Guest dieseldust Posted March 4, 2009 Share Posted March 4, 2009 Hey all does swapping to a turbo 400 from a turbo 350 really have any advantage, i hear that with the 400 it takes more HP to work it , i have been told up to 50 HP loss from 350 to 400 any comments on that tale. Cheers James Quote Link to comment Share on other sites More sharing options...
Guest dieseldust Posted March 4, 2009 Share Posted March 4, 2009 Hello Allan, You allways have good advise, i just have my stock 454 right now, that said i plan to make about 450 to 500 horsr range out of it i have some merlin cast heads i got and some other goodies to install over next winter, the Turbo 350 that is in the car now is a little worn, i have a freind that has a 400 that he just got rebuilt before he wrecked his car, it has about 500 miles on it with a stage 2 shift kit in it, he said give me 150 bucks for it. SO i guess i really dont nead the 400 but the price is right and i am pretty sure my 350 is on its way out or at least is getting old . So do i swap out for a 400 ?? or rebuild the 350 ?? Cheers James Quote Link to comment Share on other sites More sharing options...
Guest dieseldust Posted March 4, 2009 Share Posted March 4, 2009 Christmas comes more than once sometimes Allan, I just had a glance at your new parts for your front end , nice parts , if i have the time and money maybe one day i can have a gret looking car like yours Allan. Cheers James Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted March 4, 2009 Share Posted March 4, 2009 if you don't want that 400, I'll take it Quote Link to comment Share on other sites More sharing options...
Heckeng Posted March 4, 2009 Share Posted March 4, 2009 Buy the 400, then rebuild the th350! Use a kit that has the extra clutches and steels along with good clutches. If you really want to up the strength, get par number 355682 from ATI which is a heavy duty 36 element sprag assembly. A th400 is stronger than the th350, but they both have the same weaknesses. Don't downshift under engine braking load! That is what breaks the sprag race which is an extremely common problem. I optimistically have 450-500 hp and run a th350. I've gone mid 12's so far. I also have a friend in a mostly steel camaro with a 496 that runs high 9's. He also uses a th350 with nothing major done to it. 400's are nice though, and getting very hard to find. Buy it as an investment if nothing else! Quote Link to comment Share on other sites More sharing options...
Guest dieseldust Posted March 4, 2009 Share Posted March 4, 2009 Mid 12,s would be nice for me too, great advise and i got alot of work to do before i get to 12,s like you guys, but i am looking forward to the journey . Cheers James Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted March 4, 2009 Share Posted March 4, 2009 James, A 400 needs a different driveshaft Quote Link to comment Share on other sites More sharing options...
kc8oye Posted March 4, 2009 Share Posted March 4, 2009 put the 400 in.. GM never put a Th350 behind a big block.. there was problaby good reason for that. 350's can be built to handle it.. but when a stock 400 will do it..... Quote Link to comment Share on other sites More sharing options...
Heckeng Posted March 4, 2009 Share Posted March 4, 2009 They didn't put 700R4's, 2004R's, or Powerglides behind them either, but you see them all the time. And you don't need to do much if anything to have good luck with the th350 behind one. Everybody just loses faith because they know that the big brother the th400 is out there and that is just what everybody else is using. Quote Link to comment Share on other sites More sharing options...
680HPStroker Posted March 4, 2009 Share Posted March 4, 2009 Allan's advise is correct. With your performance goals a well built Turbo 350 would do ok, but at $150.00 for a 400 I say go for it as well. You can beat a stock Turbo 400 with 900HP and it will just laugh at you. It's true that a 400 will eat up some power. I went from a 700R4 with a lockup converter that was locked up making 534Hp to the wheels to a Turbo 400 that doesn't lockup making, well I don't know yet for sure as I haven't done a full dyno run, but when I had my carb modified to remove some hesitation a quick dyno pull was done and my dyno guy told me I don't want to know how much wheel power I lost. Having said that don't get to wrapped up in it as my car feels just as strong as it did before. Even if it's a little lazy off the line it will be about the same on top end and I have the added security of a tranny that can take more power than I'm showing it. Good luck. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted March 5, 2009 Share Posted March 5, 2009 what a lot of people don't understand, is that no matter how many hard parts you put into the trans, eventually the aluminum case isn't strong enough to handle the torque.. I've seen pictures of a TH350 litterly blown in half when the case failed... if you run slick and hook up well, it's even more important that your transmission be extra tough. running a700r4 behind a big block that lives on the street and can boil the balonies at the drop of the hammer is one thing.. since the tires spin, it's not _that_ hard on the drivetrain.. but you get on the track, and run slicks and hook up.. things will start breaking. That's way it's been explained to me by people who know. the one guy has a Ford Falon that runs 8.90's in the 1/4 mile with a small block ford and a powerglide trans :> Quote Link to comment Share on other sites More sharing options...
FerrariTruck Posted March 5, 2009 Share Posted March 5, 2009 get the th400.... then get a good driveshaft and you are good to launch hard. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted March 5, 2009 Share Posted March 5, 2009 what a lot of people don't understand, is that no matter how many hard parts you put into the trans, eventually the aluminum case isn't strong enough to handle the torque.. I've seen pictures of a TH350 litterly blown in half when the case failed... if you run slick and hook up well, it's even more important that your transmission be extra tough. running a700r4 behind a big block that lives on the street and can boil the balonies at the drop of the hammer is one thing.. since the tires spin, it's not _that_ hard on the drivetrain.. but you get on the track, and run slicks and hook up.. things will start breaking. That's way it's been explained to me by people who know. the one guy has a Ford Falon that runs 8.90's in the 1/4 mile with a small block ford and a powerglide trans :> There is some truth to that Tim, but the main reason cases break is chassis flex. My buddy running 9's has broken 2 or 3 th350 cases if I remember right. He started talking to racers running sub-10's at the track to see if they'd run into that as well and of course they have. They told him that the problem was that he was using solid engine and tranny mounts. When you run solid mounts, and have that much power, even with a cage, the chassis will flex some and the trans is the weakest part and you will break them. To keep the trans case from cracking, all of these racers recommended using solid motor mounts, but a rubber trans mount. That keeps a little flexibility between the tranny and the chassis and it all works with no case breakage. Quote Link to comment Share on other sites More sharing options...
Shadow Gray SS Posted March 6, 2009 Share Posted March 6, 2009 Try to get a 'K' case if you get a 700r4. They only made them for two years and they are thicker than the standard case. There is a K clearly visible on the outside. Quote Link to comment Share on other sites More sharing options...
Ian Posted March 6, 2009 Share Posted March 6, 2009 Jake are they the ones from 87-88? I got mine out of a 88 Camaro Quote Link to comment Share on other sites More sharing options...
Shadow Gray SS Posted March 6, 2009 Share Posted March 6, 2009 Ian, I could not find any place to confirm the two year info, but from what I did find the K case was a truck thing. I will call the guy that built my tranny's and see what he says. Quote Link to comment Share on other sites More sharing options...
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