AU I6 sports camshafts - interest?

[Sox]

Evening all,

I have had a JMM DEV5 camshaft to suit an AU I6 in my shed for a number of years.

I've just had it clocked up by a local cam grinder, and he felt it was a pretty decent thing.

I'm getting a couple of these made for myself, and am wondering if anyone else is interested in these?
At this point in time, a one off is near enough to $500, but if we can have a few more done, then the cost of the master can be absorbed easier and individual costs will go down.

As most would know, JMM closed down a little while back, so this is a good opportunity to resurrect a good grind which was able to make around 170rwkw in our trusty I6's, while still being very well behaved and perfectly streetable.

Heavy duty valve springs and a vernier gear would also be highly recommended, but not mandatory.
Headwork would also be advisable to get the best from this cam.
No shimming of the HLA's is required as these are billets, using a standard size base circle.


This has been approved by AFF admin.

[Sox]

I just stuck one of these in my AU Tickford RTV ute.
It has some minor porting on the head, extractors, 2.5" sports system and XR ECU.

I pulled a XR cam out and plonked this in, the difference is quite decent.
Lost next to nothing down low, picked up a healthy amount in the midrange, and bucket loads up top.
Pulls cleanly and powerful to the cut out.

I didn't change the springs and set it at '0' on the vernier gear, haven't thrown a clock on it yet.
It idles lumpy, but doesn't hunt or stall.

A good result.

[OffRoadFalcon]

I'd love to do some of this kind of work to my wagon at some stage, I do feel it could do with some more oomph. Just need the $$$!

[Sox]

Originally Posted by OffRoadFalcon

I'd love to do some of this kind of work to my wagon at some stage, I do feel it could do with some more oomph. Just need the $$$!

The main benefit with this particular cam is there's no need for a tune.
They run fantastic with just headers and a sports exhaust.

Obviously with head work and a tune they improve further, but as said, it's not mandatory.

[OffRoadFalcon]

So I could really just chuck it in and I'm off? My questions may seem stupid, engine work is still very new to me.

I have a 2.5" exhaust, and would like to also get my hands on a set of extractors and high-flow cat. What kind of extractors do you have?

[Sox]

Originally Posted by OffRoadFalcon

So I could really just chuck it in and I'm off? My questions may seem stupid, engine work is still very new to me.

I have a 2.5" exhaust, and would like to also get my hands on a set of extractors and high-flow cat. What kind of extractors do you have?

Yes, you could chuck it in without anything else and get a pretty good gain.
A vernier gear is a very good idea to go with it as then you can clock it up properly. Although I haven't done it in this car myself yet.

2.5" exhaust will work well, and extractors and cat will improve things further still.

I have a couple sets of the old JMM extractors which aren't available any more.
These have 1.5" primary pipes which is important to these I6's for road use.
There are plenty of brands with that size pipe around.

[OffRoadFalcon]

Very interesting, thanks heaps mate.
The cam definitely sounds like something I'll be interested in doing sometime.

What difference do the 1.5" primary pipes actually make?
I've read about Tri-Y extractors being good for low end torque etc?

[Sox]

Originally Posted by OffRoadFalcon

Very interesting, thanks heaps mate.
The cam definitely sounds like something I'll be interested in doing sometime.

What difference do the 1.5" primary pipes actually make?
I've read about Tri-Y extractors being good for low end torque etc?

1.5" primary pipes is pretty much the best sized pipe for the widest spread of power for road use.
Using bigger primary pipes will allow higher HP at higher revs (over 6000), at the expense of power down low.
Smaller pipes keep velocity high.
The balance must be made between high velocity and little flow restriction.
1.5" is the sweet spot.

Most headers for the I6 are tri-Y.
Tri-Y headers provide a wider spread of power across a larger RPM range.
They also provide better partial throttle response.

But they do need to be made well.
JMM made the best ones IMO, they had 1.5" primaries, 2" secondaries, and 2.5" outlet.
What made them a little better than most was the length of the secondary pipe, this provided a noticeable increase in midrange power.

I have modified other brands to emulate these headers with good results.
I haven't found a header with 2" secondaries though, which will be ok for milder engines.
The JMM pipes were good for over 175kw at the treads.

[OffRoadFalcon]

Thanks heaps for that mate, that advice is really good to have.

Yeah I'm definitely looking for the power to be more at the lower end, so I will have to find some with 1.5"!
It's a shame the JMM ones aren't available anymore, sound like the best option for me!

Over 175kw is my aim for the wagon, somewhere around there would be a nice place to be I reckon.

[Doreturnonfoot]

Stick to the quality headers - the elcheapos have thinner flanges and secondaries
Sox was thinking about a cam change - not sure if you had any spares for purchase? Btw for interest do you reckon you can post a pic of the jmm headers.