I'm trying to step up my power for this year. I'd like opinions on possible changes needed in my setup. When
I originally built my engine, I collaborated with my cam designer on the rest of the build (CID, compression, rotating assembly, heads, intake, etc). After checking back with him, he suggests leaving my long block alone assuming everything is still in spec, and just add boost (principle being more boost and fuel in a low compression motor works best).

All that being said, I'm questioning his advise at the opposition of the hive mind of Facebook which generally agrees that my build is a pile of mismatched gear all over the place. Yes, I know there are better turbos, wastegates, etc. I'm looking for design input as far as cam, springs, compression, CID.

Current long block:
Dart Little M 350CID 4.000 x 3.48
CAT steel crank with 0.5gm balance
Eagle 5.7 H-beam rods
Diamond -22cc pistons with H-13 tool steel pins
Brodix Track 1 heads and single plane 4150 intake
--Heads have original valve train as assembled
--Springs;1.550 Roller Valve Spring – GA 1000,
--240 lb Closed, 550 lb Open,
--1.950 Installed Height,
--.700 Maximum Lift
Cam is a bullet 3 piece solid roller that uses an iron distributor gear:
Intake Exhaust
Duration (.050): 243 243
Lobe Lift: .3883 .3883
Separation: 114*
Timing events (.050): Intake - Open: 13.5 Close: 49.5; Exhaust - Open: 61.5 Close: 1.5
Gross valve lift: .582 .582
Valve lash: .026 .026
Duration (.020): 276 276
Degree Intake lobe to 108

This long block with a single T6 S475 (old style from Majestic Turbo) has gone 9.50@140 at 3250 on 93 pump and 22-24psi. It would nose over at 6500 or so, although I never dynoed it. I suspect the turbo was out of gas
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I swapped to twin 7875s for more volume available with what I thought would be less heat at 15+psi. Also I thought it'd give the ability to go on up to 30-35psi given the same long block. I'm shooting for 8.50-8.20s at current weight, which is where I got the boost number.

Tapping the hive mind here for thoughts on changes in motor design.
I had considered rebuilding the short block as a 421, 9.1-9.5:1 compression or something similar, but if this will work, why change everything?
It would be real nice to keep the cam/valve train since it's sorted geometrically, lifters look good even after 10 years of use, and springs are just a tad light on intakes (so I'd swap intake and exhaust springs).

Thoughts? Bashing? Hate mail? More info needed?

Thanks

 

I personally wouldn't spend the money for more cid at this point. More turbo is a good idea as I see the 475 as small on both sides. I would invest in more head flow before more cid.

 

Curious to see how you make out with the twin 78/75’s and that cubic inch. I’m trying to decide weather to go with twin 78/75’s for mine. I have one billet 78/75 so getting another one would be easiest but I’m wondering if it might be a tad too much turbo for my 6.0.