User guide

ThunderTech Products - 6655-A Amberton Drive - Elkridge, MD - 21075 - PH: [phone] - Fax: [phone]
tu n I n G In S t r u c t I o n S
co n t I n u e D f r o m fr o n t Pa G e
Use of This Product is
Intended for Racing
Purposes Only.
VACUUM PETCOCKS
REMEMBER...
Re m e m b e R :
Tu n i n g is ev e R y T h i n g !
Re p l a c e m e n t pa R t s & se R v i c e s
MOUNTING
 We recommend replacing
any late model vacuum petcock
with a Pingel High-Flow Petcock in
performanceapplications.
 Check mixture after any Low
Speed jet change. At maximum rpm, all
three circuits are supplying fuel.  If you
add fuel to one circuit, you may have to
takeawayfromanotherasyouhavenow
enrichedtheentiremixturethroughout.
•ThunderJetkitsandjetssizes
  80-200
•SpecialS&Sjets--airbleedjets
•SpacersandInsulatorblocks
•Velocitystacks(racingonly)
•Highowairlters
•Replacementpartsand
 mountinghardware
•Completeapplication-specic
 carbswithThunderJets
•Professionalinstallationfor
 theseparts
•Specialapplicationcarbs
•InstallationFixtures
 Wehavefoundthereisaneed
forenlargingthethroatsizeintheSuper
‘G’Carbincertainbiginchapplications.
Atmid-rangerpm’s,airspeedissimply
tohighatthenozzle,resulting in a big
surge of fuel and its related stumble,
or sooty looking plugs.  Lowering the
main jet size helps the problem but
dangerously leans out the mixture for
high rpm running (result-burnt pistons).
Boringthecarbthroat willlowertheair
speedatthemaindischargetube.This
smoothesoutthefuelcurveandallows
you to run adequate main jet sizes for
thesebigengines.Ifyouchoosetodo
this modication yourself, be careful;
thereisverylittleroomforerrorhere.
no t e : Thesuggestedstartingpointsarebasedatsealevel.Whenlookingat
thescale,considerthatcam,compression,headowandespeciallyexhaust
typecangreatlyaffecteachcircuit.Openexhaustsystemssuchasdragpipes
willrelyheavilyontheThunderJetcircuitandlessonthemainjetformid-range
tohighRPMpower;tuneaccordingly.Performancesystemswillgenerallytune
tothemiddleofthesuggestedjetrange.Installbaselinejettingandtunefrom
there.RefertocircuitinstructionsaboveforhelpwithnetuningspecicRPM
ranges.Eachenginehasdifferentrequirements;timespenttuningwillyieldthe
bestresults.
MANIFOLD SPACER BLOCKS
 When tuning a long stroke
engine, increasing runner (manifold)
length may help control fuel stand-
off and improve low- and mid-range
carburetion.  Different cams, exhausts,
strokesandotherchangeswillaffectthis
areadramatically. If you are a serious
tuner,wesuggestyoupurchasespacers
andinsulatorblocksandexperimentwith
theminyourapplications.
Je t t i n g Ra n g e gu i d e Fo R th u n d e R Je t tu n i n g
 TestsontheDynoandthetrack
haveshownproperlymountedcarbswork
superiortounitsthatmoveandshakedue
toinadequatemounting.Makesurethe
carb is properlyand securely mounted.
DON’T OVERLOOK THIS AREA!
SUPER ‘G’ CARBS AND
TODAY’S LARGER ENGINES
UNDERJET