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Re: Piston Burn Pattern?
[Re: GTX MATT]
#1902861
08/30/15 11:26 PM
08/30/15 11:26 PM
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Joined: Sep 2014
Posts: 4,457
Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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Where the piston is CLEAN there is ZERO fuel.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#1903498
08/31/15 09:13 PM
08/31/15 09:13 PM
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Joined: Jun 2006
Posts: 5,195
CT
GTX MATT
OP
master
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OP
master
Joined: Jun 2006
Posts: 5,195
CT
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So what is causing that/how do I fix it? Current carb is an annular booser Holley, but Ive had a few carbs on it.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#1903655
09/01/15 12:57 AM
09/01/15 12:57 AM
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Joined: Mar 2005
Posts: 576
Texas
ChevyTS
mopar
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mopar
Joined: Mar 2005
Posts: 576
Texas
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So what is causing that/how do I fix it? Current carb is an annular booser Holley, but Ive had a few carbs on it. You don't fix it.  keeping fuel suspended is one of the great challenges of performance engine building. Liquid weighs more than air. Air and fuel moving at high speed... air makes the turn and fuel doesn't. This causes the fuel to enter the chamber atomized and as a liquid. The results clearly seen in your pistons. You might experiment with carb spacers if you have room.
T & K Performance
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Re: Piston Burn Pattern?
[Re: ChevyTS]
#1903665
09/01/15 01:30 AM
09/01/15 01:30 AM
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Joined: Sep 2014
Posts: 4,457
Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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So what is causing that/how do I fix it? Current carb is an annular booser Holley, but Ive had a few carbs on it. You don't fix it. keeping fuel suspended is one of the great challenges of performance engine building. Liquid weighs more than air. Air and fuel moving at high speed... air makes the turn and fuel doesn't. This causes the fuel to enter the chamber atomized and as a liquid. The results clearly seen in your pistons. You might experiment with carb spacers if you have room. ^^^^^^^^^^^^^^^^^^YUP^^^^^^^^^ I would spend time on the flow bench with the head first and figure out why the port is charging the bore like that, and why the fuel is separating out. Despite what I read, I have never been able to get wet flow (fuel that has fallen out of suspension) back into airflow with surface preparation. After I was happy with the port, I would put the intake on and figure out what changes with the intake. After all that crap, you still need carb work I can tell you for a fact that one well know NASCAR engine builder spent 98% of his time on carbs and intakes. He made a special fixture to tests carbs on the flow bench that simulates the intake manifold and it's adjustable. I can't wait to play with it. There is way more to it than it may appear. But your pics show some issues. Fix them and you will pick up power everywhere.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#1903669
09/01/15 01:33 AM
09/01/15 01:33 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I e-mailed some friends and one well know head porter said he thought it was too rich (already discussed) and too much timing. He thought the burn was finished before it got around to the far side away from the plug. So, something else to try. Thanks, good to know, and I would agree that it has been too rich for sure. Its rich... with that many miles it would have a tan color over to the intake valve to get a full burn... its way rich EDIT The timing is starting too late to cause all the burn over on the exhaust side(all the burn is over there) 
Last edited by MR_P_BODY; 09/01/15 01:39 AM.
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#1904089
09/01/15 01:34 PM
09/01/15 01:34 PM
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Joined: Jun 2006
Posts: 5,195
CT
GTX MATT
OP
master
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OP
master
Joined: Jun 2006
Posts: 5,195
CT
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Long story short - engine performance is not where it should be, was re-checking cam phasing and my piston stop broke off in the #1 cylinder. Cam was degreed correctly.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#3024245
03/15/22 01:32 PM
03/15/22 01:32 PM
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Joined: Dec 2021
Posts: 1,475
Loudoun County, VA
Brad_Haak
pro stock
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pro stock
Joined: Dec 2021
Posts: 1,475
Loudoun County, VA
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I don't know if it's the jetting, the timing, the chamber design, or what... but that's not what I'd consider a good burn pattern. My understanding -- and it's pretty limited -- is you "should" see a more complete burn across the quench area and more uniform coloration of the chamber.
These pics aren't ideal, but show the burn pattern for this head & piston combo is spread out more. This is either a .040" or .045" quench height and the heads were pulled after about 25+ pulls on an engine dyno. Jetting was still being worked out, but tended towards the lean side. Ignition timing was 37*, IIRC. Fuel was a 50/50 blend of 110 leaded and 93 E10 unleaded.
2021 Challenger 6.4L Scat Pack 1320
100% stock: 1.680, 11.894 at 113.75 (DA 175 ft)
weight reduction, wheels, tires, Hellcat air box: 1.661, 11.686 at 115.97 (DA 710 ft)
1973 Challenger 452 ci street/strip [2008]
pump gas, DOT radials: 1.454, 10.523 at 126.44 (DA 514 ft)
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#3024280
03/15/22 03:02 PM
03/15/22 03:02 PM
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Joined: May 2011
Posts: 4,492
northern,Ohio,USA
Clanton
master
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master
Joined: May 2011
Posts: 4,492
northern,Ohio,USA
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Does it mean anything? Can we learn anything from it? This one looks odd, what does it mean? What I see is a lot of carbon on the exh side and that is where your fuel is collecting,Maybe on overlap,maybe small exh system.
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Re: Piston Burn Pattern?
[Re: Clanton]
#3024379
03/15/22 07:22 PM
03/15/22 07:22 PM
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Joined: Jun 2006
Posts: 5,195
CT
GTX MATT
OP
master
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OP
master
Joined: Jun 2006
Posts: 5,195
CT
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This is an old post guys - I did fight this car for a bit but finally got it running as strong as it should. The main issues were a vapor locking mechanical fuel pump, mufflers that were too restrictive, and very oddly the air cleaner made a big difference as well mostly on the low end & throttle response. It had a drop base on it and the lid was a bit close to the choke tower/bowl vents. A contoured moroso made a big difference in throttle response believe it or not, but the torque came from the mufflers and electric fuel pump. It made 479 RWHP on our local chassis dyno.
The burn pattern, as best I can tell, still is about the same. But the heads are coming off soon, so we’ll see if its changed at all. I think its from a rich t slot / ifr and the car mostly cruises on the t slots. I definitely have to fix that for this summer with the price of gas.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Piston Burn Pattern?
[Re: GTX MATT]
#3024383
03/15/22 07:41 PM
03/15/22 07:41 PM
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Joined: May 2011
Posts: 4,492
northern,Ohio,USA
Clanton
master
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master
Joined: May 2011
Posts: 4,492
northern,Ohio,USA
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This is an old post guys - I did fight this car for a bit but finally got it running as strong as it should. The main issues were a vapor locking mechanical fuel pump, mufflers that were too restrictive, and very oddly the air cleaner made a big difference as well mostly on the low end & throttle response. It had a drop base on it and the lid was a bit close to the choke tower/bowl vents. A contoured moroso made a big difference in throttle response believe it or not, but the torque came from the mufflers and electric fuel pump. It made 479 RWHP on our local chassis dyno.
The burn pattern, as best I can tell, still is about the same. But the heads are coming off soon, so we’ll see if its changed at all. I think its from a rich t slot / ifr and the car mostly cruises on the t slots. I definitely have to fix that for this summer with the price of gas. Look at your exh valve from the header side when it is off and see the buildup on the valve.
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