Nos, propane, more turbos?

T

THISISMYRIFL3

New member
Well im trying to decide how I want to go about cleaning up my top end smoke. How much boost can a studded head take? Are compounds doable and safe at my levels (50 psi on single turbo). Is nos or propane viable options? I'll update my Sig but current changes are a s475 turbo. Changes to be made are swapping my full cuts to .024 delivery valves and possibly changing my 5x20s to 5x16s or 5x18s if I can't clean up the top end smoke. Just looking to gather thoughts and opinions to make an educated decision going forward. Plan to keep truck somewhat streetable. Not daily driver more Sunday driver or cruise down to the occasional car show. Thanks for sharing your knowledge.
 
Compounds are way more fun on a street 12 valve, something with a 62mm secondary. You would probably be in the 70 plus boost range with compounds, run it until the head gasket blows then get the head o-ringed. Other than the inconvienence it doesn't usually do any more damage when it goes, as long as you don't keep driving it. What timing are you running, more timing would clean the top end up, but is harder on the head gasket than boost psi.
 
I see your sig, 27 missed that. On a 5sp I bet that truck only starts to pull good at the top of 4th and 5th with an s400 single. I had the same truck years ago, similar set up with a s357 over s475 compounds and would do rolling burnouts if you rolled into in in 4th, towed awesome.
 
So since my head is already fire ringed I could back off the timing to 20° and run like a s466 with a s475 or s480 setup? I have a spare s400 frame I plan on rebuilding.
 
I have an s482. Any advise on what to as a high pressure turbo? Is a s475 to big? I could build a s466 or is that to small? This is where actual experience (the thing I'm still gaining) becomes invaluable.
 
That 75 is too big, it would have more lag than as a single. Message Smokem(Weston @ Infinite Perf) and go with his recommendation.
 
27° plus 80-90+ boost. Wouldn't that really stress the head gasket. I've been told fire rings are reliable to about 70 psi. Anything more is rolling the dice.
 
THISISMYRIFL3 said:
27° plus 80-90+ boost. Wouldn't that really stress the head gasket. I've been told fire rings are reliable to about 70 psi. Anything more is rolling the dice.
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I've ran more timing and boost with an o-ringed head with no problems. I'm sure if you wanted to hurt it you could, just don't make it a point to pull the engine down hard while on boost, don't run it hard till it's up to temp, make power in the upper rpm range, all.good.
 
After investing almost 20 grand into this truck I'd really hate to do this wrong and have to tare it back apart. The original set up made all the power up top with a s482 but I want that low end grunt that's fun to play with. The truck ain't very fun on the street with no power band to speak of. I'm thinking 20°-22° timing with a s466 s482 compound setup. If that's still way Smokey I'll drop to a smaller injector. With that much air I should be looking at 800-900 horses easily. When that starts feeling slow I'll just build it into an all out track monster.
 
An s4/s4 on a 12 will be terrible on the street. No amount of fiddling will solve that problem. But my terrible and your terrible might be two totally different things. I personally feel your pretty off base with what you want and what you need. But thats just me.
 
turbo2332 said:
An s4/s4 on a 12 will be terrible on the street. No amount of fiddling will solve that problem. But my terrible and your terrible might be two totally different things. I personally feel your pretty off base with what you want and what you need. But thats just me.
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Your terrible and my terrible probably are miles apart seeing as how this is my first high power build ever and the first turbo on it was a single s482 and currently a s475. I understand I'm secretly lacking in knowledge when it comes to tuning and turbo sizes and I understand that. Which is why I'm trying to gather as many thoughts opinions on the topic as I can. So please explain why you think an s4 s4 setup wouldn't work so I can further my knowledge. thank you.
 
because its huge. your small turbo would be one designed for a 12ish liter engine vrs something in the 7.0 range.
what kind of hp are you looking for
what kind of drivability
what kind of egts
what kind of boost

an s4 over an s4 is a 1500hp and up kinda setup. an s3 over an s4 can range from 500-1200 plus if tuned right and go frome very drivable to very un street friendly. your injectors are on the huge side. guess you need that for a massive single but in compounds. 5x16 are 700+ and 18's will be 900+. full cuts are dare I say junk in any application.

if you want a hot rod. do some 5x18's a 64-67mm compressor on your existing turbo some .024's or 191 delivery valves some pump tuning. take the timing down to the low 20's and give that a whirl. should get you well into the 700 range. and be a bit more well rounded. also will cost you several thousands less $$$$$$$$
 
What kind of hp are you looking for: whatever it takes to do a 4th gear rolling burn out cus I was told it wasn't possible.

what kind of drivability: it's gotta be drivable to/from the track about 20 minutes away and to/from local car shows. I'm not building a drag my ass to work and get groceries when I get off truck.

what kind of egts: I'd like to be able top put my foot in it and keep steady around 1100-1150. I would accept a 30 second full throttle run to 1200.

what kind of boost: whatever it takes to get there but not too much to blow it up. I've run up to 60 psi. I'm thinking if I can't get there on 100 or less I'll cut my losses and add as much fuel as I can burn with whatever compound setup I put together.

This is a old enough to build it and to young to find an excuse not to project. Not a tow the camper machine. I've got one of those. As for saving money I'm already 17 grand of learning lessons into this thing. Knowledge is expensive since few people care to share it.
 
you will struggle with the hp levels you want and the egts you want to see. heat = energy. and a big turbo takes a lot of energy to spin properly.
 
rolling burnouts in an auto at 40 can be done pretty easy with a 62mm s300 as a single. you don't need a million hp to spin the tires. super hard tires make for easy burnouts. also note that compounds take the big punch away from the boost you will see. meaning the power comes on sooner and longer. which makes doing burnouts a little harder to get going from a roll. a big single when it lights, lights all at once and you go fast, fast. compounds pull earlier and longer. a single is way more peaky. which will aid in your rolling burnouts in 4th.
 
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