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  1. #1

    Default 350 SBC 4 Bolt Main 800 to 1000 HP

    Does any one know anyone running a SBC tubo charged? Next question I have a GM 350 4 bolt main block. Will it hold up to being tubo charged? I know a merlin or bowtie block would be the way to go , but with limited funds can or will this hold up. If someone is running one now, let me know what you think about it.
    Thanks



  2. #2
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    Feb 2005
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    mo
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    If you change to billet main caps,ARP studs,it might.

    You should have the block checked by a good machine shop,have it magnfluxed,sonic test the cylinder walls,make sure its square.

    If decide to do it,you might consider 1/4 filling the block to keep it from shifting too.

  3. #3
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    Default

    You can also add bars to the two center studs on the mains to add some more strength-- kind of like the stud main reinforcement they sell for fords, but not quite as nice since the mains are not joined together.

    Aside from the mains, the other problem with a non-bowtie GM block is the cylinder wall thickness -- you get a suprising amount of wall deflection on the production steel blocks.
    1968 Camaro RS/SS, LS7 with Katech mods, T56 Magnum, C6Z06 Brakes
    1968 Camaro RS Convertible project "what was I thinking"
    2006 Corvette Z06
    2011 Corvette GS Convertible


  4. #4
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    Sep 2006
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    its a guy her in town whos building a turbo vega whit a blazer 2bolt 350 engine and a holset hx80 his sighting for about 650++ hears the site but its in swedish http://forum.savarturbo.se/viewtopic.php?t=6232

    and a nother http://forum.savarturbo.se/viewtopic...r=asc&start=15
    and a site from him in english http://aldengard.lixom.nu/gallery/Tw...ransAm_Project

  5. #5
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    Default well actually

    I would sell the 4 bolt to a local hot rodder or store it and get a 2 bolt main older style block with large pad under the alternator(mid early 70s) and then add on a set of splayed bolt main caps this setup WILL handle 1000+. A factory 4bolt even with lots of reinforcement in my honest opinion as an engine builder and tuneer around 700 to 800 and thats NA.
    The stresses created on a turbocharged engine is so quick in their rise they can and will split the blocks if not done right.
    If you are on the budget honsetly after all the machine work you can step up to a fresh World Products block and all you have to do on those is clean the thing finish bore/hone to size ,,, maybe set your deck height and your ready to assemble. considering how cheap Eagle has rotating assemblies you can get great parts a decnt price and if you dont beat on it too hard a stock GM crank properly preped will live under just about any use. I am lucky I have a local crank grinder that does lots of cranks the week of the NAtionals at Indy every year. just remember its better to spend more on your rods/pistons and then save for heads THEN get it running that to build it, blow it and then cry over not spending money. Dont gt me wrong I am not saying you need a 3000 dollar crank and titanium rods just dont skimp on the rods, Eagle, Crower, Oliver are some good names and use reputable pistons as some forged units are to fragile in turbo setups (or any boost for that matter )and can shatter. The rule is use a piston that can be set tighter (but still forged) clearances but allow for more heat.
    Good Luck and if you have any questions on machine work give me a shout.
    Lee Abel

  6. #6
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    Sep 2005
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    Ky
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    check over on turbomustangs.com they have a lot of guys over there running turbo vehicles besides mustangs, that can help you out.

  7. #7
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    Ditto on much of the above. I've done both 4 bolt and splayed 2 bolt conversions on blown 355's.

    First setups were blown w/ Procharger's D1. The first one showed moderate bearing wear after one season of street driving/racing. Approx 700hp w/ 14lbs on pump gas.

    We then switched to the 2-bolt splayed cap block and noticed the improvment. They looked slightly better but enough to keep an eye on them. We upped the power to 850hp @ 19lbs but wouldn't push it beyond that.

    When I swapped to a turbo (98mm Precision), we swapped it for the Motown Race block. We worked that deal pretty hard (28lbs) and 1600+hp. Never any signs of abnormal wear.

    To make 1000hp, that's really territory for an aftermarket block. The reliability isn't there on GM blocks, sonic checked or not. One may live well at 850hp and another can develop cranks in the mains, or valley area. I've seen and done it. If you keep it limited to 800hp, I would say it's OK. Be aware, you'll likely be $1000+ to make that factory block right w/ steel caps, it's OK if you understand it has limits.
    Dennis
    Moore Racecraft

  8. #8
    Join Date
    Oct 2004
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    dayton ohio
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    How Far Can A "010" 4 Bolt Block Go? I Think It Is From A 1979 K5.
    POLITICIANS & DIAPERS BOTH NEED TO BE CHANGED, AND FOR THE SAME REASON!

  9. #9
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    Jun 2005
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    Not to hijack the thread too much but does using a combo of turbo/nitrous or supercharger/nitrous change your 800hp threshold for the block at all?

    Say 600rwhp on boost and 200rwhp on nitrous...

    Thanks,

    Jim
    Don't take a knife to a gunfight.

    Half-Assed = Half-Fast

  10. #10
    Join Date
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    Default Again

    The best defense is a good offense. to prep a stock block for high power under boost you cna buy a Motown block.
    On the street with turbo AND the violence of NOS would split most stock blocks unles tall filled with hardblock.
    ok an 010 block (last 3 digits of casting # )from 79 will have the small pad under alternator and I would not push a thin wall block much past 600 hp and thats a stretch.
    They can take some abuse but just dont have the stability for bigger power.
    If you want to build a big power engine use older 2 bolt blocks, splayed caps and look for the 010 020 inside the timing cover area, this is the tin/nickel content, if it just has 010 and no 020 it only has tin and is not as hard.
    My preference would be an aftermarket block for anything over 800-850 hp .
    you can make better power with aftermarket blocks and better reliability. Stockers just wont handle the stress. Trust me on this.
    We had a 380 in stroker (4.125x 3 5/8) 18 degree Brodix and when this one was built no one had done it yet and cost well over 20K and the engine split cylinders even with hard block, BUT we picked up 68 hp and 53 lb ft of torque by going to GMPP CNC block and both had imperial roller cam brgs which is a mahot pain in a stocker.
    we gave CNC block a .003 shave and bored it for cam bearings and finish bored and honed with cork bond stones for the super slick finish. ANd it really makes the car it presently in run VERY good.
    Good luck.
    Lee

  11. #11
    Join Date
    Oct 2006
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    Ottawa, Ontario, Canada
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    Default

    For the price of an aftermarket block these days, you cant go wrong.

    if you strung up on using a factory block, get an earlier style 4 bolt, stud it and 1/2 fill it....it will hold up to 800HP but you might be changing the bearings often.

    I run a SBC Twin turbo but im using a Dart Little M block....nothing fancy really, good crank (Callies) and decent rods (Eagle H beam w/ L19 rod bolts), JE off the shelf pistons, etc...

    Remember every $ you put in that stock block is 1 step closer to an aftermarket.....and all my Dart block needed was a finish hone & the deck cut.

    What do you plan on using for the fuel delivery, carb's are working good these days ;)

    -Carm
    '69 Firebird Twin Turbo SBC 400" Blow-through

    9.80 @ 141 w/ 1.88 60-ft..... on 17's
    9.21 @ 153 w/ 1.45 60-ft..... on PUMP GAS
    8.60 @ 164 w/ 1.46 60-ft..... on RACE GAS

  12. #12
    Join Date
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    Southern Indiana
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    Default 4 boly vx 4 bolt splayed

    If you must use a stock block please do not try 4 bolts. They dont hold up.
    We just got done putting in an order for 4 Motown blocks as the last of the older 4bolters running in the 650 to 750 range in customer engines well after a quick check the blocks found then just plain junk, hairline cracks all over.
    For the money to prep a new block we can add a bout 50 hp by swapping in the Motowns, been there seen it.
    We took buddys engine down to dyno and split 2 cylinders from crappy MSD crank trigger pickup (4th bad one so far this year).
    Well we were just getting a good start on base lines and was going for new pull and it started puking water.
    So we was breaking it down and dyno owner comes in and offers us a Motown block if we had it at 030 as he had one on shelf.
    so we pulled it off the dyno, tore it down and in a little over 2 hours including giving it a few more swipes with hone, it was buttoned back up.
    Now remember this was FRESH engine from a previous 020 package other than a quick bore/hone to fix scuffed cylinder (not one that split) the engine checked perfect. so these parts only had warmup/and few pulls.
    We put it back on the dyno and warmed it up and set it,,, and on first pull it was sounding better too.
    This was first time I had ever ran angine on a dyno with soundwave transducers in the headers to make it easier to detect anomalies.
    First pull it was 43 hp stronger and made 69 lb ft more tourque and at a lower rpm.
    Second pull it got up to 56 and 77, and on third pull we let her run wild with the 50 shot over the carb and we got an very satifying 69 hp over the other gains.
    And it required 3 degrees less timing!
    761hp before block, 817 after/886 after fog amd in a hot dyno room with sporadic fan for fresh air (heck we got 100 bucks of dyno day and we got block for a song as it was slightly used.
    almost 900 hp and the engine wasnt even straining (we hope to set it up on a 250 foggershot next year to push a 2500 pound car into the 4's as its already doing a 5.40s na.
    PAy the money and enjoy a long happy engine life.
    Lee Abel
    AFTERMARKET PERFORMANCE

  13. #13
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    Feb 2006
    Location
    Southeast Louisiana
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    Default

    I was looking at building a mild t/t (600 fwhp) set up for my car using a 4 bolt GM block. Should I reconsider? I was told a 4 bolt GM block would be fine for what I'm trying to achieve.
    1968 Camaro, 350 SBC, TH350 w/3500 Stall, 12 Bolt, 4.56:1 Gears. Currently in progress...DSE Minitub Kit, DSE front suspension, DSE SFC's, 17" Budniks, Baer front and rear discs.

    http://www.cardomain.com/ride/2391864

  14. #14
    Join Date
    Oct 2006
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    Ottawa, Ontario, Canada
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    Default

    You'll be fine....as usual, just use quality hardware (ARP) and a quality machine shop.....without a good machinest even the best of parts wont hold up to abuse.

    -Carm
    '69 Firebird Twin Turbo SBC 400" Blow-through

    9.80 @ 141 w/ 1.88 60-ft..... on 17's
    9.21 @ 153 w/ 1.45 60-ft..... on PUMP GAS
    8.60 @ 164 w/ 1.46 60-ft..... on RACE GAS

  15. #15
    Join Date
    Nov 2006
    Location
    Glendora, So. Cal
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    17

    Default

    Can you afford to do it twice? Go with the aftermarket Block. I went with the DART little M, best money spent on the whole motor.
    This will give you an Idea!

    http://www.cardomain.com/ride/2368130

  16. #16
    Join Date
    Jan 2005
    Posts
    37

    Default

    Im making 775 at the crank with a stock four bolt main block and 16lbs of boost and I havent had any problems so far.

  17. #17
    Join Date
    Aug 2004
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    Kiler wisconson
    Posts
    400

    Default

    I have a procharged SBC running 9Psi at around 675-700hp and the block is only a 2 bolt main with arp studs...

    My machinist (who builds high dollor race engines) told me they have had more block break due to the splayed main caps being added to a 2 bolt than just a stock 4 bolt main

    I have read in several magazines that stock blocks are only good up to 800hp and that is pushing it..

    Ps... I am running SCAT forged rods and SCAT forged crank (5140 forged) got them really cheap on ebay and had them check at the machine shop... So far soo good..
    Project JUST-N-SANE

    84' Camaro Z-28, 355CID,9.0-1 compression, ATI procharger 9psi (over 650HP),T56 6 speed, 3.73 Motive gears! 11.70 at 122mph in the 1/4 while babying the throttle to keep the tires hooked ,with pump gas! (NOW INTERCOOLED)



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