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| 225 Build - Compression ratio and camshaft suggestions? https://slantsix.org/forum/viewtopic.php?t=68369 |
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| Author: | 1972.Fargo [ Sat Sep 27, 2025 5:40 pm ] |
| Post subject: | 225 Build - Compression ratio and camshaft suggestions? |
Hi all, I'm in the midst of tearing down a 225 from a John Deere to put in my 1972 Fargo 1/2 ton pickup. The goal of this venture is to get the best fuel economy I can. The #2 cylinder seems like it will need to be cleaned up so the engine will be going off to a machine shop once I figure out all the machining I want done. I'm hoping to raise the compression ratio and possibly put in larger valves. This has left me wondering what compression ratio I should be aiming for. It's my understanding that a higher compression ratio will achieve better fuel economy, but the higher octane gas required for higher compression engines costs more... I could back off the ignition timing to lower the cylinder pressures, thus allowing myself to use lower octane fuel, although I'd expect that to lead to a less efficient result. I guess I'm wondering if there's an optimal compression ratio that would net me the best "$/Litre : Litre/100km" ratio. I'm hoping to be pretty thorough with the assembly and tuning of this engine, so I'll be porting the heads, smoothing out any protrusions that could become "hot spots", tuning to the best ignition curve I can, and selecting a camshaft that would work best (which leads me into another question). I'm not all too familiar with camshaft numbers, the research I've done leads me to think I should be getting a cam that has good low/midrange torque, thus minimal valve overlap and relatively large lift? Duration I'm guessing would be limited by the LSA/valve overlap? Any suggestions on camshafts would be appreciated. I'll need to figure out which cam I want before I'm able to determine how much I need to get milled to achieve the right dynamic compression ratio. The intended use of this truck is a road trip rig, maybe a camping setup in a low-profile bed cap. It's a 2wd single cab with an 8' box. I plan on lowering it and doing some aerodynamic additions to reduce drag. It's a basic truck, no P/B, no P/S, no A/C. I'd like to put 2.9 gears in it (which should get me around 1600RPM @ 110km/h with 29" tires). I'll be putting an A-833OD behind it. I also hope to put on an aussiespeed hurricane 2bbl intake, headers into a short 3" single exhaust, and a 300CFM Holley 2bbl carb. I'm new to all of this, this will be the first engine I build, so any advice is greatly appreciated ◡̈ Thank you all in advance! |
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| Author: | SlantSixDan [ Sat Sep 27, 2025 5:47 pm ] |
| Post subject: | Re: 225 Build - Compression ratio and camshaft suggestions? |
Camshaft: Dutra RV10RDP, Oregon Cams grind № 2106R. |
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