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Help with a land speed ls engine

General engine tech -- Drag Racing to Circle Track

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jjump59
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Help with a land speed ls engine

Post by jjump59 » Fri May 15, 2020 8:30 pm

Planning stages of bonneville engine for the b class (439.9 CI or less). GM LSX cast iron block, tall deck with the edelbrock LSR heads. My question is how should I go about getting those cubic inches? Short stroke/big bore or big stroke/small bore?

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Re: Help with a land speed ls engine

Post by Coloradoracer » Mon May 18, 2020 6:48 am

Bigger bore will net more gains than bigger stroke. It helps with how the heads breathe by unshrouding valves. The way I was taught, bore first, then stroke. Stroke is used to gain cubic inches when you have no more bore available. Shorter stroke will also help reduce frictional losses over a longer stroke. Many might disagree with me on this, but that's ok. One more thing to think about with stroke is piston package. The longer the stroke, the shorter the piston has to be to get the ring package on it. On the rod length, you're going to hear "you need a rod ratio of XX". I'm going to tell you don't concern yourself at all with rod length...Warren Johnson said it best: Pick your piston and ring package, and your stroke, and connect them. Rod length doesn't matter nearly as much as many would lead you to believe. There simply is no "magic rod ratio". Determine your bore and stroke. Determine your ring package, then connect the piston to the crank. Let the rod length be what it's going to be....nothing wrong with juggling things a little bit to use a standard rod either, to save on custom parts.
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Re: Help with a land speed ls engine

Post by gunt » Mon May 18, 2020 4:18 pm

from memory

600lb tq and 380bhp will not brake 200mph but 450 tq and 450bhp will ,[ from an evo ]
alot of high speed runs always go for bhp so its bore, and i have seen some keeping with in a cc rule , the salt lake guys have always gone for destroke , and keep the bores to the max

although this is not v8 info

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Re: Help with a land speed ls engine

Post by CamKing » Mon May 18, 2020 4:31 pm

For any type of racing, like Bonneville, go with the biggest bore you can safely fit, then go with the stroke that gets you to the target CID.
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Re: Help with a land speed ls engine

Post by Joe-71 » Mon May 18, 2020 5:04 pm

I have to disagree with any rod length, when going for 5-7 miles at maximum rpm. There I would use the longest rod possible with big bore and stroke needed for cubic inches. That is a long time to keep the rpm at maximum without lifting. Joe-71
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Re: Help with a land speed ls engine

Post by gunt » Mon May 18, 2020 7:00 pm

although i do agree with rod , especially for high rpm

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Re: Help with a land speed ls engine

Post by tenxal » Tue May 19, 2020 7:06 am

Honestly, I would contact Warren and Kurt Johnson. They have a lot of expertise with the LS platform and have done work with it for a Bonneville project. A local racer has had great success with their LS engines.

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Re: Help with a land speed ls engine

Post by jjump59 » Tue May 26, 2020 12:53 am

Thanks for the advice guys.

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