I just bought a 305 tbi and the first thing i heard outta my bro's mouth was "cam, upgrade the cam" only problem is i live in nevada and from what i've heard emissions is gonna be a problem if i upgrade to a too "radical" cam....what's the max cam that i can safely use?

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The Car : 1991 Firebird V8 305 TBI, White, T-tops

IM : Shadwbeast

 

Without getting too technical, your bro is right. The cam they put in that motor sux big-time. It might possiby be the worst excuse for a cam that Chevy ever put in a small block, worse than even the ones that they used in the mid-70s when power was so bad. You are also correct that too big of a cam will cause emissions trouble; however, it also may make your car run worse than it already does. Here's the biggest one I would suggest:

COMPETITION CAMS CAMSHAFT SPECIFICATION SHEET

PART # 08-300-8
GRIND NUMBER: CS 262H-R12
ENGINE: CHEVY SM BLK 305-350
INTAKE EXHAUST
VALVE ADJUSTMENT HYD HYD
GROSS VALVE LIFT .450 .480
.006 TAPPET LIFT 262 264
VALVE TIMING OPEN CLOSE
AT .050 INT 5-BTDC 31 ABDC
EXH 41 BBDC 11-ATDC
THESE SPECS ARE FOR CAM INSTALLED
AT 108 INTAKE CENTER LINE
INTAKE EXHAUST
DURATION AT .050 206 210
LOBE LIFT .3000 .3200
LOBE SEPARATION 112
THIS CAM SHOULD USE SPRING # 981-16

Believe the spring recommendations.

You need something with an intake duration below 210°, and at that duration, a lobe separation above 112°. This cam is speifically made as a replacement for the stock one in your car and may even have a CARB number. You can call Comp's tech support and get more info if you want to, 800-999-0853

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"So many Mustangs, so little time..."

[This message has been edited by RB83L69 (edited January 15, 2001).]

 

I'd tell your bro he is right, but before you fix that crappy cam, you need to do somthing about the just as crapp exhaust. Get a good set of TES 1 5/8" headers, gut your cat if you want, and get a good, mandrel bent 3 inch cat back from hooker, edelbrock, flowmaster, ect. You need to make the engine breathe better through its exhaust before you shove a largre cam into there. Plus, once the exhaust is opended up, you will have the advantage of being able to get a larger cam than you could for the stock motor and it will remain just as driveable.
A good rule of thumb is to ALWAYS start modifying a car's exhaust before anything else, it is almost always the most restrictive part of the car.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: LT4 Hot Cam, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Gutted Catalytic Converter, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, Fully Ported TPI Plenum and Base, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

 

Wow...thanx for the info guys...i really appriciate it...and thanx for the specifics RB, i'll look into it, and dan, am i still gonna be able to pass emissions if i "gut" my cat? and what exactly does it mean to "gut" it?


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The Car : 1991 Firebird V8 305 TBI, White, T-tops

IM : Shadwbeast

 

ok i can help alot on this one i had tbi "had" i went to a carb because with tbi its twice as sensitve to even a mild cam change .comu cam or not. if you stay with tbi be real carefull what cam you use !!! just a warning trust me i have worlds of experinece in that area!sorry i forgot to expain the emmisions stuff be sure to find a cam and before you get on call the company and make sure its 50 state legal( i should talk i have no smog eqipment what so ever)..... well i make lots of smog!!:-)

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods performer rpm air gap intake (polished) and 600 edlebrock carb, comp roller cam, and way better headsa 400 defintely in the works!

[This message has been edited by burnoutrpm (edited January 16, 2001).]

 

Uh oh...I know i'm gonna get stoned or burnt at the stake for this one but...i thought tbi and carborated where the same thing? What's the difference? Thanx for your patience and help guys...

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The Car : 1991 Firebird V8 305 TBI, White, T-tops

IM : Shadwbeast

 

ok heres the difference tbi starts and carburation doesnt so well!! and carb gives more high rpm horsepower, tbi just sucks plain and simple i went from tbi to carb and 350 and gained fuel milage ( for a while ) i have aqjunk) for now untill i get another 600 edlebrock!
oh yeah tbi has injectors!??

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods performer rpm air gap intake (polished) and 600 edlebrock carb, comp roller cam, and way better headsa 400 defintely in the works!

 

"gut" to hollow out

 

Nice cam pick as usual RB...

As for gutting the cat, you can pass emissions without it, but the car has to be running right.

I'd go with the exhaust first, its easier to deal with than a cam swap.

 

A TBI fuel injection unit is basically a carburetor shell with an injector or two poised above it. The carb shell meters the air, the injector meters the fuel (no more float/bowl/needle/etc).

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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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