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How much h.p. with mild 305?


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Guest Anonymous

Hey guys, cool site.

Anyway, I recently pulled a low mileage 305 and 700r4 from a car a relative had sitting in his yard. I know that the 305 isn't the hot ticket for a swap, but the price was right ($300. for engine and trans). My question is how much power can I expect if I do a mild rebuild? Parts list; Performer intake, carb, and cam., 9.1 comp. headers, etc...

I know that I can build a real scorcher by just switching a few parts but I don't expect the engine to ever see the high side of 5000 rpm with the 700r4. Roughly, what kind of power do you think I might get? I only ask because I read all the threads re: rollbars and subframe fortification. Thanks!

 

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jer

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Though I've annoyed some people by saying this, I really think that moderate performance cars don't really benefit from roll cages etc.

 

My guess is that your stock 305 conservatively makes about 160 hp and 220 ft-lbs of torque, in real-world numbers. A more precise estimate would depend on the head casting (and valve size, and many other things). With a decent dual-plane intake manifold, four-barrel carb, 1 5/8" block hugger headers, mild cam and a little tuning, plan on about 220-250 hp and maybe 280 ft-lbs of torque. If that feels like too little, consider that my '78 454 big block, with 149 more cubic inches and a much better head design, only makes 215 hp stock, because in stock form it signs off at around 4000 rpm, if that much.

 

My admittedly unexperienced opinion is that it's better to do the conversion with the stock engine, and then hop the engine up, once the car is running and you've comfortable with the setup.

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Michael is right, with the right combo you can achieve those numbers. You gotta remember the 305 was built with fuel economy in mind But it's a decent runner and with some aftermarket parts on it, you'll get some good results. With a shift kit in the tranny same thing, but if your building this for the street for daily thumping...I mean driving modified 305's pretty good.

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Last fall Hor Rod or Car Craft did a build up of a roller 305 motor. I paid particular attention because a guy was gonna GIVE ME two motors that needed overhauling. The magazine put on the Edlebrock matched system including heads and got 345+ HP and close to 400FT# torque. That motor has some potential. The big attraction to the 305 is the fact that you can use the lower end of the performance spectrum to get some respectable numbers.

 

If it were me, I'd use the setup you are mentioning with the parts you mention, set the motor and trans up, de-bug the car and drive it some, and wait. Look in the ads for a good set of used small block aluminum heads, and snatch them when the price is right. Then you'll be set. Nothing wrong with a 305 in a 2700# car.

 

Mike

 

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"I will not be a spectator in the sport of life!"

mjk

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Guest Anonymous

Thanks everybody! You all confirmed what I had estimated, and it's nice to know that I can build a respectible little car with the parts that I have. There will be many more questions to come as the project continues.

Later

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Jerry, the 305 got kind of a bad rap because it was an "econo" motor but (other than the dished pistons and thin cast large chamber heads) it a pretty good SBC. Listen to Mike and get a good set of aluminum heads but make sure they are ~64cc unless you want to change the pistons. 64cc with stck pistons should give you right around 9.0:1 compression. Because the heads are aluminum you should be able to run regular fuel unless you go crazy with the timing. Loosing the extra weight is good and you will replace the only real limiting part of the engine.

 

I would however, suggest you consider a little better cam. I think you will find the econo version has very little duration. With a nice set of heads, alum. intake and new carb you will want it to breath just a bit better. Look for a nice "torque" cam that isn't going to be lumpy for your daily driver.

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