Cam timing + a few other queries!

[mgbv8]

I'm nearly finished on the new engine build.
I've got a cross bolted 4.6 with a 9.35:1 CR, 4.6 Thor heads, Weber 500 and an offy 360 manifold. I have fitted a Blower cam from RS and Cloyes timing gear as per my old engine.

I've always fitted the timing gear at standard timing, but I can fit it at +4 or -4 degree's of cam timing. I'm trying to get the most from the 4.6 without nitrous. According to what I've seen, the blower cam has the same lift as my old Typhoon, but it has a bigger overlap. What is the benefit of fitting the timing gear at + or - 4 degree's from standard???
Bearing in mind I will want to add a small shot of gas once its run in.

I am hoping the extra 1000cc's will get me close to what my 3500 is doing with gas.
If I can get 230 bhp without gas I'll be happy. But I do still want to use gas on track days.

Can anyone tell me what the change from an 8:1 CR 3500 to a 9.35:1 4.6 engine will feel like?

I know a lot of you get great results with the 3.9 without gas. Am I going to feel a big improvement with just the extra 1 litre??

Ian Stewart gets mid 12's from his Tina without gas. I get mid 12's on my old engine with a 150 shot, but it is an auto tranny.

Thanks
Perry

[katanaman]

You fit the cam to what the manufacturer says so you need to degree your engine and time it from there. If the +- 4 is closer to the cam specs then you would use it ir use the 0. If you don't want to degree the engine then fit it at 0 or something might hit.

Your always going to feel an extra 20-30 bhp but more than that youo will have a big change in torque because of the cc increase. Don't go by Ian's engine as its a bit of a special one plus it has one item your engine doesn't have and that's big valve ported heads. These are all important on a Rover engine. Thor heads on their own in my book aren't worth anything, they are just a better starting point for porting because of extra material in the ports. Stick a set of good heads on your engine and it will fly without the NOS not to mention what it will do with.