very very generally the cam specs will still apply - i.e. the approximate rpm ranges will be similar (or at least somewhat so). Typically, for a given cam and an engine this size, you'll probably find it extends the useful 'ceiling' of the powerband up about 500-1000rpm higher than the same cam in an engine configured for NA with similar duration/lift.

You generally want to run wider lobe separation to achieve less overlap for the same amount of duration. There are issues as discussed above, but one thing to also consider is that most diy turbo setups, anything which doesn't have equal length exhaust pipes feeding into the turbo (and which aren't the optimal i.d. and length for that matter, they could otherwise be all 'equally' wrong!) - anything without that and you'll typically see (once into decent boost levels) a much higher exhaust backpressure than boost pressure - anyhoo, the more specialised the exhaust to the turbo, the closer lobe separation you can run (relatively) for optimal results. If on the other hand you are running a modded factory cast iron single outlet, then the likely backpressure issue will potentially lead to exhaust being pushed back in, or perhaps more accurately those gases never fully make their way out, and the next compression cycle doesn't have the maximum amount of fresh air/fuel in there as some of the space is taken up by exhaust gases that didn't clear.

Hence the typical (and sensible) advice that if you are starting from scratch, and the exhaust isn't something that has seen a lot of dyno development (and educated guesses with enough experience will also close in on that ideal sizing anyway) or whatever - well in those circumstances, if you are getting a cam ground from scratch, you'd tend to look at about 2-4 degrees wider lobe separation than the same cam for the same engine/size type in NA form. A lot of engines have their own idiosynchrasies (I mean engines of the same family, not each and every a-15!) so precisely what that lobe separation ends up being varies from engine to engine. You'd probably be looking at around 110-112 tops for an a-series, but some dino V8 pushrod engines like a few degrees wider than that. Having said all that, if you already have the cam, I would suggest that whilst there would be some potential to be found with a different grind, it's a tough call to say that it'd be enough of a gain to warrant the time and expense of swapping it out there.

As to the power potential - that's a tough one. It'd heavily depend on what the static compression ratio is (I would assume it's high-ish to suit the fact it was put together with a moderately bigger than factory cam and the fact it was put together as a non turbo build from the start). So that is a big factor. THe other one is which fuel you intend to use. If it is e85, you wouldn't struggle to top 200bhp, as long as you get the fuelling and ignition timing right. On 'regular' pump fuel, it's still a tough call, because you could look at water injection, and or intercooling.

how about you just supercharge it with a cheap roots type unit?

Thought i might chime in on this a large cam does not mean it wont work....its about combination think of the characteristics of the cam N/a the overlap from a wider lobe seperation might not work well on a small turbo designed with moderate airflow at low rpm, but what it can do is aid in spooling of larger turbos buy allowing unburnt fuel to burn in the exhaust manifold like a secondary combustion chamber,as events get quicker the amount lost through overlap is slowed and the larger turbo can easly handle it....problem is this kind of set up moves everything away from being a daily to more a racer style setup as it has reduced torque down low until everything comes on song then its huge and late in the rpm
A big cam and small turbo wont work because the loss in boost pressure will see the turbo working harder to make upfor it, generating more heat as it moves further out of its efficiency meaning less power,the motor wont see its full potential because the turbo wont allow it rev
So the short if your cam isnt overly wild and your turbo isnt too tiny it probably will work fine just higher in the rpm range...
cheers

30/70 isn't an outrageous cam by any means. Just give it a go, I say...

Thanks for the help. Yeah I thought too big with turbo doesn't work that we'll. I will have to ring the cam joint and find out more specs. I had a sheet with it all on there but lost that ages ago. I have already assembled the engine and dropped it in and got it running so I'd rather use the cam I have if possible, but if I have to I can change it. Trying to save a bit of work. I will get more info tomorrow.

Biger dont always work better, if you show more light and tell us more specs about your combo we can help you better, and if you get a little more specific about the profile of cam you want or got we can help, just take in consideration my friend Alex has the higher HP A15 i know to date and he is using a custom 284 Advertise duration by 472 lift on stock rocker arms with Custom race Toyota 3TC valve springs!

Epic back fires though.

It'd be best to see your cam grinder and ask for a turbo specific profile. Or just use the stock cam.

Too much overlap and you'll be blowing your charge out before you can compress it

You don't have to change to change the cam. 160 HP with stock cam.

But if you want to rev the engine over 6000 rpm, a larger cam is called.for.

I have a 1200 ute with an a15. me and the old man just rebuilt the motor and now I'm thinking about going turbo. It has a 30-70 cam which I think is fairly large with double valve springs but wondering if it's too big for turbo? Any one know what sort of power I could expect with a t28 and the cam I have cos I'd like to keep it a-series. Id rather not pull the whole motor out to change the cam if I don't have to. Thanks.