305 camshaft selection

[woodbryce20]

So i have an 85 c10 with a 305. The motor is stock for other than long tube headers, an edelbrock preformance intake manifold and an edelcbrock 400cfm carb but i also have a 600cfm i can use. I wanna put in a new cam but am not sure what to look for. I think a roller with hydrolic roller tappets would work but am not sure of duration or lift to use and what to lool for at all really. Lookin for something with really great tone and as agressive i can get without too many mods. Would like to keep everything under $800. For cam, tappets, push rods, springs and rocker arms. Any help would be appreciated

 

[1987 GMC Jimmy]

@rich weyand is good with these questions.

 

[rich weyand]

Well, I don't know anything about rollers. Flat-tappet stuff, sure.

Read this thread for starters, beginning with this post:
http://www.gmsquarebody.com/forum/showthread.php?t=16990&page=3

 

[Rusty Nail]

A 1985 block isn't machined to accept a roller camshaft and lifters...Does that help?
Swapping to the 600 is good for horsepower, the 400? is costing you.

 

[RThiel]

The simple fact of the 305 engine is that it isn't very efficient at moving air due to a variety of factors. Small valves, small cylinder bore diameter, and low compression are the main contributing factors. The engine was designed to be a fuel efficient, yet torquey engine for pickups. I can tell you honestly, up-front that your engine will not be able to realize the full potential of a rollerized valve train. The power that is gained from a roller cam and lifters doesn't really present itself until the higher RPMs with high flowing heads, and even then, you don't get the benefits driving it on the street. If you want a good streetable cam, that will make power in the idle -4500 rpm range, stick to a hydraulic flat tappet cam, and look for something with an advertised duration around 260-262 and a lift somewhere around .440-.450. It should respond well with the 600 CFM carb, although that may be a bit too much carb. The people at Summit and Jegs can help you pick a specific camshaft in that neighborhood and it should be well under you $800 price tag. It should have a fairly decent rumble and will give you power in the RPM ranges that you will be actually driving in. Just like carburetors, there is such a thing as having too much cam.

 

[1987 GMC Jimmy]

I agree with the above. I will say, however, that you can make those 601 heads work a little better if you wanted to get them ported and polished. There's only so much you could do to them, but they'd probably be almost as or as good as the Vortec 305 heads. Head work mated with a good hydraulic flat tappet cam would be good for the sound you want and the power. You could go further by delving into the exhaust and intake, but that's about it. I feel like you could make it a 300 hp motor with the heads worked, a good cam, exhaust, and a solid ignition system. That plus getting rid of stuff that drags on the motor (i.e. AIR pump). I think the 600 CFM carb would be too much. Not a lot too much but still. I think the 400 would be too little with mods. I'd say as it sits right now, the best carb would be a Quadrajet with the second best being like a Holley Economaster or something. If you did upgrade it, I'd say the best carb would be a Quadrajet with the second best maybe being a 500 CFM Edelbrock. Point being, I think the Quadrajet would be the best way to go, but there are other options. I will also say that I don't know what kinds of bells and whistles you have on your truck, but I question how your vacuum operated devices would like a mean cam. It's an '85. It's got to have at least one thing that wants stable vacuum, even if it's just the power brakes. I'm not saying get a near stock cam, but a super lopey one may get old if things that you like in the truck don't work right.

 

[rich weyand]

From the thread I linked above:

"A "lope" means the engine is uncomfortable running at idle. So how much torque are you going to have at 1000-3000 rpm? A lope in a V-8 is the natural result of being cammed for horsepower at 5000 rpm and above. How often do you drive at 5000 rpm? If you're a racer, ALL of your driving is at 5000+ rpm. That's why racers have a lope. A street-cammed engine for driving will idle smooth as silk, and come on hard with tons of torque from the get-go, because it likes running in the low rpm range."

Get a nice, torquey cam like the Comp Cams 12-345-2, and you'll be very happy.

 

[Camar068]

Not sure what a set of 305 vortec heads would do for you. You'd have to get a new intake as well (ebay) for $125.

I'd let the other guys chime in on it before pulling the trigger. I tried googling it, but all the articles I read were putting 350 vortec heads on it and the required some work before installing. Which I'm sure would put you over the $800 mark.

 

[MikeB]

I see where the Edelbrock 500 cfm and 600 cfm carbs have the same primary and secondary venturi sizes. Secondary jets are the same, but primary jets are smaller. So I guess that means there are different primary boosters that impede air flow in the 500, but possible atomize the fuel better.

That said, there are plenty of guys running the 1406 600 cfm carbs on 283-327 Chevys and 289-302 Fords with no issues at all. Would be interesting to see if going to a 500 on those engines would make a seat of the pants improvement in throttle response. Also, the 500 might make for better fuel economy.

Tell us more about your Edelbrock 400 carb. What is the model number on the base plate? Can you post a picture?

 

[Rusty Nail]

Yes. We want to see an Edelbrock 400.
Post pics.

 

[74 Shortbed]

Never heard of a 400??????????????..

 

[Rusty Nail]

I can't recall ? It don't matter, he ain't got no pics.

But seriously, eww.

 

[Chevymanforlife]

comp cams is the way to go my friend is running a 12-239-3 cam in his 305 with comp cams lifters and push rods with ebay roller rockers sounds bad ass and it gained some pretty good power torque gained the most he hauls with it and tows does great btw im doing the same build as him with a holley 600 cfm carb good luck and build that 305 dont ditch it for a 350