end up similar anyway.

The reason the early heads aren't as good for porting is that in some places there is no metal where ideally there should be. They limit you to a less then ideal finished port shape.

so an ef xr6 head and cam p/p (port and polish)would ultimately be no better than a p/p standard au head and mild cam? or turn out roughly equal...without major working, bigger injectors, shave, j3, blah blah that is.. was always under the impression that the ef xr6 was good because of the bigger valves and large ports...more fuel, more flow, and less work needed........plus i've got one sitting in the garage!!! bear in mind i'm not after 2000rwkw! just good solid, responsive driveability and easy tuning...
was hoping for (or should i say: told to expect!) a noticeable improvement with mild p/p and stock cam on ef xr6 head, with good extractors and better air intake... am i fooling myself?

After looking at the AU cross section, I think I will have a go at the sleeve idea you mentioned in another thread Tickford_6, straightening up the port, might get a junk head from the wreckers and have a play.

Taken to the last possible 0.1CFM of flow, the standard head will do just as well as the tickford head that is based on it.

If all you after is bit of power then use what you've got.
Valve sizes are 6 and half a dozen. each head will accept the same size valves, it's just tickford heads have some of the work already done.
Also keep in mind that you can only get 41mm (tickford size) exhaust valves with the narrow AU stem. which means if you old PRE AU tickford valves are stuffed you need to fit new narrow stem guides.
If you are after every last possible KW then start with an AU head.

All good stuff guy's. Ive had a go a few times on chevs & a 253. Never took too much off, pocket port and clean up really, with 3 angle jobs on the valves, inlet valve blended, guides etc. The end results were always improved throttle response and a big gain in the mid range, all good...

...However my reason for the post was that I have a very good book on porting that would answer a lot of questions raised on here......

Title; "Practical gas flow", Author; John Dalton, ISBN# 1-855-20564-5

It shows you how to build your own gas flow bench what to consider and how to go about it. You build your own plaster cast models of your ports and carve up (port) at your leisure, checking against your own calibrated flow bench to see whether you are kidding yourself or not. It is calibrated in inches of water rather than mercury so is much more sensitive to pressure / flow changes.....He also shows the what do to do and what not to do, I notice that the head that was sectioned shows some of his port ideas.....

Have I done it? No.....

But I have built up most of the parts for what is required, just have to put it together really. I have tested the roughed up model, pulls almost 3 meters of water (nearly water vapour point) and the suction unit has to have the vacuum bled off a fair way to simulate calculated port gas speed, at Max intended RPM.......Just a matter of finding the time and project really.............

With all the s**t threads at the moment I think it is time to bring this document back up.

What heads have people cc'd in stock form so far? I'm doing an engine rebuild very soon and mainly interested in all the AU heads (i.e. standard, xr, vct, dedicated gas).

i've had alot of other stuff going on lately and havn't really touched any of the heads i have.

I have started collecting the parts to build a half decent flaoting pressure flow bench. and i was looking at buying a 'Flow quik' (use google).

I can cc the chambers of a VCT head for you, I just can't promise that I'll get it done this week.

I've also spoken to my machinist, and he is confident we can fit bigger intake valves, he will also fit larger seats if need be.

Yeah whenever you get the chance that would be awesome.

You haven't happened to have sighted an AU e-gas head off the engine have you? So many differences of opinion on whether they are different aside from valve seats...

I havn't seen the inside of an E-gas head, as far as i'm aware the AU egas motor had the same compression as the regular engine, so i couldn't see why they would be any different.

The BA egas got more compression but they did that with the pistons

Fof some reason I am lead to believe that all AU heads are identical across the board. Whether it be base model, tickford hp, tickford vct or egas.

Just to keep this thread going. Here's a little on AU stuff and the fitting of 49mm intake valves.

Below is AU VCT vs AU1 head. note the AU1 head has ridge protruding into the port near the intake valve.




The next photo show the AU1 head with the intake seats cut to take a 49mm intake valve.


the next two show the same head with finished port. I'll have some photos of the removal process of the ridge by the weekend




Valves for the above head were bough as blanks and the finishing work was done locally.
Good news is I'm investigating having the 49mm valves made and delivered ready to run.
Manley have some blanks that will work very well
The 7mm stem version will be from the severe duty range and the 8.66mm stem version will be from the race series range.

If this all works out for me I'll ba able to supply a 41mm exhaust valve in the severe range for the 7mm stem and in severe and extreme for the 8.66mm stem.

What this also means is if you are running a regrind cam we can have the valves made longer, this eliminates the need for adding extra shims to the rocker tips.

Looking like the valves will come in at about $60 each, But I still have some stuff to sort out before it final.