"hobby mode", this is an experiment and NOT a guide / how-to etc.Basically I blew up my AW11's 4AGE and thought
"I'll just clean up a spare head and do a simple 1.8ish coversion using the 7AFE block". As normal I got carried away, I thought "may as well go big valve to help the extra 200cc's worth of charge" etc and it went from there!The old 4AGE head, I think I can see what was wrong!
The standard bigport 4AGE inlets:
Modifying the inlets:
Going big-valve, note the change in the gap between standard valves and new valves!
Nice new oversize wasted-stem valves:
Finished chambers, de-shrouded the valves, opened up ports, 4-angle seats
(inlet):
Finished inlets, valve guide and boss removed!
(maybe a bit extreme...!):
Old vs recon/modded!
Exhaust manifold de-dingleberried then flowed 1mm oversize radially to improve the anti-reversion/standing wave formation step
(head flowed to match gasket, manifold is bigger:
Covers cleaned, painted in high-temp matt black then draw-filed by hand:
Not shown are inlet manifold and TVIS port-matched, exhaust valve gaps to be run way oversize to increase valve speed off seat
(increasing wave/pulse formation and pressure at the expense of a tiny bit of lift and duration), cams to be re-timed by drilling/slotting the pulleys (over and above mods needed to get in line with the 7AFE bottom end), and other bits and bobs.POWER
---------------------------------------------------Well, using very basic crazymaffs:
128bhp plus cone filter and straight through exhaust
= maybe 135bhp if I'm lucky?Assuming 135bhp, 135
/ 1.587 (1587cc) = 85.07bhp/L.85.07 x 1.762
(1762cc) = 149.9bhp.In terms of added poke, there could be a 5-15% gain in power from the ruthless flowing, call that 5%
= 149.9 x 1.05 = 157.4bhpThen the valve area has gone up by 10.1% and 16.5%, looking like this:
29.5mm dia Toyota small port in
= 683mm area (94% of the bigport valve)30.5mm dia Toyota Bigport in
= 730mm area Bigport25.5mm dia Toyota ex
= 510mm area Bigport32.0mm dia Atlantic in
= 804mm area (110.1% of the bigport valve)27.5mm dia Atlantic ex
= 594mm area (116.5% of the bigport valve)In actual fact the EFFECTIVE diamter of the new valves is even more, as I'm running much smaller seat contact areas, making it more like a 20% increase.
157.4bhp x 1.2
= 188.8bhpIn reality I'm expecting about 160bhp
+/- 10% once set up properly, at 1,000 less RPM, with much more torque due to the longer stroke. 
The theory from the point of view of air entering the port.
1
- Upper port (is this the part you refer to as the "runner"?). Standard, just had casting marks removed to maintain velocity and improve the boundary layer.2
- Valve guide boss. These are there to support/cool the guide, and also in the GE head they appear to induce rotation in the flow over each valve as they are very lopsided (plus the ports are angled in pairs when looked at from above, not parallel!). The outside curve of the port is the highest velocity area as the air tries to keep going in a straight line, so I wanted to know what effect removing them would have (this probably means more revs or more lift needed).3
- Valve guides, these were in the way of removing the guide bosses! 
Of course I know a cylinder is a pretty good aerodynamic shape so they are not a real problem if retained...4
- The throat, this is the real venturi as it's right behind the valves and is the smallest area (especially now!). All I did to these was remove the "step" caused by mis-alignment between the port and ID of the steel valve seat insert. Doing this opened the seats up to about where I wanted to go due to the bigger valves anyway. I'm keeping the standard cams, and I WAS going to stay at the same capacity to do a fair test of the effects
- but decided not to bother and to try the 7A one straight away as I've not got heaps of spare time for multiple engine configurations/comparisons. NOTE: Again this is me in
"hobby mode", I don't pretend to know my way round engines to any real level!!!
