Alot of different opinions on sizing for twins......i've seen everything from 50mm's to people saying minimal 60mm's....this question is not for me as im going single s475....but he was thinking something along this size for twins

SUPER T4 T67 TURBO CHARGER .84ar TWIN SCROLL Q-TRIM

Intake: 4 inch
Outlet: 2.5 inch
ported shroud /anti-surge machining compressor housing
Compressor trim: .70 ar
Compressor Wheel diameter: 66.33 / 83.93
Turbine Wheel diameter 73.08 / 64.23
Exhaust Trim: .84 ar
Twin scroll turbine housing
Turbine flange type: T4 flange
Down pipe flange type: 3" inch v band
Cooling type: oil and water cool only
Horsepower rating: 500-700HP

He wants make about 900 or so HP

he's got afr heads 220cc port matched to 1206 gaskets with a vic jr intake 750 holley(hanger mods) his cam is a summit grind 234 dur on the in and ex .490 lift in and ex and 114 lsa with a .60 over rotating assembly for boosted application will def see both track and street use....hasnt decided on intercooler yet.... I say get a good a to a one???? anyway lemme know what you guys think about his turbo choice....as always thanks again guys....

 

Ebay pastespam specs. ".84" is a T3 housing not T4, and a 73/64mm wheel is closest to a p-trim, not Q (Q is 68mm exducer). Who knows what the turbos will actually be, and with actual specs being 'who the fuck knows?? lol' I don't think you can accurately use anything there to make a decision, other than 'keep looking for something vaguely reputable'.

 

so these are junk ebay turbos basically is what I get out of that.....lol....i told him to look into garrett t04b's but wasnt sure if they were too big or not...

 

How about some some nice compact Precision;s

http://www.precisionturbo.net/turbochargers/street-and-race/33
With .82 A.R ???

 

For that combo, with those heads and intake, you wont need to spin up alot of rpm. Cam and heads will do work. I wouldnt go any higher than a 62mm for those goals and would suggest a p-trim T4 hotside with a 60mm. A/R in the .68 range. No larger than .82 IMO. Spool should be occuring around 2800-3000rpm with full boost in the 4000 rpm range. It will come on quick.

I ran a pair of 60's on my 401 sbc with small 195 heads and a 233 deg hyd roller. Vic E EFI intake. Only spun to 6K or so, made ~700whp in street pump gas only trim. 14-16psi most of the time on the street. Spooled quick and made power. Had plenty left. Switched to T70's no other changes and couldnt spool them as quick. Went slower on same boost. Just too much turbo. A good 60mm will be plenty for a 360" sbc. Could squeeze a 900hp out of 58mm too I would think but I'd still keep it a T4 frame on the hotside.

Is that 900 at the tires or at crank? Makes a big difference. Auto/manual? I am assuming 900 flywheel.

 

I ran 2 -54mm with a .68 a/r 383sbc ran 9.80@136mph 13psi switching to 2-70mm with the same a/r hope i didnt go to big

 

Search BADGMC... he has 70's on a 388 sbc, and had back pressure issues with .68's, and has gone to .96's

 

Whats the rest of the combination look like? Vehicle weight? Sounds like you are leaving on boost so spool may not be much of a problem but twin 70's I feel are very large for a 383 size motor unless you are pushing 1000+ whp. From the times tho, it sounds like you are well short of that. A single 70 can support a 350 motor to 500whp and sometimes alot more! Thats an easy 1000whp on twins. I've seen 1000+whp on 383's with 62mm twins. My results i wasnt too happy with the 60 to 70's swap. Now I have much more motor underneath so they should work much better.

 

3200lb 383sbc s10 373 gear world product heads 200cc meth injection, cam is a lt1 hot cam roller single plane intake blow thru carb. twin master power 70mm .68a/r

 

I'd say no more than 60-61's for that setup. Pretty mild cam and heads setup so I dont think you will be getting the most out of those turbos.

 

your probally right looking to be in the 9.50 range running a heads up 9.90 class

 

No fuel mentioned yet ?
Initial would be 64-66mm compressor
65 turbine
Pick turbine housing to suit engine rpm..