frcefed98

iTrader: (16)

WE know this is a REAR MOUNT SET UP We have quite a few members making great power with rear mount set ups.

One is already doing a big inch big turbo set up, but hasn't updated in a while.

One thing you are not getting is the backpressure a undersized turbo will create on a big inch combo. Headgaskets will be lunched regularly.

Texas, call Jose@forcedinductions.com

www.forcedinductions.com

I'd ditch the rear mount set up altogether and go the traditional front mount route. A truck manifold set up will be easy to set up and have no worries about the drawbacks to having a rear mount....i.e. intake and exhaust plumbing share the same space under the car.

BigJLS1 post results and info on your big inch rear mount combos that you have built. I'd like to see and read about them.

Texas_WS6

iTrader: (9)

I see your point. I see all of your points. I want to make 500rwhp with my present engine. It already has the 3" exhaust, but it is a custom exhaust with headers and coustom Y pipe and no cats. I will need to change that. Most likely I will put the stock manifolds back on the car and run custom exhaust with no cats (we do not do any kind of inspections here ). The present engine has the wrong cam in it for this aplication so I will be changing cams. The car has a 4000 stall in it and 3.73 gears. They will stay for this engine. I did give in to the advice to up the turbo size. Today I canceld the GT-K 850 and ordered a 76GTS with .81AR from Forced Inductions. I wanted to only buy one turbo that will meet both goals I have with both engines. I hope this one will do it. I will still have to change the turbine housing to a bigger AR once the 427 is completed, but I will get 2 years of fun out of it as is (as long as I do not destroy the present engine). Like I stated before, the goal is to remove my nitous and go turbo and still make the same power as the nitrous (well I will tune it for 500 to 550rwhp not 472) with the 348. I almost just upsized the GT-K 850 order to 1000, or to the turbonetics Super T76 (both I could have got for $1450) but I finally settled on the Forced Induction model. The reason for that was I was 100% on my own with advice with Turbonetics, but I feel better dealing with Forced Induction since now that I bought from them, I should be able to get advice from them. All the guys I talked to at Turbonetics seemed to be more 4-banger guys then LSX people. Makes me feal better at least.

So no more GT-K 850. I can not wate for the Forced Induction 76GTS to get here!!!

Now I need to find out if my present injectors and fuel rail will support 500-550RWHP. I know my fuel pump will work do to the fact it is already plenty good for the nitous I am running (255 pump). I am running SVO 30 pound injectors, which I am sure I will need to change. If I change them can I go ahead and just change them to the size I will need for the 427 at 850rwhp? I am conserned they will be too big for street driving. I still need to decide on the return oil pump size and brand, which intake, and how I want to do my PCV system.

This is getting long wined, sorry.

As for the pipping, I plan on removing both of my subframe conenctors and building new ones that will be sealed, sized for the flow, and strong enough to work as subframe conectors. Y the air from the turbo discharge and pass the air down both sides of the car threw the new subframe conectors. At the front have both go under the K-member (or over or even threw, have not made up my mind yet) and then Y back together before the intercooler. All the exhaust and air piping and the intercooler is pretty much completed as far as planning goes. I like the idea of modifying the K-member to were I can pass the air threw it while still maintaning the ground clearence. Very duable I think. It might only cause .5" to 1" of ground clearence loss due to the placement of the steering. Maybe someone could take this idea and run with it.

Texas_WS6

iTrader: (9)

Thanks, but I beet ya to it. Called them this morning and ordered a 76GTS with .81AR. I could sense the vibes from ya all the way over here .

Thanks for getting me on the right track.

Texas_WS6

iTrader: (9)

Update.

I dropped the 427 idea all together. I do not want to wait 2 years to finish the proiect. So I am now completing the 408 I already started. I should have the shortblock back from the builder by the end of January. Putting ported L92 heads and the GM performance intake (ported) on it as well. I have not bought the cam for it yet. Waiting to see the final flow numbers on the heads intake combo. Any sugestion?

Now I am rethinking the rear mount idea as well. I would realy like to do a front mount with truck manifold. Question is, will my 76GTS work up front on the 408? What size AR will I need to go to? I realy hope the turbo will support this engine and make 800rwhp.

I have seen several truck manifold setups that use both manifolds and removes the AC. Has anyone tried using just the passanger truck manifold on the drivers side, keep the F-body passenger manifold on the passenger side, and plumb the passenger side exhaust around the transmition and back up under the drivers side exhaust to Y in before the turbo? Once the alternator is relocated, would that leave enough room for both the passenger exhaust piping and the down tube piping? Just a thought.

DrTurbo

iTrader: (3)

Your going to need a .96A/R for sure now that you are upgrading to the larger engine. You can squeek some big numbers with the turbo,but it will be out of its efficiency range at that point. Its give and take in the turbo world.

smokinHawk

iTrader: (48)

i dont think the 76gt6 comes bigger then a .96ar which you will need bigger.
your getting a little better going down to the 408, but that engine is still a bit to big for the turbo, it will work but i guaranteed you will make more power out of a smaller engine with that turbo. is it to late to put the stock strok crank on there, if you do around 360ish cubes and that turbo spinning it to around 6800rpm with a good amount of boost that turbo will suport, you would be around 900rwhp or past

DrTurbo

iTrader: (3)

Yeah going from rear mount to front mount kit makes a big difference in turbo selection.

Texas_WS6

iTrader: (9)

No, I have had the crank in the gaurage for 4 or 5 years now. I hate to ditch it now.

So, if I stick with the original plan as far as the rear mount set up, would this turbo with the .96 work better with the 408? I realy do not want the turbo to come on early. I am counting on a little turbo lag to help hook the car. I have not bought the manifolds yet. I can still continue with the rear mount. I just do not like the oil pump return aspect, as well as the air inlet being under and at the rear of the car.

I am stuck with the 408, and I am not able to upgrade the turbo to a larger one at this time. So what are my options other then selling the turbo for a lose to buy a larger turbo.

What staull speed and cam size should I be thinking about? I have a 4000 staull right now. I must be getting old though, I am realy tired of all that staull.

smokinHawk

iTrader: (48)

why not sell your crank then.
the set up will work that you have but there are allot of wasteful parts that you dont need.
and you will make more power with the turbo up front.
first you will only make as much HP as that turbo can support, next to get the most out of your turbo and to make well with your engine you should size it to the turbo and desired rpm range.
you need to ask your self how much power do you want, and then were do you want that power.

Texas_WS6

iTrader: (9)

I spoke with Forced Induction about the limitations and options. I had the turbo sized for the rear of the car. Moving it to the front will require a different turbo. Taking into consideration the goals and options for this build, I will continue with the rear mount set up and complete the 408. When I bought my crankshaft, they were about 300 dollars more then they are now. So selling the crank is not an option. Of anyone wants a new still in the box 76GTS turbo from Forced Induction, I will be willing to sell it to them. But at the same price I bought it. I would then purchase a turbo sized for the front and go that route. I am sure everyone will want a less then new price for the turbo, so I will have to complete the biuld as planed.

Lessons learned, never change horses mid stride.

It will still be a great build.