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Location:
sydney
Registered:
May 2002
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bigport head on 100kw bottom end...should i do it?
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Tue, 26 November 2002 21:41
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ok,
i have a import 100kw motor which i scored for free, have the head off and all looks ok on the bottom end. i jhave a spare bigport head also, which will need a reco, but shouldnt be too much. should i slap it together and put it in my sprinter as i am using a standard bigport.
is it worht the hassle, would i notice any performance gains.
also what ecu's do people use when they have done this?
not really a problem as i have EMS running it anyway, but just curious if i should get it tuned again...
cheers
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I supported Toymods
Location:
South of Wollongong
Registered:
May 2002
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Tue, 26 November 2002 23:38
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have read that before, and i coulndt be bothere cutting and welding a 100kw inlet manifold. i know the 100kw head is better, but thats not what im asking.
will it be better to have the higher comp bottom end?
i remember hearing toby did this...
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Tue, 26 November 2002 23:50
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i would imagine so... as long as piston clearance etc etc are ok, i cant imagine there being anything wrong with this setup. Of course the 100kW head and intake are better, but like u said need to be reversed.
Myabe it might be worth reading thru someof the stuff written on the club 4ag website.... they are king for sprinters and 4ag's
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Registered:
June 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 01:12
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If it comes down to $$$ surely it would be cheaper to use the good 100kw with the reversed TB than reco the big port head!?!?!?
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 01:16
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well, i dont have the inlet manifold for it... or the throttle body etc,
if it comes to it i can take my existing head of and use that, i know thats ok...
maybe it's not worth the hassle eh,
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Location:
Melbourne
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 01:26
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we did this conversion on an aw11 - it's certainly worthwhile!!
T
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 01:28
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ok, so thats what ive been wanting to hear...
personally i like the peakier feel of bigports, and i thought the bump in compression would be good.
any other suggestion with this toby or just do a straight swap with it,
cheers
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Location:
The Central Coast
Registered:
October 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 03:24
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Sure the compression on the 100kW motor is 10.3 and on the 86kW motors it's 9.4, but what's to say that the compression isn't increased because of the design of the 100kW head ie less cc's.
At most, I reckon your compression would be closer to 10.0:1 after the swap (If your pistons/bores aint rooted)and if the compression height on the 100kW pistons are higher than the 86kW.
For one thing, the bottom end swap is good for the oil squirters (piston coolers), and depending on if you had a blue top big port motor, you could be upgrading size of cranks and rods too for good measure.
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 03:27
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the 100kw pistons have a raised area in the midlle of the piston, thats where i believe thay got the xtra compression from, so i heard. and yes it would be a tougher bottom end, and it would be a better base if i was to put some boost through, with some GZE pistons or forgies of course... but thats another story down the road 
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Location:
The Central Coast
Registered:
October 2002
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Location:
Sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 03:41
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Ok having just recently rebuilt my 100KW bottom end and 86KW head
just do it 
ACL 86KW pistons on left, ACl 100KW pistons in middle, toyota 100KW on right
Cheers
Ben
AE86 Trueno 4AGE
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 03:46
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so u just did this combo??
and approve... thats 2 yes reply's
what did u do to the head? anything special?
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Location:
Sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 03:52
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My head had been heavily ported, just to help flow and remove burrs and stuff, and then rebuilt. When i bought the car it came in this configuration. So why change a good thing??
It will be getting a tune and going on the dyno hopefully on friday, so ill let everyone know how it goes.
Cheers
Ben.
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 03:55
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hmm, excellent...
i did my current motor in my sprinter at home, including backyard porting. it seems ok. seems to scream up top a bit more than other standard 4age's that i have driven, but that could be tune or anything.
does anyone have any recommendations of where to take the head in sydney??
cheers
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Location:
Melbourne
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 04:27
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i cleaned up the ports on the 86kw head, otherwise motor was stock. we fabed up a set of extractors from a blacktop 20v to suit the mr2, and a truck muffler with a high-flow cat. car also got a blacktop 20v 6 speed at the same time (bit of work to fix up the gear linkages) - it ran better than it should have - motor was very good - it just ran out of puff around 6.5-7k rpm - a bigger set of cams would have helped here (262/276) with adjustable cam gears.
it's a cheap performance upgrade.
also - the toyota c/r are overly optimistic - 100kw is not 10.3, supposedly closer to 9.9:1. you can shave 20 to 60thou off the head though which will help fix this...
T
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Location:
The Central Coast
Registered:
October 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 04:36
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Just quoting the compression figures for Phil Bradshaw's page.
http://home.clear.net.nz/pages/phil.bradshaw/4AGE% 20into%20RWD.htm
I heard if you shave the head, you have to change the timing of the cams, because they will retart the closer they get to the block. But 20thou shouldn't make that much difference....then again, some people are pretty picky.
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 04:45
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ahh, i was wondering why the timing on my current motor was funny, and i had to turn the dizzy back heaps to get it up to about 10 degree... i had my head decked,
well, anyways i better get into this motor swap eh,
first stop, head work...
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Location:
The Central Coast
Registered:
October 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 05:00
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I think you've had a unanimous agreement. 
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 05:16
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just becuase im an idiot 
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Location:
Melbourne
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 21:55
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adjustable cam gears will fix...
T
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Location:
sydney
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Wed, 27 November 2002 22:00
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can you help me some of those toby? what are they worth, i know the hks ones are like 500 bux for a pair...
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Location:
Melbourne
Registered:
May 2002
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Re: bigport head on 100kw bottom end...should i do it?
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Thu, 28 November 2002 01:53
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well we've had 8 sets on order for a year now... so i'd like to say yes, but in reality i can't promise you anything...
if i had them i could tell you exactly how much they will be, but i'd suspect $250-300 ($300 if anodised with degree marks)
T
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