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Discussion Starter #1
I have a '69 Camaro that I'm switching from a 177 roots blower/carb to a single turbo and holley sniper efi. I'm finishing up the motor refresh and getting close to assembly. Right now I have a 76mm t4 single that is .96AR. Motor is a 400+ ci sbc built from a Dart little M block, all forged, 8.3:1 compression, small AFR heads (190cc intakes). I know the turbo I'd going to be small but I want to get it up and running and issues shaken out this year then upgrade the turbo. It's a street car running an auto but will be t56 swapped soon. Downpipe is a tiny 3" now.

My options for upgrade seem to be 88mm t4 flanged with a 3.5" to 3" downpipe reducer (cheapest) or move up to a t6 flanged 88mm+ and fab a larger downpipe. I belive I can squeeze a 4" downpipe in at least to some point under the floor pan. Any pros and cons? My goal is to have a turbo that isn't undersized and in boost at cruise mainly. I'm sure it'll make enough power for the street and 255 radial T/A's. Thanks
 

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If the 76mm is a journal bearing or Chinese descent, then it won't a little too small, it will be way too small. I ran a chinesium On3 on a street 327 with a TPI that ran out of go before 5500rpms because of the TPI, and the 76/65 was too small. Either run two or straight to the 80mm T6 IMHO.
 

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If the current turbo is Borg-Warner then go ahead and just change the turbine housing to a 1.32A/R or 1.58A/R T6 and be done with it. That setup should make all the power the current engine can stand.
 

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Discussion Starter #5
Would it be alright to run a t6 to t4 adapter or is that really going to choke a combo like mine? The 76mm I have is a cheap turbo and I'd like to get rid of it in favor of a different single. Twins arent really and option right now
 
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