Thread: Want 300hp out of chevy 305...?

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What's the cheapest way to bring a 305 to 300hp?

new heads, carb, cam etc. but it still wont be cheep

I was thinking of having the motor rebuilt, new intake and carb to match with the cam...new head also?

youll need more flow and probably more compression which will both come with aftermarket heads

Get on the internet and type in 305 chevy engine buildup. They have a post on how to get 325 out of your 305.

Thanks Chevy37!
I'm not sure if i did find exactly the same link that you said but i found very comprehensive material...will do my homework tonight.

If i do have to change the heads on my 305, what should i be looking for and how much should it cost?

Thanks for all the infos you guys!
I learned more in a few hours than spending week-ends in speed-shop talkin to some big-eggoed smart-ass (usually, also big)

Thanks again and let's talk more soon!

L31 Vortec cast iron heads GM #12558060.$400.00/Pr/assembled

Thanks again Chevy 37 for all your help! I really appreciate it!

I called GM and they told me that they do have them in stock, for 546$ Can (exchange fee...ugh!)

So that would give me what's needed?

Do you have any advice as for what kind of crank i should put in? What duration?, What kind of carb? (Someone told me only Ed makes them now???)

From what i read this week-end, i need the right heads, with the right cam, with the right exhaust sys, and with the right intake...

Is that all?

Thanks again!

OK, I'll jump in here and give you my two cents worth, even though I normally would advise against trying to build horsepower with a 305.....

Bore the block 0.030" and use Keith Black #KB143 hypereutectic pistons with a 5 cc valve relief notch. Pay close attention to their recommended piston to bore clearance and ring end clearance.

Cut the block deck so that the pistons pop up out of the bore by 0.006" at TDC.

Use World Castings iron heads #042650-1 assembled with springs for 0.560" lift. These heads are designed for use with the 305 block, using 1.94"/1.50" valves and 58 cc chambers. Bolt 'em on with Fel-Pro #1003 head gaskets, 0.041" compressed thickness. With the pistons popping up 0.006" and the 0.041" gaskets, your squish will measure 0.035" and allow you to run on premium pump gas with the calculated 9.94:1 static compression ratio.

Use an Edelbrock Performer Air-Gap intake #2601 (not the RPM model) and a 600 cfm carb such as the Edelbrock #1405 manual choke model. Manual chokes work every time and are bulletproof.

Use a cam with somewhere around 225* duration @ 0.050" such as a Crower #278H or Comp #XE268H or Crane #284H12 or Isky #270/280 Mega Hydraulic or Summit #SUM-K1104.

Use 1 5/8" headers with no larger than 2 1/4" pipes.

That's how I'd build one for 300 hp. I'd also make provision for offset dowels in the cam gear to play with advancing and retarding the cam by as much as 8 degrees either way (or use an edelbrock Hex-a-just #7331 timing chain set for plus or minus 6* using a hex key). Use 12* ignition lead at the crank and 22* centrifugal lead all in by 3,200 rpm's. I'd also use a 2,200 to 2,500 rpm stall converter to get up on the cam right away.

If I were building a 350, I'd go with Chevy 37's suggestion of the Vortec heads, but on the 305, I'd use the World heads because of the cost of modifying the Vortecs to use a cam with enough lift to make the 305 work. Vortecs are limited to about 0.430" lift as manufactured unless you opt for the modified heads or modify them yourself. The intake runners on the World heads will be more 305-friendly also.

I built a simialer 305 to what Tech suggested & believe it to be 300+ HP. KB143 pistons. block decked to "0" I used a Comp Cams XE256, Corvette L-98 aluminum heads, Performer Intake, 570 CFM Holley, 1 5/8" headers, 2.5" dual exhuast dual high flow cats & dynomax turbo mufflers, Pertronics HEI dist.
I had it in an 86 GMC Caballero with 3.08 posi, ran 13.70s & very consistant. didnt 60 ft the greatest, wasnt a real tire smoker eaither...3.42s woulda helped.

Tech Thanks for giving him the info he needed. On my 305 which was dyno at 280 at the crank, I went back to thedual plane intake with a 600cfm carb. I run a comp cam with a 218-224 dur.050 lift .462-.469 with the engine bored to 315. My pistons are Federal Mogul Hyperautectic flat top pistons. The weak spot on this engine is the stock heads. Compression is 9:2. With either vortec heads or world casting heads I probably pick up 30 HP and same torque. Of corse my 2:76 gears don't work well with this cam.

Thanks all you guys!

Great having all this infos!

I'm learning as much as i can, but i now realize thta i'll have to take my time to do it right...

Thanks again to Chevy37 for the great link (chevy305enginebuildup); i think i read 150 pages in the last 3 days...great infos.

I'll let you know how everything goes!

Does anyone know what kind of suspension parts should i buy to lower my ride 1 inch and bring it to be more rigid?

What kind of coils and shocks?

Can it ever be too stiff?

Rsvp