Hi guys just picked up a set of heads and will be getting some work done to them over the next few months. just wondering what you guys would recommend doing and what it will do for the car/engine.

thanks in advance

Hi guys just picked up a set of heads and will be getting some work done to them over the next few months. just wondering what you guys would recommend doing and what it will do for the car/engine.

thanks in advance

port, polish, deck, cc chambers, remove hotspots, hot cams, good springs, larger valves (custom) (http://www.bundy.com.au/map.html)

any idea where it can be done locally around Newcastle/central coast area

cheers brad

as i said on the phone, put a 3.5 in put 10.1 CP pistons, peen the rods with ARP bolts flow the heads with a HUGE cam and tie it all up with a ECU of sorts. should get around 180+ easily

We could've discussed this over drinks! lol

We could've discussed this over drinks! lol

damn straight!! Only issue with modding our beasts is a lot of it is new to a lot of performance guys so they are only going off the top of their heads. I wouldn't recommend sending the heads to someone who is used to doing 2 valve pushrod dinosaurs, but to someone that handles multivalve engines like evos and the like.

I know we dont have performance cars like evos, but these people will have a better understanding of the way the more modern technology works. :D

Precisely what you do to the heads depends on what sort of camshaft profile you are building around. For a "budget" serious NA build I would be looking at:

- cams around 260-270 deg duration, .320-.325" lift and lobe seperation of around 110 deg.
- DOHC Pajero 10:1 pistons
- Stiffer valvesprings
- Heads flowed to suit the cams - You'd probably call it more of a mild port job at this point.
- Piggyback ECU. Yes I know this is a bit controversial, but I'm of the opinion if you wanto keep costs down, a decent piggyback will do the job just fine.
- Walbro fuel pump, maybe adjustable FPR too. Though i recall Cthulhu made 207wkw and still had the factory fuel pump, so you can probably get away with the factory pump if you choose to.

Budget for new bearings, head gaskets and associated bits. Now IDEALLY you'd get the rods resized and shotpeened, and ARP rod bolts fitted for peace of mind. But the choice is yours, you have to draw the line somewhere, and I've been lead to believe for this sort of build the stock rods/rod bolts should hold together just fine. Ctulhu had 207wkw, was most likely revving a bit higher than this build would, and had no durability issues. But that's not a guarantee, the choice is yours.

I need to to give credit to Jasons VRX, as those cam specs and much of what I've learnt about NA builds for our motors are thanks to him. Basically the above build emulates one of his earlier builds with a few minor differences (he was able to re-map the factory ECU, went the extra mile with a bit of bottom-end strengthening).

His build made 170wkw, so that's the sort power figure I would be expecting. But perhaps more telling is he did a 1/4 run and had a trapspeed of 170km/hr - 170wkw might not sound like that much, but that really is quite quick, and I'm his wheel kw figure obviously isn't "happy".

EDIT: Bollucks, just realised your are talking about the 6G72 motor, not the 3.5L 6G74. Nonetheless, if you are sticking to that most of what I've said should still be applicable, except the cam specs I'm not sure about. Would be interesting indeed to see someone do a serious build with the 3L motor, though I'm not sure how much that 0.5L less capacity will hurt.


port, polish, deck, cc chambers, remove hotspots, hot cams, good springs, larger valves (custom) (http://www.bundy.com.au/map.html)

AFAIK larger valves really aren't necessary, jasons VRX's last build made 302 flywheel kw and I believe the valves were not upsized.

We could've discussed this over drinks! lol

yeah tomorrow night!, lets go!

ok, heres the easy on this greasy.

Spoke to Mr B today(those in the know will know who i am on about).

Basically, ignore what i have told you before, and do what i'm about to tell you. :D
The magna ports are pretty big already so porting will not net many, if any gains at all. What you should probably do is the following:

modify the base curve of the cam lobes
shim the lifters to compensate for the additional lift
have the valves and valve seats machined(you will pick up some extra lift there too)
open up the combustion chambers around the outside of the inlet valves


i think there was more, but that i can learn from reading!!

interesting, wonder if its what he is planning to do with the heads he purchased

AFAIK larger valves really aren't necessary, jasons VRX's last build made 302 flywheel kw and I believe the valves were not upsized.


Standard valves are fine on a NA motor, but if your running forced induction then fitting larger exhaust valves is a definate recommendation from me, due to the extra amount of air being pushed in by the blower (its getting forced in so the stock inlet valves are fine but bigger exhaust valves are needed to help get the larger mass of burnt gases out).

As a note the stock valve sizes are good enough on a set of ported/releived/CC'd 4valve magna heads to flow well over 450hp@480thou lift on a NA setup.