Small-Bore Pontiac Engine Build – Revenge Of The 350
Dust off Your Small-Bore Pontiac, Stroke it to 383 Cubes and Make 460+ HP
Despite the fact that the 350 Pontiac engine generally garners little attention in the hobby, HPP still receives a fair amount of questions regarding building them up. Some owners want to retain numbers-matching block status and add some tire-smoking power, and others desire to be different and not simply perform a traditional 400 or 455 swap in an effort to increase performance.
For those who fit into either category, Ken “Ace” Brewer from Pacific Performance Racing (PPR) has an answer. PPR, home of Tomahawk Performance Products, has just released a brand new 4.00-inch stroker package for the plentiful and very-inexpensive-to-buy 350 engine that transforms it into a 383-cube thumper. Follow the recipe outlined here, and you can look forward to 462 horsepower at 6,100-rpm and 436 lb-ft of torque at 4,400 rpm. The beautiful part is that the combination employs a lightweight reciprocating assembly for a quicker rate of rev, a 9.6:1 compression ratio for pump gas, valve sizes that quiet the old complaint of too much shrouding in the small bores, and it’s affordable. How affordable? Does $1,595.95 (under $1,400 with 5140 rods) for a complete balanced Ultra Lite rotating assembly with forged pistons and forged steel rods ring your bell?
Some of you may be asking, why not just build a 400? That’s a reasonable question, assuming you have one at the ready. But the fact that few Pontiac hobbyists seem to want 350s makes cores very cheap, if not free, and the 350/383 could be considered the underdog in any race against a larger engine from any camp, so there is the spoiler factor as well. If nothing else, Pontiac fans have a new number to play with.
Think how much fun it will be upstaging the Bowtie and Mopar brigades, who owned exclusive 383 bragging rights…until now. Remember, this thing actually cranks out some power. If it didn’t, we wouldn’t waste time telling you about it. Now go pull a 350 out of the scrap bin and get started!
Any '68 '77 350 Block That Passes The Usual Magnaflux And Pressure Test Inspection Is Plenty Strong Enough For The Job. Ken Brewer Says That Only Blocks Cast Between 1970 And 1975 Feature The Desirable Five Boss Motor Mount Layout, As Shown. You Can Plug These Blocks Into Any '61 '79 Pontiac Using The Stock Mounts That Came With The Car. Earlier '68 '69 Blocks Have Only Two Bosses, While Later '76 '77 Firebird Specific Blocks Have Three Bosses. These Details May Cause Motor Mount Hassles With Certain Vehicle Installations, But Adapter Mount Kits Are Available.
For Added Rigidity, Moroso Block Fill Is Poured Up To The Bottom Of The Center Freeze Plugs. Though Not Essential, It Fortifies The Bases Of The Cylinder Barrels Against The Elevated Piston Thrust Loads Brought By The 1/4 Inch Stroke Increase.
The Stock Press Fit Front Oil Galley Plugs Occasionally Pop Out When High Volume Oil Pumps Are Used. To Prevent This, The Holes Are Tapped To Receive 3/8 Inch Screw In Plugs With Teflon Paste. A Classic Mistake Is To Thread The Plugs In So They Are Flush With, Or Below The Block Face. If You Do This, You'll Obstruct The Critical Oil Feeds That Run To The Main Bearings. The Trick Is To Thread The Plugs Until Two Full Threads Are Showing (as Shown) But Go No Further. Don't Sweat About Cam Sprocket Interference, It Clears.
The Lifter Valley Oil Drain Hole Is Enlarged, And Its Bottom Is Ground Down To The Same Level As The Valley Floor. This Eliminates The Factory Lip And Speeds Oil Return To The Pan.
The Two Central Oil Drain Back Holes In The Lifter Valley Are Also Enlarged. All Rough Edges Around The Lifter Bosses Are Ground Smooth And Fully De Burred.
At The Rear Of The Block, The Internal Oil Galley Plug On The Passenger Side Is Drilled To A 0.036 Diameter Hole That Directs A Constant Stream Of Oil Toward The Distributor Drive Gear. It Helps Offset The Added Drive Load Caused By The High Volume Oil Pump.
At 3.875 Inches, The 350 Has One Of The Smallest Bore Diameters In The Pontiac Engine Family. Only The '55 287 (3.750) And '63 '67 326 (3.719) Are Smaller. Though The Stroker Crank Gains The Real Inches, A 0.030 Clean Up Was Performed. The Pen Points To Factory Issue Valve Relief Chamfers Atop The 350's Bores. On This 1973 Casting, The Chamfers Are Adjacent To The Exhaust Valves Only. Later 350 Block Castings Have Them Facing Both Valves. These Chamfers Help Unshroud The Valve Heads For Improved Breathing, But Also Add Combustion Chamber Volume For Reduced Compression Ratio. A Little Known Fact Is That Camshaft Lifts Over 0.650 Inch Will Send The Valve Heads Smashing Into The Bores On 287, 326
The Key Ingredient In This 383 Recipe Is Tomahawk's New Cast Nodular Iron Stroker Crank. It Features 3.00 Inch Mains, 2.200 Inch (big Block Chevy Size) Rod Journals, And A 4.00 Inch Stroke. It Can Be Purchased Separately For $325, And There's Even An Optional Version With 2.225 Rod Journals That'll Turn A 400 Into A 428.
Despite Its Low Price, The Tomahawk Crank Features Chamfered Oil Holes And Fully Radiused Rod Journals.
Revco Balancing Handles The Balancing Work On All Tomahawk Stroker Kits. The Fully Welded "no Holes" Internal Balance Job Leaves No Voids In The Counterweights To Catch Oil And Stir Up Windage. The Bob Weight Is 1,979.3 Grams. Photo By Dave Anderson.
The Pen Points To An Improved Thrust Bearing By King Bearing. Available As Part Of Main Bearing Set MB5511AM, It Features Notched Interfaces Between The Upper And Lower Halves That Collect Oil And Enhance Lubrication. Until Now, Pontiac Builders Had To Cut The Notches Into Stock Type Thrust Bearings (left). The Upper Halves Of The Main Bearing Shells Are Grooved, The Bottoms Are Smooth. Ken Says That Fully Grooved Main Bearings Are Best Left To Full Race Applications, As They Can Reduce Low Speed Oil Pressure In Stop And Go Traffic.
Unlike Many Aftermarket Stroker Kits For Pontiac, The Tomahawk Kit Requires Absolutely No Block Clearance Work. The Pen Points Out A Classic Trouble Spot That Has Plenty Of Clearance, Thanks To The Crank's Compact Counterweight Design. Notice The ARP Main Studs. They're Stock Sized (7/16, 1/2 Inch At Rear) But Offer Nearly Twice The Clamping Force Of Stock Bolts.
Also Included In The $1,595.95 Kit Price Are Full Floating 0.990 Pins, Double Spiral Locks, Bronze Bushed 6.8 Inch 4340 Forged Steel I Beam Rods And Forged Probe Full Skirt SRS (Sportsman Racer Series) Pistons. The Rods Weigh 756 Grams And Are Among The Lightest 4340 Rods Currently On The Market, While The Pistons Are Equally Svelte At 539.5 Grams, Including Pins. Remember When Stuff Like This Was Reserved For NASCAR?
Installed, The Pistons Yield A Zero Deck Height With Plenty Of Valve Relief Volume. The Rings Are 1/16 1/16 Moly Filled With A 3/16 Oil Pack. End Gaps Are Set At 0.018 Top, 0.021 Second.
Cutting Parasitic Drag Is The Same As Adding Power, So An Ishihara Johnson Zero Tolerance Teflon Crank Scraper Is Used. With This Innovative Design, There Is Zero Clearance Between The Crank And The Scraper. Sold As A Kit, Several Hours Are Required For Precise Fitment, But Ken Feels The Result Is Well Worth The Effort.
The Crower Hydraulic Roller Cam Provides 0.549/0.573 Lift, 290/296 Advertised Duration, And 234/242 Duration At 0.050. Ken Applies Torco MPZ (moly Phosphorous Zinc) Assembly Lube Prior To Installing It At 108 Degrees. Despite The Radical Specs, The Assembled Engine Idles Smoothly On The Dyno.
The Billet Timing Set Is By SA Gear (PN 78512W 9) And Features A Free Floating Bronze Cam Plate Bushing That Wears Better Than One Piece Factory Issue Top Gears. The Double Row Chain Incorporates Seamless Rollers For Maximum Reliability.
In Keeping With The Budget Theme, The 383 Uses Reworked Factory Iron Heads From SD Performance That Retail For $1,495, Fully Assembled With Your Choice Of Springs. Based On #16 Small Valve Castings With 77 Cc Chambers, SD Exchanges The 1.96/1.66 Valves For Better Breathing Stainless Steel Ferrea 2.08/1.71 Replacements. The Chamber Volumes Are Unaltered, Save For A Very Minor Deck Cut To Restore Flatness.
The SD Performance Heads Feature Filled Exhaust Heat Crossover Passages. These Plugs Are Made Of Molten Aluminum, Salvaged From Cast Aluminum Pistons, That Is Poured In Place, Then Cooled And Machined.
The Pen Points To The Filled Region Behind The Center Exhaust Valves Where The Heat Crossover Passages Used To Be. SD Uses A CNC Mill To Contour The Area. No Claim Is Made Of Improved Flow, But Since The Center Exhaust Ports No Longer Communicate, The Full Benefit Of Four Tube Header Scavenging Can Be Realized. Naturally, The Need For Blocked Intake Manifold Gaskets Is Eliminated.
SD Treats The 350 Intake And Exhaust Ports To An Efficient 5 Axis CNC Cut That Enlarges Them To Standard 400/455 Gasket Sizes. On The SD Flow Bench, The Massaged Heads Flow 255.7 Cfm On The Intake Ports And 212.7 On The Exhaust Ports. Ken Had SD Equip Them With Crower 130 Lb (closed)/330 Lb (at 0.573 Lift) Double Valve Springs (PN 68405) And Chrome Moly Retainers.
Thanks To Its Small Bore And Limited Demand, There Is Only One Pontiac 326/350 Head Gasket Set On The Market Today. It's Made By Victor Reinz (PN 3401VC) And Has A Compressed Thickness Of 0.039 Inch. The Good News Is It's A Decent Piece And Stands Up Well To Virtually Any Street And Strip Use.
With The ARP 1/2 Inch Head Bolts (PN 190 3607) Torqued Down To 100 Lb Ft, The Crower Roller Lifters Are Dipped In Oil And Installed. Failure To Soak The Rollers And Pins Can Result In A Dry Start Up And Galled Parts.
Replacing The Stock Stud Mounted Rocker Arms Is A New Tomahawk TSR Shaft Mount System. Retailing At $795, They Fit All Iron And Aluminum D Port Heads. The Rugged 1.6 Ratio Billet Aluminum Roller Rockers Decrease Operating Friction And Eliminate Push Rod Push Through Problems Common To Stamped Steel Pontiac Rockers.
While Most High Performance Pontiac Heads Are Threaded For Screw In Pushrod Studs, Garden Variety 350 Castings Are Not, And Must Be Tapped So The Tomahawk Billet Steel Pedestals Can Be Bolted Down. Once Installed, Lifter Preload Is Set At 0.060, About 1/2 Turn Of The Adjuster. One Piece Pushrods Are 8.8 Inches Long And Made From 0.080 Wall, 5/16 Diameter Chrome Moly Tubing.
You Already Knew This, But Sticking A Used Valley Pan On A Fresh Engine Is A Great Way To Pollute It. The Hollow Chamber Usually Fills With Grime And Is Almost Impossible To Clean Without The Hassle Of Splitting It Open And Welding It Back Together. To Solve The Problem, Try A One Piece Rolled Aluminum Tray From Ken's Speed & Machine Shop. For $35, It's An Inexpensive Problem Solver. A Continuous Bead Of RTV Prevents Oil Leaks.
Oiling Is Provided By A Melling Select Series High Volume Pump (PN 10540) And Milodon Bolt On Pickup Tube (PN 18525). The Stock Type Pickup Is A Round Press Fit Design That's Only Suited To Stock Type Oil Pans.
Milodon Just Released This Beautiful High Capacity Road Race Pan (PN 31665). It Fits '64 '72 LeMans/GTO Models And '67 '73 Firebirds. There Are Four Trap Doors Surrounding The Pickup That Resist Slosh And Prevent Oil Starvation During Braking, Acceleration And Left And Righthand Cornering. The Low Profile Side Bustle Design Provides Excellent Ground Clearance. A Tomahawk Windage Tray (PN TW $79.95) Adds Further Oil Control.
Why Use Corroded Original Parts When Brand New Front Covers And Water Pumps Are Available From PRW Industries? Ken Points To The Cast Iron Pump Impeller That Moves A Greater Volume Of Water Than Cheaper Stamped Steel Versions.
Design Of The New Tomahawk Single Plane Intake Manifold Was A Collaboration Between Ken Brewer And Dave Bisschop Of SD Performance. Based Loosely On The Old Holley Street Dominator, They've Revised The Port Contours, Eliminated The Heat Crossover And Unnecessary Vacuum Bosses, And Added Bungs To Accept Either EFI Or Nitrous Fittings. Retail Price Is $199.95. A Holley 770 Street Avenger With #71/#75 Jets And WAPP HEI Distributor Was Used For The Dyno Test.
Mounted On The PPR 1,500 Horsepower Dynomite Dual Rotor Dynamometer And Exhaling Through A Set Of Doug's D564 '64 '67 GTO Headers, Over 20 Pulls Were Made On The Fresh 383. Peak Readings Were 462.6 Horsepower At 6,090 Rpm With 436.2 Lb Ft At 4,389 Rpm. All Of This Was On 91 Octane Pump Gas With The Ignition Timing Set At 34 Degrees.
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