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Bigport 4age barrys apply here


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Yeah its pretty hard to find any clear results on the port filling thing.    then there is pretty much anyone with  "high power" / "atlantic"  4age's.  that never show their dyno results.  all the ones ive found are dead in midrange.

I have played with the idea of straightening out the  ports by cutting the port back and raising the roof up.   but  really cant go high/ deep enough into port, before breaking out into the valvetrain area.   to get much advantage.

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As i suspected   answer is:  c) wont do shit
green no bits in port.  pink bits in port
Run with my smallport 47mm itb setup

1296529297_itbfillnofill.jpg.10360302c0eea17c838df97ce88758e7.jpg

 

 

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Yup.    and i take back all the horrible things i said about bigport head.   Its almost making the same power as smallport head,  when they both have a decent intake manifold setup.

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small vs bigport?     stock there is  no difference in chambers.  only thing that's  different is the intake ports themselves.       From the port divider onwards  the early bigport head (head on engine now) actually  has the smallest ports out of all of them.  the choke area is smaller than smallport head.  

The smallport head im comparing it to has had some work done in chambers and exhaust ports. not much on intake side.

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Soo,   turns out the tvis wasn't opening all the way.  thought results seemed weird...    vid has been fixed and reuploaded   / heres the graph. 

174995343_tvisfail.png.4307694760603e4045cce16b9e351511.png

 

 

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so governing restriction is the intake valve opening/curtain area rather than the ports smallest cross section?

more cam lift or bigger valves needed to max out port flow?

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Port shape seems to be the difference between them.  smallport best shape  most power.   early bigport  2nd best.  worst is the late bigport.   I just finished testing the one @kyteler sent me.   its a few kw down on the early head in the top end. both with stock intake and itb's.   It has the biggest ports all the way to valve out of them all, also has a shitty short turn radius. So yeh, thats why redtop bigport is such a turd.   Not sure why mr toyota made the later heads worse,  maybe the engineer behind it was like screw this fwd junk

 

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6 hours ago, Testament said:

so governing restriction is the intake valve opening/curtain area rather than the ports smallest cross section?

more cam lift or bigger valves needed to max out port flow?

I think someone in Australia did a bunch of work years ago on the old 1ggte cylinder head including cross sectional surgery.. Basically the outcome was the port area yielded next to no gain, small gains at the valve guide transition area, but it was really livened up once some larger valves were added to the equation.. 

 

I'm not sure if the same rings true of the 4age, although they would be of a similar Era to a boat anchor 1ggte so maybe the same dude from yamaha/ Toyota in Japan penciled down the initial design?

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14 minutes ago, Spencer said:

Yes I have heard many a barry yarn that they need bigger valves, not sure but didn't think there is much room for that carry on.

Yeah possibly not, if only there was some means of forcing air in there a bit faster, perhaps under pressure. 

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1 hour ago, cletus said:

or perhaps adding an extra intake valve? 5 per cylinder for a total of 20 valves 

Wash your mouth out with that 20v talk.   

1 hour ago, mjrstar said:

Yeah possibly not, if only there was some means of forcing air in there a bit faster, perhaps under pressure. 

same for that turbo talk 

 

From memory the 1g valves are really small.    4age isn't too bad but can go bigger. which requires new seats installed, so starts to get spendy.    but yeah both oversize ports.

I find it amusing how its the total opposite of what people think.   bigport will be good for more top end power..

227629906_earlyheadvlateheaditbealryvlate.png.aebe6831901ae53167a5028e2ace9095.png

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2 hours ago, mjrstar said:

Yeah possibly not, if only there was some means of forcing air in there a bit faster, perhaps under pressure. 

 

LPG?

 

So keen to see petrol vs lpg.

16V vs 20V.

More vacuum cleaner oil separator

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