oldeskewltoy
oldeskewltoy UberDork
10/28/20 10:13 a.m.

core shift happens on either side of the head, this time on the exhaust side.....

 

oldeskewltoy
oldeskewltoy UberDork
2/20/21 9:56 a.m.

After porting....  3 angle, with back cut intake valves 

 

oldeskewltoy
oldeskewltoy UberDork
3/15/21 6:46 p.m.

Porsche 931 (aka 924 turbo)...  3 down........ 

 

As the the throats are already "pushing" too large (both are @ 90% of the valves diameter)  I limit my work to the bowls, and the short radius.  Untouched bowls are the last cyl on the right

 

mke
mke Dork
3/19/21 9:37 a.m.
oldeskewltoy said:

Sometimes you need more than a Dremel... sometimes you need to know to stop..........

Indeed.......

oldeskewltoy
oldeskewltoy UberDork
3/22/21 11:16 a.m.

ouch.......  did you weld that patch in, or epoxy? 

mke said:
oldeskewltoy said:

Sometimes you need more than a Dremel... sometimes you need to know to stop..........

Indeed.......

 

mke
mke Dork
3/22/21 1:26 p.m.
oldeskewltoy said:

ouch.......  did you weld that patch in, or epoxy? 

Welded. 

Sadly it was not a mistake is execution as much as of judgement so there were 23 more just like it to weld and another 12 of these because who want to strike water when you could strike oil!  If there is a wrong way to treat a head, I probably know it :(

oldeskewltoy
oldeskewltoy UberDork
4/7/21 12:51 p.m.
mke said:
oldeskewltoy said:

ouch.......  did you weld that patch in, or epoxy? 

Welded. 

Sadly it was not a mistake is execution as much as of judgement so there were 23 more just like it to weld and another 12 of these because who want to strike water when you could strike oil!  If there is a wrong way to treat a head, I probably know it :(

so...  you raised the roof... and rather substantially....

 

new intake(also custom) I assume??   

 

That kind of work I'll leave to the local (Loynings) race shop...  they do all kinds of serious mods...  like this Toyota 2GR...  not much left of the original timing (cam timing) gear left....  This one made about 440hp

 

 

 

Or this Ferrari with modified cam timing gear

 

mke
mke Dork
4/7/21 2:29 p.m.
oldeskewltoy said:

so...  you raised the roof... and rather substantially....

 

new intake(also custom) I assume??   

Yes.  The heads are from a flat 12 with the intakes pointing basically straight up and nice, but I put them on a V12...and they ended up pointing basically right at each other with no way to get a decent intake in it.  I fiddled a little bit to try to figure out a cross ram.....then gave up and moved the port and made a proper looking intake.

That loos like a 2 vavle 308 engine!  Very similar to the 4v engine I pulled out of this car.  The cam stuff looks OEM or very close to, but the waterpump had been altered,  maybe a drysump setup?  very cool.

oldeskewltoy
oldeskewltoy UberDork
5/22/21 5:13 p.m.

back to my stock in trade...... 

 

fixing, and improving old 4AG heads..

 

oldeskewltoy
oldeskewltoy UberDork
5/27/21 10:24 a.m.

for a twincharge build.....  need to make some room for exhaust flow

 

oldeskewltoy
oldeskewltoy UberDork
6/3/21 1:23 p.m.

Same head....(twincharge)   when running boost, you have to account for heat.  While the valve on the right is still technically good (FSM minimum margin .5mm), I'd rather have a bit more margin to accommodate the expected heat.

 

 

Stefan (Forum Supporter)
Stefan (Forum Supporter) MegaDork
6/15/21 3:58 p.m.

In reply to oldeskewltoy :

Any data on the flow rates for that 931 head before/after?  Just curious.  It looks great, you really do awesome work!

I should send you one of my 924 NA heads (no combustion chamber, some slight differences in port shape) just to see what you can do with it.

oldeskewltoy
oldeskewltoy UberDork
6/16/21 6:43 p.m.
Stefan (Forum Supporter) said:

In reply to oldeskewltoy :

Any data on the flow rates for that 931 head before/after?  Just curious.  It looks great, you really do awesome work!

I should send you one of my 924 NA heads (no combustion chamber, some slight differences in port shape) just to see what you can do with it.

He chose to just get the cleanup (bowl work) without the flowbench, so I can't answer you on before/after flow results

 

Same client as the 931 head.....

 

 

 

 

... and I'll be massaging a water cooled VW head for him shortly as well........

burdickjp
burdickjp Reader
7/27/21 6:27 p.m.

These are castings of a Suzuki F6A DOHC cylinder head. 657 cc. 3 cylinders.
Stock they make 65ish horsepower. With not too much effort they can be twice that.

Intake valves are 24.5 mm. Exhaust valves are 21.5 mm.
The valve seat mating face on them is about 3 mm wide. A back-cut seems like a good start here.

 

The darker molds here, the first 5 pictures, are the intake side.

The lighter molds here, the last 5 pictures, are the exhaust side.

Low hanging fruit: it looks like the head doesn't even have a 3-angled valve seat. Blending the seat machining to the port looks necessary. the short-side radius could be radius'd.

I've not played with a head with ports shaped like this. The spacing between valves is wide. The septums are thick. Thoughts?

oldeskewltoy
oldeskewltoy UberDork
7/29/21 2:21 p.m.
burdickjp said:

These are castings of a Suzuki F6A DOHC cylinder head. 657 cc. 3 cylinders.
Stock they make 65ish horsepower. With not too much effort they can be twice that.

Intake valves are 24.5 mm. Exhaust valves are 21.5 mm.
The valve seat mating face on them is about 3 mm wide. A back-cut seems like a good start here.

 

The darker molds here, the first 5 pictures, are the intake side.

The lighter molds here, the last 5 pictures, are the exhaust side.

Low hanging fruit: it looks like the head doesn't even have a 3-angled valve seat. Blending the seat machining to the port looks necessary. the short-side radius could be radius'd.

I've not played with a head with ports shaped like this. The spacing between valves is wide. The septums are thick. Thoughts?

 

 

Where are the throats currently at?   (bowl/seat id as a percentage of the valves OD).     The throats do appear to be pretty large already (85%+??)

3 angle, + a back cut typically improves low lift flow - especially if there is only one, or 2 angles originally.  working the short radius will also improves flow.  I like the basic shape of that intake port.

Both bowls appear that the valve stem[s] do impede flow some - some bowl work may increase the volume without hurting velocity.  On the exhaust side (large septum), I'd likely work the last 25mm, to allow the merging gases a shallower merge angle.  

burdickjp
burdickjp Reader
7/29/21 8:23 p.m.
oldeskewltoy said:

Where are the throats currently at?   (bowl/seat id as a percentage of the valves OD).     The throats do appear to be pretty large already (85%+??)

3 angle, + a back cut typically improves low lift flow - especially if there is only one, or 2 angles originally.  working the short radius will also improves flow.  I like the basic shape of that intake port.

Both bowls appear that the valve stem[s] do impede flow some - some bowl work may increase the volume without hurting velocity.  On the exhaust side (large septum), I'd likely work the last 25mm, to allow the merging gases a shallower merge angle.  

Intake valves are 24.5 mm in diameter. 8 mm into the ports the throats are 20.3ish mm. That's 83%. Good eye!


mke
mke Dork
7/29/21 8:33 p.m.

85-87% valve to throat is what I was taught is "right".

burdickjp
burdickjp Reader
7/30/21 7:45 a.m.

Even for 220 cc cylinders, these valves are tiny. I'm looking at my valve options.


One of my favorite starting point references is A Graham Bell's Four-Stroke Performance Tuning. It's a very empirical book, rather than academic or theoretical. It's been several years since I've read through this. My copy is falling completely to pieces. I'm getting excited all over again about it!

Table 3.1b lists valve sizes for four-valve motors. The smallest cylinder volume he lists is 250 cc with an intake valve 29.5 mm in diameter and an exhaust valve 25.4 mm in diameter. Extrapolating that table down, 220 cc would want 29 mm intake valves and 25 mm exhaust valves. This is much larger than my valve seats! I'm not sure there'd be room!

mke
mke Dork
7/30/21 10:27 a.m.

I personally don't think knowing the cylinder CC tells you very much about how to size valves.  What you can about I think is how much hp you are trying to make in the cylinder, then providing the air for that to happen.  I have a 250cc engine on my kids minibike, its 6hp@3000rpm ish, so 2 tiny valves are just fine.  If on the other hand you're looking for 200 hp/l, meaning 50hp from that 250cc cylinder then 4 valve as large as will fit in the bore might not be enough depending on the bore/stroke combination.  So what I'm saying is the first step is to decide what is is you're building, then how get there....bigger isn't also better unless its a max hp, costs be damned kind of effort.  I'll add I've worked stuff were cams are quite expensive so bigger valves but smallish ports to get good hp out of tiny cams was the order of the day.....lots of variables but it still all starts with deciding what you're trying to build exactly.

frenchyd
frenchyd UltimaDork
7/30/21 2:15 p.m.

In reply to mke :

Well said.  I have a performance trends computer program. There are ways to modify it so it will exactly reflect what you are working with (Ferrari, Jaguar, etc ).  Once you have that set up  then you can make changes and see the actual results. (+ or - 2% )  

    Cams, valves, compression, port size,  port flow,  bore, stroke, etc etc etc. 

  You actually have to give valid number to get valid data out, 

   The great thing is it's no longer guess work. You can see what the package you assemble with do without guess work. 
        It's shocking how far off some people's guesses are. They aren't trying to get things wrong they just don't realize the balance required to get real power. 
    Hint; the biggest cams, highest compression, biggest valves, and ports do not make the most power. 

mke
mke Dork
7/30/21 4:00 p.m.
frenchyd said:

In reply to mke :

Well said.  I have a performance trends computer program. There are ways to modify it so it will exactly reflect what you are working with (Ferrari, Jaguar, etc ).  Once you have that set up  then you can make changes and see the actual results. (+ or - 2% )  

    Cams, valves, compression, port size,  port flow,  bore, stroke, etc etc etc.

I use dynomation6, it gets very close

burdickjp
burdickjp Reader
8/1/21 5:40 p.m.

A Graham bell hand waves a lot in his books, but time and again I've found them to be great starting points. Whether I need to feed some analytical model or geometry to start testing, his numbers have been a great place to start.

oldeskewltoy
oldeskewltoy UberDork
8/1/21 6:38 p.m.
burdickjp said:
oldeskewltoy said:

Where are the throats currently at?   (bowl/seat id as a percentage of the valves OD).     The throats do appear to be pretty large already (85%+??)

3 angle, + a back cut typically improves low lift flow - especially if there is only one, or 2 angles originally.  working the short radius will also improves flow.  I like the basic shape of that intake port.

Both bowls appear that the valve stem[s] do impede flow some - some bowl work may increase the volume without hurting velocity.  On the exhaust side (large septum), I'd likely work the last 25mm, to allow the merging gases a shallower merge angle.  

Intake valves are 24.5 mm in diameter. 8 mm into the ports the throats are 20.3ish mm. That's 83%. Good eye!