Re: Carb help!
[Re: RustyM]
#2735306
01/21/20 03:28 PM
01/21/20 03:28 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
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I Live Here
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Love my VP-101 OXY Unleaded fuel.............
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Carb help!
[Re: RustyM]
#2735324
01/21/20 04:11 PM
01/21/20 04:11 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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I Live Here
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We did dyno testing on our known 512 /10.75 /trick flow heads engine to find out what fuel it liked and, yes, race fuel is certainly most consistent, but the engine made best power at 93-95 octane. 100 octane lost 15 hp, no timing adjustments or carb adjustments would bring that back. 110 race fuel lost almost 25 hp. I’m not going to say you didn’t see the results you’re claiming........ but I will say this....... In 30 years of dyno testing, I have never seen a loss like that by running race gas, no matter how low the CR of the engine was. Unless........ the race fuel was stale. If you had fresh 93 summer blend, and a sealed 5 gal can of VP c12....... and dynoed the two back to back on a 600-700hp TF headed 10.75:1 BB stroker with a known good carb on top...... fuel curve and timing all sorted out for the 93, then drained the fuel cell and carb........and dumped in the fresh c12.........it’s not going to lose 25hp. Not here anyway. The only time I’ve ever seen any kind of significant difference in power from swapping fuels(assuming they have adequate octane for the combo)....... is going from a non-oxygenated fuel to a heavily oxygenated fuel. Like, from c16 to q16. My experience has been that losing 25hp going from pump gas to race gas on a build like that would not be a typical result....... at all.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Carb help!
[Re: RustyM]
#2735325
01/21/20 04:13 PM
01/21/20 04:13 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
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I Live Here
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State of confusion
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No problems except for, lowet et's, higher mph and tire shredding torque......
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Carb help!
[Re: RustyM]
#2735339
01/21/20 04:54 PM
01/21/20 04:54 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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I Live Here
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Rusty, it’s certainly possible the weather contributes to the different results. I’ve never run the dyno in the type of soup you guys are stuffing with down there in the summer.
Also, not all race fuels are created equally........ and I’d never bother trying to run c16 in a 10.75:1 motor.
But frankly I’d be absolutely shocked to lose anything even remotely close to 25hp by swapping from 93 to c12 out of a sealed can(I’d be pretty surprised to see that type of combo even lose 5hp).
That would be my suggestion for the next time you go to the dyno with something that’s at least 10:1 CR. Pick up a factory sealed 5 gal can of c12....... and retry the test(if you’re so inclined).
I know of several people who have used several different brands of the lower grade race fuels(like VP Red for example), that got less than stellar results. Although I don’t know if those tests were done using fuel from sealed cans of not.
I can tell you this....... a lot of race fuels don’t keep well at all once the seal has been broken....... so if you’re not testing fuel from a container with a freshly opened seal....... imo you’re leaving the door open for misleading results.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Carb help!
[Re: fast68plymouth]
#2735366
01/21/20 06:36 PM
01/21/20 06:36 PM
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Joined: Feb 2017
Posts: 582 Texas
RustyM
mopar
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mopar
Joined: Feb 2017
Posts: 582
Texas
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Dwayne: Thats very interesting as we get our fuels from a local parts store or Jessie's and they both just pump from the 55 gallon barrels , never gave a thought about getting stale fuel with race fuel. Might be a valid reason for re-testing. The c16 from 110 and c12 was on the 13-1 motor.
i know nothing about weather up there in the summer but, here, its bad , huge water per cubic ft of air just kills us on displacing oxygen. On the other hand, when it starts getting cold and we get a good, dry, north wind for 14-20 hours, that track at 500 ft above sea level will have Da's at 1100 ft below sea level and i can up the jets a good bit. Down here, for index racing, you have to run at least a tenth under during cold/dry air in order to run your index from late May through September.
i still say burn rate is very important and running the wrong fuel for the compression/cam is a mistake- at least down here.
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Re: Carb help!
[Re: RustyM]
#2735375
01/21/20 06:50 PM
01/21/20 06:50 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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I Live Here
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On the 13:1 motor, what was the original fuel you were running?
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Carb help!
[Re: fast68plymouth]
#2735387
01/21/20 07:37 PM
01/21/20 07:37 PM
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Joined: Feb 2017
Posts: 582 Texas
RustyM
mopar
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mopar
Joined: Feb 2017
Posts: 582
Texas
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He was running 110 , Vp stated we were on the ragged edge on compression /fuel, said we should go to C12 which lined up with what the dyno operator had stated. Car didn't like anything more than 34 degrees of timing - at all. We tried it and picked up power and, it would take a little more timing, which also helped. Well, if a little fuel change is good,,, so, we tried some 16 - car did Not like it . This engine has pistons about 14 up out of the hole. Our best runs are on the C12, 35-36 degrees of timing in the heat , 34 when its cooler /dryer.
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