Unequal camshaft duration 4AGE

[Just1n_mc]

What if I were to run a 272 9.2mm intake cam with a 272 8.5mm exhaust cam. Would the lower lift of the exhaust cam have a similar effect on the exhaust flow? I see the factory setup runs 7.97mm intake and 7.6mm exhaust lift with equal duration.

[101gze]

Even Toda recommend a larger intake with their cams from 264/256 up to 288/272's and I'm sure both companies have spent ample time testing what does and doesn't want work.

Where do they do that?

What mods have you done to the engine? is it in pieces, are you looking for a drop in?

[Just1n_mc]

In this thread they do: http://www.toymods.org.au/forums/thr...ock-Bottom-End

There are other threads around as well quoting the same thing from Toda.

I rebuilt the motor a couple of years ago with ACL race bearings and ARP bolts. I've since bought a head that's been rebuilt with Toda springs and has had some head work done to it and I've got a TRD gasket to bump the compression. It'll be running a Haltech Sprint 500 For management. The car already has a full exhaust and a Tom's carbon fibre plenum with trumpets.

[101gze]

Yeah, Adrian was Toda Australia's rep. Thats a lot of difference in stagger IN/EX. Toda Japan lists part numbers relating to equal IN/EX cams.

Whilst I posted info on why an excessive EX duration might be less than beneficial, I could state the same on too little EX duration, for the exact opposed reasons.

You seem to be trying to find the perfect cam.

There is no perfect cam, there is only a "well suited cam" and that can ONLY come from designing the cam from flow bench numbers.

That is why heads are flowed, to send the numbers to a cam designer in order to engineer a cam to suit the flow characteristics.

If the head is off the engine, you may want to consider having it flowed. That will give an idea of what cam would be best suited.

You did not mention what pistons you have, pistons? thats the other factor in cam choice.

[Just1n_mc]

So what do you think about the 272 9.2mm/272 8.5mm setup?

I'll get in touch with the guy who built the head and see if he has a record of what it flowed when he built it.

The pistons are stock so I should be around 10.9:1 static compression with the TRD headgasket.

[101gze]

If stock ST pistons you will need to check with the supplier to see if they will clear with VVT operating. I would suggest an equal duration should give you enough exhaust.