OST-039: The end of the beginning....

[oldeskewltoy]

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Next few pics are just the difference from dirty, untested, to cleaned and fully pressure tested - rebuild ready.





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Hmmm, the sharp of eye might say, "hold on there... some of those exhaust valves seem to be thin of margin"......




and you'd be correct....... 4 exhaust valve were marginal on the margin



although .8mm will likely still have "enough" margin after being cut, once you add in a stronger spring, and likely hotter temps, I want exhaust valves with a bit more than the minimum, so I dug up some exhaust valves to replace those I've removed.


More to come.......

[oldeskewltoy]

Well this head is receiving a complete deburring, all machined edges get a general deburring.




and a bit closer of the area between the buckets.... this work is all designed to shed excess oil, and to remove casting flash.




and a 2 panel showing the deburring of #1 exhaust journal




more to come.......

[oldeskewltoy]

from another forum Wrote:I always love seeing your work. It's the attention to detail :idea:

I practiced that between-buckets deburring on my "junk" bigport head. Seems like a good idea to stick a "junk" bucket (or a maybe socket) in place to ensure that the Dremel bit doesn't jump over and leave a mark there.

I also practiced some block deburring. There seems to be quite a bit of casting flash inside the big oil drain on the exhaust side. Or there was on the one I was working on.

The big oil drain... isn't. The kidney shaped twin openings on the exhaust side between cyls 2 and 3 is not an oil drain, it is the breather bypass. The 4AG bigport head has 2 oil drains - both on the exhaust side, one just after cyl #1, and one at the back of the head near #4.

from another form Wrote:Thanks for the info as always! One thing I was wondering about that HKS oiling mod blocking the main galley going to the block. How big is that restrictor orifice? and does it really restrict the flow as the restrictions in the head are much smaller than the hole in the block feeding it.

seems like it is a significant restriction..... another solution would be to add passages for the head to drain the oil back into the oil pan



Work begins on #1.... the seat diameters are enlarge by about 3/4 mm... opening the valve to seat ratio to 85%, blending the bowl to the seat... as best as can be without over enlargening the seat. Since this head has no client yet, (contact me if interested...) this head is being built similarly to OST-032, built to boost air flow (volume AND velocity).





And as always... working the short radius.....


and a bit closer to show more detail on the short radius work.



more to come.......

[oldeskewltoy]

and the first exhaust port is complete...




​more to come.....

[d3nso]

Always a pleasure to look at your work
Did you widen the exhaust ports?

[oldeskewltoy]

(06-14-2016 08:01 PM)d3nso Wrote:  Always a pleasure to look at your work
Did you widen the exhaust ports?

thank you......

widen? the port outlet is a small amount larger, mostly from about 3 o'clock, to about 9 o'clock, with the width being .5mm larger and the height being about .3mm larger. So in the overall scheme of things... only a tiny amount has been removed at the port exit.........


Inside the port/bowl, thats a whole other story.....

[oldeskewltoy]

from another forum Wrote:Dude,


It will be interesting to see the before and after flow-rate comparisons.

.

Yes it would.... and so I've re-calibrated the bench....




then I fitted test valves and test springs... and put the head on the bench and got baseline numbers for intake, and exhaust






and the results....

exhaust:
.050" - 29.8 cfm
.100" - 62.4
.150" - 95.8
.200" - 112.2
.250" - 118.3
.300" - 121.3
.350" - 121.8


Intake:
.050" - 39.4
.100" - 79.8
.150" - 118.8
.200" - 150.2
.250" - 171.9
.300" - 177.8
.350" - 180.2



more to come........

[oldeskewltoy]

and a bit more detail.....








flow results to follow........


more to come.......

[oldeskewltoy]

from another forum Wrote:Dude,


It will be interesting to see the before and after flow-rate comparisons.

.

oldeskewltoy Wrote:and the results.... (before)

exhaust:
.050" - 29.8 cfm
.100" - 62.4
.150" - 95.8
.200" - 112.2
.250" - 118.3
.300" - 121.3
.350" - 121.8


Intake:
.050" - 39.4
.100" - 79.8
.150" - 118.8
.200" - 150.2
.250" - 171.9
.300" - 177.8
.350" - 180.2

and now with porting, same valves, old valve job (further improvement likely with fresh 3 angle)

Exhaust:
.050" - 30.4cfm
.100" - 64.4
.150" - 96.5
.200" - 114.3
.250" - 125.5
.300" - 129.3
.350" - 132.0


Intake:
.050" - 39.4cfm
.100" - 80.0
.150" - 122.2
.200" - 156.7
.250" - 182.2
.300" - 197.3
.350" - 204.0

.300" = 7.62mm, or just a tiny bit more lift then early stock cams(7.5mm). .350" = 8.89", or nearly 9mm.

So.... flowing through the stock ports I gain 10cfm@ .350" lift on the exhaust side, and I gained nearly 24 cfm on the intake side.

[oldeskewltoy]

been a while but OST-039 now has an owner... chamber volumes are equalized, depth of cut will determine final chamber volumes




client will be running a 262-232 cam with 8.3mm of lift


more to come.......