OST-066: I get all wavy (4AC content)

[oldeskewltoy]

note the edge of the head is wavy, this is the last iteration of the 4AC head in the USA.


Its difference from its first generational "brother" is MORE substantial, then a Blacktop head is different from a Silvertop head




So why build a 4AC head??? Partially because I haven't done one for a client.... and partially because along with the head, my client included this manifold....




Twin side draft manifold for a 4AC head




more to come......

[Power_uP]

Cool, I've never known of anyone building a 4ac before so it'll be good to see one for a change. I wouldn't even have guessed that there's much that can be done with one.

[oldeskewltoy]

(03-09-2020 05:59 PM)Power_uP Wrote:  Cool, I've never known of anyone building a 4ac before so it'll be good to see one for a change. I wouldn't even have guessed that there's much that can be done with one.

I was playing around with a 1/2 of a non wavy head about 2 years ago... yes I said half







and gains were made...



But this is a wavy (apka a swirl port) head... and while the intake opening is the same.... nothing else inside the intake port other then the valve seat is the same.....

apka - also possibly known as


but I jump a head ( )..... the client wanted this head, and cam cover, and manifold to look new... so after cleaning, it got tumbled... (zinc shot media)




more to come.....

[oldeskewltoy]

The wavy SOHC A head is oddly shaped for sure..... round entry, but NOTHING like the non wavy head, as it immediately changes shape inside the head





port work begins.... First order - DO NO HARM...


setting port size, and blending the port-to-manifold




I'll be focusing on removing sharp edges, removing poorly casted areas and blending.



Odd shapes throughout... look at that oddly shaped short radius...


.... at least the exhaust ports are conventional




more to come......

[Power_uP]

I can't wait to see the power increase on this one. It might inspire me to tune the 2E in my car instead of replacing it altogether with a 4E turbo.

[banpei]

By any chance, is your client also known as 84hachi?
If I'm correct he does own the exact same manifold on his 4AC powered hachi.

[oldeskewltoy]

(03-27-2020 05:42 PM)Power_uP Wrote:  I can't wait to see the power increase on this one. It might inspire me to tune the 2E in my car instead of replacing it altogether with a 4E turbo.

I will ask... but only a few have shared their dyno plots with me so far.... Most recently... OST-061 - 172 whp Miata 1.8

(03-27-2020 10:00 PM)banpei Wrote:  By any chance, is your client also known as 84hachi?
If I'm correct he does own the exact same manifold on his 4AC powered hachi.

That would be Steven, no this isn't his.


2 down.... 2 to go

[Dave W]

Dan
Are you doing anything inside the chamber? Looks like both the exhaust and intake could use relief help on the side walls?
Dave W

[banpei]

(03-28-2020 12:06 AM)oldeskewltoy Wrote:  

(03-27-2020 10:00 PM)banpei Wrote:  By any chance, is your client also known as 84hachi?
If I'm correct he does own the exact same manifold on his 4AC powered hachi.

That would be Steven, no this isn't his.

Yes that's him indeed.
But I just rewatched one of his videos and the manifold looks similar in shape and also has similar linkage arms, but it does differ in details. For instance this one appears to have a vacuum plug on one of the intakes.

[oldeskewltoy]

(03-28-2020 01:41 PM)Dave W Wrote:  Dan
Are you doing anything inside the chamber? Looks like both the exhaust and intake could use relief help on the side walls?
Dave W

The exhaust side of chambers 4 and 2 (far left, and 2nd from right in photo below) did get some massaging as they did encroach some on the exhaust valves of those 2 chambers.



On the intake side, I left it alone as the gap from the valves edge to the chamber wall wasn't that tight, as an example here is a small block Ford chamber (Dart 210cc port performance head) the valve - chamber wall fit is tighter




This head also required a thread repair chamber 3, it is a timesert. Timesert is the only real way to fix a spark plug hole. Using a helicoil doesn't transfer the heat properly.



A very nice 3 angle valve job....




re-assembly... using Viton rubber valve seals...



... and Sealed Power (VS-813) valve springs - They have a bit more seat pressure, and can accommodate more lift.