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JoshuaJayG
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Joined: December 23, 2010
Posts: 238
Location: The Sticks
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 Posted: Tue Aug 23, 2011 4:39 pm Post subject: Backfire |
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Some of you followed my 1835 rebuild. Since I have rebuilt it I get an occasional backfire right off idle. It is a little cough coming through the carb. I don't know why it is happening but it will only be once, MAYBE twice a day. I adjusted the valves today and nothing was real tight (chromoly push tubes), just a little snug on two of my exhaust valves. I am not perfectly jetted yet, but am working on it. Single Weber 40 IDF.
Any ideas why I may get an occasional cough through the carb? It's kind of hard on my K&N filter.
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RailBoy
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Joined: March 10, 2008
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Location: Virginia
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| Posted: Tue Aug 23, 2011 4:41 pm Post subject: |
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Can you tell us your current jetting and engine combo?
I run a Single 44 IDF on a 2110, took some doing to get it jetted right but now purs like a nappy kitten,lol... RB |
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JoshuaJayG
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Joined: December 23, 2010
Posts: 238
Location: The Sticks
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| Posted: Tue Aug 23, 2011 4:47 pm Post subject: |
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Mains - 140
Airs - 160
Idles - 57
Emulsions - F-7
I am currently changing the idles out for some 50s since I have them and my mixture screw is only 3/4 of a turn out. I will be back in a couple minutes with the results.
I was kind of wondering if jetting even could be the culprit.
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RailBoy
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Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Tue Aug 23, 2011 4:52 pm Post subject: |
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Go in steps, if you have 55 Idles try those first, go for a drive and check plugs like driving normally in 45mph zones and all, need to get a light grey plug reading, and crisp throttle responce with no back firing of course,lol.....
Just so you know, I am running 52.5 Idles in 2110 to have a good reading plug for normal driving, you run on the idles for a majority part of daily driving.... That is why I say go in steps, when you are to lean, you will here popping like fire crackers, then you know you are lean...
This is some cool info, you can read through it and get the jest, thing is what helped me out the most was the RPM scales you will come across in it, tells at which RPMs are what jets are doing what.... RB
http://www.aircooled.net/gnrlsite/resource/articles/jetting.htmRB |
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JoshuaJayG
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Joined: December 23, 2010
Posts: 238
Location: The Sticks
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| Posted: Tue Aug 23, 2011 5:15 pm Post subject: |
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I figured I was rich. I know how to read plugs and all. Soon after rebuild I checked the plugs after being at low RPMs for a while and they were pretty dark. I also checked them after high RPM and they were nearly white. I went from 135 to 140 mains at that point but didn't have any additional idles ordered yet. I had the 57 idles I ordered and the 50s that came with the carb. I haven't had the car for a week, that's why I haven't done additional jetting changes yet. I am not going to check my sparkplugs with a hot engine though. Pulling threads through hot aluminum is a great way to kill those threads.
So I just stuck the 50s in and my mixtures are out 1.5-1.75 turns. I don't get a noticeable improvement in response/acceleration under 2000 RPM. Up near 2000-2200 RPMs I really get some acceleration.
I still got the occasional cough though. I just thought, maybe my 009 is causing that. When timing it I would get down near 4 degrees BTDC at idle when timing at full advance for 28 degrees. I may be getting some ignition before the valve is completely closed. I will be checking my timing again tomorrow when I can use the timing light at work.
I am at 3500 feet with 100 degree heat. Our air density can be the same as 6500 feet at times.
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RailBoy
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Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Tue Aug 23, 2011 5:41 pm Post subject: |
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Are you running a Good Individual Runner Designed Manifold with Heat?
Also, you did check that you have 3 psi fuel pressure and your float bowl is adjusted right...? Just wanted to double check you are up to the jetting stage is all...
Timing, I have been timing my engines at 30 degrees @ 3,200 RPMs for years, both 1600 DP and my 2110.. Works for me.. RB |
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JoshuaJayG
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Joined: December 23, 2010
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Location: The Sticks
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RailBoy
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Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Tue Aug 23, 2011 5:53 pm Post subject: |
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The individual runner designed manifold does not have a cross tube below the base of the carb that connects the runners..
They say an individual runner design makes for more HP and easier tuning...
The only single I have messed with is mine, and I run a Redline Intake with the individual runner designed, so I am not sure how much harder the one with the cross tube is to tune, never done it.....
As for fuel pressure, you can get 3 psi out of a properly set-up, stock fuel pump.. Just have to have the correct year fuel pump with correct push rod, there are two diffenert length push rods for the fuel pump..... Just parts, but stock was 3 psi I think.... RB |
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JoshuaJayG
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Joined: December 23, 2010
Posts: 238
Location: The Sticks
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| Posted: Tue Aug 23, 2011 5:58 pm Post subject: |
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I still have the stock fuel pump on the original distributor gear with the rod it came with. I haven't changed any of that (but that doesn't mean it is right.) I have never had fuel problems, so I don't see why that would be it now.
My manifold is not connected between the 1/2 and 3/4 sides. Once the air enters the venturis, is never mixed again until it comes out the back as exhaust.
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RailBoy
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Location: Virginia
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| Posted: Tue Aug 23, 2011 6:00 pm Post subject: |
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Cool, do you have a fuel pressure gauge you can get at work?
Nice to know if you have the right fuel pressure, can eliviate a few problems.... RB |
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JoshuaJayG
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Joined: December 23, 2010
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Location: The Sticks
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RailBoy
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Posts: 2904
Location: Virginia
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| Posted: Tue Aug 23, 2011 6:05 pm Post subject: |
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If not I think it was Harbor Freight is were I got a combo kit, fuel pressure gauge that doubles as a vacume gauge as well, like $15 for the kit, comes with fittings and hose.....
Just make sure your float bowl is full, disconnect the fuel line, run into gauge, and start and idle, I did a few revs. with mine and got like 3.5 psi I think when reving... No need for a fancy t fitting and extra hose... Just going to let it run for about a minute... RB |
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