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Old 12-29-2005, 06:03 PM
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complete engine rebuild sb chevy 305

Hey i just started posting on this site and i am beginning to build a small block 305 from an 81 chevrolet 1/2 ton pickup that burned down 4 days after i bought it. the motor was the only thing i could salvage from the truck. The stock rochester quadrasuck carb melted down into the intake manifold. What i am doing is building a 305 from the ground up trying to get atleast 600 horsepower. Come to find out my crank shaft is forged steel. thats awesome but i was wondering if i could get bigger crank and stroke it out with some 6 inch piston rods. I want to bore it over 40 and run a weiand 6-71 or 8-71 supercharger. not sure yet but i want all the horses i can get. Any suggestions are definetly welcome and performance parts for sale are wanted. I really need a new cam the lobes on it are almost completely round.lol. and the lifters look like bowls that you could eat cereal out of i just got everything out of the block and on a stand today . But tell me what i should do to my 305

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Old 12-29-2005, 06:13 PM
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Welcome to Hotrodders...Pull up a chair and sit a spell...We are glad to have you with us. This forum is for introductions. You should ask your engine questions in the Engine forum.
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Old 12-29-2005, 06:48 PM
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welcome.....To get 600 hp, you will need a lot more than a 305 to start with.

BTW, moving this to engine forum.
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Old 12-29-2005, 07:14 PM
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I've never seen anybody try and get that kind of HP out of a 305, but it will be cool to see someone try, keep us posted
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Old 12-29-2005, 08:10 PM
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Man, the 305 is going to hold you back big time. 600 hp is going to need a lot of air flow and any cylinder heads capable of supporting that kind of power will have at least 2.02/1.60 valves, if not bigger. Correct me if I'm wrong but I dont think there is enough room fit valves that big in a 305. Also, if you want all of the horses you can get you need all the cubes you can get. You'd be better off bolting that blower on a stout a 406. Sure a 600 hp 305 would be pretty impressive but its asking a lot of such a small engine. What is the casting number on that crankshaft? Wasnt aware of any forged cranks for 305s...
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Old 12-29-2005, 08:46 PM
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Quote:
Originally Posted by Blazin72
Man, the 305 is going to hold you back big time. 600 hp is going to need a lot of air flow and any cylinder heads capable of supporting that kind of power will have at least 2.02/1.60 valves, if not bigger. Correct me if I'm wrong but I dont think there is enough room fit valves that big in a 305. Also, if you want all of the horses you can get you need all the cubes you can get. You'd be better off bolting that blower on a stout a 406. Sure a 600 hp 305 would be pretty impressive but its asking a lot of such a small engine. What is the casting number on that crankshaft? Wasnt aware of any forged cranks for 305s...

Since the 305 and the 350 share the same stroke, it could be possible to have a 350 crank in that 305. I'm not real sure, but I think they'd swap without any machine work on the throws. Nitrous will get you 600hp, if you keep the compression down around 8.5:1. As long as you don't mind walking (if) when it blows up, that is. For 600hp, there's no replacement for displacement. I'd love to encourage that kind of power from a 305, but realistically, a 305 is 300hp max. engine IMO.

Good luck all the same.


In a while, Chet.
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Old 12-29-2005, 09:16 PM
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Schnitz, I believe the 305s use smaller counterweights than the 350s.
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Old 12-30-2005, 09:44 AM
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Just my opinion here.

310 cubes x 130 % = 403 hp naturally aspirated.
You are looking for a 50 % hp increase using the blower. = 600

Tripling the power on a 305 will not be inexpensive nor conducive to longevity.

I think that you should rethink your goals and begin with a really super heavy duty 350 or 400, and consider 100 hp less for a total.

If you can't afford to do it right the first time, how much will it cost to do it over?

As I am prone to say: "Insufficient" parts work just fine right up to the time the engine explodes unexpectedly, suddenly, usually spectacularly, and certainly expensively.
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Old 12-30-2005, 03:03 PM
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its me

hey ok heres the thing i bought this 81 chevy 1\2 ton pickup and was told it was a 5.7 350 i was dissapointed when i pulled it out after my truck burned down and read the casting number on that crank im not 100 percent sure its forged but it makes the noise of a forged material. i know its very hard to get that kind of horse power out of a 305 but im going to try i also have a 350 that im starting soon. but the 305 is my project for now. i need to know exactly what i can do about the bore and pistons. i was thinking about using 6 inch rods. i also need to know valve size and pushrod size and what kind of heads i should use im pretty sure i cant use the stock heads and get that much power. I was going to put a 100 shot of nos and a 8-71 weiand supercharger. any and all suggestions and constructive critisism are welcome later.
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Old 12-30-2005, 04:22 PM
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If you're bent on souping up the 305 and nothing we can say is gonna stop you.......stroke it.

A 400 crank machined to fit the 2.45" mains on the 305, 5.565" 400 rods and regular old 305 pistons will do the trick. It might make 300hp and 350lbft of torque if you pick the right carb, intake and cam for it.

Get it balanced. If the shop you go to tells you otherwise.....walk out. Don't even bother discussing it. Find one that will do as you ask or recommend it before you ask.

It'll be a learning experience if nothing else.

Larry
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