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Location:
Lost in the K hole
Registered:
May 2002
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Curious :: 4age / 7mge intake ports
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Thu, 31 October 2002 12:49
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ok this is an interesting one!!
stripped an early (87) and also a late (91) model 7mge head today (and i believe the 4age head is remarkably similar -thats why its in the title) and i noticed an interesting difference in the intake ports b/w the two models....
see image below:
this is basically an internal 3D view of the intake and valve ports of the two models of head (1987 and 1991). the red is the dividing wall, as seen inside the intake port, that separates the incomming airflow into (towards) the two valve ports.
now the earlier model has a longer divider that ends with its leading edge comming to a sharp finish. the later model's dividing wall is a LOT shorter, with its edge much closer to the valve ports, and it ends much more bluntly.
considering that in either case (ie whichever head i chose to build up) i will be doing some tungsten work on the intakes, and the leading edge of either wall will eventually be knifedged... "which intake port separator - the long or short - will give the better result" ???
cheers
ed
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Thu, 31 October 2002 13:00
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Yo dude, I think you'd have to define what better is in your definition 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Thu, 31 October 2002 13:22
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ok...
perhaps not "better"
rather, what are the points of discussion that result as a consequence of these differences? ie low torque loss but better flow characteristics in the shorter separator? i have no idea really. i could make up a few points, but want to see what others have to say 
cheers
ed
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Location:
Sydney
Registered:
July 2002
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Re: Curious :: 4age / 7mge intake ports
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Fri, 01 November 2002 02:50
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what do these two engines produce on the dyno?
perhaps it was a method of cost cutting rather than a performance issue?
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Toymods Board Member
I supported Toymods
Location:
Turramurra, Sydney.
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Fri, 01 November 2002 06:35
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Where abouts are the injectors pointing?
Sounds/looks like it might have something to do with atomisation. It certainly flies in the face of convention.....
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Sydney
Registered:
July 2002
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Re: Curious :: 4age / 7mge intake ports
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Fri, 01 November 2002 07:22
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Are they the single jet type injectors or the newer ones designed for 2 intake valves?.. perhaps thats it.
I know the earlier big port 4age have the single jet style.. thtas because 4 valves per cylinder wernt that common.
the later 100kw and the GZE has teh dual spray injectors
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Location:
Eastern Sydney
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Fri, 01 November 2002 09:19
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I have to ask,where does the 4AGE come into this thread? I haven't seen anything related to them so far,other than saying the head design has a similar layout...like pretty much any 4 valve head does...
Justin...
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Fri, 01 November 2002 13:56
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4age and 7mge have remakably identical heads, except obviously the 7m has 6 cyl. any info that people may have about the 4age in this specific regard may be able to shed some light.
thanks for your curiosity.
cheers
ed
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Sat, 02 November 2002 08:39
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Ed I would be very carefull about knife edging the port divider. you may find the 7MG head is like that to improve vapourisation of the fuel, particularly because of the short length of the runner, by knife edging it you will reduce the surface area and then maybe your fuel mixture will be poor and you could develop hot spots on the pistons. If you are going to do anything a mere polish job will make a significant difference and if youve got the money bigger valves are worthwhile too.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Sat, 02 November 2002 14:11
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micheal (and anyone else who cares),
ive done a fair whack of reading over the last few days, and ive come to the conclusion that knife edgeing isnt all its cracked up to be. it has its applications, but they are very specific indeed.
as it is anyway, ive decided to go with the short divider intake configuration basically due to the fact that that head is in extreemly good nick compared to the long divider head.
with that in mind there are some very obvious areas that ill be attacking with the tungsten, the port separator not really being one of them (though i will radius the face of it a little, smooth it off, and blend its edges little better.)
these include matching and blending the port bowel, the valve seat machined shoulders, the short side radius, and also blending the roof of the main port, and its apprach to the port divider and the valve stem guides.
on top of that, a general smoothing over, and dag revomal etc.
unfortunately, as far as vlave sizes go, im kinda stuck! i would love to knock them up a size, but they end up interfering badly at high lift  . im not exactly sure what the overlap of the cams is going to be like yet, but ballparking it, the valves are going to get mightly close to each other!!
cheers
ed
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Sun, 03 November 2002 03:29
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If you are going to go with bigger cams be very carefull how short you cut the valve guides, although this was a common practice amoungst early single cam engines with good results there was a tendency for bent valves, im not sure what length they are on the two heads youre talknig about but on the 3AC head they were quite long and I cut about 4mm off them with no ill effect (that I can recall) obviously the airflow is improved but I dont think it was dramatic for the effort involved doing it.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Sun, 03 November 2002 12:32
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yeah, i had a look at the valve guides, and decided not to lop them off, rather i contoured the leading and trailing edges of them, and swept their lip up the valve stem a bit.
am even thinking, might try and find some jb weld, and fill in some areas around the base of the guides, help sweep them into the flow a bit better.
fu_king tedious work tho. took me 4 hours to do one cyl (in and ex) though, i have to say, whilst id call it a pretty 'mild' job (i didnt really change the shape of the ports that much) i managed to gain 2mm dia on each of the ex valve ports, and 1mm dia on each of the intake valve ports.
i ended up mildly tapering the leading edge of the divider, well not even tapering, just radiused it with a bit of a taper.
and can i say ONE thing EVERYONE should do if they have a 7m head off, grind the short radius... ITS A MESS!!! freaking valve seat machining is a meat axe job in there!
anyway, gotta find me a flow beanch, i wanna test this puppy!
cheers
ed
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Mon, 11 November 2002 05:44
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howd it go on the flowbench?? what is a stock one flowed at btw?
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Curious :: 4age / 7mge intake ports
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Mon, 11 November 2002 06:57
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michael...
still saving up the $80-$90 im going to blow on the flow bench adventure...
anyone curious about the 7m head flows that wants to contribute some $ towards getting the test done?? 
hmmm, sponsorship, now theres an idea....
cheers
ed
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