[n2ogpsj462]

I've been thinking non stop about what Tom said regarding hot side pipe diameter and his comment that dual 2" would easily support 1000hp. Is there an equation or general rule to picking the housing size? I went with 1.32 because 'big motors need big housings' also why I went with 2 1/2 pipes. I was going to change my crossover but thought it would be incredibly easier to swap housings. Back when I did mine I think our choices were 1.32 or .96 which seems drastic but I think I saw in between options available now? Strictly street deal under 15psi. Cabin fever and extra money now has me ripping my car back apart to do things alittle different/right.

[BruceWilkie]

With your turbo I'd stay with 1.32 housing and merge TWO 2.25"-2.5" at the turbine flange.(assuming it's a twin scroll turbine housing) if building headers 1.75" OD primary's into 2.25" should be a good match for boost range your planning on. If going all out race 30+ psi then 1.875" into 2.5" would be a better choice.
Coming off turbine... big as you can fit, make a large expansion off turbo and taper it as long as you can fit(and as "fat" as you can fit.)

[Tom Vaught]

Whose Turbo were you looking at?

A Borg Warner S471 T4 71/74 100/83 177248
for example comes in .90, 1.00, 1.10 & 1.25 A/R
ratios on the Turbine.

But here is a Tip that might save you some money. If you already have the Turbo with the 1.32 Turbine housing RUN THAT FIRST and see how THE ENGINE PACKAGE performs.

Then IF you need to go smaller on the A/R ratio
as long as the basic Turbine Housing configuration is the same (T-4 Housing or T-6 Housing) then the fabricated exhaust pieces should not change. Hope this helps.

A 1.32 housing will definitely spool slower on a 455 engine vs a .96 Turbine housing and the boost will come on later.

Tom V.

ps Bruce W's recommendations on the header pipe diameters is right on the money.

[n2ogpsj462]

Sorry for the confusion Bruce but my blowthru has been Done since early 09 but off the road for about 5 because young kids and general life ate up extra income. I've always knew a ton of things needed to be changed so I pulled everything apart for freshen up and to change what I knew was wrong for boost (cam,intake,compression etc) actually everything was wrong, I just threw away my big nitrous cam and slapped everything together.


Sorry for the rant but anyway I thought I was fine with my 2.5 crossover but Toms comment about crossover size got me thinking. A lot easier to address now. I wouldn't get boost until damn near 4500. I read guys getting boost damn near off idle with these. Also I'm not sure why or how my post was doubled up or how to delete it

[n2ogpsj462]

Tom, sticking with my s475 1.32 t6

[v869tr6]

Your combo in the signature looks pretty good to me, but you don't have a converter listed. Many times a high dollar converter is what's needed to wake up a combo.

[70 bird]

You might have something going on? I have full boost by 36-3800

[n2ogpsj462]

Originally Posted by 70 bird

You might have something going on? I have full boost by 36-3800

That's kinda why I'm changing some things. It was my plan all along. I'm using a 10" non lock up 700r4. I had it tightened up but can't recall where it stalls. The trans could be part of the problem to with the 1st gear.

So stick with the 1.32?

[Tom Vaught]

Originally Posted by n2ogpsj462

The trans could be part of the problem to with the 1st gear.

So stick with the 1.32?

For Now I would. Resolve the problem you currently have, don't compound the problem further by "Changing Horses in the middle of the Stream." (Old Southwest Cowboy saying).

Tom V.

[n2ogpsj462]

That's pretty much the plan but started second guessing after your comments about 2" crossover.

[70 bird]

I would keep that 1.32 for now It should work good with with your 462. I have played around with different gear ratios, converter stall speeds even ignition timing on my Pontiac and Ford and they all can make a huge difference in performance and boost levels. I have a PTC nitrous converter in my t400 which I sent back and told them to make it as tight as they could. They installed a 380 stator and said I wouldnt like it and it would be too tight, The converter stalls around 2600 and I love it! hit it with some boost and the stall goes up.
My rear axle ratio is a 3.08 and that works good, I changed from a 3.55 which was almost dangerous as the car had little traction even with drag radials.
My hotside is 2.25 but I dont see where you changing to 2in. would offer much benefit. My 351w in my ford has a 2.5 hotside and has no problem spooling a s480. jmo.

[n2ogpsj462]

The 700 1st gear probably has a lot to do with it but I'll never give up the OD. Yrs ago I had 3.90s and it left so hard it would lift the drivers tire but first gear was useless other than light to light showing off. Picked up almost a half a sec switching to 3.42s and after going turbo I toyed with going to 308 but I've also strongly been considering the 4l80e. Like I said I'm finally back to playing with the car after a 5-6yr hiatus.

[70 bird]

Yeah I like the 3.08 its like the poor mans overdrive.lol. I have also thought about a 4L80e but for me its not worth the hassle. I dont drive on the eway much and when I do the 3.08 isnt that bad. If I remember right Im at 2600 @ 70 I can live with that.

Its all trial and error now that you have time build it the way you like!