Massive Lag with 6780S

[BEATAV8]

I would talk to Dusty about your converter options, I know you don't want to swap it again, but it sounds a bit mismatched even for a street car. I absolutely love my 9.5 n/l and it only gained 200rpm on highway cruises.
Some things that have helped me hold more boost on the footbrake:
- Boxed lower control arms with new bushings (gained 5psi holding power)
- Vacuum resevoir as I have vacuum brakes
- Line lock to save the rear brakes during burnouts
- S-10 rear brake cylinders

X2... you're combo is pretty wild for a street car and the 9.5" non lock would do it some justice.

This was how a custom PTC 9.5 spooled with PT6776 and a 210/210 cam. It ran 7% slip on the big end @ 128MPH.

 

[bison]

A 6780 with a 2900 stall. You need about 1000 more rpm stall. With a mph of 122 you must have something else missing since you should be running a muh higher mph.

 

[MNwe4]

Ok, I think I may try a smaller used turbo before making any radical decisions. A coworker of mine has a 6776 P-trim turbo, but the turbine housing is not for a buick. He has no problem letting me test with it and potentially buy it, but we need a way to get it on the car. Anybody know of any P-trim housings floating around?

 

[DCVING 6]

I would think a converter change would be easier and the car will be a beast as is. If that 6776 isn't a ball bearing unit, it probably won't spool for crap with the 2900 stall your seeing anyways.

 

[Chuck Leeper]

Back psi is?

 

[Mr.Spool]

the 10.5 inch wont do the s-trim.just went this route the 9.5 ptc really wakes up the s-trim i feel its a must have piece with this turbo and the driveability really opened up my eyes.i do have nitrous on mine but for a primary street car i don't want to lay a 50 shot on it to be happy.inmo spend the coin for the 9 inch or move down to the 65/p trim.the 10.5 inch will get the smaller wheel goin as long as the ex housing isn't to big.

 

[MNwe4]

Don't know what the back pressure of the exhaust is, but running with the dump pipe open made very little difference. Is there any way to measure pressure before the turbo by removing the O2 and using a pressure gage there, or will the car run like total crap without the O2 hooked up?

Just called Precision and they confirmed that this specific turbo needs a true 3800 stall to get everything out of it. Also confirmed that using another guy's 6776 does require a few hundred less rpm and having a roller cam drops the requirement as well, but won't be enough in my case. So why then would PTC call it a 3500-3800 when it truly isn't? I really don't want another converter lying around since I already have two basically new ones sitting in my garage, but at the same time I like the power I'm getting out of this turbo and would like to keep using it. Anybody need a newish converter, there's many options. :biggrin:

Back on topic, what's you're opinions? What's the best way to go when looking at the rest of my combo? I'd like to be able to hit 10.99 in a year from now if everything works out. It still has to be a street car though. I drive it to the tracks.

 

[Alky V6]

Looks like you have to go with a smaller turbo, tighter exhaust housing, looser torque converter, and lose the L/U.

 

[84BuickGNYorkPA]

Looks like you have to go with a smaller turbo, tighter exhaust housing, looser torque converter, and lose the L/U.

+1 on the smaller turbo/exhaust housing, I bet a 6262/6265 billet would make the car rock. Or a old school TE-63 (my magna brother took his 63 into the 10's) If you decide on a new turbo then contact Dusty for a converter, I would stay with the lock-up on the street car, just don't lock it at the track.

Chuck

 

[Dusty Bradford]

Just called Precision and they confirmed that this specific turbo needs a true 3800 stall to get everything out of it. So why then would PTC call it a 3500-3800 when it truly isn't?


Back on topic, what's you're opinions? What's the best way to go when looking at the rest of my combo? I'd like to be able to hit 10.99 in a year from now if everything works out. It still has to be a street car though. I drive it to the tracks.

A 3200 stall 9.5 non lock will spool it. You don't need a 3800 unless they are talking a 5# rpm reading.

I don't know who you ordered it from. PTC like all other converter companies have people who specialize in certain types of set-ups. I'm a distributor for PTC and did most of the development work to get these converter combinations figured out for them. This converter may go 3800 behind a stout smallblock, but it's not enough for a 6780 on a V6. If you got a salesman who does mostly V8 combo's then his estimate was just off. It happens all the time. Converter behavior changes with many, many variables of an engine combo. Even variables inside the trans can throw a stall speed off some.

Get me the part # off the box the converter came in and I'll see what you have to work with.

If you like having a tight converter for street manners then a turbo swap is in order. A 6780 is a 9 second turbo. If all you want is a 10.90, a 6262 will spool much quicker and run 10.90's with ease.

As for the lock-up vs non lock. I have put several people into non lock converters that prefer lock-up. They are just simply light years ahead of the old non lock stuff. Driveability is nothing like the older 9" converters. I spent alot of time getting these 9.5's to spool and drive as well as they do.

 

[JOHNDEEREGN]

A 3200 stall 9.5 non lock will spool it. You don't need a 3800 unless they are talking a 5# rpm reading.

I don't know who you ordered it from. PTC like all other converter companies have people who specialize in certain types of set-ups. I'm a distributor for PTC and did most of the development work to get these converter combinations figured out for them. This converter may go 3800 behind a stout smallblock, but it's not enough for a 6780 on a V6. If you got a salesman who does mostly V8 combo's then his estimate was just off. It happens all the time. Converter behavior changes with many, many variables of an engine combo. Even variables inside the trans can throw a stall speed off some.

Get me the part # off the box the converter came in and I'll see what you have to work with.

If you like having a tight converter for street manners then a turbo swap is in order. A 6780 is a 9 second turbo. If all you want is a 10.90, a 6262 will spool much quicker and run 10.90's with ease.

As for the lock-up vs non lock. I have put several people into non lock converters that prefer lock-up. They are just simply light years ahead of the old non lock stuff. Driveability is nothing like the older 9" converters. I spent alot of time getting these 9.5's to spool and drive as well as they do.

That my friends is a very special person to the Turbo Community, thanks for helping out Dusty.

 

[Otto J]

Is the 6780 new? I know of the 67-65 and 67-68, but I have not heard of the 67-80.
Who recommended this turbo for your combination?

 

[Dusty Bradford]

That my friends is a very special person to the Turbo Community, thanks for helping out Dusty.

Thanks for compliment. I do strive to get people the best combination of parts so they all work together to make the owner a happy person:biggrin:

 

[turboc87gn]

Interesting thread...

 

[MNwe4]

Dusty,

From best I can read the p/n on the box is RT6-10-700-27-LUSS. The questionable part is the RT6, maybe it's PTC, which would make more sense. I had the converter ordered and work done through a local shop that deals with turbo buicks on a regular basis. You're help is very much appreciated. I'm not set on keeping a tighter converter, just want something that remains streetable.

Otto,

To my knowledge this is not a new turbo, maybe within the last 3 years or so. When I called Precision today they simply referred to it as a 67GTQ. If you go to their website, look under small frame turbos. The compressor housing reads 6780S and the turbine housing reads THB3-80.

 

[John Wilde]

That my friends is a very special person to the Turbo Community, thanks for helping out Dusty.

I agree, we are lucky to have Dusty.

 

[turboc87gn]

I agree, we are lucky to have Dusty.

Yup i pmed him with the part number of a converter that was new in the box that i bought off a friend of mine he advised me that it was great for my combo. Even though he wasnt making a cent!!!!!! A lesser person out to make a quick buck could have told me i needed something else or to send it in for a restall etc etc.. I appreciate that and ill send as many people his way as i can as good people are hard to find now a days......

 

[Slow91z]

I really don't want another converter lying around since I already have two basically new ones sitting in my garage, but at the same time I like the power I'm getting out of this turbo and would like to keep using it. Anybody need a newish converter, there's many options. :biggrin:

Back on topic, what's you're opinions? What's the best way to go when looking at the rest of my combo? I'd like to be able to hit 10.99 in a year from now if everything works out. It still has to be a street car though. I drive it to the tracks.

That's what the for sale section is for, someone can use them I'm sure.

Change converters and go 10's now, not a year from now.

 

[Dusty Bradford]

Dusty,

From best I can read the p/n on the box is RT6-10-700-27-LUSS. The questionable part is the RT6, maybe it's PTC, which would make more sense. I had the converter ordered and work done through a local shop that deals with turbo buicks on a regular basis. You're help is very much appreciated. I'm not set on keeping a tighter converter, just want something that remains streetable.

PM sent

 

[jasjamz]

PM sent

Dusty, sent you an email with powerllogger files.