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Discussion Starter #1
Do the NA and TT heads have the same valve specs? I think I read that the cam specs are the same. Are parts interchangable between the heads (exc. cam w/ distributor drive)?

Has anyone flow tested each head?
 
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Discussion Starter #2
i am pretty sure the NA head flows better than the TT head.

Hamid
 

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all motor baby!
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NA head has different manifold bolt pattern. TT exhaust ports are smaller than NA and ports 1&3 and 4 & 6 are directed towards ports 2 & 5 respectively to assist with flow to provide more continuity with the exhaust manifold/twin turbos - the NA ports come straight out. From what I understand the valve sizes are the same exhaust 29 mm, and intake 33.6 mm. Ferrea (www.ferrea.com) make 1mm oversize valves.
The valve activation is via a 'shim over bucket' mechanism. The buckets are 31 mm diam, shims 28mm.
Unfortunately I can't tell you about the comparative cam specs, the NA lift is around 8-8.5 mm, but I haven't had them profiled yet. No idea about the TT, but Crower cams (www.crower.com) have a listing for a range of 2JZGTE cams.

For more info regarding the TT head I would direct you to www.t04r.com. There are some beastly Supras there!

I too would like some more info on the GE/GTE cam specs.
 

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King of the NA-T's
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The na head also has more restrictive intake ports.

The cam specs are virtually identical. Valve lift between the two are identical, and duration is 233.

intake lift .325"
exhaust lift .331"

Intake open and closing numbers are also identical:

open 3 deg BTDC
close 50 deg ABDC

The exhaust open and closing numbers are slightly different

TT open 52 deg BBDC
TT close 4 deg ATDC

NA open 53 deg BBDC
NA close 3 deg ATDC
 
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Discussion Starter #5
Good info.

What about flow #'s? Has anyone seen any?
 

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all motor baby!
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Thanks DaveH. That's very handy.

I will be flowing a NA head (for an NA application) in the next fortnight or so. I'll happily post some pre and post porting flows then. However, I'm sure a lot of people have done this already.

Just to slightly hijack the thread, does anyone know how the valvetrain copes with high lift cams given that it is shim over bucket? Is there a propensity for the shims to be 'spat' out? Does anyone out there have any experience with this?
I'm converting to shim under bucket anyway, but I'd like to know for future reference.

Cheers Dave.
 
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Discussion Starter #7
gianttomato,

Do you have a source for aftermarket cams?
 

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all motor baby!
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Not brand new billets - I'm getting the lobes welded up and then a new profile ground on. I appreciate this is not ideal, but it is a lot cheaper and I've never had probs.
Looking at a 304 deg profile with 11.5 mm lift for a BEAMS 3SGE.
 

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So I take it the GTE Head will bolt on to a 2JZGE ? what modifications will have to be done? and what do I Do about the crank driven distributor? or is there away to mod it to work? Please help me out Thanks BRett
 

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King of the NA-T's
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gianttomato: I'd definitely be interested in seeing some flow numbers. :) This is for the stock head?

Xdreamer: the gte head will bolt on, but it is about impossible to get it to work with the na ecu (since it needs the distributor). If you do the gte head, you should change to the gte ecu.... which is really opening a can of worms.
 

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Back in Long Island =)
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Can I get a piggyback or motec setup to control this? Has it been done if so give me more info please. Thanks
 

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DAVEH:

dave, how many miles are on your supra? sorry for the off topic but im curious as to that. when is it considered "too late" mileage wise to go na-t?

bob
 

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King of the NA-T's
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I had 52k miles on it when I converted... I have around 72k now. IMO, if you have over 120k miles, you would want to check your engine over carefully (compression/leakdown tests ect) before thinking about turboing it. Most likely even at that mileage things will be fine... but that is when I would check things before turboing.
 
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