Cam timing

Martin (stunned, over the speeding ticket)

Yep will try, going for 108 on both banks, have a little man who will run me up some offset dowels for the cams/sprocket.

Also have some photo's of the heads to send you, guy did a really nice job on the swirl flowing and fitting the profiled valve quides.

200bhp+ here we come!!! Latest liberation method is to dump the water pump (and all that 'orrible pipe work) and fit a Miezire unit, should gain all of 0.5bhp for that!!!

Andy
Smart as ten, now where is my file and that large billet of steel, its going to be a winner

200bhp+ here we come!!! Latest liberation method is to dump the water pump (and all that 'orrible pipe work) and fit a Miezire unit, should gain all of 0.5bhp for that!!!

Or, I can do you some forged pistons and steel liners that increase the capacity to 3.5l on the standard crank and raise the compression to 11.5:1, and don't have more problems than standard pistons for valve clearance...

Intrested, but not, engine remains unchanged apart from induction side

Intrested, but not, engine remains unchanged apart from induction side

Have you not increased the compression?

Compression is increased, but not as high a 11.5/1, closer to 10.4/1

Was intent on creating an engine that will evolve, rather than going to a screaming 'nutter' in one fell swoop ( I already have 2 cars with more than enough bhp (Porsche at 450bhp and T1 at 210/240 BHP).

[Alpineandy]

Have you had the throats opened/flowed?

Oh yes, heads have been modified big time! And big money

Modifictions include, Gas and Swirl flowed inlets and outlets, nucleus valve guides, combustion chamber modification, Valve seat reprofiling, valve spring base modification (to prevent spring binding), bigger inlets etc etc.

In addition the 3 barrel inlet manifolds have also been enlarged and gas flowed, with 2nd'ry ventura added.

Rolling road will tell though to the future, still trying to get those cams spot on.

[Alpineandy]

Oh yes, heads have been modified big time! And big money

Would you mind suggesting an 'area' that would have cost.
As an atmo engine man, I understand that it's the main thing that holds the engine back, and It would be useful to have an Idea how much I need to save

Oh yes, heads have been modified big time! And big money

Would you mind suggesting an 'area' that would have cost.
As an atmo engine man, I understand that it's the main thing that holds the engine back, and It would be useful to have an Idea how much I need to save

There's many options, fit oversize Z7X valves into your heads for the best gains, not cheap though, about £600-800 to get done properly.

The other expensive thing is getting the static compression way up, as the more lift and duration you add to the cams, the lower the dynamic ratio goes down, and sometimes you can even be running a lower ratio than a standard setup, simply because you've gone so wild with the overlap..

The 310 engine runs much more overlap than the GTA as standard, hence why they raised the static compression to 10.5:1 from the factory...

[Alpineandy]

It's the cost of getting the throats opened/smoothed which seems to be the pivot around which everything elses effectiveness revolves.

It's the cost of getting the throats opened/smoothed which seems to be the pivot around which everything elses effectiveness revolves.

Porting and polishing is far cheaper than having larger valves fitted, but is obviously only beneficial if you are running decent inlet manifolds and throttle body diameters...

You have to work out the diameter of your valve, by the amount of lift and work out of the air flowing and velocity is larger in volume than the standard port can flow..

On a standard inlet manifold, you may find the runners are smaller diameter or more restrictive than the ports in the head, so machining the head may make didly squat difference...

And then there is trade offs between different heads, for instance you could spend a fortune on a Z6W head fitting larger valves and trying to remove the restriction around the inlet valve stem, whereas a Z7X head has both of these benefits as standard, and it would be possible to convert a complete Z7X engine to oddfire if you wished, and still be cheaper than modifying your heads..

[Alpineandy]

Porting and polishing is far cheaper than having larger valves fitted, but is obviously only beneficial if you are running decent inlet manifolds and throttle body diameters....

Is there any point fitting throttle bodies or big carbs etc unless the ports have been opened? It may give a tiny benefit but wouldn't be a 'value for money' purchase without.

Porting and polishing is far cheaper than having larger valves fitted, but is obviously only beneficial if you are running decent inlet manifolds and throttle body diameters....

Is there any point fitting throttle bodies or big carbs etc unless the ports have been opened? It may give a tiny benefit but wouldn't be a 'value for money' purchase without.

Yep, for instance, the inlet valves on the V6 Z7X are 46mm, and you can get 40-50mm bodies, but you won't get your ports near 46mm, maybe 42mm max, but you still get a gain fitting the large bodies, but probably not much of a gain above 44mm

End of the day, you just look at the restrictions in the intake system - if the inlet manifold runners are smaller diameter than the ports, then increasing them will make a gain..

I was showing Stephen Dell the other day, the plastic intake pipe that diverts hot air into the air filter chamber on a GTA atmo, via a flap, but the overall diameter of the intake pipe that the engine breathes through is smaller in area than the total area of the carb venturi's, so theres a loss there to start with at high rpm, but the main thing was the flap never fully moved itself out of the air flow, so it was restricted once more. I have always binned this on all my GTA's and it makes a difference, and we did it to Steves on a long journey through France which we have done many times and guaranteed, it was more economical on fuel by quite a margin and had better top end pull, proving even a simple restriction removed on an standard engine makes a difference.

French air is denser though