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Thread: Chevy 305 turned into a 340 stroker????

  1. #1
    Full Member claytonfrnk's Avatar
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    Question Chevy 305 turned into a 340 stroker????

    I have a 85 K10. When i bought the truck it had a tired 305 with a loud knock. Pulled the motor turns out to be the #7 and #8 piston were bouncing off the heads. I have a reman 350 to throw in the truck. Then i got a good idea. THe 305 wasn't in too bad of shape so why not rebuild it. Good idea turned bad and i did some research. THere is a company here is their website, www.speedomotive.com, claiming you can stroke a 305 into a 340. The crank is a 3.750 stroke and the pistons are 3.763 in dia. That is a 305 bored .030 over. The rods are 5.700 inch long. This sounds like a 400 crank, 350 rods, and pistons bored .030 over. I can get the crank, pistons, and rods for a lot cheaper than 755.00. To make a long story short my question is. Is their any special machining that anybody out there knows about that is neccesary for this 340 stroker? Or can i just piece my own custom kit together? And also what could be a ballpark hp rating for a 340 stroker.

    P.S. i called the company and they told be the rod lenghts.

    Thanks Guys

  2. #2
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    If you are gonna do a stroker why not put the 400 crank in the 350 and get 383 inches. You are now talking about equal machining dollars because the block will have to be machined to accept any crank. that is a free 48 cubes, and a much better combo. Having a good 350, and going backwards to a smaller displacement engine, does not sound logical. 350 blocks are a dime a dozen, and 5.7" rods can just about be found at the local grocery store. (personally I would use a 6.00" rod, the extra piston duration has big advantages, and relieves some cylinder side loads.) Unless I was racing a specific class that limited cubic inches to less than 350, this would not be the way to go for me.

  3. #3
    Full Member claytonfrnk's Avatar
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    The 350 has a 3 yr warranty so i don't want to mess with it at the moment. I figure why jsut rebuild the 305 when i can get a little more out of it. Just a thought.

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    A stroked 305 isn't bad.It will give more power.I prefer a stroked 350 to a 379,you want have the heat problems associated with boring to a 383. Just keep the 350 stock until the warranty is up,this will give you time to decide on what goodies to put in later

  5. #5
    Senior Member 87c10slammer's Avatar
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    from what i get from that he want to stoke the 305 not the 350. but besides that i would keep the 350 in there for know and build the 305 for when you wanna have some fun. both motors are really identical so parts are a dime a dozen and you should be able to put it together for less then 800. i know i saw a 350 kit on ebay for around 600 but am reluctant on getting it because i dont have a spare motor if it isnt any good and they only will replace the parts they send to you. but other then that i would go for it

  6. #6
    Full Member Shodrite1's Avatar
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    Im dont really know for sure on the 305. But I have built a few 302 into 347s I know its ford but cut me some slack.... anyway you will probably have to trim the bottom of the cylinders some to clear the rods...at least thats the bulk of the work to be done for the 302 to 347 conversion

  7. #7
    Senior Member chevyguy's Avatar
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    Quote Originally Posted by jlsavoy View Post
    A stroked 305 isn't bad.It will give more power.I prefer a stroked 350 to a 379,you want have the heat problems associated with boring to a 383. Just keep the 350 stock until the warranty is up,this will give you time to decide on what goodies to put in later

    Heat problems with a 383????? Its a 350 with 400 crank and rods. Now the 388 has a thinnner cylinder wall so if has a tad more heat, but nothing you cannot manage easily with a decent radiotor.
    The 400 is missing the center cooling jacket, They could have heat issues pretty quick if you let them.
    Window tint its for window, Not for tail lights. Don't be that guy .

  8. #8
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    i have had several 334 (305) strokers and 383s (350), no problem with either in late model chevy trucks!

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