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Discussion Starter · #1 ·
hi

my engine is chevy l6 250 with factory camshaft

now i want to change this camshaft to a new high rpm cams...

my info about factory camshaft is :
Basic Operating RPM Range: idle - 3800
Torque : 1800 195 n
horsepower : 3800 110h

my car is chevy nova 79 now my usage is street every day usage not race or drag racing or offload !!! just street and Routine using ..

i want to tune up this low rpm engine .

in my opinion this camshaft good for me :
http://www.summitracing.com/int/parts/cca-61-232-4/overview/make/chevrolet
or
http://www.summitracing.com/parts/crn-203901/overview/make/chevrolet
but in ur opinion what is the best for me ?

what is Lobe Separation (degrees): ?
my book say this value if go higher engine run in Smooth and nice idle and low rpm and middle rpm power is very good but this value go down engine run in lopy and rough idle and higher rpm is better power and torque but lower rpm havent power and throttle response is bad !
 

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have you already added headers/intake and carb? The 6 is quite low compression ratio,even the smaller cam listed might be big? If the engine is coming apart then that is the time to change cams to match the rest of the combo
 

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Discussion Starter · #3 ·
have you already added headers/intake and carb? The 6 is quite low compression ratio,even the smaller cam listed might be big? If the engine is coming apart then that is the time to change cams to match the rest of the combo
intake is offenhouser and carb is holley 4bbl
but i havent headers !
i will buy ...
 

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You asked what LSA is
LSA means lobe separation angle it is the anle of separation between the intake and exhaust lobe on the cam
LSA is an important variable that greatly influences engine behavior... as a rule of thumb the lesser the LSA for instance 104 degrees the rougher the idle will be and the lesser manifold vacumm will be at idle... if we shirnk the LSA that brings the valve events closer to each other...the opposite is true if we sperad them further away from each other...I think a cam is probably the least understood component in an I.C. engine...everyrhing has to work with it...IE valve springs xhaust and intake...tuning...headers...induction etc etc etc
If you want good idle vacumm and a small amount of performance gains choose one with about 106 LSA or so...but I would seriously study camshafts first...Call someone at Comp Cams...Crane Cams...Isky Cams and they will have some good advice for you..Im sure
I hope this helps
 

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Is the base engine stock? Are you concerned about mileage? That motor was built with notoriously low compression.

Both of the cams you listed will need more compression, the Crane especially. I'm runnning the 61-232-4 and my compression is just under 9:1 and it could use more. I'm running cast iron headers and my 250 likes to run at about 26-3000 rpms. But even with the bigger cam and more compression it is all done by 4500.

My opinion, if you are looking for just a cam swap only, then don't go much bigger than a Marine cam. If you want to go much larger, then you're going to need headwork (lumps) and more compression.

Check out inliners.org and click on the Tech Tips section and see the tab for cam specs.
 

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Discussion Starter · #6 ·
tnx a lot
http://inliners.org/tech/cams250.pdf
this data is good but what color meaning ?
Company ModelGrind Power Range Total Duration Total Lift0.050 DurationLobe Sep.

Chevrolet3864819Non-Integrated Head 270 / 270 @ 0.004 0.389 / 0.389 172 / 172 105
6262809Integrated Head 272 / 276 @ 0.004 0.389 / 0.406 172 / 188 102
3891590Mercruiser Marine 288 / 288 @ 0.004 0.403 / 0.403 192 / 192 112

the 3891590Mercruiser Marine is this factory cam for chevy nova sedan ?

my main goal is the standard engine tuning to one level up no very high

this camshaft is Too low rpm
http://img.overpic.net/images/1/a/b/x1abqzwowdf6tvu28f1tx.jpg
This specs is declared in Iran

i don't like loose vacuum in idle and i like economy engine i thing factory camshaft is bad for economy !

these are all camshafts for l6 250
http://www.summitracing.com/search/part-type/camshafts/department/engines-components/make/chevrolet/engine-size/4-1l-250/engine-family/gm-inline-6-cylinder?N=4294891642%2B4294949512&SortBy=Default&SortOrder=Ascending

plz help me
 

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The 250 inline is not good for fuel economy or power. It will cost a lot for improvements on either side.The engine has 60 year old design.converting to modern fuel injection will make a big improvement for mileage but its not going to be cheap
 

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Discussion Starter · #9 · (Edited)
The 250 inline is not good for fuel economy or power. It will cost a lot for improvements on either side.The engine has 60 year old design.converting to modern fuel injection will make a big improvement for mileage but its not going to be cheap
no no the l6 250 vs v8 350 or 305 have very lower fuel consumption
the Chevy nova and Buick skylark vs all American cars have lighter weight .( all available american cars in iran )

low weight and lower engine volume is important for fuel economy

now i dont have any selection on another car ! because i love American cars just american !

now 250 vs 350 have Great difference in volume

fuel injetction Almost expensive but what exactly diffidence With carburetor ?
and is this better than carb in power and torque or is bad ?!!

In my opinion if your going to keep most of the engine stock, you would like this cam,
http://www.summitracing.com/parts/cc...make/chevrolet
FWIW,
ssmonty
why this ?
see this compare :
http://img.overpic.net/images/j/c/v/xjcvxitwvo0sbjs387y.jpg

valve lift is important in camshaft then lobe and duration @ 0.050

one question about valve spring !
some of camshafts say valve spring is required what is meaning ?
another than factory ?
 

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inline 6 cylinder chevrolet engines of that era do not have a cross flow head and the long intake design makes for poor fuel distribution. The outside cylinders have a different A/F ratio compared to the middle. If you had 6 injectors the mix would be more even. That would give more power and less fuel consumption.

Like I said before,the design is 60 years old. poor fuel distribution,poor head flow,and lazy combustion chambers. By the time you re engineer the old 6 cylinder you could have purchased something more modern,,,Keep mods to a minimum,dont expect miracles
 

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Discussion Starter · #11 ·
inline 6 cylinder chevrolet engines of that era do not have a cross flow head and the long intake design makes for poor fuel distribution. The outside cylinders have a different A/F ratio compared to the middle. If you had 6 injectors the mix would be more even. That would give more power and less fuel consumption.

Like I said before,the design is 60 years old. poor fuel distribution,poor head flow,and lazy combustion chambers. By the time you re engineer the old 6 cylinder you could have purchased something more modern,,,Keep mods to a minimum,dont expect miracles
tnq
but fuel injection kit for this engine and for every cylinder have one injector is very very expensive !!!! my carburetor system with all like carb intake manifold camshaft headers is1000 $ just 1000$ but for buying a full fuel injection system must be a lot of costs ! like 2000$ or more
i pay 2 times money for import from usa !
2000$ = 2000x2=4000x35000 rials = 14.000.000 !!!!!!!!!!!!!!!!!!!!!
but carb = half of it
 

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Discussion Starter · #13 ·
Are you using one carb or 6 small ones. A single carb per cyl with custom manifold would be cheap if you can get motorcycle carbs cheaply. You can get someone local to machine some type of simple manifold. Anything over 20mm per throttle bore would be fine. Not an easy setup but if you can go with standard aftermarket parts may be the best way to make some better power.

A fuel injected 350 out of an older truck would make alot more power and only use a tiny amount more fuel. It also could get better milage if you drive it gently. A 350 will tug your car arpund town barley going above idle using almost no fuel. Where the low compression 6 you will be pushing it alot more rpm and using more fuel. Sounds strange but many truck owners here have found out a four barrle carb can get much better gas milage than a two barrel. Because of how hard it is driven when actual fuel consuption is figured. Of course wide open throttle the 350 will use more fuel but not nearly as much as you may think. Just depends on what engines you can get your hands on. Some jag engines also bolt up to gm transmissions.

Also the v8 parts are used in several countrys so you may find parts alot closer to hame for the normal v8. Could offset the cost of alot of gas.
tnq for replying

motorcycle carbs haven't accelerate pump and have Variable venturi ! and venturi connected ro the gas pedal ! if you fast open full throttle engine will be off !

I think there should be more about 350 and injection ... ( cost & buy & setup & ...)

tnx

TPI 305 would be the best performer/fuel economy combo that just bolts in with little wiring.
throttle body fuel injection ? like chevy caprice 1988
fuel injection
 
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