Twin turbo or single?

[8gsofresh]

Hey everyone just a few quick questions


just bought a 2000 6g74 long block form a scrap yard ( planing on a swap soon)
also purchased forged rods and pistons from 3sx (8.5:1 Comp ratio)
my questions is to squeeze the most HP out of this motor


Single or Twin turbo? i would really like to turn the boost up 15+ Psi


and what turbo(s) are recommended

[reiketsutsukigami]

go single twin turbos would be a project from hell and you can easily make 15+ psi with a single turbo try some thing around a .50 trim

[8gsofresh]

i have nothing but time and money trying to hit the 700+ HP mark

[Galantfan88]

Youll be fine with single, and as far with Hpower wise...what other work you doing on the motor besides forged Pistons and rods?

[8gsofresh]

From what i understand the crank is also forged and with the four bolt main i should be good on the lower internals

as far as the upper im having a custom port and polish and soon purchasing a rpw custom camshaft,camshaft gears,
their valve kit also for the 6g74 and a complete stud kit to keep everything together

[mrg7243]

talk to SPD_FRK, if i remeber he was going twin turbo at one point, maybe he still is idk, but he is a good resource for these motors.

[Galantfan88]

ARP Studs I hope? and What stage camshaft did you go with?

[8gsofresh]

will do thanks for your help

[8gsofresh]

Yes arp all the way...


as far as the camshaft stage two for now

[Galant306m]

DOHC swap it!

[midnight]

DOHC ftw

[TahitianGreen]

I hope you plan on spending a lot of money on the trans............

[M-Rod]

you should have went with the 6g75. Stock 75 heads flow so much better than p&p'ed 72/74 heads. Plus the extra displacement from the start is well worth it as well.

[8gsofresh]

@Galant306m Dohc swap? heads from Montero?


@TahitianGreen im planing on a 5 speed swap but i hope the differential can handle the power


@M-Rod now you tell me ! ha ha I'm actually thinking of using a 75 crank not sure how its all gonna fit together but i think the added stroke should put me in the 3.6-3.7 range

just worried the the deck isn't high enough

[M-Rod]

you can use the 75 crank since the 74 and 75 share the same deck height. A previous member here used a 74 block with a 75 crank and heads. Do keep in mind he used higher compression pistons since the 75 heads have a larger combustion chamber. If I'm not mistaken he was at 3.7 to 3.75 liters of displacement.

[8gsofresh]

@M-Rod i Purchased low comp pistons (8.5:1) from 3sx to accommodate the turbo i plan on slapping on there. Also what 75 heads (what car?) should i use i dont want to deal with mivec

or is here a thread where i can find all this info

[Rach3T8G]

Look thru SPD_FRK's build thread that should help you out & just get the non-mivec heads
https://www.thegalantcenter.org/show...hlight=SPD_FRK

[8gsofresh]

thanks @ Rach

[Rach3T8G]

your welcome

[SPD_FRK]

Twin turbo setup is not a far reach on these motors, nobody on the 8g or 3g platform has really done it yet though to prove the point. There is a lot to factor in with a twin setup though which with the smallest overlook of something can be damaging.

A single charger setup will easily put you at 15+psi of boost depending on the turbo you run. Which I would need to ask, what turbo/s have you looked at using for the build at this point in time? A .50 A/R turbine side will spool rather quickly on RPMs and kill any mid-top end performance (where a good turbo setup usually builds boost and the peak power). You for a single charger you would want a turbine housing with at least a .70 A/R to spool in the 3000-3500+ RPM range.

One other thing to mention is the CR you are building, be aware that the engine will be a total "dog" until you hit boost pressure. Running that low of a CR will be "OK" for a turo application, but you will have very little to sluggish throttle response outside of boost. An ideal setup for this would be in the 8.5-8.7 CR range where you still have some throttle response outside of boost, yet still a safe CR to run a fair amount of boost pressure.

The last we know of the 6g72 turbo build that was done for boost made over 530WHP which is pretty good. Making it to the 700HP mark is more realistic for a drag car and not a FWD sedan. Keep in mind the 74 heads are identical to the prevous 6g72 heads and will have no flow (even with heavy PnP work) in the top end where you will need it. The best way to reach that power goal for a drag car will require extensive head work (best route is the 75 Non-MIVEC heads) and using a set of Stage 3 or higher RPW cams. with higher boost pressure (30-40psi), you will need a massive fuel system to feed the engine, and with the help of a methanol injection system it could be done.


I would suggest sitting down and taking a closer look at what your ultimate goal is for the driving activity of the vehicle. As it sits now, you could have a decent street/strip setup with the right turbo matched to the build so far. My only fear for you right now is with the CR and running a larger turbo that you will not be happy with the end results of the "slug" feel outside of boost.


I don't get on the forums much anymore, but if you or anybody else needs some help feel free to shoot me an email.