Mr.427

I have a LSX Block 434 ci build with all forged internals and six bolt World Heads. 9.2 to 1 compression, Jessel rockers with very low 7xx lift cam and 114 lsa. I am running twin Turbonetics GT-K 650's, I know too small. The ar is 68 and they are great down low boosting right at 3000RPM but as you would expect fall out about 5800 RPM. Fun to drive but I am used to the power and now it feels a bit slow. I am wanting to move up to larger size but not totally lose all the quick spool time. Here is what I am looking at through Forced Inductions. I like the Turbonetics TC 78 and the GTM 72. Keep in mind we are talking about twins here not a single. I also really like the Garrett GTX 4220 and GTX 4254 but not sure they are worth the extra dough as they are steep in price. On pump gas I am dynoing the mid 900's RWHP on the current set up and am looking for something in the 1100 to 1250 range rear wheel. I currently have the fuel system to handle the anticipated increased power. Would love to see it spool up starting at or near 3800 to 4000RPM. Not sure of the ar I need but I know I want something larger than .68. It is mainly a street car with some track use. Would love to hear your thoughts on turbo choice and perhaps ar selection. I have e-mailed Dr. Turbo for his thoughts as well as he has been helpful in the past. Please don't get bogged down into cam selection or any changes to set up other than just turbos......thanks so much for your input.

93formto98T/A

iTrader: (28)

Just give Jose @ forced inductions a call. He'll set you straight. There are few others with that level of hands on turbo experience and R&D time.

Mr.427

I have already sent him an e-mail through their site. I just would like to hear others thoughts. Information is power!

Mr.427

70 views and no opinions? WOW...............

dschmittie1

iTrader: (64)

1fastbird has twin tc 76 turbos. He had a hard time getting them to spool with his 402. I think some of it had to do with the compression being very low. He was also told by several people that he had more turbo than he really needed.

PS he is also talking about selling the whole kit and going single or selling the turbos and going a little smaller with something that better suits his needs

Mr.427

Thanks.........yep the last thing I want to do is "overcompensate" but these two 66's are just not enough in the mid to higher RPM's. Thanks for the info.

dschmittie1

iTrader: (64)

Well there are a lot of things that can effect spool. You do have 30 more CI than he did. What is you CR. His was like 8.5ish:1 Too low IMHO I think those turbos with more CR and better cam selection would have spooled better on his 402

westtexasbuff

iTrader: (40)

Is it manual or auto?

Mr.427

Six speed manual.

Mr.427

Compression ratio is 9.2 to 1 My ar on the 66's is only .68 which I THINK ALSO HOLDS ME DOWN. Thinking about something around .80 to .90. Again, I appreciate any opinions. Thanks.....

Mr.427

Any other opinions or input??????????????????

Mr.427

Talked with Jose at Forced Inductions and he suggested going with Turbonetics HPS 76 twins with a .81 a/r.

TracyRR

iTrader: (8)

If i had 427 cubes, i would already have twin 76's... the only issue is of course the manual trans. I would suggest you just hang some larger exh housings since they are relatively cheap and it may suit you for a while. I just went down in housing size from 1.0 to a .68 and it made a pretty big difference.... i'm sure going the opposite way (larger) it would make a difference. Great car!!

Mr.427

Thanks for the input Tracy.

black98ws6ta

iTrader: (77)

I also agree with trying larger housings for your current turbo's. If that dont fix it... 76's will. I have a pair of them on a 427 sbc motor but with a th400, the converter dictates alot of the spool time.

kmracer

iTrader: (1)

https://ls1tech.com/forums/forced-in...-kytp-kit.html


i'd think twin 76's would suit you well..

onfire

iTrader: (17)

TC76's with 96 turbine ar's will get you 1100 - 1200 rwhp under 30psi of boost with your engine. If you have the room use the t76 with the S series compressor cover. Next step up would be Precision 76's with a 81 turbine ar...those are big power twins.

Fbodyjunkie06

iTrader: (10)

I was going to say the same thing as ^. Twin PT76's would be suhweet. Easy 1300whp there with those two turbo's not even close to full song. I don't think you'lll ever run out of turbo with those.

Mr.427

heck, I am getting 940 on pump gas with just 15 pounds of boost with twin 66's on a .68 ar. Jose (forced inductions) has suggested Twin HPS 76's with a .82 ar. Still good for the street and full spool around 4300RPM. That should reep about 1150 on pump gas. Looking for more street ability than track use.