OST-029: California here I come.....

[oldeskewltoy]

As I always do... my client is anonymous, unless he wants to share. This head is sold to a client in California. This is his daily driver, that gets a track beating/work out every few months or so. Retaining emissions compliance is paramount, but we can get a bit more without offending the sniffer.


This is a largeport head, it is the stock thickness, having never been re-surfaced.




A key for me in figuring out overall "wear" is often judged on the condition of the old valve seals. The old seals that came from this head were still "pliable" (read as didn't crumble under finger pressure) - A few intake valves did show signs of build-up, the exhaust valves were all dry.




#4 exhaust port




Its pretty crowded in there, but a bit of seat to bowl blending, and a re-taper of the port will allow the exhaust gasses an easier path


Now that it is stripped, its off the the machine shop to get cleaned, and de-carboned. Maybe they can get rid of that horrid paint for me too




More to come......

[oldeskewltoy]

The one head I sent out for cleaning, and pressure testing has pretty significant flaws....





Chamber #3 is not quite the same depth as chamber 4... you can see this by comparing "a" and "b' in both heads. and you can see heavy machining. Chambers 2 and 3 are pretty bad, 1 is just a little bad, and 4 is "ok". All those chambers have significant flaws, and it just isn't economically feasible to fix the flaws.... so I'm after another head.....


Anyone in here know if I can use the head on the left in a transverse application - MR2


more to come......

[Bean]

not sure what these too bolt wholes are for but EPC mentions the same partnumber for MR2 and AE86 for the plate inbetween the cam gears and head (that would cover them up). As far as I know the right hand engine mount is mounted to the block and not the head. Ask your customer to check that... if the mount is on the block I don't see a reason why it wouldn't work
The only variant I found using these bolt locations is the 4A-GZE and not sure if something critical bolt up there as the engine mount is also on the block.

[oldeskewltoy]

Take 2........





The old head on top, the replacement below.... chambers are far better shaped!




More to come........

[oldeskewltoy]

Easiest way to begin is showing you another 2 panel of chambers 3 and 4.... the top one you've seen before...



... the bottom one is new - Cylinder 4(on left) is where we begin.... all four bowls and seats have been blended, as well as the chamber deshrouded and intake guides minimized, the seats in #4 just need their valve job.


How observant are you???? What else have I done that I didn't tell you?? :wtf:


The intake bowls, and seats - 4 is shaped(on left), 3 is untouched.. Bowls are now round, blended out to meet the seats, the shape is carried out to the port. The short radius transitions smoothly from port floor to the valve seats, and the guides have been minimized.




Chamber... Intake.... and now exhaust


A comparison between 4 (on left) and 3




and a 2 panel showing progression of #4 from half shaped, to fully shaped




More to come....

[Bean]

the intake valve on the right got slightly more space to breath...

[oldeskewltoy]

(01-21-2015 08:12 AM)Bean Bandit Wrote:  the intake valve on the right got slightly more space to breath...

The chambers edge around the right intake valve has changed a tiny bit, so technically you are correct, but the answer I was seeking was the "softening" of the machined edge around the spark plug.

from another forum Wrote:The magic has begun!

(above pic was posted to one of my earlier build threads... had to use it again.... )




.... and now back to reality....

from another forum Wrote:How often do you come across variations in the chamber depths? I can't say I noticed it on my spare head, but I didn't look closely either.

The head this thread began with, that since has been replaced is the worst head I've seen. I've had to discard other heads because of flaws before*, but this is the worst head, at least in regards to correct chamber shape, that I've seen.

* - http://hachiroku.net/forums/showpost.php...ostcount=7


A short annotated photo showing the areas of work, and the similar area before work - no "hogging" here



the translucent redline shows us the port floor

1) The short radius - a gentle curve to the valves edge to promote cylinder filling
2 & 3 ) shaping the bowl to the seat, further promote cylinder filling
4) "Opening" the passage between the splitter and the guide, allowing the airflow easier passage past the guide - once again to aid in cylinder filling.

Nothing drastic, just taking a mass produced part and making it better




More to come......

[Bean]

(01-21-2015 07:37 PM)oldeskewltoy Wrote:  

(01-21-2015 08:12 AM)Bean Bandit Wrote:  the intake valve on the right got slightly more space to breath...

The chambers edge around the right intake valve has changed a tiny bit, so technically you are correct, but the answer I was seeking was the "softening" of the machined edge around the spark plug.

seen that too but was too obvious, so I put that towards deshrouding the chamber

[oldeskewltoy]

(01-21-2015 07:37 PM)oldeskewltoy Wrote:  

(01-21-2015 08:12 AM)Bean Bandit Wrote:  the intake valve on the right got slightly more space to breath...

The chambers edge around the right intake valve has changed a tiny bit, so technically you are correct,

Why did it change??

Chamber edge... this time cylinder 3. On top is the chamber edge before any work, you can see the old gasket, so that edge "sat" in the combustion chamber



Note how significant a flaw the edge of the chamber actually is.... when measured... it is .48mm "tall", and it is .73mm "deep", or sticking into the chamber is a sharp edge. So how significant is it...??? see the little green arrow, that arrow shows where I placed the dental pick....




Edges are NOT GOOD, they promote detonation, and this one stick "in" like a sore thumb


So... that is why the edge of chamber four around the right hand valve now has a bit more room to breath....


More to come......

[oldeskewltoy]

Since the last post was a brief discussion about that edge... I thought a short gif of the progression of the chamber walls....


although "polished" in the last scene, it wont be finished till after I have chamber volumes, and adjust accordingly



And now for exhaust port #3






More to come......