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05-25-2010, 09:16 AM | #21 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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05-25-2010, 12:42 PM | #22 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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05-25-2010, 11:03 PM | #23 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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Thank you for clearing that up. I just didn't want anyone who may not know about this to unknowingly create a new problem while trying to solve another.
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05-25-2010, 11:41 PM | #24 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
What is your intake? My intake Runs so cool I had to go rich. It took me a week to make it run good. I forgot what power valve I ended up with but my main jets are 58s. I was running 56 mains but on the dyno it was showing a little lean. I put over 2000 miles on this set up ran mint til I broke a piston.
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05-26-2010, 05:06 AM | #25 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
That's a very cool banger set-up. I am still running the stock 40 Merc intake so I don't have the cold runner issue that you do. It's interesting that you are running jets so much richer than my stock .051s. I will definitely try running richer when I can get over to the drag strip to check my times on the "poor man's dyno". I put the carb back together last night and spent some time driving and just listening to the motor at higher rpms and am beginning to think that the comments that I still have an ignition problem might be right. I think I will put my fresh points in and see what effect that has next. It will be a while before I can get to it but will be sure and let everyone know how it goes. Thanks again.
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05-26-2010, 06:26 AM | #26 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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POPPING out the exhaust = rich or a miss in the ignition POPPING out the intake = lean |
05-26-2010, 09:01 AM | #27 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
F-1 I posted this a while ago and from the details of your post it seems to be related to the same issue. I had a slight skip at higher sustained RPM and always attributed it to poor point contacts from a condenser going bad. I also experienced a slower acceleration than I thought would be adequate. In short everything ran but just not what believed up to par.
Last year I had some vapor lock issues with another car and discussed this with a fellow that worked for a big 3 auto company. The conversation centered around new formulated fuels and their effects on earlier carburetor engines. The end result of this was the determination that the early fuel systems were designed to run on a gasoline mixture significantly different than the 10% ethanol fuels available at most gas stations now. Because of the difference in fuel molecular volume, with the addition of the ethanol derivative, the carburetor jetting must be increased to compensate for this larger molecule fuel. Using the original jetting based upon a pure gasoline fuel this would make your vehicle run on the slightly lean side. To run on new fuel you may have to increase your jet sizes by 2-4 numbers to readjust the air fuel ratio for correct performance. I did this and it made my engine run like a new car. My position is that if you are driving any vehicle today with an older style fuel system you must increase the jet size for better performance. I also would suggest that you clean your contact points of corrosion but I believe that your engine is running slightly to the lean side, thus the skip.
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05-26-2010, 12:29 PM | #28 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
You should really have your distributor tested on a machine. There could be wear in the components that allow some wobble at higher rpms. As for the jetting, I have never experienced the need for increasing with todays fuels. I just don't think there is that much difference if using only 10% ethanol. There are fuels that do not have any ethanol at all.
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05-26-2010, 02:03 PM | #29 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
Dick,
Thanks for the excellent insight. That's the first response that I've received that trys to explain why my stock jets may be too lean. I think you also raise a very good point in that an engine that is on the lean side will more likely missfire if something is not 100% in the ignition system. I think I will try throwing some slightly larger jets in to evaluate the effect. Where's the best place to get jets? Are they just standard Holley jets? Thanks again for the response. Dan |
05-26-2010, 02:08 PM | #30 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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Thanks, Dan |
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05-26-2010, 02:37 PM | #31 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
F-1-- What do the plugs look like? They will tell you by looking at each plug how the mixture is. I like to see a few dark spots on the flat surface below the bottom end of the threads. If it is lean there will be no black and will be a very light tan. To rich and they will be covered with black soot. I have adjustable main jets and can tune them by looking at the plugs or with an exhaust gas anylizer. One jet could be a differant size or have dirt in it also. The front plug on each side represents the different sides of the carb that feed them. One side of the carb don't feed one side of the engine, it chriscrosses. If I recall with a steel intake the passenger jet feeds the front plug on the passenger side. The drivers side main jet feeds the front plug on the drivers side. With an aluminum intake the passenger main jet feeds the front plug on the drivers side. I may have the alum and steel backwards but you can look at the manifold and track the fuel, air "runs". In some of the Ford service bulletins there are diagrams showing the flow through the maniflod. Try the Marvel Mystery Oil to free a sticky valve before you get into "neverland. G.M.
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05-26-2010, 03:01 PM | #32 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
I had a mis at higher RPM, tried jets. Replaced the condenser and solved my problem. Recomend when you do, solder a longer lead on it and re-locate it to a more accessable location. Good Luck.
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05-27-2010, 06:21 AM | #33 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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I bought a new 6 volt coil and matching condenser from Napa and it cleared up 75% of my problem. I made my own remote coil adapter and mounted the condenser on top of it just like the kit that is available. My coil is now mounted on the front of the firewall. It's possible that my new condenser is bad and maybe I'll try another one just to be sure. Thanks Last edited by F1 Flathead; 05-27-2010 at 06:37 AM. |
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05-27-2010, 06:24 AM | #34 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
G.M.,
The plugs look pretty clean and lean which is what got me headed down this road. I really need to to a w.o.t, shut it down and then have a look. I'll do that and get a better reading. Thanks for the info and reminder. Dan |
05-27-2010, 11:48 AM | #35 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
F1FLATHEAD . . . . . . . . . .
I really liked your two videos on starting up and the first drive. They were very cool and fun ! MIKE |
05-28-2010, 05:59 AM | #36 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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Dan |
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05-28-2010, 06:52 AM | #37 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
Running two 94's on a 53, I purchased new power valves during set up and after much trial and error found the correct value, just chucked them in my lathe and with a thin parting bit squared off the radius, that was 8 years ago works and seals perfect.
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05-28-2010, 07:33 AM | #38 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
A thick gasket with give takes care of that radius, have done lots of them and no leakers. G.M.
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05-30-2010, 07:30 AM | #39 | |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
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Ran the motor hard at W.O.T. and then switched it off, coasted to a stop and pulled the front two plugs. They are very light tan to nothing at all. I would read that at as a tad too lean. I'm going shopping for a set of 53s and a set of 55s. We'll see what difference that makes. Dan |
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05-30-2010, 12:27 PM | #40 |
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Re: Holly 94 jet recommendation for a flathead running open exhaust?
I would read that as being just fine. It is much harder to get a good read with todays fuel. How did it run at WOT? 51's should be just right for your area.
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