Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - need help with choosing the right combination..
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Old 09-27-2008, 03:35 PM
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j.d.brown.042964 j.d.brown.042964 is offline
406 Caprice:Rust Never Sleeps!
 
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The choice of of runner volume and valvesize should be matched not only to the displacement, but also to intended USEABLE rpm range as well. Everything has to work well together, AS A SYSTEM, to get the best results. As far as 5.7" rodlength, that is what is most popular and "standard" to 350's, although with a change of pistons (having different wristpin location) some builds might use 6.0" rods for reasons specific to that PARTICULAR build. In addition to the WIKI forum, you can gain alot of useable information from searching the knowledge base on this site as well. Many of the factors you need to consider will revolve around what rpm band you will primarily use this engine for. Smaller intake runners will keep lo-rpm velocity and give great torque in the lower rpm range, great throttle response, best overall economy (due to actually UTILIZING most of the fuel mixture being supplied), -but at something of a loss of higher rpm horsepower. Valvesizes figure into this somewhat as well. AS a generic example; a build of a 434 (stroker) smallblock would do very well with 230cc intake runner size and 2.055, or 2.08 intake valves, even at 5500 max rpm,simply due to the larger cubes to fill, whereas to be of any use at all on a 327 you'd have to spin it to 7500 for those sizings to be of benefit, and it would have poor combustion below 3000, (and require a bulletproof bottomend to do so on a continual and ongoing basis). Cam duration and overlap plays into this "usage" equation greatly as well. I would suggest that if you like the shortblock that you are considering, you spend a good deal of time researching what topend components would work well with the existing pistons/cam combo. and choose accordingly. Better to spend alot of time reading now than trying to undo a mismatch later. It appears that's what you are attempting to do now, by asking these questions, and that is well-advised. Try some searches on the knowledgebase and the wiki articles with a few different keywords and/or phrases, and you'll be well-rewarded with very useful stuff. Also check back to this post, as there's some really great knowledge in many of these members years of experience(s). Happy Reading. -Jim.
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