Stage II street turbo for 5" dp question...

[we4Mateo]

My Buick guy wants to turn his car back into a more streetable ride this year and has a turbo recomendation question. His current setup is 270 something inch stage II, fast xfi, heads, solid lifter cam, full suspension, everything basically. He currently has a billet precision 4788 sp cover with 5" vband downpipe. Is there a turbo out there that will feed this thing but still spool better for street use and still be able to reuse the downpipe?

Please advise and thanks in advance.

 

[bison]

So he plans on changing cam and torque converter also id hope. He will have to have a fabricator adapt the new turbo to the current pipe. Nothing will just bolt in its place that i would say is a street turbo.

 

[we4Mateo]

That's what I was thinking. He's trying to get buy with buying as few different parts as possible. Any suggestions on a size though? I thought a 6776 would feed it but he thinks 7676 at a minimum with .85 A/R. He has a 3500 or so stall I think.

 

[ttypewhite]

I run a GT42-76 with a 5" downpipe on the street. Great street manners, reacts quickly and has enough power to get a Buick motor in the 8's, provided the right parts are in place. I had the matching flange to my downpipe welded to the exh housing of my turbo. I did not cut off the existing flange on the turbo, just welded the 5" flange to it.

 

[Mike E]

What exhaust housing does the GT4788 have? I would assume it has a T6 housing.

Precision sells their PT8884 turbo with a T4 .96 A/R housing. That 8884 appears to be based on a GT4788. You should call them and see if their T4 housing will work on the GT47. It uses a ~4" downpipe flange, but that would be a cheap upgrade that should help spooling tremendously.

 

[we4Mateo]

I run a GT42-76 with a 5" downpipe on the street. Great street manners, reacts quickly and has enough power to get a Buick motor in the 8's, provided the right parts are in place. I had the matching flange to my downpipe welded to the exh housing of my turbo. I did not cut off the existing flange on the turbo, just welded the 5" flange to it.

Thanks for the pics and info. Beautiful setup!

 

[bison]

That's what I was thinking. He's trying to get buy with buying as few different parts as possible. Any suggestions on a size though? I thought a 6776 would feed it but he thinks 7676 at a minimum with .85 A/R. He has a 3500 or so stall I think.

To make it work even close to how it should he will need a cam, 9.5" ptc, and a different turbo. If you leave out any if the 3 the thing will be a waste. You didn't mention what mph he was looking for. Once you figure that out you can get a ballpark on the turbo, converter and cam. This is about a $4000 changeover not including labor.

 

[we4Mateo]

To make it work even close to how it should he will need a cam, 9.5" ptc, and a different turbo. If you leave out any if the 3 the thing will be a waste. You didn't mention what mph he was looking for. Once you figure that out you can get a ballpark on the turbo, converter and cam. This is about a $4000 changeover not including labor.

Labor isn't an issue, he probably has a dozen or so converters, including two from Dusty, and he knows he needs to swap to a more streetable cam and probably leave the solid lifters. He just doesn't want to buy another downpipe if he doesn't need to do so. He's trapping 153-155 now in a 3550lb car so I know he doesn't want a slug but 140+ should be good. His wife's TA motor traps 138mph on low 20 something psi boost from a 76 but that turbo already has a home and won't work with the 5" downpipe either. I told him it was doubtful he'd be able to use the downpipe over, but I like what ttypewhite has done. I'll pass along this information Friday when I see him. Thanks again.

 

[bison]

He could do it on a hyd cam but still needs the correct converter. He
Will need more than a p trim if he's looking for 140+. Any of the
Common Tsm turbos will get it done.

 

[seeya v6]

RJC MAKES A 5" DOWN PIPE THAT USES A BOLT ON FLANGE TO THE TURBINE HOUSING MADE OUT OF BILLET TO ACCEPT THE V BAND...I JUST INSTALED ONE... CHECK THE WEB SITE IT SHOWS A PIC AND U CAN BUY THE FLANGE SEPERATE..... JUST TRYING TO HELP?
'

 

[we4Mateo]

RJC MAKES A 5" DOWN PIPE THAT USES A BOLT ON FLANGE TO THE TURBINE HOUSING MADE OUT OF BILLET TO ACCEPT THE V BAND...I JUST INSTALED ONE... CHECK THE WEB SITE IT SHOWS A PIC AND U CAN BUY THE FLANGE SEPERATE..... JUST TRYING TO HELP?
'

Thanks!