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Discussion Starter · #1 · (Edited)
matching comboS

all the parts in an engine combo must match the intended RPM RANGE and AIRFLOW, in order to make the required hp level. lets take my 1985 corvette for an example, you can use your own combo, but as a general guide follow how a correctly matched combo is figgured out
the intake choices are. STOCK OR MODIFIED TPI,which falls on its nose at 4500-4700rpm air flow wise, the MINI RAM has very short runners that tend to work better at rpm levels above 5500rpm. a STEALTH RAM OR SUPER RAM intakes with their wider and lower tq ranges which better match the rpm limits of hydrolic lifter cams and a max REDLINE RPM of about 6400rpm for my 383 and will tend to have advantages in a street/strip car combo, the super ram tends to work great in the 2500rpm-5500rpm range,and flows about 245cfm out of the box, the stealth ram in the 4000rpm-6400rpm range, and flows about 275cfm out of the box, both can gain about 25cfm with porting.
a cam that works correctly in that 4000rpm -6400rpm range will have at least 220-230 degrees duration (230-240 would match well,(being driven on the street I picked a cam with 230 duration)to get the full potential
(IM useing a CRANE 119661)(installed 6 degrees retarded) (with that cam I need a STATIC COMPRESSION RATIO OF 11:1 and a DYNAMIC COMPRESSION RATIO UNDER 8:1 WHICH I HAVE)
http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=119661&B1=Display+Card
EFI systems and sensors tend to run better with a cam having a LSA of 112 or greater.
you stall speed should be in the 2600rpm-3200rpm or greater range
your rear gearing should be in the 3.73-4.88 range with a 700r4 and 26" tires

these are the valve timeing overlap ranges that are most likely to work correctly

trucks/good mileage towing 10-35 degs overlap
daily driven low rpm performance 30-55degs overlap
hot street performance 50-75 degs overlap
http://www.prestage.com/Car+Math/Gear+Ratios+and+Tire+Sizes+/Optimum+Gear+Ratio/default.aspx

http://www.btinternet.com/~mezporting/exhaust_length.html

http://home.isoa.net/~mharrisj/pistspd.html

http://www.rbracing-rsr.com/runnertorquecalc.html


http://www.prestage.com/Car+Math/Gear+Ratios+and+Tire+Sizes+/Finish+Line+MPH/default.aspx

your cylinder heads should flow a minimum of 245cfm-260cfm @.500 lift to reach the full potential of the intake that you choose that is able to flow slightly higher flow numbers to make the required hp/tq curve and to keep the engine in the proper rpm range youll be trying to stay in that 4000rpm-6400rpm max tq in the dyno curve.
http://www.prestage.com/Car+Math/Car+Math+Formulas/default.aspx
http://users.erols.com/srweiss/calcafhp.htm
http://users.erols.com/srweiss/calchpaf.htm

the bottom line is that a correctly built combo requires carefully matched parts designed to work at the SAME HP and RPM levels,MISS-MATCHED COMBOS DON,T TEND TO REACH THIER POTENTIAL,and BADLY MISS-MATCHED PARTS WILL TEND TO WORK AGAIST EACH OTHER AND COST YOU HP!
example, lets say, just to show how you build a combo that pushes my corvette weights 3500lbs with you in it and you have a 700r4 trans and a 383 that you intend to run 11-9- 12 flat 1/4 miles times with,
well first thing youll need to know is the required hp levels at the rear wheels and the likely rpm levels http://www.prestage.com/Car+Math/ET+and+Horsepower+Calculators/Calculate+ET+and+MPH+using+HP+and+Weight+/default.aspx

we see we will need about 399 rear wheel hp and be running about 112mph, youll want to be just under 6000rpm at 112mph and youll be in third gear in the lites for best accelleration but youll most likely have a trans that shifts before 6000rpm so youll be in high overdrive, if your in third a 3.73 gear is correct, if in overdrive a 4.88 rear gear would be correct on a racing only corvette.
youll need about 450 flywheel hp to get 400 rear wheel hp, that will require about 245cfm-260cfm per port cylinder head flow and intake flow at .500 lift, (my cam only gets to .595 lift with the 1.6 ratio rockershttp://users.erols.com/srweiss/calchpaf.htm
http://www.prestage.com/Car+Math/Gear+Ratios+and+Tire+Sizes+/Finish+Line+RPM/default.aspx
youll need a cam in about the [email protected] duration range
[image]http://www.babcox.com/editorial/ar/elements/30228b.gif[/image]
and that will be best matched with about a 2800rpm- 3200rpm stall speed
now if your willing to run nitrous you can get there with less effort and expence but if your running street tire that combo will get you close.
now IM NOT saying you need a full 450 flywheel hp to run 11.9 1/4 miles but thats about what youll need with street tires , and relieing on the last 1/2 track charge with little traction, in a full 3500lb corvette with no suspension work and a stock 700r4 with a 350 and its narrow tq curve, a 383-406 with its wider tq curve can use slightly lower peak numbers because it stays in the higher tq ranges longer
heres what I built
custom 383 full roller ,11:1 cpr,engine CRANE #119661 0.21 thick copper head gasket/.o20 deck/piston height ,hydrolic roller (installed retarded 6 degrees) cam,ported trickflow 200cc heads,(about 210cc now)custom stealth ram, 32lb (testing 36lbs now) injectors,custom chip,custom built plenum,58mm throttle body,6" rods, slp forged pistons,total seal gapless rings 9.5 qt baffled custom oil pan,milodon windage screen,jackson gear drive,1 3/4 x36" with custom merge collector headers, full 3" exhaust, 1.6 erson roller rockers, 200hp nitrous plate,all forged rotateing internally ballanced assembly,fluidamper ballancer polished combustion chambers,ballanced engine , splayed 4 bolt block, LS7 oil pump,all internals pollished, and no I won,t tell you my E.T. or HP other than to say , C-5 ZO6s aren,t a challange and they run mid 12s
LOOK BACK THRU THE LINKS and try to figure your own goals and how to get there! now keep in mind my goal was not to have a race car but to have a corvette that would beat the Zo6 corvettes and still drive well enough on the street to use as a daily driver in an emergency

if anyone cares to work that out on DD-2000, let me know what you get, BTW the stealth ram is a EFI tunnel ram intake with an 1050cfm throttle body)
 

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Dang, I'm dizzy from all those figures......didn't hear anything in there about a 6 pack ? Don't you like beer ?
 

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Discussion Starter · #4 ·
beers OK but I prefer BRANDY
 

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Discussion Starter · #6 ·
do yourself a big favor,don,t guess,use data thats very easy for you to get!
(1) get in your corvette,find a light weight friend to ride with you and take notes while you drive, he/she will need a stop watch, a note pad and a couple pens, find a long deserted place/road to test on.
(2) floor the car, and have the friend watch at what rpm level the car launches at and where the car shifts (rpm) and in what gear your in at 110mph) and how long you were in each gear!
now if your driveing a almost stock corvette with a 700r4 youll launch at about 2000rpm and shift at 5200rpm-5700rpm, that rpm range just barely gets into the most effective rpm for that mini ram, youll be better off with that rear gear with a super ram or stealth ram simply because they are both designed to run more efficiently in the slightly lower rpm ranges.
IF YOUR RUNNING A MANUAL TRANS, you will be able to keep the engine in gear to higher rpm levels but the cam and your valve float redline might still limit you somewhat!
TPI runs out of air about 4000rpm-4400rpm (depends on porting, heads cam,ETC.)
SUPER RAM adds about 1000rpm-1200rpm(depends on porting, heads cam,ETC.)

STEALTH RAM with custom plenum runs best in the 4000rpm-6500rpm range(depends on porting, heads cam,ETC.)

mini ram runs best about 1000rpm higher(depends on porting, heads cam,ETC.)

first find out where your corvette spends all its time!
now Im not SAYING YOU CAN,T USE ANY OF THEINTAKES OUT SIDE OF THOSE RPM RANGES, I AM STRONGLY SUGGESTING THAT MATCHING THE CAM TIMING, CYLINDER HEAD FLOW AND THE CORVETTES GEARING AND STALL SPEEDS AND TRANSMISION SHIFT POINTS TO MATCH THOSE RPM RANGES WILL PRODUCE BY FAR THE BEST RESULTS
BTW http://www.eecis.udel.edu/~davis/z28/winter01/dyno/dyno021105/webpage021105.html
IVE GOT STEALTH RAM INTAKES WITH CUSTOM PLENUMS,FUEL RAILS, AND STANDARD PRESSURE REG PLUS INSTRUCTIONS FOR $750
 
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