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Discussion Starter #1
So I have a fresh 545 with AFR bullit heads, hyd flat tappet cam, AFR intake. At about 4300 rpm I'm getting a popping in the exhaust and the motor falls off. I currently have a Holley 950 with 84's on all 4 corners. My fuel pump is 145 gal per hour and 6 lbs steady with a return. I am using a Pertronix Flamethrower Dist and coil. I have tried 3 different ignition systems so I think I can rule that out. The cam was broken in per the instructions and I have checked for a flat cam lobe. As far as I can tell the cam is good. I checked with Comp Cams on my cam/spring compatibility and all is good. Any help would be great.
 

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A couple of questions and then some things to look at.
1. Does the popping happen only under load?
2. What have you set the initial timing?
2a. Total advance?

I would look at these items:
1. Fuel line restriction.
2. Partially obscured fuel filter.
3. Partially clogged main jets.
4. Take a look at the spark plugs to see if it's a lean condition. #84 jets in a 950CFM carb seems a little on the lean side to me.

Good luck.
 

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Discussion Starter #3
It will pop at slow acceleration or WOT.
Initial is 11 deg and 32 total at 2300 RPM

No known restrictions 1/2 from the tank to AN8 to a HUGE fuel log. I am upgrading to a 1.3 fuel needle/seat. By the way 1.3 is the largest available. My carb currently has a 1.2.
Screen type filter. Clean as a whistle
Brand new carb. I disassembled and is beautiful
Plugs are not bad. slight brown tint with some white spots/wash .

Going forward
Plug the return to the tank
Increase fuel pressure to 7 lbs.
Increase all 4 corners jet size. I will go to 90's
install 1.3 inlet valve

If I see no improvement with that I will install a o2 gauge. I really don't want that in my car. It just doesn't look good in a 69 Mustang
 

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The 950 isn't going to be big enough either. Could be out of both air n gas.

950 on a 545 that thing on a diet............i run a 545 aluminum heads on a big tire car i have 2 1200 cfm throttle bodies my afr runs 13-8 and run 38 total locked dizzy may want to check push rod length and valve preload a motor that serious like mine set each valve independently 1 at a time set the lash on the base circle is there any way you can check you exhaust temp at the exhaust header flange for each cylinder should be some where around 450-550 i believe at idle, or check the old school way put it somewhere nice and dark wind it up see if you tubes are glowing
 

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Discussion Starter #7
I talked to holly and they told me the carb would easily support 800 hp. I'm no were close to that. I would love to slap a dominator on it to test but I can't afford to just go buy one to test. I just rechecked my valve spring hight and pressure just for piece of mind and they are spot on. I bumped the fuel pressure to 7 and put 90 jets in. There was Zero change. Anyone in the 60410 that has a carb I could borrow for an hour?
 

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950 is fine for a 545.

Not really knowing anything about your build, my first guess would be valve spring related. Like maybe the right spring but set to the wrong installed height and not providing the proper rate to keep the valves under control.

I randomly ran across this old thread. Seems customblackbird had a similar situation.

 

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The AFR heads have the valve cover bolts drilled through into the exhaust ports on the four corners, did you put sealer on the bolts? I remember a thread awhile back, a guy was having lean issues and Scotty J was helping him, Scotty had a memory bubble about the valve cover bolts and having to use sealer on the corner bolts due to vacuum leaks around the bolts, problem solved. Adding it to the mix.

Edit: the above would cause popping in the exhaust more on deceleration....

Dan
 

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Discussion Starter #10
After months of switching distributors, coil's ,carbs, fuel system parts,checking valve spring hight and pressures I brought the car to a shop and connected it to a 20 year old system analyzer we connected it to my car and took it out for a few hits. At 4100 RPM the ignition system collapsed and I started getting popping out of the exhaust. After a little bit of analyzing we found the MSD spark plug wires were defective we put on an old set of just regular spark plug wires and the motor immediately went to 6100 RPM and everything is good. It's amazing out of all of the people and Tech groups I have talked to the spark plug wires were never brought up. The mechanic that found it ,my brother-in-law, said its hard to fix something you can't see. And that's where an old engine analyzer at a shop came in handy.
 
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