Patrick's Twin Turbo 350 Build Thread

Discussion in 'Small Block Tech' started by patwhac, Apr 8, 2019.

  1. patwhac

    patwhac Well-Known Member

    Hello Buick comrades!

    I am finally starting an actual build thread for my car. I have posted a lot of random questions over the last 2 years but now I will try to keep all my progress in one place. I will most likely be very slow on posts/updates, I don't have a lot of time to dedicate to the car right now but I try and squeeze a few hours here and there.

    The general plan is to build a "mild" 8psi twin turbo 350 out of a running spare 350 I bought (late year smog motor). Car is a 1970 Skylark Custom, originally equipped with an SP code 350. Currently not running due to leaking freeze plug behind an engine mount and low compression in cylinders #7 and #8.

    This is what I'm staring with. When I went to look at it it was mounted on a run stand and it fired right up. Let it warm up and then we shut it down and I checked the compression. Every cylinder checked in at 150 psi, with only 1 cylinder at 148psi! This was with a brand new compression tester. I ended up paying $600 for it because of how well it did. Apparently it was in his son's full size 75 or 76 Buick something. He was fiddling with the radio and wrapped it around a tree!




    Here are the parts I have so far:

    -Mark Burton Twin Turbo Manifolds (mild steel)
    -2 lightly used CXRacing T3/T04E hybrid turbochargers
    -2 used Tial Sport 38mm Wastegates, 2 bolt flange type.
    -2 fabricated downpipes (by previous turbo kit owner). Mild steel, made to fit 70-72 Skylark engine bay. Provisions for wastegate 2 bolt return.
    -1 Polished CSU 3.5" inlet carb hat
    -Devil's own Stage 2 progressive methanol/water injection kit.

    So far I've spent a total of $1,681 for all the items listed above and the engine. Arg it's painful when I add it all up like that! o_O

    At the end is a list of the parts I intend to purchase and their respective pricing. Sorry, it's a long list! I will try and keep track of how much I'm spending as well.

    I plan to refresh the engine but not touch anything on the bottom end. Getting heads redone with larger TA stainless valves. New Scott Brown turbo cam. New timing set, oil pump rebuild, all gaskets, freeze plugs, etc. Basically all the wear items that don't require machine work besides the heads).

    So far I have performed just a basic tear down. There are 4 clues that are leading me to believe that this engine has already been rebuilt, or is a re-manufactured engine.

    -Engine/valve covers seem to be painted black.
    -To my surprise both the exhaust manifold bolts and water pump bolts came out without any trouble.
    -The 2 digit engine code on the deck seems to have disappeared.
    -The upper timing gear looks to be steel, not an OEM nylon coated piece (can someone confirm?)

    Well that's it for my first installment. Hopefully in the next week I will be pulling the heads and looking at the bores/pistons, and pulling the camshaft. Like I said, progress will be slow though!

    Twin Turbo Buick 350 Buy/Spec/Build List:
    Main Items to buy:

    -BOV: $250
    -MSD Street Fire Ignition Box - $165
    -Holley Super Sniper Blow Through TB EFI: $1200 - $1500
    -RobbMC Surge Tank or Tanks Inc. EFI Ready Tank: $300 - $500
    -Treadstone 2-in 1-out Intercooler: $500
    -USA Made Aluminum Radiator: $500
    -Braille Battery and Tender - $250

    (From Scott Brown:)
    Custom Nitrided Turbo Camshaft - $310 ($199 cam, $110 nitrite)
    Magnum Pro Comp Lifters $110
    Valve Springs - $80

    Smaller Items to buy:

    -Meth Injection Nozzle Bungs, install kit
    -2 Dial indicators
    -Cam Degree wheel
    -Cam bearing install/removal tool
    -Turbo oil feed lines and fittings (NPT?)
    -Turbo oil drain lines and flanges (-10AN minimum, -12AN preferred)
    -Boost Gauge
    -Manual Boost Controller?
    -O2 Bungs for downpipes
    -Remflex manifold/turbo gaskets or copper RTV?
    -Stage 8 Manifold Bolts
    -Vacuum line
    -Wastegate Springs
    -V-bands for Downpipes to replace 3 bolt flanges
    -Header Wrap
    -Header paint for Manifolds/Turbos (Jet Hot costs $300)
    -Turbo Blankets
    -General Heat Shielding
    -New Brake Booster/Master Assembly
    -AC Delete Box/Heater Core/Blower Motor
    -Turbo inlet air filters
    TA Performance Items to Buy:

    SP3 - $390
    High Flow Water Pump - $195
    Nylon Rocker Buttons - $15
    Dual Groove Cam Bearings - $80
    Stainless Valve Set - $225
    Billet Timing Set - $145
    Valve Spring Retainers - $60
    Valve Spring Locaters? - $30 - $60
    Valve Spring Keepers - $30
    Viton Valve Stem Seals - $30
    Basic Gasket Kit - $60
    Oil Pump Rebuild Kit - $80
    FelPro Head Gasket - $45
    TA Intake Gasket - $20
    Neoprene Front Main Seal for GM Cover- $10
    Neoprene RearMain Seal - $17 (only if 350 is leaking)
    Freeze plugs - $10
    Oil gallery plugs - $8 (TA1519)
    Donuts & Peelouts likes this.
  2. patwhac

    patwhac Well-Known Member

    More pics.

    Am I right in seeing that as an aftermarket timing set?


    Cleaned off where the deck stamp should be with a Scotchbrite pad, looks milled?


    Pile of removed parts. Anyone need some??

    Donuts & Peelouts and Houmark like this.
  3. Houmark

    Houmark Well-Known Member

    1681$ is in my eyes not a lot for a complete good engine and turbokit.. Just look at the price of a set headers.. :(
    DauntlessSB92 likes this.
  4. alec296

    alec296 i need another buick

    Why a meth kit with an intercoler for just 8 psi.
  5. patwhac

    patwhac Well-Known Member

    I guess that's true! My parts list sure adds up though. I only put stuff on that I think is necessary but still it's alot.

    Well I just happened to be looking at the meth kits during a SEMA 50% off sale, couldn't help it! I only paid $256 shipped. I figured the more safeguards against detonation the better. Also, it would be really cool to transfer all this stuff over to a 455 one day when I have the $$ and time to actually do a full engine build with forged pistons etc. I figure buying parts that I can reuse on any turbo engine is something I won't regret in the long run.

    I have been reading Maximum Boost by Corky Bell and it really stresses that an effective intercooler is good idea in any system regardless of boost level. Also, I would only have to fabricate the cold side once!
    Last edited: Apr 9, 2019
  6. alec296

    alec296 i need another buick

    Meth/water injection is the equivalent of a cooler, so at lower levels one or the other is adaquate.
    More temp drop requires more fuel .
    The 84-85 grand national runs 15-17 psi
    without a cooler . Considered a “hot air”
  7. patwhac

    patwhac Well-Known Member

    I see! Well the TBI would be controlling the tune, and I can change fuel curves with the laptop. It'll let me set a target fuel pressure and timing per psi of boost. I mean I'm not opposed to running more boost but I do want the motor to survive. I wasn't planning on spinning it past 5000ish rpm and I figured low boost would be easy on it.
  8. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Why put a built 455 in it later when you're setup for boost? A sbb 350 block is stronger than a BBB 455 block well seems to handle more HP without breaking anyway.

    IIRC a factory block 455 can handle 800 to 900 HP WITH a jockstrap and one of those jockstraps to buy and install on your 455 block would be around $1,500. That doesn't include any other machining the block will need for the build. If you do go with a 455 block, probably buy it from JW ready to build with the jockstrap installed and the other machining needed complete. The reason why would be that he has a pile of blocks that are sonic checked to choose a good one for your build that has minimum core shift so the cylinders aren't to thin. If you buy a core 455 chances are around 50/50 that you will get a good enough block the first core purchase.:eek:

    OR you could stay with the sbb 350 and put that $$ towards a billet crank. Maybe Ken Betts will be setup for making the billet cranks by then? With forced induction you can crank up the boost to make the same power you want with the sbb 350 that the 455 can make. Should be even easier with the new aluminum heads to get there.

    Not sure what kind of power you're looking for though? If you want to race the car, already with the 8 psi on the 350 you'll probably be under 11.50 in the QM(that is if you have the suspension dialed in to hook up?) which would be to fast without a roll bar. IIRC if in the car is under 10.0 it will require a 4 point cage and under 8.0 it will need a 6 point cage. Don't quote me on the safety requirements though I'm going off my CRS memory.
  9. patwhac

    patwhac Well-Known Member

    Derek you make a valid point. I guess I just assumed that 455 + turbo > 350 + turbo. But if I can run 11s with a turbo 350, I would be ecstatic. My enthusiastic goal is 400hp to the wheels, and I would perfectly happy with 12s in the 1/4 mile! The 455 idea was more of a "if I have lots of extra money laying around" scenario.

    Suspension is stock for now but I will dive into that as needed after the car is together. A 3.08 posi rear end is sitting in my garage that I plan to use, and maybe a Hellwig rear sway bar and some stickier tires for the track. I'd say it's going to be a 90% street car though.
    300sbb_overkill likes this.
  10. alec296

    alec296 i need another buick

    You would do better with 3.23 gears and a 2500 or 3000 converter. You need more rpm to get exhaust flow up to bring boost up faster.
  11. patwhac

    patwhac Well-Known Member

    I'm planning on a convertor from Jim Weise once I swap out the TH350 for a 2004R. But that's lower priority than finishing the engine. Shooting for 2800 - 3000 stall. Someday I want to go 3.23 or 3.55 but since I already have the 3.08 read I will give it a try first.

    Anyone have any info on black painted Buick 350s? I tried decoding both the head casting numbers and block casting number on the bellhousing and both decode to 1962 - 1980 350. Not very helpful haha. Though the heads have the note "with AIR" so I guess I can assume it is 73 or later (capscrew rods)? I will be pulling the oil pan to replace the gasket so I can look at the rods then.

    Thanks for the feedback so far guys!
  12. hugger

    hugger Well-Known Member

    Just a reman engine
    sean Buick 76 and MrSony like this.
  13. patwhac

    patwhac Well-Known Member

    Ah, well maybe it was rebuilt in the 80s or 90s and that's why it still makes decent compression? I wish there was a way for me to tell when it was rebuilt!
  14. sean Buick 76

    sean Buick 76 Buick Nut

    Use a scope camera to take a pic of the pistons, that will tell you a lot about the engine
    MrSony likes this.
  15. Mark Demko

    Mark Demko Well-Known Member

    I would keep the 3.08 gears for now, that ratio will put more load on the engine, which turbos like and respond to better:cool:
    300sbb_overkill likes this.
  16. sean Buick 76

    sean Buick 76 Buick Nut

    Yes the 3.08 gears will give the tires a half a chance
  17. alec296

    alec296 i need another buick

    Yea, to go up in smoke when the boost comes in
  18. Thumper (aka greatscat)

    Thumper (aka greatscat) Well-Known Member

    Patrick, looks like a fun project with the right parts. If you turn up the wick you may want a girdle. We have one left.
    Dano likes this.
  19. patwhac

    patwhac Well-Known Member

    I'm planning on pulling the heads soon (see below) so I'll be able to post some pictures of the bores/pistons!

    That's kinda what I was thinking, glad it's not just me! Good for mileage hopefully too.

    Thanks! I'm planning on going to the garage today and pulling the original camshaft out. Maybe the heads too if I feel up to it!
    sean Buick 76 likes this.
  20. patwhac

    patwhac Well-Known Member

    Well the camshaft is out! Progress is very slow, but right now I am saving up the $500 or so for a cam(nitrated)/lifters/springs combo from Scott Brown. Here are some pictures of the cam bearings. How do they look?

    I also bought a never used camshaft tool from a board member, hope to test it out soon by pulling those bearings. Is it worth it to do all of the bearings or should In just do the front one?




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