Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958246
11/26/15 11:30 AM
11/26/15 11:30 AM
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Joined: Jan 2003
Posts: 5,903 Florida
Locomotion
master
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master
Joined: Jan 2003
Posts: 5,903
Florida
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Could it be an over-rich condition when the accellerator pump duration overlaps the main circuit activation, which may happen to be at 3,600?
I've had issues with a bog/flat spot footbraking and been working on shortening the pump duration. Don't have an A/F meter yet.
Bringing the rpm up to 2,200-2,500 may start the main circuit, but it also reduces the volume and duration of pump shot delivery over what you get from idle.
Last edited by Locomotion; 11/26/15 11:39 AM.
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Re: Ok fellas I'm stumped.
[Re: Jerry Kathe]
#1958261
11/26/15 12:09 PM
11/26/15 12:09 PM
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Joined: Jan 2003
Posts: 5,903 Florida
Locomotion
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Florida
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A rich transition would do that, but I cant believe he used the same carb from gas to e85....on gas it would puff a cloud of black smoke during the occurrence....kinda easy to see on a pipe rack and freaky odds that two carbs would have the same problem. I think it may be a common problem which could exist in both carbs. It's sometimes difficult to convince yourself that "less" is better as opposed to "bigger is better". It's not always obvious. I recently replaced a well used engine with one having basically the same parts/combo. That changed the carb tune-up to the point that I originally thought I screwed something up in the build! Must have been the ring seal. But as they say...."Leave no stone unturned." If expected fixes don't work, you have to start with the unexpected ones. Does over-rich E85 cause black smoke as bad as gas?
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958271
11/26/15 12:26 PM
11/26/15 12:26 PM
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Joined: Oct 2003
Posts: 7,506 Az
Crizila
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master
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Az
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If adding timing helps, it's going lean at that rpm. Could try smaller hi speed air bleeds.
Fastest 300
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958272
11/26/15 12:27 PM
11/26/15 12:27 PM
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Joined: Jan 2003
Posts: 19,543 Las Vegas
Al_Alguire
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OP
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Las Vegas
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TDC WAS accurate upon assembly. After I left for DC my son and a friend had to change balancers(from Chevy to Mopar front) so possibly there was an issue there I was not here so not sure. It happened on both gas and E85 with 2 different carbs. I have been overly cautious with the timing but cannot and do not believe it is actually at 48, am assuming that something has happened there. BUt the plugs are showing it wants more timing still. Definitely has me baffled for sure. Oh yeah did it with 2 different E85 carbs as well, so pretty sure it is NOT a carb issue.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958306
11/26/15 01:24 PM
11/26/15 01:24 PM
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Joined: Feb 2011
Posts: 1,454 Glendora Ca.
Just-a-dart
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pro stock
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Glendora Ca.
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Fun stuff Al. If I could not use a spark plug type piston stop to verify TDC, and the plugs are a reasonable heat range. I would keep putting timing in it until it quit improving or it slowed down and check the plugs to verify.
But I have also been known to color outside the lines.
"Just a Bracket car dressed up like a streetcar"
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958311
11/26/15 01:32 PM
11/26/15 01:32 PM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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bean town ....Ca
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If you don't have time to verify TDC.. add two degrees at a time until comes up on the brake cleanly. With the two step out of the equation equation I don't think you'll get 85 to detonate with that engine combo just my two cents.good luck 🚦👍
In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958323
11/26/15 01:50 PM
11/26/15 01:50 PM
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Joined: Jan 2005
Posts: 4,243 Charlotte, North Carolina
sgcuda
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Charlotte, North Carolina
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Sounds like you have narrowed it down to an ignition problem. First, I would drill a 3/8" hole in the cap inline from plug 1 to coil lead. Use a timing light to verify rotor phasing. I suspect it is off and spark is jumping to the next cylinder in line. If it does show OK, an easy patch would be wire up a timing retard to kick in just above launch rpm and crank up your base timing to get it up on the chip. To be safe, pull out the same amount to the retard module, that you are adding to base timing.
[image][/image]
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958393
11/26/15 03:40 PM
11/26/15 03:40 PM
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Joined: Jan 2003
Posts: 10,088 Frostbitefalls MN (Rocky&Bullw...
gregsdart
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I Live Here
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I was going to say fat mid range, but you have tried two carbs. I had a fuel injector that was super fat in the mid throttle settings and caused similar grief. Will it flash when not fully up to temp? I am thinking of a test when it is as cold as you can without hurting parts. That might give you some info. You could also go way tight on plug gap for a test, to see if the ignition is going away (.020?)
8.582, 160.18 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Ok fellas I'm stumped.
[Re: Al_Alguire]
#1958404
11/26/15 04:04 PM
11/26/15 04:04 PM
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Joined: Oct 2003
Posts: 7,506 Az
Crizila
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master
Joined: Oct 2003
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Az
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Got an A/F gauge on it? That could eliminate a fuel issue.
Fastest 300
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Re: Ok fellas I'm stumped.
[Re: AndyF]
#1958410
11/26/15 04:11 PM
11/26/15 04:11 PM
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Joined: Jan 2003
Posts: 8,225 Plymouth, MI
Blusmbl
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Plymouth, MI
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Do you have a compression gauge with you? Might be interesting to pull the plugs and spin it over and see what the cranking compression is. My guess is that it is super low. x2. If it isn't the carb (worth putting a wideband on it for a pass just to check), my next guess is just a combination of E85, the altitude, 11:1 CR, aluminum heads and a roller cam. On E85 I would be surprised if you could get it to detonate at all. Might be worth advancing the cam a couple degrees to get cylinder pressure up and pick up midrange torque to pull through the converter more cleanly.
'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
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