sellecting a cam to maximize your combo N/A or nitrous



sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » December 9th, 2008, 3:31 pm

READ THRU THIS CAREFULLY
http://www.compcams.com/Community/Artic ... 2026144213

http://www.kennedysdynotune.com/Nitrous ... 20Tips.htm

http://www.compcams.com/CAMQUEST/

http://www.dragstuff.com/techarticles/P ... hafts.html

http://www.pontiacstreetperformance.com ... rArms.html

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=1751

http://www.compcams.com/Community/Artic ... 2026144213

http://www.chevyhiperformance.com/techa ... index.html

viewtopic.php?f=52&t=1070

http://www.aa1car.com/library/camshafts.htm

viewtopic.php?f=52&t=1477

I will try to answer that as simply as possible.
A nitrous cam is designed to work with more cylinder pressure and more exhaust voluum. than a N/A cam design



NITROUS use developed similar INCREASED exhaust pressure and VOLUMES of exhaust gases, to a super charged application, because atmospheric air,run in a N/A engine holds about 21% oxygen and you run a fuel air ratio about 12.6 pounds of air for every pound of gasoline.
with nitrous theres about 40% oxygen content available in the same volume of air as you would have with a supercharger at about 15 psi of boost, but without the intake being pressurized and with out the heat and weight a supercharger has, in fact nitrous is injected and radically cools the intake charge making it denser,so to maintain that similar 12.6:1 fuel air ratio you adding and burning a good deal more fuel,(obviously depending on the percentage of nitrous added to the outside air the engine ingests, vs pure nitrous and fuel which would require a bit more that twice as much fuel to maintain the ideal fuel/air ratio that extra fuel being burnt is where your getting the extra power nitrous used generates, thus the extra exhaust gas volume, you might want to think of nitrous as generating up to twice the volume of exhaust gases from about the same intake volume, thats running and burning extra fuel to generate higher cylinder pressures,up too, twice the oxygen content, means up to twice the fuel being burnt per compression,power and exhaust stroke.


LOOK AT THESE TWO DYNO GRAPHS

Image

Image

http://mb-soft.com/public2/engine.html

below are two extremely similar cams, both have identical lift and duration, only the LSA differs

its always a good idea to call the cam manufacturer and ask what is the correct matching cam gear and distributor gear set,and how its correctly installed.

this one is considered better with nitrous
wide 114 LSA
http://www.crower.com/misc/cam_spec/cam ... 4&x=51&y=9
INTAKE Opens: 15.0 BTDC
Closes: 55.0 ABDC
EXHAUST Opens: 68.0 BBDC
Closes: 12.0 ATDC

tight 108 LSA
http://www.crower.com/misc/cam_spec/cam ... 7&x=51&y=9
INTAKE Opens: 21.0 BTDC
Closes: 49.0 ABDC
EXHAUST Opens: 62.0 BBDC
Closes: 18.0 ATDC
why?? well look closely, the 00234 compared to the 00227 the exhaust opens earlier on the 00234, and theres less overlap

a N/A engine runs on a fuel air mix ratio of between 12.7:1 to 14.7:1, oxygen content of normal air is approximately 20%
nitrous has approximately TWICE the oxygen content at about 40% and can effectively burn up to twice the fuel per cylinder full, now that produces a great deal higher pressures and a huge increase in exhaust volume, that extra volume produced the extra pressure that makes the power possible but it can also cause significant PUMPING LOSSES if the pressure in the cylinders does not drop off before the piston starts back up on the exhaust stroke and can limit the intake charge volume flowing into the cylinders if theres still positive cylinder pressure as the intake valve opens.
the intake valve opends at 29 degrees BTDC with the #114681 it opens at 34 degrees with the #110921,(5 degrees sooner) that makes the differance 5 degrees later opening for the #114681, this is not a problem when your filling the cylinders with the enriched nitrous/fuel mix
this effectively allows a greater time for the exhaust possitive pressure to blow off and less overlap time when both valves are open at the same time.
the later intake valve opening, matched to the lower overlap and earlier exhaust valve opening lowers the engines pumping losses when useing nitrous,gains of 30 hp plus have been shown swapping from the N/A to the NITROUS design WHEN ON NITROUS, but look for a few less hp running N/A with the nitrous cam simply because the nitrous cam does not scavage the cylinders as effectively due to lower overlap N/A at high rpms

these are the valve timing 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
oval track racing 70-95degs overlap
dragster/comp eliminator engines 90-115 degs overlap

but all engines will need the correct matching dcr for those overlap figures to correctly scavage the cylinders in the rpm ranges that apply to each engines use range.

example
http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=114681&B1=Display+Card

here is a hot street cam that works great in many 383 camaros with at least 10.5 static cpr with 3.5-4.1 gears
now the timeing is intake opens 29.0 btdc, closes 71.0 abdc exhaust opens 77.0 bbdc, closes 31.0 atdc so if we add the 29 to the 31 we get the overlap duration of 60 degs of which makes this cam fall in the center of HOT STREET



short answer, 110 LSA if its a engine used mostly at high RPM, 112 LSA if its street driven
(need more info,..look below)


The LSA, or lobe separation angle, is ground into the cam and cannot be changed. It is the angle that separates the intake and exhaust lobe for a particular cylinder, and is measured in camshaft degrees. The intake lobe center line is measured in crankshaft degrees. The #1 intake lobe center line is usually between 100° to 110° ATDC and is what you use to degree the cam. The cam manufacturer will publish the specs for the cam based on a given intake lobe center line. Comp Cams, for instance, produces a large number of cams with 110*° LSA ground 4° advanced, so they list the specs for the cam with a 106° intake lobe center line. You can calculate the ILC by adding the intake opening angle in °BTDC, the intake closing angle in °ABDC, plus 180° for the distance from TDC to BDC. Divide by 2 and subtract the intake opening angle and you will have the ILC. For example a 12-430-8 Comp Cam lists IO at 34°BTDC, IC at 66° ATDC, so 34 + 66 + 180 = 280. 280/2 = 140. 140 - 34 = 106° ILC Image
Figure 3 is a picture of both an intake and an exhaust lobe of a camshaft, seen end-on. It shows the relationship between the lobes, shows the overlap area, and illustrates this next section.

Overlap has a great deal to do with overall engine performance. Small overlap makes low-end torque but less high-end power. Large overlap reduces low-end torque but increases high-end power.
Overlap is determined by two other cam specifications, Duration and Lobe Center Angle.
Duration is the time, measured in crankshaft degrees, that a valve is open. A duration of 204 degrees means that while the valve is open, the crankshaft rotates through 204 degrees.
Duration is measured on two "standards," "advertised duration" and "duration at 0.050"." Advertised duration is measured from when the valve just starts to lift off its seat to when it just touches the seat again. This is measured in different ways by different manufacturers. Some measure when the valve lifter is raised 0.004", some at 0.006", and some at different points yet. So the industry agreed to another standard that was supposed to make it easier to compare cams. In this standard, the duration is measured between the point where the lifter is raised by 0.050", and the point where it is lowered again to 0.050".
The 0.050" standard is great for side-by-side "catalog" comparisons between cams. But if you use engine prediction software on your computer, the software is much more accurate when you can feed it "advertised" duration numbers.
Lobe Center Angle is the distance in degrees between the centers of the lobes on the camshaft.
To increase duration, cam makers grind the lobes wider on the base circle of the cam. This makes the lobes overlap each other more, increasing overlap. More duration = more overlap.
To increase overlap without changing duration, cam makers will grind the lobes closer together, making a smaller lobe center angle. Less lobe center angle = more overlap.
Overlap and duration are the two big factors in cam design. More overlap moves the power band up in the engine's RPM range.
Longer duration keeps the valves open longer, so more air/fuel or exhaust can flow at higher speeds. It works out that increasing the duration of the camshaft by 10 degrees moves the engine's power band up by about 500 rpm.
A smaller lobe separation increases overlap, so a smaller lobe separation angle causes the engine's torque to peak early in the power band. Torque builds rapidly, peaks out, then falls off quickly. More lobe separation causes torque to build more slowly and peak later, but it is spread more evenly over the power band. So a larger lobe separation angle creates a flatter torque curve.
So you can see how a cam maker can tailor the camshaft specs to produce a particular power band in an engine--

Short duration with a wide separation angle might be best for towing, producing a strong, smooth low-end torque curve.
Long duration with a short separation angle might be suited for high-rpm drag racing, with a high-end, sharp torque peak.
Moderate duration with wide separation angle might be best suited for an all-around street performance engine, producing a longer, smoother torque band that can still breathe well at higher RPM.
Remember, there's always a compromise made in this process.

One last item to consider is the lobe center line. The lobe center line is the angle of the lobe's center peak, measured in crankshaft degrees when the piston is at Top Dead Center (TDC). In general (but not always), when a cam is installed "straight up," the intake lobe center line and the lobe separation angle are the same.
The lobe center line can be altered when the camshaft is installed, by advancing or retarding the camshaft's position in relation to the crankshaft. Advancing the camshaft by 4 degrees will move the power band about 200 RPM lower in the RPM band. Retarding the cam by 4 degrees will likewise move the power band 200 RPM higher in the RPM band. This allows you to fine-tune the engine's performance according to your needs.
BTW once EITHER the duration exceeds about 225 @ .050 or the lift exceeds about .520 in a 383 SBC youll probably have clearance issues with stock connecting rods,and the cam lobes, aftermarket (H) or SOME (I) style stroker rods with 7/16" capscrew bolts are stronger and profiled to clear and use of both a small base billet roller cam and stroker profile rods will usually prevent that



if cams are a mystery please take the time to read these, it will get you a good start


http://www.iskycams.com/techtips.php


http://www.wighat.com/fcr3/confusion.htm

http://www.idavette.net/hib/camcon.htm

http://www.totalengineairflow.com/tech/valvelashing.htm

http://www.wighat.com/fcr3/camtruth.htm

http://www.wighat.com/fcr3/confusion.htm

viewtopic.php?f=50&t=575

http://www.babcox.com/editorial/ar/ar119736.htm

http://home.wxs.nl/~meine119/tech/camqa.html

https://www.holley.com/Map/Instructions7.asp

More than just the engines cam duration and lift must be considered when choosing a cam. the cam must work correctly with the intake and exhausts designed rpm band , a high-stall converter and lower (higher numerically) rear end gears, will allow the engine to accelerate thru its rpm band faster and stay in the upper rpm range longer, the engine will perform better with a bigger cam than if the car has a stock converter and highway gears, if matched to the correct components and drive train.. A heavy car is harder to get moving than a light car, so it needs more torque down low and that usually requires less duration.

when you select an intake manifold the goal is usually to maximize the engines volumetric efficiency, in the engines intended power band,(how efficiently you can fill the cylinders with a full fresh charge of fuel/air mix)
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting a cam to maximize nitrous

Postby grumpyvette » December 20th, 2008, 8:49 pm

http://www.popularhotrodding.com/tech/0 ... index.html

you really need to read thru this carefully also and with ANY CAM CHOICE youll need to check ALL clearances and probably replace the old valve springs to maximize the results,

sellecting the correct cam for YOUR combo

look you may not want too hear this but...IF YOU FOLLOW the advice BELOW EXACTLY, youll have a decent cam, ignore it and your very likely to find youve sellected a cam that won,t run correctly in YOUR APPLICATION

heres a semi-fool proof method


write a list of all factors that will influence the choice DON,T LIE tell them EXACTLY what you expect and what you have currently ,installed that the cam must work with NOW, NOT what you intend to install later
YES you NEED too KNOW your COMPRESSION RATIO, and all the other answers to the questions below BEFORE calling....
car weigh?
rear gear ratio?
tire dia.
trans and gear ratios?
stall speed if its an auto?
displacement?
COMPRESSION RATIO
HEADS (flow numbers)(lift restrictions)
intake type
tire size
intended use
max rpms
launch rpms
MIMIMUM IDLE
fuel octane
carbs,mpfi? CFM
ETC.

call a minimum of 5 major cam companys, (6-8 is better)
write down thier recommended cam type,its lift, and duration at .050 and LCA.

read off the list to each manufactures tech guys, but DON,T DISCUSS IN ANY WAY WHAT OTHER MANUFACTURERS SUGGESTED

AVERAGE THE RESULTING LIFT DURRATION and LCA info from each cam, and buy the cam thats CLOSEST TOO THAT AVERAGE, (ALL the MAJOR MANUFACTURERS HAVE DECENT CAMS) this tends to give consistantly good results
keep in mind solid lifters generally have an rpm advantage and roller cams generally out perform flat tappet designs but cost more

http://www.crower.com/

http://www.cranecams.com/

http://pbmperformance.com/store.php?cat ... parent=327

http://www.lunaticams.com/

http://www.survivalmotorsports.com/camshafts.html

http://www.chetherbert.com/newchet.html

http://www.iskycams.com/

http://www.reedcams.com/

http://www.schneidercams.com/cams/20.htm

http://www.lazercams.com/CamTables.html

http://www.englecams.com/

NO! ONE SIZE LARGER WON,T GENERALLY WORK BETTER, IN FACT ITS FAR MORE LIKELY TO BE A HUGE P.I.T.A to DRIVE AND HURT PERFORMANCE thumbsup:

BTW
its MORE critical that the converter stall speed and rear gear ratio match the cam timing and compression ratio if its an AUTO TRANS,......
than if you have a manual trans, which is far more flexiable as to what it will function with.
but having the rear gear ratio and compression ratio match the cam is mandatory for good results
and the larger the displacement and the better the heads flow the more likely it is that youll find both good low rpm tq and mid to upper rpm hp youll want in a street/strip combo, Ive seen many bad combos put together due to sellecting a cam based on, the flawed logic
(well my buddies running cam (X) his car runs good...and I want to beat him so ILL buy the NEXT more aggessive cam with just a bit more durration and outrun him)
in most cases youll be far better off, researching and sellecting a combo with better cylinder heads, intake flow rates and larger displacement, rather than trying to go with a wilder cam.
remember your rarely going to make a huge improvement in hp per cubic inch with cam upgrades once youve reached about 1.25 hp per cubic inch displacement, but increasing the displacement, compression ratio and DISPLACEMENT tends to give a good boost over similar combos with lower displacement/cpr and head flow rates
if a 350 with 9.5:1 cpr that makes 1.25 hp per cubic inch thats 437 hp
build a similar stroker combo that has 401 cubic inchs and 10.5:1 cpr and your far more likely to have about 520hp based on similar components
(the same 1.25 hp per cubic inch plus .04 increased tq due to the higher cpr and increased stroke ) plus all that at a slightly LOWER rpm thats easier on the valve train stress.
you might want to remember that a restrictive exhaust will kill much of the power potential, so decent TUNNED headers and a low restiction exhaust is a necessary part of any build, and unless you can maintain the correct fuel/air ratio you can,t make good hp, so matching the fuel delivery and injector size to the applications mandatory

Image

install it like this, then rotate the engine one time 360 degrees the cam gear will now be at 12 oclock just like the crank gear, then install the distrib pointing at cylinder #1
this may help
on most aftermarket and on cloyes timing chain sets there are 3 keyways with 3 different marks. There is a:
circle
square
triangle



on the crank gear

0 - Indicates standard cam timing
A - Advances the cam timing 4°
R or a square - Retards the cam timing 4°
how come its 180 degs out of phase? I get this question all the time, well heres something I see lots of guys don,t understand,ONCE YOUVE INSTALLED A CAM WITH THE TIMEING MARKS YOU MUST ROTATE THE CRANK 360 DEGRESS BEFORE DROPPING IN THE DISTRIBUTOR
... while its true that if the
timeing marks are possitioned so the crank is at 12 o,clock and the cam gear
is at 6 o,clock that the cam lobes will be in the possition that fires #6
cylinder that HAS NO EFFECT AT ALL (on finding TDC,) for aligning the degree wheel with TDC,or THE timeing tab pointer, for degreeing in the cam, the piston passes thru
TDC TWICE in every fireing cycle once on the fireing/power stroke and once
on the exhaust stroke, the cam rotates at exactly 1/2 the speed of the crank
so to make it easy to line up the marks they install it with the marks at
the closest point 6/12 for easy indexing, rotate the engine 360 degrees to
the #1 TDC power stroke and the crank gear will still be at 12 oclock 12/12
but the cam will be at 12 o,clock also, rotate another 360 degrees and your
back where you started. its simply easier to index the cam at the point
where the index marks align closely. look at how the cam lobes themselfs
open the valves when the cam is just installed the #1 cylinder valves are
slightly open and the #6 are closed
per "Lunati"
""YES YOU ARE RIGHT - WHEN CRANK IS AT TWELVE AND CAM IS AT SIX THEN #6 CYL IS FIRING
AFTER YOU LINE UP YOUR MARKS AND INSTALL GEAR THEN ROTATE YOUR CRANK ONE REVOLUTION AND THEN DROP THE DIST. IN - AT THAT POINT #1 IS FIRING""

use of the dots, as index points will work most of the time in theory, youll be close to correct, if you want things dead on correct you need to take the time to degree it in, the difference can be 5-20hp depending on how lucky you get with tolerances
take the time to read thru the whole thread and sub linked info
its well worth the effort

viewtopic.php?f=52&t=90&p=114#p114
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » January 30th, 2009, 11:46 am

from the CAMCRAFT SITE
http://www.camcraft-cams.com/index.php? ... ting-a-cam


Some thoughts on choosing a proper cam...

Section 1: for Stock Cars

1- To many racers the best cam is the one in the car when they get the chassis sorted out and the driver finally gets the track figured out.

2- Short duration cams with wider lobe separations usually yield much flatter torque curves

3- Longer rod motors prefer a shorter duration cam with wider lobe separation

4- Longer duration cams require tighter lobe separation to have any power off the corner. (not usually a preferable combination in 2 bbl classes.)

5- Stock exhaust manifolds or a highly restricted exhaust usually respond well to shorter exhaust duration and wider lobe separation. Power increases are most evident at higher rpm where exhaust backpressure is greatest and reversion is most prevalent.

6- Most unported heads approach 85 or 95 % of peak flow at .400 to .450 lift and do not need or want a maximum valve lift over .540 to.555. Often a low cam lift with 1.65 or 1.7 ratio rockers is very helpful on the intake side as long as lift is kept to about .550. Exhaust is less critical with 1.5 or 1.55 being the most popular.

7- Dyno testing doesn’t test drivability or throttle response of the engine.

8- The important numbers on a dyno sheet are about a thousand RPM above and below peak torque and peak horsepower. Peak numbers are for bragging purposes and high peak numbers do not win races.

9- The benefit of high ratio rockers is faster valve movement and the added lift is frequently detrimental in unported heads. It often helps to utilize a lower cam lift with high ratio rockers.

10- Changing the valve lash is a good way to get an indication of which way to go for your next cam change. You won’t hurt anything by going too tight but too loose will let the valves slam shut, causing damage to valves and seats. .004 to .006 loose is usually OK.

11- Look at the Major Intensity numbers to get an idea as to how radical the profile is.( major intensity is the difference between the .020 duration and the .050 duration.) Lower numbers are more radical but anything less than 27 or 28 degrees may be very hard on the valve train. Our 26-degree SXTL profiles are a notable exception to this.

12- Glowing exhaust pipes may be an indication of over scavenging by the exhaust. A shorter exhaust duration. Smaller headers, or even a restrictor plate at the header may help. The problem is often mixture burning in the exhaust rather than in the cylinder. Many people think a lean mixture causes it. Be sure to ascertain which problem you have as the lean mixture is a much more serious problem and can cause quick meltdown.


Camshaft intensity is a measurement term coined by Harvey Crane to compare ramp characteristics of camshafts.

Hydraulic Intensity is the difference between the .004 duration and the .050 duration.
Minor intensity is the difference between the .010 duration and the .050 duration.
Major intensity is the difference between the .020 duration and the .050 duration

Lower numbers indicate more radical profiles but too low can be too radical and lead to noisy valve train and even to broken parts.


Section 2: For drag cars

1- Cars with small tires or poor suspension may need a larger cam to kill some power off the line in order have a consistent launch without overpowering the suspension.

2- Hard tail dragsters usually run quicker with shorter duration cams but then lose consistency because the harder launch overpowers the track. Soft tail cars can adjust for the harder launch and remain consistent.

3- Be absolutely sure of your gear ratio when selecting a cam. Just cause your buddy told you that trick new rear is a 3.73 or 4.10 doesn’t mean it really is. If you pick a cam to go with a 3.73 rear and it turns out you have a 2.73 The difference would be 3529 rpm with 2.73 gears and 26” tires @ 100mph or 4822 rpm with 3.73 gears. The same cam won’t work real well in both scenarios.

4- The first thing to do in selecting a cam is to determine top speed in high gear. If 6,000 rpm = 150 mph in high gear and you will never see that speed then you definitely don’t need a cam with 6,000 rpm power. Tuning for power at too high an rpm is a very common mistake.

5- You need to make good power below the converter stall speed (not flash rpm) in order to hit the converter hard. This becomes more critical as car weight goes up. Peak power should be slightly below the rpm through the lights.


Section 3: For street cars

Be absolutely sure of your gear ratio when selecting a cam.

1- The first thing to do in selecting a cam is to determine top speed in high gear (not overdrive). If 6,000 rpm = 150 mph in high gear and you will never see that speed then you definitely don’t need a cam with 6,000 rpm power. Tuning for power at too high an rpm is a very common mistake.

2- A car with 3.08 gears will go 150+ mph @ 6,000 rpm. 5,000 rpm still = 125+ mph while 2,600 = 70 mph. It makes a lot more sense to tune the engine for power in the 2,000 to 4,500 rpm range. You can get good fuel economy as well as better performance. Any cam bigger than stock will make more power at high rpm. It just doesn’t make sense to select a cam with max power at 5,000 rpm if it will spend most of its life below 3,000 rpm. Below are common rpm=speed ratios. All are based on a 26-inch diameter tire.

2.73 @3000 = 85 mph, 3.55 @3000 = 66 mph, 4.10 @3000= 57 mph
3.08 @3000 = 76 mph, 3.73 @3000= 62 mph
3.23 @3000 = 72 mph, 3.90 @3000= 60 mph

3- If you have big heads you definitely need a smaller cam than if you used the stock heads. Failure to realize this will result is a big loss in low end and midrange throttle response. It will likely make great power at rpm levels you don’t even want to see.

4- Be careful of using big carbs. A 650 cfm carb is plenty for all but the most radical 350 engines, even for strictly racing. A 750 may make more top end power but it gives up a lot in low-end throttle response and midrange torque. This is especially true when you have big heads. The fact that your buddy ran faster with your 750 than his 650 only means there was something wrong with his 650.

© Copyright 2004-2009 - CMS Made Simple
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » February 1st, 2009, 2:11 pm

http://www.dingdongtx.org/1968/jharticl ... icles5.htm

even though this is pontiac related its well worth reading thru for great info
if your just guessing at your compression ratio and gear ratios and component flow rates , in any engine, its very unlikely youll get the correct cam selected to match the combos needs,


without knowing, and using the CORRECT info on,
the cars transmission,
rear gear ratio,
stall speed(if its auto transmission)
compression ratio,
tire dia.
exhaust system specs
and valve train clearance issues
probable intake and head flow rates
selecting a cam is just wild guess work

this might help
viewtopic.php?f=52&t=82&p=105#p105

while you can surely get a decent cam installed that way,(GUESSING) chances are low that youll get a cam thats not leaving some hp/tq on the table simply because of the wide variation in the flow rates and compression ratio of the components
the link I posted will tend to reduce the potential for a less than ideal cam being selected.
most guys don,t realize that that lopey idle they want is caused by crappy low rpm airflow and fuel air ratio control in the ports, that cause it to run rough, due to reversion pulses at idle speeds, a cam thats designed to kick butt at 7000rpm is going to run far less than ideally at 800-1100rpm (hence the lope) , if you spend 90% of your time between 1500rpm-5500rpm like most street cars a really lopey cam, with a good deal of overlap, is bound to be costing you some low and mid rpm torquebut there ARE ways around the problem, and in most cases it will envolve slightly less durration and overlap, yes you mioght give up a few peak hp and it might not idle as rough, but it will produce better average hp/tq and the car will be faster. you can either build for max useable hp/tq in your true rpm range or pick the cam to maximize the lopey idle, youll rarely get both bases covered with the same cam
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » March 27th, 2009, 8:37 am

HEY GRUMPYVETTE?
does anyone have a quick list of cam company ph #s? i used to have one. ill call them all for recommended cam specs

sorry if all this is already here somewhere else, im just not good at searching online


viewtopic.php?f=52&t=82

the cams duration effects both the dynamic compression and the effective rpm band that the cylinders fill efficiently in, while its true a low compression and a mild cam could easily have the same dynamic compression ratio as a high compression and much longer duration cam, combo the effective rpm band would be much different and the low and high rpm performance would be vastly different

heres free cam selection software to narrow your choices

http://www.compcams.com/Camquest/default.asp

btw once you use it to find that approximate lift ,duration and lca, you can buy any companies cams with similar specs.


CROWER cams
http://www.crower.com/misc/contact.shtml


ENGLE CAMS
http://www.englecams.com/index.php
Tel: (310) 450-0806
Fax: (310) 452-3753

ISKY CAMS
http://www.iskycams.com/

phone: 323.770.0930
fax: 310.515.5730


ERSON
http://pbmperformance.com/store.php?catId=327

Lunati
technical support is available by phone Monday through Friday 7AM to 5PM CST @
662 892-1500

http://www.popularhotrodding.com/tech/0 ... index.html


btw if you want to run nitrous this would be a good idea

http://www.kb-silvolite.com/article.php ... ad&A_id=64
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » September 1st, 2009, 11:01 am

factors to keep in mind when selecting your engines camshaft.

The following remarks are intended to help you select the correct camshaft,for your application, but obviously the other components selected effect results



(1) If the cylinder head your using is flowing more than the old one it replaced (has been ported, or is a better aftermarket design) the lobe center line ( LSA) can be slightly tighter, as the increased air flow tends to benefit from more overlap in many cases, and exhaust scavenging should improve with well designed headers and a low restriction exhaust

(2) a wider lsa tends to benefit lower compression engines with restrictive ports



(3)The tighter the lobe center line (LSA). and the higher the compression ratio,the more obvious it will be when the cam starts to run in its intended power band IE the engine comes up into the cams designed operational power band

(4) If a hydraulic cam is being replaced with a solid cam, the 0.050" duration needs to increase by about 10 degrees to maintain the same effective power in its rpm band but solids generally have a noticeable advantage in the 5500-6000rpm plus range


(5) what goes in needs to go out so tuning the exhaust scavenging helps the intake ports draw in the charge, but with headers and a low restriction exhaust longer exhaust duration on a N/A engine is not always helpful, the inlet duration generally has more influence on the power band.

(6) longer strokes in relation to bore size tend to favor tighter LSA cam designs, or put a different way, a 383 or 496 stroker will tend to run a bit better with a tighter LSA than the 350 or 454 they were built from if all other factors remain consistent

"can injectors be installed in the intake runners?"

hell YES! infact thats how many high hp systems are installed
Image


you might want to look into this, it fits inside the air cleaner
Image

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=180142&prmenbr=361
[/QUOTE] Thanks Grumpy! I like this setup Image

better that the hidden one as it will look real tricked out & I will not have to worry about hood clearance...I am running a 2" element & think it might not work?:huh: Do you know if i can put a 100 shot with the frst one you showed me or do I have to go bigger...I dont want to go over 100 shot.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » September 30th, 2009, 5:13 pm

don,t forget to retard the ignition total advance and work up to the point in the ignition advance just before you get detonation indicators, but the truth is if your seeing any drop in fuel pressure the fuel system needs to be upgraded, you probably need bigger lines and a better fuel pump and better fuel pressure regulators


http://www.centuryperformance.com/fuelish-tendencies-understanding-fuel-pressure-and-volume-spg-140.html

http://forum.grumpysperformance.com/viewtopic.php?f=55&t=211

Image

Image

in this diagram the dead head regulators are some what optional, but the rest of the diagram holds true, damn I wish you were local, we could have a real good time
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: sellecting a cam to maximize your combo N/A or nitrous

Postby grumpyvette » January 12th, 2010, 3:13 pm

Ok lets assume your current 350-383 sbc has a hydraulic roller cam in the 225-235 intake duration range like many hot sbc combos have and you decide to use NITROUS or a SUPERCHARGER, and all your buddies tell you your current, cams LSA is too tight at its current 108-110 lsa........
don,t panic , everything's a compromise in one area or another,the tighter 108-110 LSA on that will allow some extra fuel/air charge to sweep in the intake valve and flush right out the exhaust, too a higher degree than your common 112-114 LSA cam timing would but in exchange the cars torque curve will be a bit better in the low rpm torque curve before the supercharger starts making boost effectively, or you get the full potential from the nitrous, and its extra cylinder pressure.
your merely trading a few hp up higher in the rpm band for a few more in the lower rpm band,and thats not always a bad compromise, because it tends to cool the exhaust valve and more effectively scavenge the cylinder.
you can help compensate for the tighter LSA with a supercharger,or nitrous in most cases by use of 1.6:1 ratio rockers on the intake and 1.5:1 ratio rockers on the exhaust

if you would rather have a supercharger/nitrous grind with similar specs, heres a couple,



http://www.cranecams.com/index.php?show=browseParts&action=partSpec&partNumber=119661&lvl=2&prt=5

E119847-4

http://www.pbm-erson.com/store.php?catId=691&parent=327


but as always have a long talk with a minimum of 5 of the cam manufacturers before selecting your cam and re-read this thread

viewtopic.php?f=52&t=82
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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