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| Need Advice Tuning Holley 390 / 8007 https://slantsix.org/forum/viewtopic.php?t=40310 |
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| Author: | wjajr [ Fri May 21, 2010 10:06 am ] |
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Got to the valve lash adjustment session this morning. I must have been consuming adult beverages during the last adjustment as they were a mess. Only problem with the theory is I don’t drink when working on the car, in fact hardly drink at all these days… Damn lipid pills. I E 1. 22 17 2. 21 22 3. 21 22 4. 21 20 5. 23 21 6. 16 20 Today’s adjustment, based on valve clatter, idle quality & vacuum gage reading ended up all intake at 0.013â€, and exhaust at 0.020†Than I took my vacuum gage for a ride, to see just what readings were associated with typical rpm, or road speeds. Generally the gage under light footed control read 8 to 15 inches of hg in the 1500 to 2800 rpm range or 20 to 50 mph on rolling hills. Up hill 8 to 10 Hg was normal, down that hill 17 to 18 inches of Hg. Than I decided to see what reading I would get at higher rpm, shifted into second gear ran the rpm up and down between 3800 and 4500 rpm. or 40 to 65 mph more or less. Vacuum readings jumped up a good five inches. From the third gear readings over the same few miles of road. So instead of seeing 13 “ Hg at 50 mph, I was getting 18’ of hg. This test at higher rpm never occurred to me to perform in past vacuum studies. While running in second gear going up a hill steep enough for a truck lane the car began exhibiting much greater acceleration rates feeling like a smooth solid surge of thrust. I’m guessing the secondary’s were opening when hitting 4000rpm and above under WOT. This engine pulls real hard over 4000 rpm., unfortunately this rpm range is unusable under normal driving conditions as she shifts in automatic mode at 4000 rpm, and that translated to 65 -70 mph which is ticket time around here on secondary roads. However holding the transmission in second for a run-up to 5000 rpm., taking advantage of the second half of this 4v, makes for a quick pass. I than headed for my red-neck dyno, the one at the dead end of my road for few test pulls shall we say… First test: ¾ mash of the go peddle while in reverse, less any braking, resulted in 15 to 20 feet of twin script on bare dry pavement. This test was conducted several times for consistency, and results averaged…LAL Car had never been able to do this before today. Second test: Power brake, mash peddle to the floor, and another 15 to 20 feet of vulcanized rubber was put down. These are old tires with lots of tread that are just begging to be recycled into street art… Third test: No power braking, just a full throttle jab from a dead stop, and she spun’em. This also was beyond its capabilities previous to this carburetor & valve lash tuning. Also I checked #2, 4, and 6 plug again. The 4,5, & 6 cylinders look to be running a bit leaner, #2 plug is defiantly trending leaner. Perhaps a larger main jet is in order. I’m current using a 51 jet. I recall reading the rule of thumb for jet size change is to jump up two or three sizes at a time. Is this true, I should be looking at possibly a 55 jet if the plugs continue to lighted up? A few of the old car guys from Downeast riding up this way to visit the [url=http://www.sealcoveautomuseum.org/contact.html] Seal Cove Auto Museum [/url]on Saturday. I will be joining them on route. This is perhaps a 100 mile round trip on secondary roads for me, which will afford a chance to get an indication if fuel consumption has improved. Even if it hasn’t, the car is running much stronger, so I am happy. |
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| Author: | hellion_locdogg [ Fri May 21, 2010 2:10 pm ] |
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Remember you are changing two jets at a time, I would try the 53 that I suggested. This will make your sec feel rich, but that means the sec needs tuning. ,Cliff |
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| Author: | wjajr [ Fri May 21, 2010 6:45 pm ] |
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hellion_locdogg: Remember you are changing two jets at a time, I would try the 53 that I suggested. This will make your sec feel rich, but that means the sec needs tuning. I realize that there are two jets on the primary side. However, my carburetor is equipped with a non tunable metering plate in the secondary side, no jets, accelerator pump, or power valve. I have a copy of a post by D.Idiot dated Nov. 21, 2008 explaining that the plate can be replaced with a kit consisting of a secondary metering block which main jets can be fitted He said that a 8007 came with 51 primary main jets, and secondary conversion using 52/53’s is common. |
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| Author: | wjajr [ Sun May 23, 2010 6:07 am ] |
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Based on Saturdays short cruse of a little over 100 miles, and a lot of foot in the throttle, just because it felt good (she pulls real good mid 3 to 4 K rpm), fuel mileage looks not so good, down to 16 mpg. I know this is a very small sample of miles. I’m thinking that perhaps I need to move up secondary spring strength a notch or two to. Would this help, along with less boot? If only one could see the secondary throttle plates opening while under way, they would be much easer to tune, or at least know at what rpm fuel consumption starts to increase. All of the charts I have seen for this carburetor show only two “popular displacement†engines for secondary activation rpm,. Surprisingly, 225 six ain’t one of’em. Plug up-date; they are looking real good, so I’ll keep my 51 jets for now. Now that the 2.5 power valve is installed, and engine shut-down takes place at a steady 900 to 1000 rpm., kick-back is 90% gone. Still an occasional clunk-clunk happens, resulting in extra cranking on next start. |
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