Ok, first off, there is no such thing as a 6776gtqb and here's why.
67 = 67mm inducer compressor wheel
76 = "P" 76 trim turbine wheel
gtq = GT-Q 80 trim turbine wheel
b = no earthly idea
So, you can see that your part number would indicate that it would have two turbine wheels. Not trying to be picky or mess with ya, it's just I have seen people make this very same mistake before, and I know that the numbering system can get very confusing. Especially with this new PTE turbo listing that just came out.
The difference between gt and pt is this, Full Throttle calls their turbos gt, and Precision, who makes the turbos, calls them PT.
There is no difference between a PT6776H and a GT6776H turbo, just the letters. The first question you have pertaining to the pt67gtqbb & the pt70gtqbb, is going to be a hard question to answer because no one has either of these turbos on their cars yet who have posted results that I know of. Both of these turbos were just recently listed on PTEs updated turbo listing. There are people on here that currently have the PT70 GTQ dual ball bearing turbo on back order as we speak. The official part numbers off of PTEs new listing for these two turbos that you are asking about are,
6780RH This shold be a PT67 GT-Q dual ball bearing turbo with a standard H compressor cover, and a .85 A/R 3-bolt turbine housing.
70HPQRH This should be the PT70 GT-Q dual ball bearing turbo with an H compressor cover, and a .85 A/R 3-bolt turbine housing.
Now, there is such as thing as an HB designation in the part number, but that only means that the compressor cover is an H cover with a 6" inlet bell pressed onto the inlet. And it will not work on a stock location oriented 3-bolt setup.
But for what you have listed in your combo, and depending on how fast you want to go, here's my take.
The PT6776RS will take you easily into the 10.40's with what you have listed done to your combo, and will spool way too fast with a 3800 converter.
The PT6780RH or 6780RH as PTE lists it, would surely go into the 10.00s and not nearly spool as lightening quick as it's P-trim turbine wheel equipped brother.
The PT7080H or 70HPQRH as PTE lists it, will go mid 9's and still spool up very well with your 3800 stall.
Now, with 75#ers, you have enough injector to safely make 900 fwhp, if basing a turbo decision on your injectors, then the PT6780RH would be a better match for the injectors. If you're looking for something that's basically going to be un-controllable as far as spinning tires on the street with your converter, then the PT6776RS would be the ticket.
In my opinion, with your combo, I would go with the PT6776RS, or the PT6776RH and have fun. You would be able to lower your stall on the converter to flash stall to 3300-3400 and still spool up this turbo very fast.
As soon as people start getting these new ball bearing equipped 67GTQ through 76GTQ turbos on their 3-bolt Buick applications and start posting results, we will all be more the wiser.
Again, not trying to be smart or anything, just saying what I know. Hopefully we will get more answers soon from PTE about these new 67-76 GTQ ball bearing series turbos.
Hope this helps.
Patrick
i don't make drag whit the car just a very fast street car !and some time strip but 2-3 a year not more !
