Sins of the father ?

How many of the GTA's tuning restrictions were carried over to the 610

Well ill list all the similarities and differences so you can work it out..

Identical manifolds and turbo backplate
Much larger exhaust turbine housing and compressor wheel on turbo, but same restrictive 2"1/4 turbo outlet to downpipe.
Same 55mm throttle body
244 degree cams instead of 228 degree duration - same valve lift
46mm and 39mm valves verses 44mm and 37mm
Identical sized ports (but unrestricted valve guide area on A610)
Intercooler is angled towards spoiler and flows from one side to the other.
Reprogrammable ecu.
Lower compression
Weaker pistons on A610
Thinner liners on A610
Slightly larger inlet manifold design, but roughly the same

dave when does the throttle body start becoming restrictive?

No problem with 55mm, the engine will never rev high enough to warrant being larger, and if it did, would require all the boost hoses and intercooler inlet and outlets to be matched to the same size too..

The flow of the throttle body is higher than the flow of the inlet valves at full lift/duration..

David do you think its worthwhile changing to the bigger valves in my ATMO with my multi throttle bodies and long duration cams . Do the A610 valves fit with machining, I intend on fitting double valve springs.
Are the standard pistons ok.

Chris W

I have fitted the larger valves to my turbo heads and found that the valves were virtually as big as the valve seat inserts. So I fitted larger valve seat inserts to both the inlet and exhaust valves. Also when porting I took quite a bit of the large boss that supports the valve guide in the exhaust port away.

There is not much spare material in the exhaust ports before you hit water, except where the boss is. In the turbo heads at least, the inlet ports are fine and only need cleaning up.

Surprisingly the conrods are identical between the GTA Turbo and the Volvo B280F I stripped.

David,
Do you know the sizes of the turbo housings on the A610?

David do you think its worthwhile changing to the bigger valves in my ATMO with my multi throttle bodies and long duration cams . Do the A610 valves fit with machining, I intend on fitting double valve springs.
Are the standard pistons ok.

Chris W

I don't think you will gain much due to the fact you already have high lift long duration cams. Standard pistons are fine for non turbo application. They have a raised crown whereas the A610 pistons are dead flat.

I have fitted the larger valves to my turbo heads and found that the valves were virtually as big as the valve seat inserts. So I fitted larger valve seat inserts to both the inlet and exhaust valves. Also when porting I took quite a bit of the large boss that supports the valve guide in the exhaust port away.

There is not much spare material in the exhaust ports before you hit water, except where the boss is. In the turbo heads at least, the inlet ports are fine and only need cleaning up.

Surprisingly the conrods are identical between the GTA Turbo and the Volvo B280F I stripped.

David,
Do you know the sizes of the turbo housings on the A610?

Alan, the Z7X heads have that boss around the valve guide removed as standard. Basically, the 2.5 Turbo and atmo heads have a minimum internal port size of 40.5mm, where as the later heads have 46mm, due to that metal being removed..

All the conrods on all the PRV's are the same.

The specs on the A610 turbo charger is a 60 trim compressor wheel (60mm exducer and 46mm inducer) in a 0.42 T3 compressor housing, and a 0.63 AR exhaust housing with a 60mm T3 turbine wheel)