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| How high CR on 91 octane? https://slantsix.org/forum/viewtopic.php?t=27046 |
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| Author: | Ineptnewb [ Thu Feb 07, 2008 12:40 am ] |
| Post subject: | How high CR on 91 octane? |
I have an Australian 1974 VJ Ranger XL - currently running it on 91 with factory compression @ sea-level - the whole thing is stock, with a 245 and twin carb. I understand it something of a fuzzy question, but hoping for some input as to what I might be able to push the compression ratio to - especially if anyone has increased theirs. Ultimately, I'm hoping to improve economy and power, but with the least amount of change ie as stock as possible - I was thinking of changing the pistons to increase CR - far less drastic than turbo-charging... |
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| Author: | Aggressive Ted [ Thu Feb 07, 2008 10:16 am ] |
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I am running 9.5 CR on my Slant Six and can use either 89 or 92 octane with out pinging. My 440's are 10 to 1 and we use 92 with no pinging or detonation. The key is to recurve the distributor. |
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| Author: | Doc [ Thu Feb 07, 2008 10:17 am ] |
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What is your current static compression ratio? What is the "cranking compression" in PSI, taken in all cylinders with all the plugs out and throttle wide open? Does your current combination ever ping or spark knock using 91 R/M fuel? DD |
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| Author: | Ineptnewb [ Thu Feb 07, 2008 10:23 am ] |
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Hey - thanks for the look in guys. Current is 9.5 - haven't tested cranking. No pinging or knock currently. Seems to me CR is already fairly high - I'm thinking not too much as far as performance gains to be had by increasing it just a couple... |
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