2TG info

[merc-blue]

hey guys,
Im thinking of building a engine for my TA and it will either be a 4AGE (so much work with EFI, eletrics and fuel system) or a worked 2TG, im thinking at this stage dual carbies agressive cams equal length extractors and bore it out,
what sorta power would i expect out of sumthing like this in my mind it seems like a combo that would be fun to drive and pretty easy to build as i dont really wanna bother with shaving heads and flycutting pistons with the 3T hybrif or the issues with fuel delivery and electronics of the 4AGE

[SeptemberSquall]

What pistons did you plan to use for your overbore? 18R-G pistons? or custom or forged pistons? If you're going so far as to get pistons made up to suit a substantial overbore, the work required to ensure they clear the appropriate valves is going to be insignificant by comparison.

If you use the 70mm crank your rod to stroke ratio would be pretty good but the engine would be all top end with no healthy midrange delivery, you'd consequently need to wring its neck to extract it's potential and hence would need to prepare the bottom end appropriately for such abuse.

In another thread Rodger from Canberra mentioned using 44PHH Mikunis on a single cam 2T motor at approx +1mm overbore on 70mm crank for approx 1615cc displacement and turning approx 75rwkw at 7000+rpm. for that output i presume he had some long duration high lift cams and some good static compression.

[merc-blue]

wow 75RWKW in a 2T single cam

i would probly be going forged pisions, but damn you recon i wouldnt get any low end?

whos worked the tits of a 2TG before cause im really keen on starting work on it, the other idea is if i built up a 2TG how much more work would it be to hybrid it i havnt looking into teh hybrid much but would i be able to just bolt on the head and cut some pistons? like a 202 with the falcon head (backward)

[ATOYOTA]

im about to build a 2tg3t hybrid on nos. you could use the crank and rods of a 3tgte there alot stronger that strokes it to 1800 matched with a set of forges droped compression (i think the compresion will be to high) and some nice cams and sidedrafts and youll have heaps of fun

[merc-blue]

great suggestion thats about perfect,
i have sourced a engine in need of a rebuild so i just gotta find me the bits i need

so instead of boring it out just use the 3t crank and rods (with new pistons) to put it out to 1800
high compression would indicate that i wont have a low end problem like boring it out?(im onl new to building motors i know enough to keep myself out of trouble but i deffently dont know as much as you guys)

to drop compression i would just space the head out?

[jeffro ra28]

to drop compression i would just space the head out?

You can do this with a thicker HG, but by doing so you are losing the affect of your valuable squish area. This is probably not all that desirable but not a biggy in a streeter.

You can also drop compression by cutting material from the pistons, cutting your valve seat deeper into the chamber and machining bowls in the head of your valves. All of this would need to be done professionally tho.

If it was a compact wedge chamber design on the other hand then it would be no problem to reshape the chambers to allow for more volume and less compression.


jeffro

[merc-blue]

any idea on cost of professional machining them?
cause realisticly a thicker HG was the origional idea and seems to be the cheapest

also do i really wanna go cutting up nice expesnsive forged pistons?

[merc-blue]

just got told that forged pistons are not needed on a non turbo? would they be worthwhile in the high compression? or just get a decent piston? at the moment they are my main concern as cams and cranks and stuff are not THAT bad to get setup (well not in the few engines i have built)

[jeffro ra28]

Before any major cuts were taken to your pistons the machinist would measure crown thickness to make sure that they could not be cut to thin. The piston manufacturers allow a fair safety margin for crown thickness to allow for large amounts of boost etc. Are you sure you can get forgies for a 2tg of the shelf? If not they are going to have to be custom, that way you can design them for watever comp ratio you want. However this is not cheap

aprox $200 at a guess to cut your valve seats deeper. A little machine work on the valves shouldnt cost you much more then $200 either.

Yes a thick MHG is the cheapest option. But can u space the head out far enough to compensate?

[merc-blue]

good point
forgies for the 2t off the shelf i doubt it, i dunno what im doing piston wise hence all the piston questions

maybe while puting in the 3T rods and crank i should go the 3T head (maybe with a thick HG) cause they seem to lower the compression a touch hence they are normaly shaved? to this i would have to bore it out wouldnt i casue the head is suited to a 1800? or would the extra room fit the bill?

400 bux to lower the compression isnt bad maybe i should leave it and blow the head off (or would it blow the crank?)

[jeffro ra28]

you would blow holes in your pistons from detonation before the head or crank would give way. Im not sure of the ratios involved here, but the highest streetable comp ratio in a hemi chamber is 12.1 and thats with premium unleaded with octane booster, u would want to be sure your tune up was spot on also.

Again, using a 3t head which i assume has a larger chamber diametere would take away that important squish area on the deck of the head. so yes boring it out would be appropriate. Please bare in mind that i am no T engine nut so all of what im speaking is in general and not specific to the T engine.

[merc-blue]

jeff im no engine expert and dont know much about any engine
as for the blowing the head and crank idea that comes from racing nitro RC cars if you take to much spacing of the head you can blow it into orbit (well very high)

i will do abit more investigation and wait for some T nuts to post and so forth before buying anything but yeah
seems the go is the 3t crack and rods, standard pistons and 2 HGs to lower the comp seems to be abit of a dodge way around and really innacuate to get the right compression ratio
would it be possible to get a compression plate machined at the right thickness? would that be cheaper than machingin the valves and valve seats

cheers for all your info

[jeffro ra28]

If you could not find a thick enough gasket of the shelf you can get them custom made by ACL, they are pricy tho. Dont use 2 of them!

[merc-blue]

cant there ever be a cheap easy option.. lol bloody hell

oh well it will all be worth it in the end (until i blow the rear diff)

[SeptemberSquall]

Pistons can be had through Wiesco or etc. in the US. Mostly for 3T compression height though. I'd still recommend using the 3T crank anyway.

HJ gaskets in Melbourne have a pattern to make a multi-layer composite gasket in a range of thicknesses, I'll probably be using one of these too.

If you want to get away from colloquial talk of "blowing this" or "blowing that" and learn a bit about how to do this, let me know. Between myself and my friend we have two half-built T motors here, in Melbourne too. Come get some ideas maybe.