OST-013: Massaging a virgin ;)

[oldeskewltoy]

I can do flow testing... BUT that usually costs MUCH extra do to time required to set up and then remove, port a bit, and then re-set the flow bench. In fact flow testing a head is often the difference in a $750 porting cost, and a $7500 porting cost (as in the cost of an Atlantic head)

Concerning 3 angle (or in some cases multi angle) I do not have the machining equipment to do this, I have Loynings do these for me. I TRUST Loynings work, they are an active racing machine shop who have built many hundreds of 4AGE engines... as well as others. Loynings has 27 SCCA championships accredited to their work, they are the shop that ported my smallport head... with which I've planted 145whp and 112#/ft, also measured @ the wheels... that is also emissions friendly

The ports you are seeing are intake ports, so the un-tapered part is away from the air stream - tucked behind the valve. The area behind this is very small and is very disturbed air, by not tapering the back more I'm minimizing this and minimizing the disturned airflow behind the guide. Part of the tapered guides is to "follow" the minimized guide boss, since the guide boss is minimized, the flow up to the guide would be more disturbed if not tapered.

I have had my work checked on a flowbench - note the spec they are measured @ is 25", most flowbenches use 28". If you do the math, the intakes would flow @ 212cfm if measured @ 28"




Each head is different, you bring up the Miata head, 175whp is unheard of... the head is crappy, and the intake ports are to long horizontally, to make very good power in N/A form... the head is a big reason why most Miata guys go turbo because not a lot is achieved by porting a 1.6 BP head. The 4AGE head is better, and the old Ford Cosworth head even better then the 4AG head.

Interesting thread on Miata engines/builds - http://forum.miata.net/vb/showthread.php?t=365171

Concerning the 4AGE head, the key areas to port to gain power is on the exhaust side. The port and the bowls are decent, but some serious taper work allows the exhaust flow to merge at a better angle allow less turbulence, and superior flow. While the exhaust tends to be the "problem" with 4AG heads, the intakes can be bumped to flow significantly more overall as well.

Finally.... a point about flowbenches... they are very good @ measuring flow... BUT not as good @ measuring how an engine responds to this flow... the reason for this appears to be that an engine is not continuous flow, but actually is interrupted flow because of valve opening and closing events..... the flow bench can not measure these effects since it runs continuously.