Last week I sent the A13 Race head to Hans @ HIGH PORT to get flowed before reassembly. He does cylinder heads for most of the A series mini sprinters in Melbourne including Kevin Baileys (top car in Australia). The head flowed 169 hp @ 0.550 lift with 25 inches water pressure. This is a full 10 hp better than any other A series head he has flowed or heard of. The exhaust flow percentage is 69.5% of exhaust flow.
He also identified the head as a works Nismo casting by the inlet port castings extending into the rocker area. In his words this is rarer then my L series FIA head!
Makes me wonder what the little beast would do if it went onto a good A14/A15 hybrid, (1600 cc) bottom end, keeping the engine speed down to say 8000 rpm?

Do you mean the horsepower potential is 169 HP? Head flow figures I've seen are measured in CFM. Either way it sounds very impressive!

Yes, the air flow at the 25" water pressure is enough to make 169 hp at that pressure. I am waiting till monday to get the actual CFM figures at the whole range of lifts. This is well up there with the Nissan Micra 4 valve heads!!!! The A series heads have really surprising performance potential from 2 valves!!!! Go the A series

yep go the A series,

i am glad Hans is getting my GXhead i am very sure that he will do some awsome work on it

I'm scared to ask but........

How does my flow chart I sent you compare to the flow figures of this one Errol ?

The chart you sent me has 141 cfm @ .600" lift and 25" water pressure, gives a potential hp of 153 hp. The head I have gives 155 cfm @0.550" lift and 25"water pressure. Im told the differnce comes from the pot casting being higher in the head.

The interesting thing about the chart you snet me is that the exhaust is flowing 93% of the inlets at 0.600" lift.

Most A series heads including mine struggle to get to 70% of the inlet flow, especially if you have large valves.

Some literature I have seen on port development seems to say design for 70% Ex/In flow, in non cross flow engines with one port per cylinder. But whatever works for your setup is what its all about.

All I need now is a decent cam and pistons so I can actually get the figures.

This proves the beauty of the OHV compared to twin cam equivalents in terms of bore and stroke. The A series rules!!! and craps all over many tc engines. Datman100 as for 90% exhaust flow... that would make a great turbo head!

I'd be interested in comparing my head with this head, but I don't have access to the equipment to do it. Mine would be simular hp I suspect.
It would interesting to compare torque as well, can torque be measured/estimated in a simular way?

When the exhaust ports flow like that (higher/lower than "optimum" compared to the intakes), use an asymetrical camshaft ... in other words, the cam grinder will use less duration on the exhaust lobes for naturally-aspirated engine. I think ... if I correctly remember the articles I've read.