3tgte bore diameters?

**Sam_Q** · 01-05-2007, 08:25 PM

when the engines are bored out to 87mm what does the displacement start with and end up at?

**jeffro ra28** · 01-05-2007, 09:43 PM

Im a bit unfamiliar with copper head gaskets on the 2tg's but previous experiences with blown 5L holdens and chevs prove that it can be a problem for sealing water, combustion not so much of an issue because of the o-rings.

**TheToyman75** · 01-05-2007, 11:13 PM

Copper head gaskets need to be torqued down correctly and you need to use the right sealant. If thats done then they work very well.

Otherwise Cometic do an 87mm bore Headgasket for the twin cam T series head. The part number is listed on there website.

Steve O,

The late model 2T-GEU and all the 3T-GTE have double valve springs. Performance Springs is a Toymods Sponsor and do valve springs to suit. I use the RR4 and they sound like the right choice for your new engine build.

Sam Q,

A quick google search will get you the formula to calculate compression. Its late and I'm to tired to bother sorry.

**YelloRolla** · 01-05-2007, 11:58 PM

Originally Posted by Sam_Q

when the engines are bored out to 87mm what does the displacement start with and end up at?

Starts at 1770cc @ stock bore of 85mm and winds up 1854cc @ 87mm.
CR winds up close to stock IF you use the 87mm Wiseco pistons and 1mm head gasket. From memory it is 7.8:1.

FWIW I run 22 psi at close to 8.8:1 CR and pump fuel, I have 86mm bore stock head gasket and O rings.

Heads are stock with double valve springs - the RR4's from Performance Springs offer 90lbs on the seat.

edit/ useful link http://users.erols.com/srweiss/

**steve-O** · 03-05-2007, 08:05 AM

cheers guys this thread has been really helpful.
think i know what i'll be doing now

**GasedT18** · 03-05-2007, 10:47 AM

A few novice questions: What's the go with piston rings, in general, and for stock and some of the oversized pistons; are they easily sourced; preferences for brands etc?

If a bore is glazed can it be honed to freshen it up and 'oversized' rings fitted if they exist or is a rebore necessary and larger pistons?

What are the typical tolerances for ring-bore clearance and ring-groove etc? - This is temperature dependent too isn't it - e.g., LPG runs hotter.

Do rings need to be 'run in'?

What are gapless rings, how are they fitted and are they worth it?

As I understand it bores become oval over time and after a 'certain amount' a re-hone won't be enough and a rebore will require a step up in piston size?

I've seen honing tools in tool shops - can you DIY? I've briefly seen there's quite an art and science behind surface finish.

Sorry lots of questions, not much time for homework ATM.

David

**TA22 GT** · 03-05-2007, 08:19 PM

Originally Posted by GasedT18

A few novice questions: What's the go with piston rings, in general, and for stock and some of the oversized pistons; are they easily sourced; preferences for brands etc?

If a bore is glazed can it be honed to freshen it up and 'oversized' rings fitted if they exist or is a rebore necessary and larger pistons?

What are the typical tolerances for ring-bore clearance and ring-groove etc? - This is temperature dependent too isn't it - e.g., LPG runs hotter.

Do rings need to be 'run in'?

What are gapless rings, how are they fitted and are they worth it?

As I understand it bores become oval over time and after a 'certain amount' a re-hone won't be enough and a rebore will require a step up in piston size?

I've seen honing tools in tool shops - can you DIY? I've briefly seen there's quite an art and science behind surface finish.

Sorry lots of questions, not much time for homework ATM.

David

Typically the clearance for cast pistons is around 2 thou and 3 or 4 for forged pistons as they expand a bit more with temperature. So, if the bore is oval and to get it right you hone out and end up with a clearance of say 10 or 15 thou, then you really need bigger pistons to suit....

If the bore is just glazed then it is possible to do a light hone and then just fit new rings. All depends on what you're trying to achieve. You could try and use old gaskets too, but is it really worth the hassle....
From memory the top ring gap is around 16 thou and about 14 for th esecond ring, someone else should be able to confirm the exact gaps.

You should always let the engine run in after a rebuild and change the oil after the first 500 or 1000km.

Hope this helps,
Simon

**jeffro ra28** · 03-05-2007, 09:23 PM

Simon is spot on.
Ring gaps are right aswell, except yes, for blown, turbo, gas or nitrous applications the ring gap is increased due to the increased heat.

Gapless rings are excellent, basically they have either a regular top or second ring. But one of them will be the gapless, usually the second. They will never have the top and second ring being gapless. Only one or the other.

The gapless ring consists of somthing similar to the oil control rail, and a similar to normal ring but with a groove to allow for the rail to be installed in the same groove. The gaps are stagared so there is no open space for combustion pressure to leak past.

They are an excellent investment but are not cheap. For a set of 8 of top qaulity gapless rings will set you back around 300-$400