Ok so I have a Classic, running TD05, STI bottom end, WRX heads and 440cc injectors.

It makes a healthy 335bhp. It will be capable of 350bhp with the 550cc injectors

The heads have to be changed soon due to wobbly camshafts, causing some oil seepage past the cam seals.

I have some choices to be made!

While the engine is out of the car I will be:
- having 550cc injectors installed
- Have the 5 speed gearbox syncro's replaced (1st and 4th are showing signs of going, but its not so noticeable yet)
- Port wastegate - sometimes overboosts if flat out in 4th

The second choice I have to make is this.. the heads. WRX or STI.

I know the STI heads will give the car another 1k rpm to play with. But does it mean that it will rob some power low down, and put more up top? - I wouldn't be too happy with having to rev the car harder to achieve the same results. Or doesn't it work like that? Will it allow the car to make more power earlier on and hold the power right up to the new redline?

Would the turbo spool be affected by the different heads?

If I went for the cheaper WRX heads, I would probably ask that they split the box and replace the big end bearings to give it another lease of life. Engine has covered approx. 75k miles. I don't know if the bearings have ever been done in its lifetime.

What would you do?

Any input welcome!

 

Replacing gears which will be close their limit at 350bhp with gears that will be close their limit at 350bhp wouldn't be the direction I would choose.

 

Nor me.

 

Ok scrap the ideas about the gearbox, what about the heads?

The car's run its current setup fine for about 6 months and the gearbox is holding strong. the syncro for 1st and 4th have always been a tad crunchy, even before the new turbo fitted. if it blows it blows