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Thread: Ancient mid 12's secrets for your Buick *350*

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    Ancient mid 12's secrets for your Buick *350*

    all of this information is transcribed from a 1984 newsletter from Kenne-Bell. i assume all responsibility for typographical errors.

    for those who may not know, Kenne-Bell got out of the Buick business quite a few years back, so none of these part numbers really mean much anymore.

    Specialists in Performance Proven Buick Racing Equipment





    The test car used was a 1971 GS 350 stocker (with TH-350 transmission). Compression ratio was stock 8:1. The 1968 4bbl versions had 10.25 (compression) ratios. 2bbl engines all used 9.0 (compression ratio) pistons. The car itself weighed in at 3550 lbs. The only options being a radio and heater. The rear end was a 3.64, an ideal street/bracket. A 3.90 or 4.10 is about maximum for street use while the lower 4.30 and 4.78 ( Buick ) or 4.56 / 4.88 / 5.12 ( Chevy ) should be used for racing only. 9" slicks were used for traction consistency.


    1       83.1  15.76    Test car as described
    2       83.6  15.70    KB350-2 Shift Improver Kit
    3       84.0  15.65    KB55009 Stinger 1 Distributor Ignition or KB88114 
                           Stinger 1 Points Conversion Ignition.  Use KB583904
                           Stinger 1 HEI conversion for 1975 and later HEI
                           distributors or KB33117 HEI Spark Intensifier Kit if
                           budget is limited.  KB33101 or KB33102 Advance
                           Curve Kit and KB/Stinger ignition wires.
    4       85.0  15.55    Remove stock air cleaner
    5       85.1  15.53    KB46002 Hi-flow low profile air cleaner
    6       86.1  15.41    KB84001 Mufflers and 2 1/2" tail pipes and
                           crossover pipe
    7       No Change      KB84001 Mufflers and 2 1/4" tail pipes and
                           crossover pipe
    8       87.6  15.25    KB81003 Headers
    9       89.2  15.09    Unplug Headers ( open exhaust )
    10      91.2  14.89    KB Mark 1H Cam Kit with KB 17501 Double Roller
                           Chain and KB11302 Valve Seals
    11      92.3  14.88    KB Mark 2H Cam
    12      94.8  14.62    KB Mark C118 Cam
    13      96.5  14.54    KB44200 Manifold, KB88048 Intake Manifold Bolts,
                           KB4594 Electric Pump with stock re-jetted carburetor
                           ( Jetting instructions included with carburetor )
    14      97.1  14.47    KB9310 Carter 800 CFM Carburetor ( Jetting
                           instructions included with carburetor )
    15      No Change      Holley 850
    16      96.0  14.59    Holley 660
    17      95.2  14.68    Holley 600
    18      No Change      Carter 625
    19      94.0  14.81    Carter 500
    20      97.1  14.47    KB Carter 9810 ( demonstrating that even a
                           350 like a bigger carb )
    21      97.9  14.39    KB48002 Plenum
    22      99.0  14.28    KB19903 Deep Oil Pan with KB89004 "Spinlock"
                           Oil Pan Bolts and KB42502 Magnetic Drain Plug
                           ( deep pan helps control oil windage )
    23      99.5  14.13    KB1618 Convertor
    24     100.0  13.93    KB149 Switch Pitch Convertor and KB400SP
                           Switch Pitch Street/Strip Transmission
    25     101.0  13.84    Shut off Switch Pitch immediately after launch
                           in low gear
    26     103.3  13.62    KB61004 10.2 Budget forged pistons with 
                           KB13006 rings
    27     No Change       KB50007 10.2 7000 RPM cast pistons with 
                           KB13006 rings
    28     105.4  13.39    Ed Mosler Big Valve ported heads
    29     105.6  13.37    KB9302 Roller Rocker Arms, KB9405 Shafts and
                           KB9508 Rocker Arm installation kit
    30     106.2  13.32    KB Aluminum Crank, Water Pump and Alternator 
    31     106.8  13.26    KB60004 Super-Lite Forged 12.5 Pistons and 
                           KB13106 1/16" Rings
    32     106.8  13.16    4.55 gears
    33     No Change       4.88 gears
    34     108.1  13.05    KB Mark 3H Cam kit
    35     109.5  12.99    KB Mark 5H Cam
    36     109.9  12.89    KB16155 10" Trackmaster
    37     109.6  12.84    Bore Engine .030" ( 355 cu )
    38     No Change       Aluminum Rods
    39     No Change       Increase Rod and Main Bearing Clearances to .003"
    40     112.7  12.54    4 Speed Munci and KB Clutch, Pressure Plate
                           and Steel Flywheel
    41     114.2  12.40    KB Mark 6S Cam
    All 350's have a 3.80" bore with a 3.85" stroke. The relatively long stroke makes for an ideal high torque, lightweight, high horsepower street powerplant. They also cost considerably less than a Chevy, Ford or Mopar. Actually, the 350 Buick is an excellent choice for a performance engine either in stock body Buicks or conversions, particularly with the introduction of the new equipment by Kenne-Bell.

    The 350 remains relatively unchanged and uncomplicated from it's introduction in 1968 until it was discontinued in 1979 ( this is incorrect, the Buick 350 can be found into OEM installs into 1981 ). The 1968-1970 2bbl engines all had 9:1 compression ratios while the 4bbl versions were equipped with 10.25:1 pistons. 1971 and later V6's complied with Federal restrictions and suffered from a reduction in compression to 8:1. Rods were improved in 1975. They incorporate the more desirable cap screws. Pre-1974 rods were still adequate to 7000 rpm occasionally.

    A KB18202 Oil Pump Kit is the number 1 modification to any 350 Buick.

    The following drag strip tests were conducted to illustrate the performance gains of the various Kenne-Bell products. We highly recommend you purchase a Kenne-Bell Power Speed Calculator if interested in determining the true horsepower of a particular combination. It'll answer many of your questions and make you more aware of the real world performance relationships. Don't forget to add the driver weights and allow for the automatic transmission when computing horsepower.

    Two water pumps, a short and a long, are available. The 350 is an excellent choice for conversion into any street rod or GM H cars ( Vega, Skyhawk, Astre, Monza, Starfire, Sunbird ) because it is lightweight ( 415lbs [ i presume this to be an engine configured with alum intake and headers, bob k ] ), plentiful and economical to purchase and modify.

    The factory never offered a single performance part for the 350 - no aluminum manifold, head, cam, carburetor, etc.

    Headers, cam manifold and pistons are therefore the pieces that offer the greatest performance increase and dollar value. If any one of these parts are unavailable, the true performance potential of the particular engine can never be realized. This has been the case in past years. However, with the introduction of the Ed Mosler designed TA Stage 1 manifold, the Buick 350 is no longer lacking in any area. You can now buy virtually anything for a Buick that you can for a Chevrolet.

    Since the Kenne-Bell parts are designed specifically for the Buick 350, the actual selection should be less confusing. Our 350 parts combinations are well thought out and designed to work in harmony with each other to provide maximum performance the first time. There is no guesswork or trial and error for Kenne-Bell customers.

    The new KB50000 Series 7000 RPM Cast Pistons are adequate for the overwhelming majority of applications. Notched pistons are not necessary with Mark 1H and 2H cams as these cams were designed to clear all stock and KB pistons. These pistons are the same compression ratio as the factory 1970 10.25 pistons. There is no performance gain to be realized from a forged piston like the KB60004 Super Lite if the compression ratios are the same. The gains emanate from higher compression and 1/16" rings.

    Notched pistons allow the use of a bigger cam at a later date, carbon build up and a future head or block milling. If the block and heads are milled over .030" use notched pistons. The Kenne-Bell MKC118, MK3H, MK5H and MK6S need notched pistons. The KB40306 Ring Compressor is good insurance if you're building your own 350.

    Kenne-Bell or stock Buick rings work best with Buick 350 block material.

    Ratios above 10.25 ( rated ) are impractical for street use. Furthermore, the actual performance (gain) is relatively small ( see Buick News Vol. 5, No. 51 ).

    We used pressed pins for all applications except all out race engines.

    Higher compression inevitably decreases fuel consumption. Going from 8.1 to 10.25 pistons gives 1-2 mpg better economy.


    KB12803 360° Grooved Main Bearings are a must. Never groove or cross drill a crankshaft. .002" clearance on rod and main bearings for all applications. Never exceed .002" on mains. Buick or Kenne-Bell rod and cam bearings work equally as well.

    Use a Kenne-Bell KB44326 Front Cover Seal to replace the leak prone old fashioned stock rope seal.

    Valve seals recommended on intake and exhaust valves.


    The Buick 350 runs best between 160°-185°. The KB19102 Blow Hard Fan, KB19106 Fan Spacer Kit and the KB580322 160° Thermostat - any 160° Thermostat works equally as well - are designed to lower engine operating temperature. Stock 350's typically run too hot. A hot engine also increases oil temperature and reduces oil pressure - both of which are undesirable.

    We like ACCEL spark plugs. NGK is our second choice. The 350 likes 34° total timing. Get all advance in by 2500 rpm. Use stock heat range for that particular compression ratio. Use one heat range cooler for 11:1 and two heat ranges cooler for 12:1.

    Points distributors are obsolete. Convert the points distributor to magnetic pulse with a Stinger KB88114 Points Conversion Kit or replace the stock distributor with a Stinger KB55009 Distributor Ignition. The Stinger 54 does not work as well on these engines. 1974 and later Buick 350's were equipped with HEI distributors. The Kenne-Bell KB33117 HEI Spark Intensifier Kit is an economical way to upgrade the stock HEI. The Stinger KB883904 is a more serious ignition set up.

    Always check distributor shaft wobble or run out. It often costs more to rebuild a distributor than it's worth. A good method of checking ignition wire condition is to rev the engine - with the hood open of course - in the dark. The shorts will be obvious.

    The KB18403 4 3/4" Crank Pulley and KB18406 7" Water Pump Pulley reduce water pump speed and increase horsepower. They must be used with the longer (??) water pump. These are the same pullies used on the V6.


    The 350 oils like the 215, 300, 340, 400, 430, 455 and V6's so it inherits the same weakness - oiling. Install a KB18202 or KB18214 to protect your engine under any and all conditions.

    KB18210 Adjustable Oil Pressure Regulator recommended for fine tuning. Stock pick up tube is adequate. Oil galleries OK as is for street/strip use. Remember, KB18202 Oil Pump Kit is a must for any performance engine. KB18214 is standard procedure for any Buick 350 rebuild even if it's only driven to the market on Sundays. KB19902 Deep Sump Oil Pan recommended for performance street engines. A KB40201 Oil Pump Primer should be used when rebuilding the engine. Pack oil pump gears in vaseline before assembly.

    Two ( 2 ) KB89001 Mufflers with 2" or 2 1/4" tailpipes and KB81003 Headers with a crossover pipe is the best exhaust combination. Make crossover pipe one size smaller than header pipes. Our KB81003 fits almost any Buick the 350 ever came in. The above combination wil increase fuel economy 2 mpg over the stock set up.


    At last - an aluminum intake manifold for the 350. Kenne-Bell calibrated 800 cfm Carter is the best carburetor for stock or Stage 1 TA manifold. Stock carb is 750 cfm, so don't waste money on a 600, 625, 650, 660, 725 or 750 carb. The little 350 likes the larger 800 Carter [ also good would be an 800cfm QJ from a 455, bob k ]. The 850 Holley also works but the TA manifold is designed for a spread bore type carburetor in the 730-850 cfm range. The Kenne-Bell KB46002 Air Cleaner is designed to fit the Carter 9800 carburetor while clearing the stock Skylark/GS hood. The KB46002 is so efficient it will not decrease performance or horsepower. In other words, the 350 will run as well with the Kenne-Bell Air Cleaner as it does with no air cleaner at all.

    Use stock steel intake gaskets. An electric fuel pump is good insurance. The 350 needs 5-7 psi of fuel pressure. Don't forget, a fuel filter like the KB48010. Transparent filters give a good indication of fuel quality. The stock QJ carb also works very well on our new Stage 1 / TA manifold.


    The best chain set up for the 350 is the KB17501 Double Roller Chain. Higher spring pressures and performance cams accelerate chain wear. The stock chain and gear assembly is marginal.
    Last edited by bob k. mando; 05-25-2010 at 03:26 PM.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

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    this is a continuation of the above post, as it seems i've hit the maximum character count for a post.


    Stock 350's strain to attain even 4500 rpm with peak power at 4200. The stock cam profiles are awful - all of them! Kenne-Bell coordinated cam kits will let the 350 rev into the 6000-7000 range with stock rocker arms. Although the Kenne-Bell Roller Rockers are a must with KB10701 springs and Mark 3H, 5H and 6S cams above 6500, the stock rocker arms cannot handle high spring loads above 6500 rpm. Kenne-Bell cams are all unique designs that will allow high lift and unmatched performance with minimal valve train stress.

    For best results, buy the correct cam kit for a particular Kenne-Bell cam. Don't mix parts from various manufacturers. Running a Brand A cam, Brand B lifters, Brand C pushrods, Brand D springs, Brand E retainers, etc is not "status" or being "cool". It's asking for trouble!

    Don't attempt to run 1968-69 rocker assemblies on 1970 and later engines with oil through push rods and lifters. Kenne-Bell Roller Rockers work equally as well on all engines but must use Kenne-Bell rocker shafts.

    Be careful of pushrod, lifter and rocker arm cup ball sizes. Most of the other cam manufacturers aren't aware of all the differences.

    Rocker Arm Installation Kits are now available from Kenne-Bell.

    Tthe transmission was a stock TH-350 with the usual "shift lag". The Kenne-Bell 350-2 Shift Kit made a car length ( .1 second ) difference. We always recommend the TH-400 with a Switch Pitch convertor for 350's. You get all the advantages of a high stall convertor ( better acceleration and performance ) without the built in ill effects of any high stall convertor ( reduced transmission life, higher fluid temperature and poor gas mileage ). Cost is another consideration. "True" 3000 stall convertors are expensive, requiring the use of a 10" convertor core. These units range in cost from $400-$500 and cannot be driven on the street. The Kenne-Bell Switch Pitch will give you a "true" 3000 rpm stall speed when called upon and the ability to shut it off to 2000 with the flick of a switch. The 350, being a smaller, lower torque motor than the 455 Buick simply likes a high stall convertor like the KB149 2000 or 3000 especially with street 3.64 or 3.90 gears.

    If you stay with the TH-350, the Kenne-Bell KB1618 is the maximum for street use.


    In 1972, Buick added two bosses to the block to seat new cored holes in the upcoming 1973 head.

    In 1973 the blocks and heads had these two bosses or scallops located at the upper center of the block face. 1973-75 heads require the use of a 1972 or later block to seal these holes ( see Buick News Vol. 4, No. 39 ).

    Late intake manifolds had A.I.R. holes for California emissions.

    The 350 blocks were identical except for the bosses or scallops that were introduced in 1973. The main caps were "skirted"by the block. The block webbing hangs below the centerline of the crankshaft. Four ( 4 ) bolt main caps or girdles are not necessary.

    KB32103 Main Studs strengthen the lower end sufficiently.

    KB32003 Head Studs are a good investment if using a high compression ratio.

    Maximum recommended overbore is .032". 350 heads typically had 50-51 cc and were equipped with 1.875" intake and 1.55" exhaust valves.

    1970 and later heads oiled through the push rods while 1968-69 heads oiled through the rocker arm shafts.

    Kenne-Bell and Ed Mosler have developed some excellent large valve heads that make the 350 a real street killer.

    Stock 350 heads flow quite well and are far superior to the earlier 300 / 340 heads that shared port design and size with the V6's.

    Never cut valve spring head pads over .060".


    The best performance values for the 350 Buick are obviously the headers, cam kit and manifold-carburetor-air cleaner package.

    The KB169 Switch Pitch Trans and Convertor help off the line acceleration considerably ( .3 second ) and is a perfect combination for street use. The TH-400 bolts right in.

    Smaller than stock carburetors are obviously not the way to go. Ultra high compression ( above 10.25 ) gives a relatively small performance increase.

    Aluminum rods offer no improvement. Don't plan on all that expensive machine work adding performance either. Spend your money on parts. Align bore should be checked. If the crank spins freely, without binding, leave it as is. Surfacing the heads and block is good insurance. If using our pistons, it is not necessary to rebalance the engine.
    Last edited by bob k. mando; 05-25-2010 at 03:31 PM.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

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    Kenne-Bell almost got into the 11's with another test car but you can't directly compare the results as they were using 11" slicks instead of 9" slicks.



    Basic test car was a 1971 Skylark weighing 3500 lbs. with 4.30 gears, stock trans and converter shifted at 5500 rpm, 1971 Quadrajet carb, 11" slicks ( for consistency ), 8:1 compression ration, stock dual exhaust, stock suspension, 30° timing and no air cleaner.

    ET and speeds are the average of 5 runs at Irwindale Drag Strip. They were rounded off to the nearest .5 mph and .05 second ET.
    Speed        ET          Test
    78.0        16.80        Basic car as described above
    79.0        16.50        KB200 SHIFT KIT for TH-350 trans
    80.0*       16.40*       Blueprint and clearance engine
    81.0        16.30        KB85001 Turbo Mufflers
    85.0        15.90        KB81003 Headers ( no extensions )
    90.0        15.40        KB Mark 2 Cam Kit
    91.0        14.90        KB161 Converter
    91.0        14.90        KB400SP Switch Pitch Trans and KB149 Converter
    91.0        14.80        Shut off KB149 Converter after launching
    94.5        14.15        KB610004 Pistons and KB13100 Rings
    97.0        13.90        KB60004 Super Lite Pistons and KB13100 Rings
    99.0        13.60        Carter TQ9800 with special jetting and KB19002
                             Fuel Pump
    101.5       13.45        KB44901 Ram Air ( min. 4" hose ) or 4" hood scoop
    102.5       13.35        KB19903 Pan and KB19802 Windage Tray
    104.0       13.10        KB32501 Ignition at 37° with special jets
    107.0       12.80        KB Mark 3 Cam
    110.0       12.30        Big Valve Heads
    111.0       12.20        KB18302 and 18401 Pulleys
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  4. #4
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    What a great bit to have! Real interesting to watch what order they choose to do the mods in.

    WEBNOTE: When inserting an email in a posting, use the "smilie" @ so that web robots don't pick up your address and send you more junk mail!
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    i think it's interesting that the "oil pump kit" is their only recommendation for oiling improvement on the 350. that's somewhat surprising to me.

    i also don't care much for their insistence on the SP TH-400. that's a lot of extra rotating mass to be slinging around. you'll notice the big jump in times when they take out the TH-400 and put in the stick. a lot of that is simply the much lower rotating mass in the manual transmission.

    and then it's far too easy nowadays to get a race prepped TH-350 or 200r4 with a SP and/or lockup convertor.
    Last edited by bob k. mando; 05-25-2010 at 06:45 PM.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  6. #6
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    Yes, although in the day that switchpitch was tough to beat for a drivable performance transmission.

    WEBNOTE: When inserting an email in a posting, use the "smilie" @ so that web robots don't pick up your address and send you more junk mail!
    Members can be contacted by clicking on their "handle", but you are much better off to post to the thread!

  7. #7
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    Good info here....

    I like the Sp400 option since it is a great way to keep a HOT 350 street freindly....

    Now days we have such great converters we can get a 3000 stall converter for a th350 that gives up only 3% on the big end of the quarter.

    In the end, the best option for most 350 powered rigs is the 2004R trans with a lockup conveter.... I swear by this combo since I can have a 4000 stall converter and 0% slip when lockup is engaged by me vi toggle switch.

    For over 500 HP the TH400 is best in most cases... I only paid $2000 for a TH400 built for 1200 hp so that is way better than any other option at that power level.
    Sean G
    70 Skylark-Twin turbo 350 powered
    75 Regal-350
    76 Century-350
    78 Skyhawk-V6
    and 18 spare Buick 350s in the barn.

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