Should I switch to a 6776 from PT70

[Tfreestyle]

Hello all. I have an 86 GN that im restoring that I got from a guy that mostly built it for drag, not so much street driving. Well im going to be driving my car on the street a hell of alot more then on the track so I was debating bumping down the turbo a bit. I currently have a precision T70 that I got here on the forums to replace my blown limit engineering T70 that came with the car. Lately ive been thinking I might have made a mistake not going with a 6776 since im going to be driving alot more on the street. Also since the car has a 3800 stall non lock up converter will that be to much? Im still alittle new to the buick scene and the lingo but here is a quick list of mods to my car...

- built 109 block w/ forged rotating assembly under 300 miles and no track passes yet. BuilT by Archie from GN1 performance
- T70 from precision
- 55lb Siemens (upgrading to 72lb and alky any day now)
- Kenne Bell 70mm Throttle Body and Plenum
- Kenne Bell Fuel Pressure Regulator
- GN1 Performance Front Mount intercooler w/3in Piping
- 3in Cold air intake
- 3in Downpipe with external wastegate
- Single Shot 3" Exhaust
- Headers from Hye Tech Performance
- Ported and Polished Heads
- 212/212 Isky Cam
- double roller timing chain
- Built trans w/3800 stall non-lockup
- ATR Rear sway bar
- Boxed upper and lower control arms
- B-body 12" brakes w/ tubular upper arms
- new Walbro pump with Full Throttle Hot Wire Kit
- Turbo Saver Oil Cooler(need to install)
- Dual ramcharger fans
- Translator Plus
- Scanmaster
- Powerlogger(just installed yesterday)

 

[Tfreestyle]

also, forgot to list. the pt70 I have currently has a 4" inlet and 3" outlet

 

[salvageV6]

I don't think the turbo size will matter much, drive it and see how you like it.

I'd probably want closer to a 3500 stall lockup with that turbo assuming good spooling code in the engine management which the translator system can give you, and good wastegate control for spooling.

And I'd want a lockup converter for more daily driving economy.

If you change the turbo most likely you will be changing the converter anyways, I'd start there and probably leave the turbo in there.

Lots of people have spooled a regular bearing 70 turbo with ported heads with 3400-3600 stall converters from what I've read over the years.

Assuming the T70 is a p-trim turbo.

 

[Tfreestyle]

Yes the turbo is a P-trim. I was thinking the same thing with the converter even with the t70. Ive just read so many great reviews on the 6776 dbb turbos and how fun they are on the street compared to the journal bearing 70mm turbos that some guys had before that its got me thinking I made a mistake. Any recommendations on converters(im about to search but figure I would ask anyways)?

 

[Black Power]

My buddy has a 6776bb on his Gn with champion iron heads, 3" downpipe, roller cam, etc and it spools like a maniac with a 3200 Art Carr...Pulls hard at 16 psi also.

 

[salvageV6]

If you intend to ever lock it up at the track the only one I've seen that can handle a lot of power is the 5 disk Vigilante, if you can live with the idle rattle some of them exhibit when street driving.

I guess there's a few newer non-lockup efficient converters out there now you could try. Search feature should work for that info.

I'd still shoot for the lowest stall possible for a driver. 3400 perhaps.

You've got plenty of flow in the motor and good engine management and hopefully wastegate control, so I think you should be able to leave that turbo on there.