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oldeskewltoy

OST-044: What the "F"?

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What you see below is a 2nd gen "F" head with 4 downward sloping intake ports.

 

Before_work_starts.jpg

 

My client is planning on running about 10#s of boost though this........

 

 

More to come........  :D

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7 hours ago, 7000rpm said:

Cool

which turbo are they looking at running?

I've asked... hopefully I'll get a response........

 

 

Those 2nd gen intake ports are so steep.

That they are.....

showing_chamber_pair_and_exhaust_port_di


The intake valves are also bigger, 1st gen 30mm, 2nd gen 31mm   ;) 

 

 

That is the extent of the good news... the bad news....  the front oil drain still interferes with the exhaust flow on #1 exhaust port   :( 

_1_exhaust_port_interference3.jpg


exhaust_port__1_4_2_panel.jpg

 

 


more to come.......    cheer.gif

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On 6/27/2017 at 1:01 AM, 7000rpm said:

Cool

which turbo are they looking at running?

Garrett GT2554R (aka GT25R) Ball Bearing Turbo 

 

Dual Ball Bearing GT25R Turbo assembly with internal wastegated turbine housng assembly. T25 .64A/R   turbine with 5 bolt flanged outlet. Very Good turbo response for 4 Cyl applications. This turbo has a flow capacity of about 250HP.

Turbine
-Wheel: 53mm w/ 62 trim
-Housing: .64 ar


Compressor
-Wheel: 54.3mm w/ 60 trim
-Housing: .80 ar

 

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So before I can dig into this, I'll need to get it on my flowbench and see what is in her.  To do that I need a new valve setting jig.  

 

This pair of contraptions are what I used 7 years ago.... 

flowbench_tool_from_OST-011.jpg

 

It worked.... kinda... but it took most of a day to get readings :(

 

Since this is a clients head, a more reliable, and accurate tool must be made.... and so it began life as most of my valve setting tools do... in plastic

flowbench_tool_milti_panel.jpg

 

Not only is this tool far better, and far more accurate, it takes only a few minutes to set it up.

 

 

and now that I have the tool, the numbers... please

 

flowbench_before.jpg

 

 

 

more to come..... :D

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On 29 June 2017 at 4:07 AM, oldeskewltoy said:

Garrett GT2554R (aka GT25R) Ball Bearing Turbo 

 

Dual Ball Bearing GT25R Turbo assembly with internal wastegated turbine housng assembly. T25 .64A/R   turbine with 5 bolt flanged outlet. Very Good turbo response for 4 Cyl applications. This turbo has a flow capacity of about 250HP.

Turbine
-Wheel: 53mm w/ 62 trim
-Housing: .64 ar


Compressor
-Wheel: 54.3mm w/ 60 trim
-Housing: .80 ar

 

Should go well 

 

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Interesting how it drops the two small aperture volumes. Are they just the margin of error?

I assume if the velocity went up then they would perform better than stock too.

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On 7/7/2017 at 10:21 PM, altezzaclub said:

Interesting how it drops the two small aperture volumes. Are they just the margin of error?

I assume if the velocity went up then they would perform better than stock too.

no margin of error, there are small drops in volume @ .050, and .100 - after the new valve job I'm hoping to gain some of these #s back

To keep it as simple as I can for a wide audience....   Part of the bowls shape, and part of the bowls/ports size, as well as the original valve job "helped" the .050, and .100 lift #s, but the first 2 seriously restricted volume.     In essence the original port/bowl shape was to "extend" the 3rd angle(throat angle) of the valve job to an extreme to maximize port velocity, at the expense of volume and the 7AF has very good port velocity - just find a dyno print out of a stock 7A and you will see it makes a nice torque curve.  But @ 115hp it leaves volume on the table. 

The goal here is to increase cylinder filling, and while I know some of the velocity has dropped do to porting, the drop is minor compared to the gains.   From a bit of digging (3rd post down - http://www.wheelsjamaica.com/wheels_forum/index.php?topic=165509.0 )  The 2nd gen camshafts are 224 duration overall.  

2nd GEN
Overlap: 8.00 degrees
Intake Duration: 224.00 degrees
Exhaust Duration: 224.00 degrees
Intake Installed Centerline of 106.00 degrees ATDC.
Exhaust Installed Centerline of 110.00 degrees BTDC.

We can do a bit of math, and a bit of guessing( duration @ .050")  18 degrees of ramp(36 total - up and down) are common on 4AG cams, so we can assume this, and then subtract 36 degrees to find the duration @ .050" for the 4/7AF cams:  36-224=186.   ASSUMING the ramp is correct, or even close we are @ or near 186 degrees duration @ .050".  Now we are given the centerline @ 106, so there is half of our 186 before 106, and the other half after it.   Subtract 93 from 106 and we make an educated guess the cam is open .050" @ 13 degrees after top dead center, 13 degrees off TDC the downward moving piston is not yet at peak draw.    At this point the cam lift is opening faster now, in the next 93 degrees, the lobe will open to .338".  And this is where the volume advantage will fill the cylinder better, for the cylinder will be at its peak vacuum, when the valve is open higher.

 

I hope that wasn't too overwhelming.........

 

For those who like numbers:  add up all the volumes at all the lift points except .350" as the cams don't lift to here, now double the result.  Now compare before vs after.... Before 1236.2 cfm total, vs after 1354.2 cfm

 

 

Edited by oldeskewltoy

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Not overwhelming, it just took a picture of a circle with a cross in it on the back of an envelope...

Have you ever seen a K head Dan?? or shall we send one over for you to play with??  I think it would be an amazing educaton for all of us on here!

 

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12 hours ago, altezzaclub said:

 

Have you ever seen a K head Dan?? or shall we send one over for you to play with??  I think it would be an amazing educaton for all of us on here!

 

a LONG time ago... back when I began, a local friend had a 84 Starlet(?) with a 4KE, and he had spent $$ on a ported head, and intake.   Well his ported head had a crack, and so after we bought a replacement KE head, I GENTLY did some porting, mostly to try and match his head to the ported intake.  I did a tiny (insufficient) amount of exhaust porting as well.  The most significant work I did on it was to clear away casting marks in the top of the head to allow for better oil drainage

untitled40.jpg

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I love sitting back and reading over these heads you've done OST, I have learned a lot too, Thank you for sharing!

on that note, when I get my 4A-C head back from the shop (getting the clean and straightening) I might just try to chew on the old cracked head to see what damage I can do.

unless you want to look at/destroy it for educational purposes?

..then I'll get back to my 7A project.

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