IS-F heads may need porting/flow work
09-02-13, 01:57 PM
#1
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IS-F heads may need porting/flow work
I finally got around to pulling the valves out of an IS-F cylinder head. The short of it, the bowl area of the port appears to need a bit of work. I'll take some pictures if anyone around here is interested?
09-02-13, 02:48 PM
#2
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I remember seeing testing videos and images were mixture formation was to the right of the piston bowl during DI operation.
09-03-13, 04:27 AM
#3
Pit Crew
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It's not the short turn area, rather the back wall and sides have the typical ridges and bumps remaining after machining the throat. I say may need work, as sometimes ports flow in mysterious ways.
09-05-13, 01:31 PM
#4
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Ports always flow in mysterious ways. If it were intuitive, it would be easy.
Many times these are unique to the casting. Core shift in the casting process can turn a normal head into junk. I once did a Supra GTE head with the seats more than 2mm off center because the head wasn't indexed to the ports when they cut the holes for the seats. If the owner hadn't been going for way oversized valves, I would have told him to get a better head. I've seen other heads where the seats were unbelievably concentric and there was very little to do to improve on the factory job. Luck of the draw for sure.
This is a GE head I did. I've done a bit of this stuff from time to time. The car it is on runs 8's.
This is a GE head I did. I've done a bit of this stuff from time to time. The car it is on runs 8's.
Last edited by lobuxracer; 09-05-13 at 07:37 PM.
09-07-13, 06:13 AM
#5
Pit Crew
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Have a look, red arrows point at the typical steps/ridges that remain after machining. However, valve seat work looks excellent with what are probably 60/45/30 angles.... intake valves are back cut 30 degrees, too.
09-09-13, 09:05 PM
#6
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Actually the thing I find most interesting is the carbon in the squish area. I'd be working very hard to get the squish right so there's no carbon at all where the piston comes close to the head. Obviously in this head it's nowhere near close enough.
The machining you're seeing is typical Yamaha factory work. Basic blending the seat into the port, and this is highly individual. Yes, there's opportunity in the head in the photo, but I'd be looking at either 7 angle or full radius seats if I wanted more along with blending the seats a little better and looking at the throat diameter to valve diameter ratio. Plus a couple of other things...
The machining you're seeing is typical Yamaha factory work. Basic blending the seat into the port, and this is highly individual. Yes, there's opportunity in the head in the photo, but I'd be looking at either 7 angle or full radius seats if I wanted more along with blending the seats a little better and looking at the throat diameter to valve diameter ratio. Plus a couple of other things...
09-10-13, 05:58 AM
#7
Pit Crew
Thread Starter
Yes, as expected on many a DI engine, this one has significant carbon on the intake valves and combustion chambers. The chamber in the head, which is 95mm in diameter, is recessed .3mm around the entire circumference, and of course tapers deeper from there.
The machine work on the ports doesn't look any better than the Tundra 3UR heads. The valves are the same diameter between the two heads, valve jobs appear to be the same, also. Valves are splayed at the same angles. The upper sections of the ports are larger on the 2UR, no surprise there. I do know the flow on a stock 3UR intake port at .5" lift is an excellent 295 cfm, so I can imagine what the 2UR can do... flow numbers are not everything, just a piece of the puzzle to working out more go power.
The machine work on the ports doesn't look any better than the Tundra 3UR heads. The valves are the same diameter between the two heads, valve jobs appear to be the same, also. Valves are splayed at the same angles. The upper sections of the ports are larger on the 2UR, no surprise there. I do know the flow on a stock 3UR intake port at .5" lift is an excellent 295 cfm, so I can imagine what the 2UR can do... flow numbers are not everything, just a piece of the puzzle to working out more go power.
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09-10-13, 09:03 PM
#9
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Yes, as expected on many a DI engine, this one has significant carbon on the intake valves and combustion chambers. The chamber in the head, which is 95mm in diameter, is recessed .3mm around the entire circumference, and of course tapers deeper from there.
The machine work on the ports doesn't look any better than the Tundra 3UR heads. The valves are the same diameter between the two heads, valve jobs appear to be the same, also. Valves are splayed at the same angles. The upper sections of the ports are larger on the 2UR, no surprise there. I do know the flow on a stock 3UR intake port at .5" lift is an excellent 295 cfm, so I can imagine what the 2UR can do... flow numbers are not everything, just a piece of the puzzle to working out more go power.
The machine work on the ports doesn't look any better than the Tundra 3UR heads. The valves are the same diameter between the two heads, valve jobs appear to be the same, also. Valves are splayed at the same angles. The upper sections of the ports are larger on the 2UR, no surprise there. I do know the flow on a stock 3UR intake port at .5" lift is an excellent 295 cfm, so I can imagine what the 2UR can do... flow numbers are not everything, just a piece of the puzzle to working out more go power.
10-07-13, 10:10 AM
#11
Cylinder Head Flow
I've been fascinated by cylinder heads for forty years. Done a really lot of two valve heads and have seen quite a lot of power at higher RPM. I've never done four valve heads but had a 1989 Ford SHO, with Yamaha heads, that I worked on for 20+ years. The thing was nearly as fast as my F to over a hundred MPH. One of the reasons I bought the F was because I heard Yamaha had a hand in developing the motor.
I've not seen the IS F combustion chambers until now. From the photos I would clean up the ports under the valve seats. The transition from the port to the seat needs to be smooth. Get rid of that ridge under the seat insert. Smooth the port all the way from the intake to the seat. Same with the exhaust side. Clean up the valve guide boss by blending the ridge and call it good. There could be 5 or 10 horsepower there. A five angle valve job at 6800 RPM will not get you much. I'm not sure I would do much more with the combustion chamber except to remove sharp ridges.
If these four valve heads can flow 295 CFM at whatever Hg? That's awfully good. More won't get you much until the motor goes more than 7500 RPM.
So if these heads are similar to Tundra heads where is Yamaha's hand in this motor. I thought they were the ones that made the high RPM power. Maybe they did the camshafts.
I've not seen the IS F combustion chambers until now. From the photos I would clean up the ports under the valve seats. The transition from the port to the seat needs to be smooth. Get rid of that ridge under the seat insert. Smooth the port all the way from the intake to the seat. Same with the exhaust side. Clean up the valve guide boss by blending the ridge and call it good. There could be 5 or 10 horsepower there. A five angle valve job at 6800 RPM will not get you much. I'm not sure I would do much more with the combustion chamber except to remove sharp ridges.
If these four valve heads can flow 295 CFM at whatever Hg? That's awfully good. More won't get you much until the motor goes more than 7500 RPM.
So if these heads are similar to Tundra heads where is Yamaha's hand in this motor. I thought they were the ones that made the high RPM power. Maybe they did the camshafts.
10-08-13, 07:09 AM
#12
Pit Crew
Thread Starter
The CFM info came from member over on one of the Tundra forums.
The ISF and Tundra(also the LS V8) share valve size/dimensions and head gaskets, otherwise the Yamaha head is very different... though obviously based on the Tundra, port cross section is larger, possible steeper, solid lifters, pics if you want em.
The ISF and Tundra(also the LS V8) share valve size/dimensions and head gaskets, otherwise the Yamaha head is very different... though obviously based on the Tundra, port cross section is larger, possible steeper, solid lifters, pics if you want em.
10-08-13, 11:38 AM
#13
I'm of course, fascinated by this stuff. I'm not about to take my motor apart just to look inside the heads, so if you could, I'd love to see the ports on a set of the Yamaha heads. Yamaha really does have a reputation for quality cylinder head designs.
I can understand that valves on four valve heads do not need to be large unless the motor runs at very high RPM. I'd rather believe that a good clean port, smooth but not enlarged, possibly like your GE head would be the ideal design. Don't know much about motors with port injection plus direct injection, but would still guess that smooth air flow would be the ticket. The 11.8 to one compression is certainly a big bonus.
Love to see the ports?
I can understand that valves on four valve heads do not need to be large unless the motor runs at very high RPM. I'd rather believe that a good clean port, smooth but not enlarged, possibly like your GE head would be the ideal design. Don't know much about motors with port injection plus direct injection, but would still guess that smooth air flow would be the ticket. The 11.8 to one compression is certainly a big bonus.
Love to see the ports?
