OST-013: Massaging a virgin ;)

[NoHachi]

oldeskewltoy Wrote: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

I have no doubt that Loynings know what they are doing. Similarly I fully believe that its possible to reproduce port work on another head that you know has been proven to work on previous flow bench tests. I was just curious how you developed your ports since all the old scool guys with flow benches say that it is easier to ruin a modern head (ala 4AGE) then to improve on it. (just to be clear, I'm not insinuating you ruin a head, quite the opposite, hence the curious questions... I want to learn.)

oldeskewltoy Wrote: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.

This doesn't jive with the water drop shape idea, its actually the exact opposite. Many things happen inside a port so it probably isn't a straightforward thing. Do the Atlantic heads use similar profiles?

oldeskewltoy Wrote: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"
http://i79.photobucket.com/albums/j143/o...after2.jpg

That is a very nice result indeed.

oldeskewltoy Wrote: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.

Actually the later 99+ miata heads aren't as bad as their predecessors. They'll flow 200CFM at 28" out of the box. 140whp with only bolt-ons.
Spec Miata has seeded much development work. So reliable ported street engines sit at 165-170whp with mostly modified stock parts (all be it expensive Rebello street engines) and 7300rpm rev limits. Those built for higher rpm are far above that. What the pro miata builders have discovered after doing many spec customer engines is how to match their cam profiles to port shapes and vice versa. Which is quite interesting.