Rob Carlson

i was originally going to do a dbb gt5533r-91mm... but I'm thinking of going with twins... i have a 403ci ls2 between 9.1-9.3 CR and its got a 4000 stall UCC converter on one bad *** th400. i want 1000rwhp or more with less than 20psi... even though the motor could see 25-30+psi anyways... I'm just looking for input and if anybody can tell me where these turbos would spool realistically. ***and yes- I've overturned everything i could find on searches. I'm considering the following. *borg warner s366's, *journal bearing precision billet 6768's (but worried about their reliability), * precision journal bearing billet 7675's. there's no doubt that the 76mm twins would make way more power than i need, but if they wouldn't spool horribly... maybe i'll rock those. one part of me wants the car to go 8's on kill mode (which should come easy) but the other part of me doesn't care so long as i destroy everything around me on the street. any idea on spool time with any of these turbos on specific A/R's on similar motors would be greatly appreciated. thanks in advance!

stevieturbo

If going for the 366 BW's, you can get them with a billet compressor wheel for only a small added cost, and also a smaller turbine wheel if spool was a major issue.

6766's would be better than the 6768, the 66mm turbine wheel is a better more efficient design than their 68mm.

As for the 70mm range, no real need to jump straight to 76mm, they have plenty from 71mm up

But I'm sure the 6766's would do what you need. Plus with Precision or any similar type of turbo, you will have a much wider range of turbine housings to play with if needed.

There are a few TT guys on this forum, maybe get some ideas there..

http://www.camaro5.com/forums/forumdisplay.php?f=74

Rob Carlson

awesome. i appreciate you taking the time to respond. what are your thoughts on the journal bearing precision 6766's...? they're all over the place getting bashed, partially because of shucks that install everything *** backwards- i'm sure... but the ball bearing units are out of the question for me... before i spend that money- i'll just go do the borg warners. i don't think i'll have a problem spooling a bigger turbine wheel (s366) anyways with my displacement... and i did see their 10 blade billet wheel option- i'd definitely go that route if i go with them. i like the precisions because they're lighter, and physically a good bit smaller (and that's huge to me) but i don't want to buy some turds if they're going to puke from the seals all the time! there's no denying that ALOT of people seem to have bad luck with those JB precisions. i personally know of two cars running around with billet 6262 JB's (same turbo) with no problems BUT... they haven't seen 25psi either!

Rob Carlson

if you had to compare a billet 6766 with a .96ar, to a borg warner billet wheel .88ar t4... any idea which one would make better power, and what the spool characteristics would look like? i think the BW is hands down the more reliable unit... but if you can attest to JB 6766's that have been reliable definitely share your input

stevieturbo

Well...Ive just bought a pair of 364FMW BW's for mine from Southeast Power Systems, circa 382. Ive no issues about using whatever boost needed to make it go fast though, and being manual and not a drag car, spool is a major issue for me.

https://www.facebook.com/media/set/?...7276710&type=3

I could have opted for the Precisions in a 6266 or 6766 journal, and they would have been physically a little more compact.

I still opted for the BW's

You could have a pair of Garrett based units, or Turbonetic etc etc to similar spec to the Precisions.
Hard to know which is the most reliable though. I was almost about to go down that road or the billet 66mm BW when I found out about the new BW FMW units.
I'd prefer to buy an original BW unit than a custom unit with unknown original billet wheels.

I think the BW offers the best value vs performance and reliability all round though.

The 366 is marginally bigger externally than the 3xxFMW units.

skinnies

iTrader: (33)

I ran a simple setup last year on my mustang, tc76 .81 housings on a 408 and they spooled great and those are cheap turbos. Im going tup to the 7675 this year with a .96 housing when we are moving the turbos behind the front tires.

https://ls1tech.com/forums/forced-in...uilt-year.html

Rob Carlson

oh... no **** a 408 isn't too far off of my 403. what's your CR if you don't mind my asking? where do you think a set of billet 7675's would spool on that motor? you had an issue with the 6766's? how much boost and power did you make with them as they **** the bed?

Rob Carlson

do you think the 7675's would work to kick ***** on the street, or just too much turbo?

LS1NOVA

iTrader: (12)

Precision 7175's with .81ar.

skinnies

iTrader: (33)

I ran the 6766 on 24.5lbs on a 347, it broke the shaft and exited both wheels while I was racing. It's not uncommon, it was a risk I knew I was taking when I bought the precision 6766's, but was trying to be class legal for a local race. The guy putting on the race outlawed the twin 6766's so that is why I went to the 7668's(tc76's). This year Im going to turboentics ball bearing 7875's since I am redoing my kit. The 7675 billet precision is a lot of turbo, I wouldn't use those unless you want 1400+ rwhp.

I'm 10.3:1 compression on my 408

Mel Carlson

Cool. I'm sorry- were the 6766's JB or BB? Did they shatter the first time they saw 24psi? What boost level were you seeing with them prior? and would the 7175's spool any better than the 7675's as seeing as they share the same turbine? Thanks again

Mel Carlson

TTT... still seeking any advice to weigh these out!!!

p8ntslinger676

6766 with .81 or .96 T4 housing or a comparable turbo. You'll never use the full potential of twin 7175's or 7675's on the stock block so there isnt really any good reason you should sacrifice spool just to have big turbos. 67's will make more power then the rest of your build will be able to handle. Im running 6266's and they should hold up to 1200ish at the tire on full kill but the limits of my build are my motor and trans. If you are planning on an aftermarket block (LSX, Dart, LSM, Katech)with a billet crank, good rods and heads down the road, then the bigger turbos might make sense to buy now. As for turbos, we've stopped using precision turbos on our kits because of failure rate and lack of good customer service from precision the only reason im running them is because of the price, we've had really good results with Garrett and Forced Performance turbos and i would go that direction if money isnt an issue. What are the full specs on your build?

skinnies

iTrader: (33)

They were JB turbos. We ran them at 24 psi for a little while before we had the issue, not like we just turned it up and it broke that day. The 71's should spool better, not sure how much tho as I've never ran both back to back.

Rob Carlson

exact specs are 403ci, ls2... 4.000 stroker crank. callies rods, diamond custom inboard forged pistons (18cc dish) 9.1-9.3CR... CNC LS3 heads, 231/232 .595 .617 on a 116 comp cam... any more input as to what i can get away with for turbos... car has a 4000 stall in it

LS1NOVA

iTrader: (12)

Turbonetics 6668's.