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Thread: Boost pressure in 6.5l

  1. #1
    Registered User dieselburner94's Avatar
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    question Boost pressure in 6.5l


    Just a quick question, i was wondering how much boost a stock 6.5l TD can really handle, considering the 21.5:1 compression? Ive heard of heath diesels pushing 22psi of boost with stock pistons, but yet ive also heard of others not being able to handle more than 15psi or so, then breaking crankshafts or destroying pistons when pushed too hard. Just wondering if anyone has any thoughts or info. Ive had mine hitting 15psi with no trailer or weight, and i dont want to do any damage if it builds any more when pulling hard.

    My Truck-
    1994 GMC 2500 4x4
    6.5L Turbo Diesel
    K&N Cold Air Intake
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    Custom dash mounted boost controller
    Custom 4" Exhaust straight pipe with dual 5" Stacks
    2004 GMC aluminum rims with HD 10ply tires
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    Lots of LED lights and strobes
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    many other ad ons

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    nitro junkie nitrohogg's Avatar
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    ran mine fer years with about 15-16 PSI max......then the head gasket on the pass front started sucking antifreeze into the cylinder, and then out the front of the head!!!
    97 Chevy crew cab dually, 6.5 turbo diesel, wide open exhaust, hand made pmd cooler in the process of a complete rebuild with 18.1's and mucho upgrades including a homemade IC.
    120 cubic inch, 7.386 et, 197 mph pro fuel Harley

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    is that turbo timed or stock? whats the stock output supose to be

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    nitro junkie nitrohogg's Avatar
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    talking to me? I had a homemade wastegate controller on mine, stock is right around 7 psi
    97 Chevy crew cab dually, 6.5 turbo diesel, wide open exhaust, hand made pmd cooler in the process of a complete rebuild with 18.1's and mucho upgrades including a homemade IC.
    120 cubic inch, 7.386 et, 197 mph pro fuel Harley

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    Full Access Member silverfoot's Avatar
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    We feel that the boost can go that (15psi) high, if 3 conditions are met, install exhaust temp gauge, pre-turbo and stay below 1100'F, change head gaskets to at least .010'' over thickness ( compression ratio drop) and head studs. The other is buy a main bearing girdle to hold the bottom end together.

    Otherwise just buy a pyro guage and keep WOP boost below 10psi and you should not have problems.....

    Have you re-flashed your computer ? Error messages ? Or are you mechanical IP ?

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    You can run the stock pistons (as long as they are anodized top for best results) but you still gotta do something about the compression, either as silverfoot said by running thicker head gaskets, or by modifying the valve seats for lower compression. Otherwise, you are straight asking for trouble anywhere over 15 psi.
    1995 K1500 HD Suburban, 182,000 miles, 6.5TD (currently getting a fresh unit courtesy of "Big D"), 4L80e auto, 265/75/16 rolling stock, pretty original for now.... now with remote PMD, 130gpm water pump, ARP head studs, high volume/high pressure oil pump, WarpSpeed 2.5" crossover pipe, cat delete

    1990 Lincoln Towncar, 5.0, AOD auto
    1986 Nissan 300ZX, 3.0NA, 5-speed
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    1991 Ford E350 Club Wagon XLT 12 pass extended, 7.3 IDI N/A, E4OD auto
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    1993 K2500 Silverado RCLB, 6.5TD, 4L60e auto
    1986 K5 Blazer Silverado "Big D" 6.5NA GM crate engine, 700R4 auto w/ upgrades

  7. #7
    nitro junkie nitrohogg's Avatar
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    not trying to step on toe's but! you don't wanna change valve seat depth's! I'll dig up my book and post the info as soon as I can!
    97 Chevy crew cab dually, 6.5 turbo diesel, wide open exhaust, hand made pmd cooler in the process of a complete rebuild with 18.1's and mucho upgrades including a homemade IC.
    120 cubic inch, 7.386 et, 197 mph pro fuel Harley

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