I have a dart block 349 here for a car i'm helping build for my brother, wondering if anyone has any experience with a pair of T70's on a 349 inch motor, IE: how do they drive at low boost, what's the spool up like, etc. I have a pair of non ball bearing T70's here with .58 and .68 housings, probably going to use the .68 housings, along with dual 3.5" downpipes and a big air/air core, and feed it through a turbo 400. Any info would be great.

 

Hope you find a dyno that can actually support the power that thing would put out at max boost. You did not tell us how much power you are looki8ng to make. Twin t70's are a little overkill for a street car. You did not tell us if this is a full time track, or some street miles involved. Sounds like a stout block you have there. Good luck with it.

 

About 80/20 street/strip, which is why we're concerned about low boost power. Looking to make enough to go maybe mid 8's @ 160-165 on high boost/race gas, and something that'll go low 10's on pump gas/drag radials.

 

talk to josh... hes runnin twin 72's... its a big sticky in the junk yard forum, chek it out, be prepared to read alot

 

I've read basically every post there, and I'm amazed at the quality of the work. Doesn't have too much experience driving it yet, though

 

turbocrazed had either a twin t72 or twin t70 kit before he parted the car out

made somehting like 1200hp out of a 327ci with solid roller turbo grind, afr225's, hogan intake, and a powerglide

not a clue on spool, but i know he *drove it* a little on the street

 

BAH!

 

Agreed! I run twin 74's and love them.

 

granted alot of people on here are not what most would consider mentaly stable

 

1200hp never killed no body, build it, run it, and make a video so we can all watch :rockon: :tu:

 

I run twin 66mm turbos on a 334 with .83 A/R housings. My car is 85/15% race/street. There is no way to spool up those big turbos quick without running a lot of stall in your converter. I run a 4000 stall, and it takes about 2 seconds on the brake to spool up. Same thing on the street if I just punch it from cruise RPM. If the car is really going to be 80/20 street/strip, I would recommend smaller turbos. Sure, the big ones will make big high RPM power, but they will be pigs/sluggish on the street. You will have a lot more fun on the street with smaller turbos. With 4000 stall, my transmission gets hot (Lentech AOD), and I have to run two B&M transmission coolers with two 8" PermaCool fans. For fast spool, you would want a 5000 stall, or maybe even more. Talk about heat on the street. Personally, if I were going to make a 80/20 street/strip car, I would run dual 60's or 62's. Also, I would go for the ball bearing option. You could probably run a 3000 stall and still get in the 8s. Perhaps you could find someone willing to trade?

 

We were thinking they would be alright on the street, you say you don't like it, then you look at Turbo50Mike's car and he likes the twin T70's. I'm sure the .83 housings arn't helping you any for spool on the street. I think we're just gonna try the T70's, and if we don't like em then trade down.

 

BTW, the trans is built for turbos with a 4500 stall and a transbrake, rad is a bigass ron davis with dual SPAL fans, probably gonna run 2 trans coolers while we're at it.

 

Well, if you already have the turbos then it can't hurt to try 'em. I really think you would like the quicker response of smaller turbos for a 80% street car, but that is a personal decision. I'm curious how much the .69 A/R turbine housing would affect my top end power compared to the .83s.

 

How high are you spinning the motor? From what i've heard the .68's on a mid sized (66-72mm) twin setup are going to be good to atleast 7500 RPM's. I know a guy with an LS1 running twin T66's with .68 housings and he's spinning the motor to 7200+ RPM's and making lots of power.

 

I'm running my motor to 8000 and getting around 1500 HP. I think it is more a HP/flow thing than a RPM thing. I wonder if the smaller housing would limit me to 1300HP or something. It might be worth it if the spool up was a lot better.

 

DASHIP

Sounds like you are really maxing out your T66s.

My T66 compressor is only rated for about 720 crank HP.

I have been told that on a single T66 setup the 0.69 turbine A/R will become "restrictive" at ~450RWHP. This was from a PTK rep. This doesn't mean that you cannot make more than that, just that beyond that point it is likely wise to go larger.

So if you are making over 900 RWHP with twins, then it is likely that you will operating with signifacent pre-turbine pressure.

Based on this, if you are trying to achieve ~1300-1500 RWHP then the smaller turbine would seem detrimental. Of course, the term "restrictive" is somewhat vague. Something more concrete like "backpressure/boost ratio goes over 2" would be much more useful.

 

Thanks for the info. I kinda suspected that, but it is good to have some reinforcement. Yeah, I am maxing out my 66's. That was my plan from the start... use the smallest turbos that will get me to 1500HP.

 

why only 1500hp:hammer:

 

Your best bet would be a pair of master power T70's with the .68 A/R. Due to the lighter shaft in the MP units they will spool quite well for a 70mm unit.

Jose