Classic Mustangs (Tech)Technical discussions about the Mustangs of yester-year.
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I have a 1973 Mustang grande with a 351 cleveland 2v engine and automatic 3 speed tranny. It has headers, a 4 barrel vac secondary summit 750 carb and weiand alum intake. All this was on the car when i got it. It did not pop then. Both header gaskets were leaking and needed replacement, which I did.
I replaced plug wires with street fire spiral 8MM from oriellys. And a new set of plugs accel 0576S-4 with a 045 gap. It started the popping after I fixed the intake gasket which was blown out when I got the car. I am pretty sure I put the distributor back just like it was. The car has a GM HEI distributor. The weird thing is when I went to check the timing I have to connect my light to the number 5 cylinder to line up with the marks on the harmonic balancer. I am not sure how this happened.
Any way the engine cranks and runs great and it has good power, I can do a good burn out. but when I give it hard to mid range acceleration it starts a slight popping sound that is worse at first then almost goes away after I build up some speed. The pops have about a 1 sec interval. The distributor cap and rotor seem to be in fairly new condition.
The popping is not as bad since I changed the plug wires and plugs. timing set a 6 BTDC is better than 10 BTDC. 2 BTDC is about the same as 6.
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Those HEI distributors will run even if the plug wires are mixed up.
IF you have to have the timing light on the number 5 wire to light up on the mark then you likely have the dizzy out 180. I know its messed up but those hei dizzys will jump spark all over inside that cap.
Bring the number one cylinder up to TDC pull the cap and see where the roter is pointing I would bet you are way out. .
There is no way you should have to clip the number 5 wire to read timing.
Just pull the number one plug and rotate the engine by hand to verify. Either way, the things timing is definately off somewhere. You shouldnt be running at 2btdc. Does the popping sound like marbles in a tin can?
69 Grande' 351W/AOD Performer Intake/Cam, 670 Holley Avenger, Hooker Headers, 3.70 9"TracLoc
67 Fastback A Code: 64k Miles, all original project for the wife.
The popping sounds like a small back fire. I took the timing chain off, it was pretty slack, I am going to replace it with a Zoom double roller set. But when I took off the valve covers I think I may have found some real problems, both the 6 and 8 had loose rockers. The previous owner "rebuilt" the heads so he said. I hope he did a better job on the valves than He did on the rockers.
I wanted to give an update. After replacing the plug wires, plugs and checking timing, I checked the rocker arms, several seemed loose, So I pulled the cam, sure enough I had wear extreme on 6 lobes, 2 were rounded off. Best thing I could figure is that the previous owner did not properly oil the new cam and lifters with a high zinc oil. I got it all back together and it is running great now. thanks for the help and I hope this thread may help someone in the future.
I use to have an old 68 Firebird with a 400 and was running an HEI and had the distributor 180 out. It started and ran around the block but when I laid in to it it all went to hell. It coughed, popped and farted all over itself but I was able to nurse it back home.
I was under the hood and hadn't figured out what the problem was so I was frustrated and did the only logical thing I could think to do in my 20 year old mind and revved the **** out of it. It backfired hard enough so that it blew my mufflers apart and peppered my legs with dirt & gravel hard enough to draw blood.
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Last edited by fastbackford351; 09-17-2013 at 06:14 AM.
I have heard about the spark skipping around in these dizzy HEI distributors. But I have tried setting the distributor to the 0 TDC mark on the HB and then tried it 180 degrees and it will only back fire. I set it to the #5 with the HB on 0 TDC and it fires right up and runs great. Let me stress, my engine is running perfectly like this. I can smoke the tires down with my posi 9" rear end.
It must be revenge for using a brand x dizzy and timing to #5...why?
69Mach1 - warmed up 395W (AFR 185s) and broken POS Gforce T5 with hydraulic clutch, 3.5" Alum DS, 3.50:1 posi, rack&pinion/tilt, 235/50ZR17x8 front & 285/40ZR18x9 rear, American Racing Nova wheels, all MSD, Holley 750, custom paint, headlight relays, Shelby drop & 2" lower all around, Hotwheels Redline scale is 1 to 1. http://photobucket.com/albums/v618/danaranda/69stang
the timing for my engine is. 1 3 7 2 6 5 4 8 ... so the #5 is no where near the #1 on the distributor cap. No one thinks this could be the wrong harmonic balancer??? I will check #1 for TDC but my money is that TDC on the HB will line up with TDC on the #5.
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