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post #1 of (permalink) Old 10-01-2003, 04:05 AM Thread Starter
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G13 head flow test results

Hey guys

I'm about to do some porting on a spare head for my zook, and I've just flowed my totally stock g13 head on our flowbench at work. Here is the graph.



The interesting thing is that the exhaust flow is way up on the intake flow, especially at low lift. Typical heads have a the exhaust port flow 70-75% of the intake port right through the range. Some go as low as 60%, and over 80% is generally only used in turbo applications.

The zook is running at 100% up to 0.150" lift! It stays at around 80-85% at large lifts. I almost don't believe this, so I might just have to re-flow it to check!

I read with interest that everyone is putting 2.5mm larger diameter 1.6 exhaust valves in their head and claiming to get better performance. I've seen a pic of a head with them installed, and it made me wonder... It looks like there hasn't been much chamber work done, and the valve could actually be shrouded worse than the stock valves? Maybe they actually flow worse? This could even out the flow ratio and possibly improve performance.

Its not uncommon for an over exhausted head to run poorly, and go much better when the flow is reduced in the port, sometimes by cutting poor valve seats or otherwise impeding exhaust flow.

Anybody else actually done any flowbench work, or have an opinion? Sarge? DaveAZ?

Also, does anyone know what the stock valve lift is? My spare cam is in storage so I can't measure it at the moment.


Ben
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post #2 of (permalink) Old 10-01-2003, 06:30 AM
 
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Re: G13 head flow test results

Now thats good tech [img]images/graemlins/goodpost.gif[/img]
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post #3 of (permalink) Old 10-01-2003, 01:26 PM
 
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Re: G13 head flow test results

Maybe it flows that way because your south of the equator? [img]images/graemlins/chairfall.gif[/img]

[img]images/graemlins/beach.gif[/img]

Seriously, keep us posted!
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post #4 of (permalink) Old 10-01-2003, 05:53 PM
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Re: G13 head flow test results

Yeah, I get it, it's like the water emptying down the sink. Down here it turns the opposite way to up there. So it prolly works that the exhaust gases turn the right way for the head flow too. But only if the head is facing west
yeah ?
Yes Ben that is good tech indeed.
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post #5 of (permalink) Old 10-01-2003, 08:09 PM
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Re: G13 head flow test results

With the larger exhaust valve , and some serious bowl work behind both valves , those numbers will go way up . Try the lift/flow equations again with .414" of lift at the valve , see what happens .....
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post #6 of (permalink) Old 10-01-2003, 11:07 PM
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Re: G13 head flow test results

Ben, there is a special price on New Boggers for our club members in our newsletter.
31x12.5 Boggers reduced to $511.00 each.( $585 with tax and freight.)
Tempting ?
(He he eat yer heart out you mericans,)
Alfie
post #7 of (permalink) Old 10-02-2003, 02:25 AM Thread Starter
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Re: G13 head flow test results

Hey Sarge.

At 0.400 lift the flow ratio is around 86% still.

The plan first off is to remove that stupid brass tube and fill the hole, and cut the seats out closer to the valve size with some raduised exhaust seats.



Then fix the horrible short turn and bowl area, clean up the guide boss and remove as much of the bulge in the exhaust port as possible. Seriously, those short turns are some of the worst I've ever seen.
After that, we'll un-shroud the valves a bit in the chamber and clean that up, mill it down to get about 10:1 compression.

I don't think I'll try the bigger exhausts first up. We'll try to keep the flow ratio more constant right through the range.
Once I've done these mod's I'll re flow it and see what I've got.

I've been thinking about making up some new phosphor bronze guides, and maybe even copper berrylium seats, but we'll see. That might just be getting silly. [img]images/graemlins/smile.gif[/img]

Does anyone have the 'dynomation' engine simulation software? I'd be interested to do some simulations if anyone has access to a copy.

I'll let everyone know how things go as I progress along.

Ben
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post #8 of (permalink) Old 10-02-2003, 02:40 AM Thread Starter
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Re: G13 head flow test results

</font><blockquote><font class="small">In reply to:</font><hr />
Ben, there is a special price on New Boggers for our club members in our newsletter.
31x12.5 Boggers reduced to $511.00 each.( $585 with tax and freight.)
Tempting ?

[/ QUOTE ]

Hmmm. Thats getting better than $800, but someones still making a killing importing these things... There's still $215 per tyre going somewhere, and that cant be going on shipping. [img]images/graemlins/cussing.gif[/img] [img]images/graemlins/chair.gif[/img]
One of the guys at work is into hot rods, and has a freind who imports tyres by the container load, so he's looking into them for me at the moment to se what he could get them here for.

Ben
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post #9 of (permalink) Old 10-02-2003, 05:40 PM
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Re: G13 head flow test results

What about just using the 1.6 head (8 valave) would this give the bigger valves and better flow ? Anyone done this care to comment?

As for the cost of imported tyres, well, it's called profit. Everyone including the Gov't and freighters who touches the tyres (or just has their hand out) gets a cut.
Alfie
post #10 of (permalink) Old 10-02-2003, 09:03 PM
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Re: G13 head flow test results

The 1.6 head has larger chambers , so you'll actually lose compression . If you cut out the bowls , taper off the ends of the guides , and smooth out the turns as much as you can ( I cut mine out almost 1/4" ) you will need a larger exhaust valve . From my testing during the head work , as soon as the intake area was cleaned up the temp went up with it under a hard load . The engine pulled ok , but it sure pulled a lot better with the larger valves . Maybe just do some port work , and keep testing to see what yeilds . Be nice to have several heads to play with along with that flow bench [img]images/graemlins/smile.gif[/img]....
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