4AG head porting - OST-031: A delicate dance

[oldeskewltoy]

A delicate dance...

titled as such because OST-031 and OST-030 will be built almost simultaneously.





As you can see... OST-030 in the background, with 2 heads in front



Clients head on the left.... anyone see an issue??


How about if we isolate the two sets of chambers.... clients head on top



It's replacement on the bottom


See anything now??


Closer??




I've dismantled the replacement and I've sent it on to get cleaned and pressure checked....

So with it @ the shop to get cleaned, the delicate dance proceeds as I move back to OST-030





More to come...

[oldeskewltoy]

So with it @ the shop to get cleaned, the delicate dance proceeds



More to come...

So now that OST-030 is @ the shop getting its valve job, work on OST-031 begins.....

A slightly different angle view on the intake bowls, and chambers... a bit more vertical



This view allows us to see the back of the bowl where it meets the valve seat.



Now when I titled this thread "A delicate dance" originally it was based on working OST-030 side by side with OST-031... BUT OST-031's title has new meaning....




Note how close the gasket edge is to the port outlet roofs... best noticed on end ports, 4 is done, #1 on right is yet to be touched

On #4 (the one done) there was less that .010" to the edge of the gasket. Typically I have over 1/2mm (.0197") or even more!



more to come.......

[oldeskewltoy]

Don't tell anyone, all gasket manufacturers are the only ones to really know the real speed secrets of every head.

I hear what I BELIEVE you are saying... I only use OEM gaskets when I work the head, because OEM tends to have more consistancy........



I've gotten a bit further since my last post.....




and in more detail.... 2 slightly different views...


1st internally exhaust port #2's transition





and from a slightly different POV...... #3's transition





More to come......

[fixeruperer]

dammit ! you made me check my spare head and its the same as your clients head haha. i never looked close before. because it was given to me a few months ago.





looks like i have to find another head.

[Cuzzo]

Excuse my ignorance but whats the problem?

Enlarged plug seats?

[fixeruperer]

look at the distance, between intake seats, intake to exhaust seats and between seats and spark plug. its a way more bizy chamber with more edges. i dont like edges in chambers.

i dont know if they cc different, but the bizy head looks like it could be tighter.
its gonna take me more work to get the bizy head how i want it, when i can just start off with a early(?) bigport head.

[oldeskewltoy]

Excuse my ignorance but whats the problem?

Enlarged plug seats?

Far easier to work a better casting, the amount of time required to get chambers equalized once all the sharp edges have been gone over and blended away just adds too much cost for most of my clients, where as getting a replacement head typically is far cheaper. This head is far easier to sell to an Atlantic builder I know who basically overbores all the valve seats anyway to install larger seats for the larger Atlantic type valves.

[MWP]

Wouldn't these "bad" heads have better pressure recovery zones?

[oldeskewltoy]

Wouldn't these "bad" heads have better pressure recovery zones?

not disputed.... BUT.. the time required/amount of work involved makes it significantly less desirable. Also to consider is the irregularity of the "flaw"s occurance.



chamber #1 has no "flaw"... chamber #4 has only a minor "flaw". Do I weld up chambers 1 and 4 and shape them to equal the finished chambers of 2 and 3? My typical finished head goes out the door for under $1500, some under $1000

so... to again answer your question... Yes... these heads would have better pressure recovery, but the work involved makes it less affordable/attractive.

[oldeskewltoy]

With OST-030 heading back to its owner, and OST-032 at the shop getting cleaned and pressure checked, there is a window of time to check chamber volumes on OST-031, and then re-assemble.






This time I got 35.6 on #1, and #2, #3 was 35.3, and #4 was 35.5

Soooo... I did a little adjustment on chambers 3 and 4 and got both to 35.6

Chamber and bowls... before.... and after



Assembly to follow......

[oldeskewltoy]

If you had to guess how many hours would you say went into this one?

port work - about 30 hours : chamber deshrouding, and equalizing chamber volumes - 6 hours : waiting for the machine shop to do their thing - 2 weeks


Found another suspect retainer... swapped it out




The head is now ready for its cams.....





More to come.......

[oldeskewltoy]

The dance continues.... although now I'm dancing with the valve clearances...




with 13 valves headed back to the machine shop to get tipped...

[trdee]

what happened to the other three?

[oldeskewltoy]

what happened to the other three?

if you crank your neck 85 degrees to the left....

you can see intake valve #2 is currently @ .010" (spec is .008"), with a .1122" shim. This means replacing with an .1142" shim should get me to spec. The other 2 intake valve, 5 and 6, are currently @ .008" with the .1122 shim. The other 13 were significantly tighter, and if I had a full stock of thin shims (.0984" through .1024") I might just shim it... but I TRY to think of the client/next guy... and if I keep common shim types in there, when this client goes for camshafts in his future... he should still be within standard - common size shim distances.