3tgte bore diameters?

[steve-O]

hey everyone. i pulled the head off my 3tgte today. and to my suprise there are some score marks in the cylinders. so its goin to need a rebore or i've gotta source a new block. its already been bore out 20 thou. so i'm just curious what bores people are running and if you've encountered any problems etc.
cheers

[lilcrash]

i think the biggest u can go is 80 thou/89mm

[w810sc]

i know you can get 90mm pistons for the 2T-G/3T hybrid. keep us updated on the rebuild

[TA22 GT]

I wouldn't recommend going over 87mm for a turbo application as the bore wall thickness is getting too thin.
89mm bore for a 2TG is ok.

I'm planning to rebuild my 3T GTE shortly and will be using 87mm pistons.

Cheers,
Simon

[3T-GTE]

Hey Steve-O
Totally agree with Simon on this one...

I've tried going with 89mm with at 3T-GTE and while it will work, I would strongly recommend against it. It doesn't leave enough 'meat' in the cylinder walls for my liking.
Comparing it with various other 3T-GTEs, even with a good tune and intercooler setup and keeping the boost quite low - it always ran up to +10 degrees hotter than any other 3T-GTE I've built in the past.

87mm is the max I would go for a decent boosted engine.

I was actually about to rebuild the 3T-GTE in my white TA-22 using 87mm pistons, but I've got a proven 300rwkw+ 13BT rotary engine setup with a GT3540 sitting on the workshop floor that needs a new home...
so I'll probably have a 'few' spares soon if you need anything

Cheers,
3T-GTE

[steve-O]

thanks guys i've heard that 89mm is about the limit. i wasn't even thinking of goin that far. maybe 87mm but. it all depends whether the machine shop recons my pistons are no good anymore, and if the block is salvagable.
nice to know that there are a few spares out the if i need them though
i was thining of running about 20 psi.
what sort of boost do you guys run?

[jeffro ra28]

i think the biggest u can go is 80 thou/89mm

40 thou per mm. 3tgte bore =85mm. So 80 thou overbore = 87mm

Although another .020" (20 thou) = a total of 1mm overbore in your case will be fine to clean up your scoring marks on your bores.

Basic rule of thumb is .100" per 100hp. So if your 4 cylinder makes 400hp, then .100" bore thickness is plentyfull.
A 3t-gte with an overbore off 88.5mm has atleast 2-3mm of thickness as i check this today on my own engine. This is eqaul to atleast .080" bore thickness. So unless the thing is making 350hp, 88.5 mm bore shall be fine.

Just so people can have a bit of confidence we ave been succusefully using .100" bore thickness on 800hp naturally aspirated engines consistantly.

I

[TheToyman75]

Jeffro,

AT 89mm bore size its VERY common to require sleeving as the boring process "finds" the water jacket. As such I would recommend against anything over 88.5mm for an N/A engine.

For a Boosted T series I personally lean towards the 87mm bore as what I consider a healthy Max bore size.

[jeffro ra28]

Hmm thats fair enough Rod.
This block was infact a 3t-gte block? Would that have any affect on bore thickness differences?? Is it the same casting as 2t?

Perhaps the thickness at the top of the bore was a fair amount thicker as this is wear i checked it.

[TheToyman75]

Jeffro,

Theblocks are indeed allot thicker at the top to maximise the mating surface for the head gasket.

[TA22 GT]

i was thining of running about 20 psi.
what sort of boost do you guys run?

I'm running 14psi now and plan to go to around 20psi. At the moment I still have completely stock internals with an intercooler, full 3 inch exhaust, custom exhuast manifold and GT25 BB turbo. Having said that I think its about the limit for the stock set up. I do want to increase boost to around 20psi and to do this I plan to upgrade the valve springs, use forged pistons, ARP head bolts and eagle rods.

Hope this helps,
Simon

[jeffro ra28]

Jeffro,

Theblocks are indeed allot thicker at the top to maximise the mating surface for the head gasket.

Yes at the very top, but lets talk about level with the top of the welsh plug hole height, this is were i measured it. At the very top it would was atleast 5mm thicker i realise.

[steve-O]

yeah i'm running cp forgies. i'm gonna do the eagle rods o-ring head and block, copper gasket etc. do you think that the valve spings would need? where can you get better valve springs from anyway. done anything to ya cams?

[jeffro ra28]

performance springs.
Either you can simply slide an inner valve spring inside of the current single, or you can buy a whole new set from performance springs.

Copper gaskets are a bitch to seal, specially for street motors.
O-ring and composit gaskets are still being used and working well.

[steve-O]

i thought the heads had double valve springs already.
problems sealing compression or oil and water?