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Twin Precision 6766's

29K views 56 replies 25 participants last post by  PrecisionTurbo 
#1 ·
Just curious, but how much power (RWHP) will twin 6766's support on a 404ci ls ? im really new to the turbo scene so im just trying to get a feel for what i have planned out, pros and cons, thanks.
 
#14 ·
What sort of diameters or CSA do the different housings have ?

ie T3, T3 V-Band, and T4 say even for a same number A/R ?

We seen a thread discussing crossover diameter for a single setup, and it seemed that 2.5" OD was excessive in many cases, and than 2.25 or even 2" was better suited to keep faster spool, but no real negative effect on performance

So for a twin application, would even a large T3 V-banded turbine housing be much smaller than say 2" ?

What sort of pipe diameters entering the turbo is considered ideal for twins ?

Ive started to weld up some truck manifolds, and was going to stick a 90deg Sch10 2" ID pipe onto it. Would that be too small for the likes of a pair of 6766's and 1300hp or so ?

2.5" OD would be my other easy option with thinner wall tubing, although those bends are much longer radius, so might be difficult to fit.

And is w/g placement critical to overall flow ?

I'd be taking the w/g almost directly off where the cast is cut, so prior to, or part of the 90deg bend
 
#15 ·
I have a sbf 331 with twin 6266, I had the t3 v band housings on and at. 18 psi she went. 9.30. Then we were seeing high back pressure so we switched to the t4. .81 housings. We did not change nothing I the tune and with just the housing changes we went 8.7 at 163 with same 18 psi. The t3 housings are big restrictions.
 
#17 ·
I have a sbf 331 with twin 6266, I had the t3 v band housings on and at. 18 psi she went. 9.30. Then we were seeing high back pressure so we switched to the t4. .81 housings. We did not change nothing I the tune and with just the housing changes we went 8.7 at 163 with same 18 psi. The t3 housings are big restrictions.
What was the backpressure before and after. How much rpm?
 
#18 ·
The turbine side will become the restriction before the compressor side runs out of steam. Put some big turbine housings on them!
 
#19 ·
Heat Effected Zone, what engine size? How aggressive cam duration?
No hard horsepower or back pressure numbers from me. But here's what I have to offer: 370" 3555# 159mph trap speed, 6262 .81 v-band housings 21# boost fairly aggressive cam. Added 2# boost IAT went up 24-26* car went 159 again.
 
#28 ·
No one said it was perfect, but it has been done many times. I am not being argumentative....just have seen the results first hand. Tim's Pinto, the Orange Camaro on drag week (he even had the V-band housings!) just un-real and worked. It's not what I would do but hard to argue with the results.
 
#29 ·
so how about if i kept the engine in the 365-380ci range (havent installed the 4 inch crank yet) with the 6766's ? would i see more than 1000RWHP ?

Or should i just scratch all of that and go 427LSX with pt7675's ? I know this would put me where i wanna be, but it might be overkill for the street.
 
#32 · (Edited)
Or should i just scratch all of that and go 427LSX with pt7675's ? I know this would put me where i wanna be, but it might be overkill for the street.
That would be ridiculous on the street, and hardly useable!

I have 60mms on my car with a 374" motor and out of the box AFR 205cc heads and it is crazy on the street with just pump gas. I have been 148mph just as the car looks in my avatar on 93 octane. I bet you could make 850+rwhp or so on strait 93 octane with an around 400" setup and twin 6766s. Obviously on Race Gas or Ethanol, you could make a lot more.
 
#34 ·
Thanks, I don't have a link, but here is some info on it!

Motor: 374" Windsor
AFR 205s out of the box
.590 lift HR cam
Super Victor Intake

Turbo Kit:
Twin s300sx3 60mm from Work Turbochargers
1.5" flipped JBA shorty headers
Air/Air Intercooler

Trans: 4l80e
PTC Converter with lockup

My best time on the 17s is in my sig, it's been been quicker/faster on 15s though.

Couple vids:

https://www.youtube.com/watch?v=enVd2vTIVGY

https://www.youtube.com/watch?v=59V36CjsUYc

Couple pics:

http://s20.photobucket.com/user/YellowNotch/media/enginebaynew3_zpsb1795981.jpg.html?sort=3&o=12

http://s20.photobucket.com/user/YellowNotch/media/dells_zps91701d32.jpg.html?sort=3&o=23
 
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