Return to the track....questions, hopefully answers!
#1044458
08/01/11 08:51 AM
08/01/11 08:51 AM
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MikeyT
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Hi all Hey, I went to the track yesterday and had a couple wierd things happen. Hopefully you guys can give me some insight. I went to GLD yesterday, and I got two runs. Weather was hot as hades and humid to boot First run car ran pretty well despite the heat. I clocked 13.4 at 104 mph. Yet, at the end of the run as I let off it seemed to backfire more then usual. I run open exhaust at the track and it does this from time to time. First question: What causes it to backfire like that? Ok second run I tried to adjust my launch by getting out of the hole at 2500, this did not work as well. I ended up redlighting ![](/ubbthreads/images/graemlins/blush.gif) . Now despite the redlight car seemed to run ok, i shifted slightly higher then usual to try. 1st shift 5800, second shift 5800 , but when i shifted into third it started off llike a hitch all the way up too 5000 rpms, where it just fell flat! It wouldn't go beyond it! I typically shift this car St 5600 or so. Anyway run finishes up and again more backfire! Worst run I've had in the coronet in years. Ok second question: Why do you think it just seemed to run out of gas at 5000 rpms like that? Info on car 440 9:1 stealth heads, 274xe comp cam, 770 Holley avenger carb, street dominator intake Hedmam shorty headers. 727 with 3:91 gears. I run msg digital 6 with msg distributor 4000 lb with me in car. Any idea guys? I hope that give some info to help with this question, thanks racing guru's Mike ![](/ubbthreads/images/graemlins/thumbs.gif)
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: MikeyT]
#1044459
08/01/11 10:26 AM
08/01/11 10:26 AM
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Posts: 52,972 Romeo MI
MR_P_BODY
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Is it back firing through the exhaust or intake... question 2... you could be running out of fuel, maybe a low float level... also it could be boiling the fuel on these HOT days ![](/ubbthreads/images/graemlins/wave.gif)
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Re: Return to the track....questions, hopefully answers!
[Re: MR_P_BODY]
#1044460
08/01/11 11:32 AM
08/01/11 11:32 AM
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MikeyT
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Mike
Thanks for the help! I believe thru the exhaust, it only seems to happen when I uncork the headers, but let's say for argument it is exhaust side.
Mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: MikeyT]
#1044461
08/01/11 11:41 AM
08/01/11 11:41 AM
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MikeyT
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And..... on the chance I hear it wrong and the backfire is thru the intake?
I've just had some bad luck this year , so just a tad paranoid
Mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: MikeyT]
#1044462
08/01/11 11:57 AM
08/01/11 11:57 AM
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MR_P_BODY
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Quote:
Mike
Thanks for the help! I believe thru the exhaust, it only seems to happen when I uncork the headers, but let's say for argument it is exhaust side.
Mike
The flame chases the fuel so it could be running fat and you have some unburnt fuel in the tubes... check your timing also ![](/ubbthreads/images/graemlins/wave.gif)
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Re: Return to the track....questions, hopefully answers!
[Re: MR_P_BODY]
#1044463
08/01/11 12:53 PM
08/01/11 12:53 PM
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MikeyT
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Ok that makes sense, would too much timing cause it to pop thru the intake? Now, that you mention it I did run it at 36 all in by 3000, and it did have a half second struggle to start.
Mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: babarracuda]
#1044466
08/01/11 04:55 PM
08/01/11 04:55 PM
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MikeyT
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Well it is a good question the pump is the bigger pump, but I can't verify the lines all the way back are NOT 5/16" ![](/ubbthreads/images/graemlins/1343795-scratchchin.gif) perhaps I should check it out. car ran well up to 5800 in first and second gear, so me thinks not valve float , but running out of gas at top of third quite possible
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: forphorty]
#1044468
08/01/11 10:14 PM
08/01/11 10:14 PM
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MikeyT
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Gosh, that I guess is an option, but man I'm not sure I want to go that far with this car, it is mostly a street car.
Thanks for the help too guys.
Mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: Cab_Burge]
#1044470
08/01/11 10:36 PM
08/01/11 10:36 PM
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MikeyT
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Cab
Well it does make sense, except I'm a little bit down. I thought I fixed this issue last year, bigger mechanical fuel pump. I got the big carter one on it and I guess the only thing would be to look at that fuel lines. I can't verify that they are not 5/16, but I doubt it, at least 3/8's on it.
mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: Cab_Burge]
#1044471
08/01/11 10:38 PM
08/01/11 10:38 PM
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JAKE68
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If it is going flat at the big end it is most likely running out of fuel with the looks of that fuel system. I would add atleast a small elect fuel pump back by the tank . We install alot of the small carters with a micro switch on the secondaties so that when they kick on so does the pump. That way you do not have to remember to turn on or off the pump. Now on the back firing on decell it sounds like you have a header leak and that will back fire in decell. Jake
JAKES AUTOMOTIVE
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Re: Return to the track....questions, hopefully answers!
[Re: JAKE68]
#1044472
08/01/11 10:41 PM
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MikeyT
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The only time it backfires like this is when I'm on it at the track with the headers fully opened. I've done a few closed header spirited runs on a country road by our house ![](/ubbthreads/images/graemlins/whistling.gif) I like the small electric fuel pump idea, the question I have is what size of fuel lines are people running in their cars? I mean should I be upgrading to 1/2 in or bigger? Mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: MikeyT]
#1044473
08/01/11 10:51 PM
08/01/11 10:51 PM
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Joined: Dec 2005
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JAKE68
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You could get away with the stock 5/16 if you put the pump on. 3/8 is not a bad idea. 1/2 is way over kill. Ron Mancini went 8.98@155 with 5/16 fuel iline and 2 carter pumps. Everyone told him he would go faster with a better fuel system. So he goes and spends $1200. on a complete fuel system and never went any faster. Now back to your back fire I still say it is a header leak. You would not hear the back fire with closed exaust.
JAKES AUTOMOTIVE
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Re: Return to the track....questions, hopefully answers!
[Re: JAKE68]
#1044474
08/01/11 10:57 PM
08/01/11 10:57 PM
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MikeyT
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Jake
That is a good point about the exhaust I never thought about it. I'll look at the headers. I might be spoiled, but since I've run copper gaskets I haven't had a leak since high school, might be my luck ran out.
How difficult is it to set up this electric pump?
Recommendations of what you would use? Mike
1969 Dodge Dart Swinger
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Re: Return to the track....questions, hopefully answers!
[Re: MikeyT]
#1044475
08/01/11 11:04 PM
08/01/11 11:04 PM
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JAKE68
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Piece of cake. Buy a no2 switch that mounts on carb. Use that to control the ground for the pump. Run a fused 12v to pump and your done. Now everytime you nail it it will come on and when cruising its off. No need to remember after the fact to turn on pump or remember to turn it back off when done. ready to go 24-7 Jake Oh finished reading your post. I think the mechanical pump is fine for the driving around etc. I put on the carter pump that is 6lb. and does not require a regulator. It worked in my car that could go 11.40's in street trim .
Last edited by JAKE68; 08/01/11 11:12 PM.
JAKES AUTOMOTIVE
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Re: Return to the track....questions, hopefully answers!
[Re: JAKE68]
#1044476
08/02/11 02:03 AM
08/02/11 02:03 AM
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MikeyT
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As always you folks are very helpful!
Mike
1969 Dodge Dart Swinger
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