new rear mount turbo project

opnwide · 08-21-08, 07:32PM

Hello, everyone,
I just wanted to say Hi and to introduce my '76 SE to you guys. My car is a couple of months from paint and I have been considering the drivetrain. My goal with this car is a fast street machine able to keep up with my Viper (120mph in the 1/4mile) and not do too much to destroy originality.

I've done a procharged '72 Vette before, so some of this stuff is familiar, but alot is new as well. This forum has been a great source of info since I found it two weeks ago.

Any recommendations on a rear turbo. My goal is 700hp using a single rear mount turbo. I would like to run RamAir long branch manifolds into two 2.5" pipes down the passenger side, through two 2.5 hi-flow cats and then neck down to feed a dual scroll hot side turbine. Outlet would be split into two for a stock appearance using factory tailpipes. On the compressor side, I would like to run a single 3" pipe back up the driver's side, using a highly modified factory aircleaner for a carb hat. Carb would probably be a 750DP, and the cam a generic summit 224/224 114lobe sep.

I'm keeping stock mildly ported 6X heads and stock block, but going with nice aftermarket rods and forged pistons.

I've been looking at the Garrett GT42s. A GT45 may work, but I'm concerned with turbo lag.

Anybody have any questions or comments on this idea?

I've got a couple of new GT3040 turbos sitting around, but I haven't seen a twin turbo system with AC and PS yet. That's why I though I'd move the turbo to the rear.

Did I mention this was a great forum?

turbo69BIRD · 08-22-08, 01:07AM

Sounds like a great build it would be nice to see a remote mount build getting started.
The big thing is to keep the heat in and to keep the exhaust AR real tight.

Oil pump is needed with remote mount as well all the rest is the same ole Stuff.

GOAT8U2 · 08-23-08, 08:11PM

admin@turbopontiacs.com
I don't think he's making twin turbo header kits anymore but worth asking, his twin 455 was sweet.

I'd think the rear setup would be harder to pull off than a single setup, many are mounting the turbo off the passenger frame so accessories aren't a big deal.

opnwide · 08-23-08, 10:47PM

I've seen those single turbos like yours and turbo69bird's. Those are pretty cool but there is definitely no hiding them when you're at the drive-in. I'm looking to do something a little more unusual, and frankly, rear mount turbos are a bit of the dark horse right now. Sizing seems to be the biggest issue. I'm tempted to go smaller than what most people are doing since I need to keep the exhaust velocity high. Also hoping to keep decent sized exhaust and intake pipes under the car to avoid scraping on speed bumps with a 3" drop.

I started welding together my narrowed gas tank today and hopefully will be welding in a sump this week sometime. Should I go with one or two 1/2 outlets on the sump? Will a -8 AN line support 700 hp or should I use two 1/2" outlets and Tee them into a -10AN before the pump?
I plan to have a same-size return dump in through the stock location.

turbo69BIRD · 08-24-08, 11:53AM

The rear mounted turbo deal is a fairly easy thing to set up.
It biggest issues are making brackets strong enough to hold for long periods of time, and pumping oil back. small holding tank is the best way for oil drain back.

The size of the tubing is not a huge concern a smaller pipe is not going to hurt you that badly. I will still be a fast car.

The big thing is sizing the turbine size. The compressor size still needs to be the same efficiency.

There are sites out there that give up all the sizing secrets if you look for them. mostly LS1 sites.

Worst case scenario you have to buy and sell a few turbos to test with. THe set up will be easier.

Go to hemitruckclub.com I am a member over there and there are lots of guys remote mount turboing hemi trucks.
check it out.
Gotta know what everyone is doing to stay sharp right!!!!

Poison heart · 08-27-08, 04:38AM

What's your name on Hemitruckclub? I'm over there too. Lot's of quick trucks

turbo69BIRD · 08-27-08, 10:59AM

Robert,
I am cstockbird over there don't get there too much this place keeps me busy.LOL
Between the offfshoreonly.com site and here I get way to much computer time.
LOL

opnwide · 08-27-08, 11:44PM

I've been checking out those forums (ls1tech.com and hemitruckclub.com. It looks like a T76 will be a pretty good turbo, too, if I can find one with a turbine A/R under 1.0. I'm also eyeing the demon blowthrough 750. Is a -10 line overkill? Aeromotive suggests a -12 from tank to pump and then -10 to carb, but other sites suggest I can get away with a -8 all the way! Where's the concensus?

Maybe I'll split the difference. I'm welding the gas tank sump as we speak (yes, its been blasted clean). I think I'll just order the -10 weld in bung and run -10 feed and return lines.

turbo69BIRD · 08-28-08, 10:43AM

Its been so long since I had to look I cant remember for sure but I think I have -12 to the pump, -10 from pump to reg and -8 to carb bowls.
I run a -8 back to the tank wich is a no no but I do it cause I can.LOL

I had it here and ran it and it worked OK so I didn't change it
A tv7101 is basicall a T76 and you can get a .96 housing for it. they are relatively cheap compared to a T76 turbonetics. Less than half the price.

They even made a tighter housing but I haven't seen one in some time.(havent really looked either though)
They are out there but are $$$$ maybe $350 for just the housing if you can find one.

opnwide · 08-28-08, 09:22PM

Thanks, Turbo69 bird, I'm ordering a -12 tonight

and checking out the TV7101, too.

marks73ta · 08-31-08, 12:03PM

I run an A1000 pump, twin -8 from the two cell sump outlets to the pump. I found a 13 foot -10 with a single AN -10 straight end on E-bay for 5 bucks so jumped on it and won. Once I got it on the car it turned out the end was an AN -10 but the actual line was -12?? I had to get an -AN 12 to -10 adapter end to finish the hook up. Anywho. I run -6 from the regulator to the carb. My bypass return line is also a -8, because that is what I originally ran from pump to reg on my N/A setup. If needed I will change to a -10 return but for now I am OK. I still have a lot of tuning to do so things may have to change. Mark L

onebadpontiac · 01-18-09, 04:38PM

opnwide,
1100 hp will not cost a lot more than 700.
Jeff is correct about the small turbine size and bigger compressor.
Fill us in on it a little more. What is the budget? Do you plan on running an intercooler or meth injection? Tell us more about your overall goals to paint a good picture.

opnwide · 01-21-09, 10:27PM

The Goal is not to hurt the stock block

Yeah, Turbo69bird is making 900+hp on a stock '76 block, but I want to play it a little more conservatively.
Building the shortblock now. I've got Ross flattop pistons, eagle 4.25 crank and 6.8 rods. Custom solid roller cam from Butler/CompCams 236/242 114 LC and 600 lift.

Will be home porting stock 6H heads according to Hand's book, installing 1.77 ex valves.

750cfm Demon Blow through carb, thanks GTO65LVR.

Using modified shorty Hedman headers.

10-15psi with this combo should be good for 700-800hp. I just want to spank those new corvettes

SPDMETL · 03-01-09, 07:46PM

Anything new ? Rear mounts sure make an evil and unmistakable noise !

onebadpontiac · 03-01-09, 11:09PM

Quote:

Originally Posted by opnwide

The Goal is not to hurt the stock block

Yeah, Turbo69bird is making 900+hp on a stock '76 block, but I want to play it a little more conservatively.
Building the shortblock now. I've got Ross flattop pistons, eagle 4.25 crank and 6.8 rods. Custom solid roller cam from Butler/CompCams 236/242 114 LC and 600 lift.

Will be home porting stock 6H heads according to Hand's book, installing 1.77 ex valves.

750cfm Demon Blow through carb, thanks GTO65LVR.

Using modified shorty Hedman headers.

10-15psi with this combo should be good for 700-800hp. I just want to spank those new corvettes

You can keep it together by going efi. You really need to control the timing accurately and at many different conditions.

gto65lvr · 03-05-09, 01:07AM

cannot wait to see photos of your modified headers. I wish times were not getting so damn tough I really wanted/want to do the turbo thing but it is not meant to be. Maybe later so to speak still have another car up my sleeve and by the time I get it done maybe must maybe a low buck build. Shoot by then someone will have a low cost turbo header LOL

opnwide · 03-11-09, 11:34PM

Still building the engine. Shortblock is together, and the heads are going out next week for a valve job. I ported them myself according to Hand's book. Killer short duration roller cam from Butler. Those guys have treated me right. My last deal on the Hedman shorty headers didn't work out. When I received them, they were stock log-style exhaust manifolds????? so I sent them back. Really, who confuses stock ex manifolds for shorty headers? Looking again for some used ones to cut up.

I guaranty I'll post photos when the opportunity arises, but times are tough and I'm lucky to still be working. Actually, I'm working my butt off hoping to have something saved for the hard times that are still likely to come. At least I'm working. LOL

turbo69BIRD · 03-12-09, 01:04AM

Why not put regular headers if going rear mount?

opnwide · 03-12-09, 11:03PM

I have a couple of concerns with a single rear turbo, like space. I also already have two Gt3040s sitting around. I like the idea of the twins, if I can get the manifold issue sorted out. If I do the rear turbo thing, I'll do headers or ramair manifolds. Engine is almost done, so its time to make up my mind.

What would you guys like to see?

marks73ta · 03-13-09, 05:34PM

I hate to ask this but any possibility that, if you go rear mount, you could build it with RA manifolds first and then switch to the headers? It would make a great comparison and probably much easier done on the rear mount set up than a front mount. Again, very understandable if you can't build it both ways. Mark L