Stroking the 305 SBC

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econo racer
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Stroking the 305 SBC

Post by econo racer »

Anyone done it? I have a set of 400 rods just had ARP;s and reconditioned. I woud like to put them on the 305 pistons but then need some crank to clear the throws How much does that cost. I alrady bought the Comp cam hd flat tappet 268 hi intensity. Edelbrock RPM intake 600 dbbl pumper. It is gonna get hit 125 hp all day :shock: Might be going in a BUBBLE CHEVY
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Re: Stroking the 305 SBC

Post by rfoll »

The only way that will work is if you cut down a stock 400 crank main journals. Then it would need to be balanced. Stock 305 pistons are terrible unless you have the stock flat tops. There are pistons made for using 5.7 rods with a 3.75 stroke, and there are rotating assemblies. I have yet to see an aftermarket crank for the 5.565 rod.
So much to do, so little time...
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Re: Stroking the 305 SBC

Post by cardo0 »

Stroking a 305 is nothing new. You can find some serious efforts on Third Gen dot com if you try a search there. But I have never read of using the short 5.565" rods in a 305 block. Most everyone uses the 5.7" rod or longer. So I don't know where you can find pistons for that rod/stroke/bore. And I think you still have to clearance the block even with shorter rods.
With a 3.75 stroke you end up with something like 331ci.
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Re: Stroking the 305 SBC

Post by rustbucket79 »

The 400 rods allow any stock replacement 305 piston to work with a factory 400 crank with the mains reduced to large journal specs. Whether the counterweights will clear the piston skirts is another question, and standard 383 clearancing for the block applies. At least you won’t have to worry about cam clearance.
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Re: Stroking the 305 SBC

Post by JodyB »

Nowdays a one piece rear main seal rebuildable 350 goes for 300 bucks. No reason to build a 305.
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Re: Stroking the 305 SBC

Post by JodyB »

I am the pot callin the kettle black tho. I got a pile of 305's that will die by turbo😁 I'll learn then build a good motor
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Re: Stroking the 305 SBC

Post by ProPower engines »

Using a stock 400 crank is a waste of money and effort to fit it. A 3.750 stroke purpose made for the application is much more cost effective in the labor end of the build. Fitment time and the custom grind as well as the extra balance cost outweighs the savings of an old 400 crank cut down.
Yes we all did it back in the day before they were available and a PITA they were. Did a few so guys could run them in a 305 only class but they were so much extra work and the notching of the block for valve clearance to get a decent head to fit was really not worth the extra time to internally balance them to conceal the stroke gain and still run the small balancer and still wind up with a really short stock rod length.
While the power gain versus cost was that of making them about 12-1 ish comp and just using the longer 5.7 rod and piston combo's of the day was about the same in the end. And the 5.7 rod engines would rev much better
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Re: Stroking the 305 SBC

Post by Orr89rocz »

JodyB wrote: Sat Apr 11, 2020 11:31 pm I am the pot callin the kettle black tho. I got a pile of 305's that will die by turbo😁 I'll learn then build a good motor
They are perfect for learning boost and make good power. Just upgrade to a roller cam if not already, and upgrade valve springs to something abit stiffer if using the oem roller cam motors. I loved my rear mounted 70mm 305 tpi. 8 psi made it around 330-340 hp crank my guess compared to 230 stock lol. 110 mph traps at i think 3300-3350 lbs?



I would aggree if you want to stroke it just drop in a cheap cast stroker crank. Do the 5.7 rods and pistons.
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Re: Stroking the 305 SBC

Post by Walter R. Malik »

econo racer wrote: Sat Apr 11, 2020 5:09 pm Anyone done it? I have a set of 400 rods just had ARP;s and reconditioned. I woud like to put them on the 305 pistons but then need some crank to clear the throws How much does that cost. I alrady bought the Comp cam hd flat tappet 268 hi intensity. Edelbrock RPM intake 600 dbbl pumper. It is gonna get hit 125 hp all day :shock: Might be going in a BUBBLE CHEVY
Yep ... built several of then 30 or so years ago with machined 400" Chevrolet crank & rods to take the place of a 350 C.I.D. engine with throttle body injected pick-up trucks, for a fleet.

Worked very well with stock truck O.E.M. 350 injectors & ECM; only the cam we used was a Chevrolet 305 H.O. hydraulic flat tappet.
I think it is only around 202/206@.050"

I can't understand building a high performance street/strip engine, though. Build a 383.
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Re: Stroking the 305 SBC

Post by ProPower engines »

Funny you seen the same deal with the cam choice as I did.
It always seemed they ran the best with a HO 305 FT cam when using the stock injection system components and ECM.
Even just a stock replacement 350 cam was too much for the systems to handle #-o
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Re: Stroking the 305 SBC

Post by PackardV8 »

Walter R. Malik wrote: Sun Apr 12, 2020 1:12 pmBuild a 383.
Walter, I'm hearing Big Joe Sherman calling, "Hell, why does no one build 406"s any more?"
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Re: Stroking the 305 SBC

Post by Kenny M »

I built one on the cheap side for my Iroc.
103523750571 Eagle Crank $290
Scat 5.700 Ibeam rods 3-ICR5700 $250.
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Re: Stroking the 305 SBC

Post by rfoll »

330 cubes I think I would rather use a small journal 327. They can be had cheap these days
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Re: Stroking the 305 SBC

Post by Walter R. Malik »

PackardV8 wrote: Sun Apr 12, 2020 3:00 pm
Walter R. Malik wrote: Sun Apr 12, 2020 1:12 pmBuild a 383.
Walter, I'm hearing Big Joe Sherman calling, "Hell, why does no one build 406"s any more?"
350 blocks are easy to find and they are inexpensive; unlike the 400.
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