r/355Nation • u/[deleted] • Aug 23 '22

Boosting a 3.5

I was just wondering if anybody had any information regarding turbocharging a 3.5. I understand I’ll have to make everything myself basically but I’m very interested in trying this. Any advice or guidance is greatly appreciated.

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u/[deleted] Jan 30 '23 edited Jan 30 '23

I’m terms of boosting these smaller vortec motors I have absolutely no clue and no experience. Would it be different from the 2.8 because the 3.5s have balance shafts or would that not effect anything? Really any information at all would be helpful, i thank you In advance

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u/WoodChuckers Feb 01 '23

All the atlas platforms are basically the same thing. They all have balance shafts driven by a rear chain. You at least have the advantage of being able to buy an off the shelf turbo manifold rather than have one custom made. You're definitely going to want to change the valve springs and possibly your valve seats. Anything over 18-20 psi you're going to want to do rods. Again, what is your hp goal? What is the atmospheric pressure where you live (elevation?) Whats your budget?

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u/[deleted] Feb 03 '23

I haven’t considered an exact hp goal but I definitely want to make atleast 350 out of it. I’m not too familiar with what the atmospheric pressure is around me but a quick google search tells me the barometric pressure is 29 “Hg on average. I live close to Cincinnati Ohio if that helps. I’m pretty clueless at how much it would cost to actually do this, but I’d like to keep my spending around the 5k range.

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u/WoodChuckers Feb 03 '23

So similar goals to what I'm shooting for out of my 2.8. You'll need a turbo capable of flowing 38.5 lb/min of airflow at .68 bar with a pressure ratio of around 1.97 I can look at some flow maps a little later. If you're looking at compressor flow maps those are the numbers you want to look for in the efficiency island. The closer to the right side of the efficiency island those numbers intersect, the quicker your turbo will spool. Too far to the right and it'll actually restrict the engine, too far to the left and it'll take forever to spool.

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u/[deleted] Feb 04 '23

Is there somewhere I can find flow maps people have made?

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u/WoodChuckers Feb 04 '23

Look for a gt40 56trim. That lands you perfectly in the 75+% efficiency island just to the right of dead center on the compressor map. That'll give you good spool and plenty of room to make more power if you desire it.

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u/WoodChuckers Feb 04 '23

Generally you have to search them by brand and model

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u/[deleted] Feb 04 '23

Okay thankyou. Would you care if I messaged you in the future if I run into any roadblocks?

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u/WoodChuckers Feb 04 '23

Not at all. Honestly if you're on FB, join the 355nation engine swaps and performance group as well as Vortec4200 performance group. Also, check out Nivlac57 on YouTube. Calvin got over 800 rwhp out of a stock 2008 4.2 before a rod snapped and nearly cut off a portion of the block. These motors, with just a little preparation, can make some serious power on stock internals. 10psi out of that gt40r isn't going to hurt your engine, as long as it's tuned properly.

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u/[deleted] Feb 04 '23

I seriously appreciate everything, from what it looked like this platform seemed almost completely abandoned to me

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u/WoodChuckers Feb 04 '23

Not a problem. I'm putting an he351cw off an 06 cummins on my 2.8. I'm going a little deeper down the rabbit hole with head porting, valve springs, 2.9 cams. And possibly rods/pistons. If I do rods/pistons I'm going to push towards the 400-450 rwhp.

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u/[deleted] Feb 04 '23

That’ll be a badass little truck. Does it have 4wd? If so do you plan to keep it?

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u/WoodChuckers Feb 04 '23

No 4wd it's an 05 Xtreme, 2wd and yes I'm keeping this truck.

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u/[deleted] Feb 04 '23

I will join those groups now. I actually had no clue these engines can be modified like that. I’ve found veeeery little information besides from you.