Hi guys,

Anyone who has or knows a lot about the specs on AU II XR8 heads please help.
I'm looking at doing heads and cam on my AU II XR8 ute.
I want to bump the comp up a bit.
What head specs would people recommend?
Looking at 62cc combustion and 195cc intake runner
And want to run a comp cam.
What combos work well and what have other people run?
Any help would be great.
Thanks guys

I'm in the same boat as you and have been doing a lot of research on V8 engine building and H/C/I combos. I'm certainly no expert but here's my 10c worth.

Have you looked at the AFR or the Trickflow Twisted Wedge heads? Some guys are importing them from the USA, which is cheaper than buying them here. With the 195cc intakes, are you planning to use a big cam and run the engine at high revs? IMO 165cc or 175cc would be better suited to a 5.0L street engine. Edelbrock do an entry level alloy head but these have had mixed reviews. Depends on your budget...

I've just bought a Comp Cams XE264HR-14 cam from the US to use with 1.72 roller rockers. This is supposed to be good for low to mid range torque (and I don't rev the engine over 5500rpm anyway). The next one up is the XE270HR. The cam you choose is dependant on where you want your power.

Don't forget your intake manifold. Better flowing heads and a more agressive cam can be choked by a poor flowing intake manifold. Instead of buying individual components, you could also buy a Trickflow H/C/I package.

Thanks mate!
Seeing it's a stock bottom end I probably wouldn't
Take it past 6000rpm so a nice mid range cam.
Really want to put more comp in so I don't want big heads. Smaller ports and smaller cc.
I have looked at the AFR heads. I've found cheap a** heads that aren't quite as good but I've
Heard good things about them. They have nice thick walls, unlike edelbrock.
I've also heard the standard explorer manifold flows good for a mild street engine.

If your replacement heads have the same combustion ccs as the GT40Ps, you could take 20thou off each and be OK. But, with valve reliefs in the pistons already, it would be a good idea to check the piston to valve clearance first.

I read somewhere that the stock Explorer manifold was only good for 200cfm, which is OK for stock GT40Ps. Of course, it needs some work when you go to aftermarket heads.

With the cheap heads, there's been some comments about head bolt holes not lining up and poor castings. Then you wonder if the valves, springs and rockers, that come with them, are going to have problems.

Crap. I'm trying to do it on a budget. It's only a daily I don't want to throw $$$ at it.
Have you done your setup or still getting parts?

What's your budget for the upgrade and are you planning to do the work yourself? The costs start to balloon out when you open a V8. I'm collecting parts at present. Just bought a degree wheel for the cam install. I already have:

- Comp Cam XE264HR-14
- Crane beehive springs
- Scorpion 1.72 roller rockers
- a Chinese copy of the Edelbrock Performer manifold
- a phenolic spacer for the the above
- Raptor SC and WTA bits
- ceramic-coated Hurricane Headers fitted with a 3" exhaust

I considered buying alloy heads but ATM can't justify the cost for weekend driver. Most people will tell you to ditch the GT40Ps in favour of alloy heads. If you can do the porting yourself, you can get some good gains in flow. In your case, you would need to buy another set of heads to work on while you're using you car. One professional guy in the US was able to get 248 cfm from porting and bigger valves. That's beyond what a back yard mechanic like me can get without a flow bench. The heads can still be shaved to bring the compression up.

If you're lucky, you might find suitable secondhand heads and a cam. I've been looking for months and they're rare on eBay and Gumtree.

You will also have to factor in replacing the timing chain and gears, check pushrod length & replace them if required, a VRS set, maybe a new oil pump & shaft, sump gasket, front and rear crankshaft seals and welsh plugs. I'll be doing these things with the engine out.

A decent combo would be

either a E303 or a comp cams XE270HR
set of AFR 165 renegades
1.7 RR's
Crane or Isky valve springs, I would lean towards the Isky's
You can easily get away with the Explorer manifold, they are a pretty good unit
Phenolic spacer is a good purchase, but get the non metal/non plastic ones, they either transfer heat or crack under engine harmonics

That being said, The 40p's are pretty much the best of the iron heads out there, a bit of a tickle and a larger exhaust valve will see good results too.

This is the combo I was considering before I decided I was time poor and got an engine builder to screw a 347 together for me. I went in with no real budget, but didn't want to spend a fortune. It will be in the car running for under 10k. Seriously consider what your budget is.

V8's cost money, it costs good money to pull honest, consistent power out of them too.

I'm in the same boat re wanting to upgrade the heads/cam on my XR8.

I've got a query re tuning after the mods.

When do you get to the point where the stock ECU can't adapt to the changes?

I've read that it can quite easily cope with better breathing in terms of CAI and better headers, but what about heads and a cam?

In terms of my situation, I've got a stock AUIIXR8 with Tri-Y Pacemakers, but am about to pull the trigger on a set of AFR 165cc heads and a cam in the 2000-5500rpm range (re the cam, that's the hold up atm, trying to decide which brand and the exact specs).

Given the lack of info I've provided in relation to the cam, will I need to get a custom tune after these mods?

tuning wise its fine with exhaust, cai and even heads. its not until you change the cam where tuning is required...but that also depends on the cam you fit also...

I haven't seen any information that draws the line on when to start using a chip, or get a flash tune. I read through a few of the Mustang forums and guys were saying the 5.0L ECU will cope if LSA stays at 114 (probably for cams up to 0.50 lift at a guess).

If you can get AFRs for the right price, grab them. Have a look at the cam specs for a Comp Cam XE270HR, Crane E303 (2030) and Crow 151550.

Ahhh EFI! Not like the old days when you could just throw a bigger carby on a change the jets!

Haha, bloody oath. Used to be so much simpler and diy! I know there are guys out there doing their own tuning with quarterhorses, but just seems a bit more daunting than the old carb.