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Old 11-18-2012, 09:31 PM
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Performance Chevy 305 (Don't hate me)

So i just finished rebuilding my first engine, its a 1984 Chevy 305, don't hate me for that, haha. Anyway i am running an 11:1 compression ratio and a mild cam, how much horse power can i expect to get out of it?

Cam specs:

Intake Duration at 050 inch Lift: 234

Exhaust Duration at 050 inch Lift: 244

Advertised Intake Duration: 292

Advertised Exhaust Duration: 302.

Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.


Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.

Lobe Separation Angle: 114

I am also using an intake and Quadrajet carb off a late 70s Chevy 400

I just got it mounted on the break-in stand and will be firing it up one day soon!

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Old 11-18-2012, 09:44 PM
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you check piston to valve clearance?
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Old 11-18-2012, 09:45 PM
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depends on what your heads flow on a small bore? 240 plus?
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Old 11-18-2012, 09:50 PM
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The pistons do clear the valves, and i am not sure what the heads flow, how could i find out?
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Old 11-18-2012, 10:04 PM
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you need a flow bench.The bore size has to be adjusted to match your engine.The tech will take readings at .3,.4,.5 inches of lift. with near stock parts you will get moderate improvements over stock ratings
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Old 11-18-2012, 10:13 PM
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I believe the heads are stock except they were milled down from 58cc to 54cc, i was told that would be close to an 11:1 compression ratio and i am using the cam listed in the original post
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Old 11-18-2012, 10:24 PM
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that cam with stock heads and high compression,stock intake and carb? what about headers and exhaust?Lets ask techinspector to do a cr cam match for you
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Old 11-18-2012, 10:29 PM
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The intake and carb were off a late 70s Chevy 400 engine, right now the engine is on a break-in stand and as far as exhaust all i have on it is headers, they have 3in outlets, thats all i know about them, i am borrowing them
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Old 11-18-2012, 10:58 PM
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I think that cam is a poor choice for the parts you have listed
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Old 11-18-2012, 11:00 PM
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Like i said this is my first build, i am just trying to learn. Why do you think it is a bad choice?
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Old 11-18-2012, 11:08 PM
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Thats not a Mild cam" when used in a 305. It will have lame power below 3500+ rpm.
Will need a loose very high stall race converter and very high rear end gears.
Event the best of the 305 heads have very modest port flow in stock OEM form.
Don;t expect big power from this motor with stock non ported cylinder heads.
If you were to fully port the stock heads and use a better intake+ headers it would make some power

The engine will be a dog below 3500 rpm . No torque and won;t make the big power you think.

The compression ratio will not be even close to 11:1 without a domed 305 piston.
with a flat top 305 piston and .040" gasket and 54cc heads the cr will be almost 10:1
I hope you got some 4.56 gears an a 4000 stall race converter..

Good thing there are many more cams to choose from.
pick a much smaller camshaft that matches the vehicle, engine and purpose.

To get the 305 to idle with this big cam in it lock out the distributor mechanical advance system and set the locked fixed timing at 34-36deg BTDC, then plug the vacuum advance to the ported vac source on the carb. Big cammed motors need a lot lot of spark advance at idle to idle nice.
Otherwise it will cough spit, heat up, back fire and stall etc etc. 34-36deg locked timing at idle.

what is the Vehicle this motor is going into?

Last edited by F-BIRD'88; 11-18-2012 at 11:19 PM.
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Old 11-18-2012, 11:12 PM
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Quote:
Originally Posted by twenglish1 View Post
So i just finished rebuilding my first engine, its a 1984 Chevy 305, don't hate me for that, haha. Anyway i am running an 11:1 compression ratio and a mild cam, how much horse power can i expect to get out of it?
We don't hate ya. Congratulations on your first engine. Now you can spend the rest of your life trying to build your "BEST" engine.

Horsepower? Well..... not much i'm afraid.

First rule of engine building: "there is no substitute for cubic inches"

Second rule: "power-adders are your friend!"

Third rule: "be rich. this is not a poor mans hobby"

( That's all for now. Good luck )

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Old 11-18-2012, 11:17 PM
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Quote:
Originally Posted by twenglish1 View Post
Like i said this is my first build, i am just trying to learn. Why do you think it is a bad choice?
Nothing wrong with wanting to learn. We all had to start someplace.

Your cam is bad, but even worse... you started with a 305.
It's okay though. I'm sure you learned some good lessons you can apply to your next engine build.

( Think: CUBIC INCHES )

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Old 11-18-2012, 11:19 PM
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Originally Posted by 632Mantis View Post

Horsepower? Well..... not much i'm afraid.
Think it could be close to 300 hp? even though i would be happy if it just runs
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Old 11-18-2012, 11:22 PM
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Quote:
Originally Posted by 632Mantis View Post
Nothing wrong with wanting to learn. We all had to start someplace.

Your cam is bad, but even worse... you started with a 305.
It's okay though. I'm sure you learned some good lessons you can apply to your next engine build.

( Think: CUBIC INCHES )

Whats wrong with the cam? too big for the 305?
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