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Discussion Starter #1
I apologize in advance for the length, but I am stumped and need some input from those more experienced than I am.

A little over a year ago, I was able to finally purchase my dream car project, specifically, a 1967 Camaro with a 468 big block.

When I bought it, it ran great. And clean. It had great throttle response and I was looking forward to getting it on the road.

I have not gotten it to the point of being able to actually drive it yet, so it has been sitting in my garage while I work on it.

One of the first things I did was rewire it from front to back with an American Autowire kit. The car has an electric fuel pump and while I was in the process of rewiring it, I inadvertently left the key on while doing some testing and did not disconnect the fuel pump. I realized it when I noticed that the fuel pressure gauge was reading somewhere around 12 - 13 lbs of fuel pressure. This is much higher than it should be for a carburetor, so I immediately switched the key off. I have since installed a switch on the fuel pump that only allows it to run for three seconds when the key is switched on unless it detects a signal from the tach wire.

Since that happened, the car has been running extremely rich. I'm talking burn your eyes and looks like the garage is on fire rich. I figured that having the pressure that high had overloaded the needle and seat or something like that to cause the problem. However, I have not been able to resolve the issue. I had basically rebuilt the carb and gotten no improvement, so I broke down and ordered a new carb and put it on. The car runs pretty much exactly like it did before, which has me wondering what the problem might be.

Let me tell you what I know about the engine, which is actually very little. The guy I got it from had gotten it in a trade and didn't have much information on the build, other than what he was told. The engine is a 3999289 casting, which tells me it started out as a 454 from the early to mid 70s. I am assuming it has been bored to get to the 468 cid. There is also a nitrous plate and the associated solenoids installed on the intake but I did not connect the wiring during the rewire. The transmission is a TH400 and the guy I bought it from said that it had been built for racing by a transmission shop at a cost of $3,800. I was told it had a 3,500 RPM stall converter in it.

The carb that was on it was a Holley double pumper, but I could not find any numbers on it to narrow it down beyond that. There is no choke on it. This was another thing that led me to replacing it in an attempt to resolve the rich running condition. I replaced it with a Holley Aluminum Street HP (0-82851SA) 850 cfm unit.

The intake is a Brodix single plane, but I do not know what model it is exactly, but it looks a lot like the BM2017. There is about a 1" spacer between the carb and the nitrous plate.

I have removed the valve cover on the driver's side to see what heads are on it and they are World Products Merlins with a casting number of 1-043. When I looked those up, everyone had a letter at the end of the casting number on theirs but I don't really see one on mine. There is something there and, if anything, it looks like a C, which would mean they have 320cc intake runners, a 119cc chamber and rectangle ports.

There are PRW 7/16" 1.7 roller rockers and Comp Cams 4806 rod guides installed on the heads. That is about all I can tell without further disassembly, which I am hoping I don't have to do.

I have no idea as to the internals on the short block. The idle is not overly "lopey" but it does sound healthy and still has great throttle response, even though it is running crazy rich.

The ignition consists of a MSD 6A box, Part No. 6200 and a MSD Pro-Billet Distributor, Part No. 85551.

Exhaust exits through Hooker headers.

When starting the car, I will usually pump the gas twice and then start it. When I first turn the key, it turns over like it has a low battery (newer Optima Red Top, purchased when I bought the car, and a MSD starter). It will do this for a couple of turns and then it will backfire, usually through the carb (with varying degrees of severity) but sometimes through the exhaust. After it does this, it will turn faster and usually fire up within a couple of rotations.

Since it has been running so rich, I pulled the plugs and found very different results on each of them, ranging from being completely black and fouled to a couple of them looking practically brand new, so something is definitely up. I replaced the plugs with the same brand that were in it, NGK V-Power UR4. Since then, I have only ran it for short periods and I pulled the plugs the other day to do a compression test and found basically the same thing I found when I pulled the original ones, they ranged from being heavily fouled to a couple still looking brand new.

The results of the compression test were:
1 = 180
3 = 180
5 = 170
7 = 190

2 = 135
4 = 180
6 = 180
8 = 180

I am a bit concerned with the #2 cylinder reading but the others are pretty consistent, even though they seem a bit high from what I have read about the results others have had.

Anyway, to wrap it up, does anyone have any ideas as to what might be causing the extremely rich condition, keeping in mind that it runs almost exactly same with the brand new carb installed.

I am thinking it may be timing related, but I guess it could be something internal with a valve or something. I purchased a timing light in order to attempt to check the timing but I must be doing something wrong. When I connect the light and shoot it on the balancer, I can barely see the timing mark coming around when the engine is idling, even with the advance knob turned all the way up. To me, that would make the timing way advanced and I am thinking the distributor would have to be locked out for it to be that far advanced at idle. I honestly don't even know how it would run, but it does. I loosened the hold down and rotated the distributor counterclockwise a small bit and it definitely ran worse until I put it back where it was.

I doubt anyone will read this, given the length but, if you do, I would be most appreciative of any clues as to what to do next.

Thanks,
Tim
 

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You know you have a timing problem or an issue with the mark on the balancer so you could start with checking the balancer mark for TDC using a piston stop. Once you have that done the timing is easy to dial in. Your compression numbers are fine except that #2 cylinder which has a significant problem, does that plug look oil fouled? You need to do a leak down test on that cylinder to figure out if it's a valve or ring issue.
 

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Mike
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Good advise given by srode. Confirm TDC with a piston stop before moving forward with additional troubleshooting.

You also mentioned that you were seeing 12-13 lbs of fuel pressure with the electric fuel pump running.
  • Is the 12-13 lbs of fuel pressure going into the carb?... or do you have a fuel pressure regulator between the fuel pressure gauge and the carb?
If your running 12-13 lbs of fuel pressure to the Holley carb, that is too much. It need to be regulated to about 7 lbs of fuel pressure to the carb. Too high of fuel pressure to the carb could be causing the overly rich condition... even with new needles & seats + properly adjusted floats.

Slow cranking and backfire thru carb usually indicates that the timing is too much advanced. When you turned your distributor counterclockwise, you advanced the timing even more. You would need to turn your distributor clockwise to retard the timing.

The #2 cylinder pressure does look odd compared to the rest of the cylinder pressures. I would first squirt a little oil into the #2 cylinder (thru the spark plug port) and retest compression. If the compression goes up, there could be a sealing issue with the rings on that cylinder.
You may also want to remove the valve cover on the passenger side (location of #2 cylinder) and start the engine.
  • Are the rocker arms for the #2 cylinder moving the same amount as the other rocker arms?
You may also try to readjust the valves/lifters on the #2 cylinder to see if that helps.
  • Roller or flat tappet cam?
 
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Discussion Starter #6
Good advise given by srode. Confirm TDC with a piston stop before moving forward with additional troubleshooting.

You also mentioned that you were seeing 12-13 lbs of fuel pressure with the electric fuel pump running.
  • Is the 12-13 lbs of fuel pressure going into the carb?... or do you have a fuel pressure regulator between the fuel pressure gauge and the carb?
If your running 12-13 lbs of fuel pressure to the Holley carb, that is too much. It need to be regulated to about 7 lbs of fuel pressure to the carb. Too high of fuel pressure to the carb could be causing the overly rich condition... even with new needles & seats + properly adjusted floats.

Slow cranking and backfire thru carb usually indicates that the timing is too much advanced. When you turned your distributor counterclockwise, you advanced the timing even more. You would need to turn your distributor clockwise to retard the timing.

The #2 cylinder pressure does look odd compared to the rest of the cylinder pressures. I would first squirt a little oil into the #2 cylinder (thru the spark plug port) and retest compression. If the compression goes up, there could be a sealing issue with the rings on that cylinder.
You may also want to remove the valve cover on the passenger side (location of #2 cylinder) and start the engine.
  • Are the rocker arms for the #2 cylinder moving the same amount as the other rocker arms?
You may also try to readjust the valves/lifters on the #2 cylinder to see if that helps.
  • Roller or flat tappet cam?
When the engine is running, the fuel pressure is around 6 PSI, it was only that high because I had the switch on without the engine running and it pushed it that high. The gauge is mounted to an Aeromotive regulator.

I will work on the timing issue with a piston stop to see where it is really at and go from there.

And yes, you are correct in that I was advancing the timing more by turning the distributor counterclockwise. Not sure what I was thinking there.

Also, I have no clue what type cam is in the engine, other than it has PRW 1.7 roller rockers and Comp Cams pushrod guides. Adjusting the valves has come to mind, but I am not really sure how to approach that without knowing the cam info.

Thanks for the pointers. I really appreciate them.
 

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Discussion Starter #7
You know you have a timing problem or an issue with the mark on the balancer so you could start with checking the balancer mark for TDC using a piston stop. Once you have that done the timing is easy to dial in. Your compression numbers are fine except that #2 cylinder which has a significant problem, does that plug look oil fouled? You need to do a leak down test on that cylinder to figure out if it's a valve or ring issue.
Thank you for the response. I will definitely take your advice and go from there.
 

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Mike
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When the engine is running, the fuel pressure is around 6 PSI, it was only that high because I had the switch on without the engine running and it pushed it that high. The gauge is mounted to an Aeromotive regulator.
Does the above situation seem odd to anyone else. I am not familiar the Aeromotive regulator, but it is my understanding the the gauge port in the regulator is for pressure regulated/controlled fuel.
I would think it shouldn't matter whether the engine was running or not. The regulator should have kept the fuel pressure to the carb at 6 psi (if adjusted to 6 psi max pressure) no matter how long the pump was running... even with the engine off.
  • Does your fuel pressure regulator have a bypass valve/line to direct a portion of the pressurized fuel back to the gas tank?
 

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Discussion Starter #9
Does the above situation seem odd to anyone else. I am not familiar the Aeromotive regulator, but it is my understanding the the gauge port in the regulator is for pressure regulated/controlled fuel.
I would think it shouldn't matter whether the engine was running or not. The regulator should have kept the fuel pressure to the carb at 6 psi (if adjusted to 6 psi max pressure) no matter how long the pump was running... even with the engine off.
  • Does your fuel pressure regulator have a bypass valve/line to direct a portion of the pressurized fuel back to the gas tank?
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IMG_20200207_170413992~2.jpg


This is what I have. I don't think there is anything running back to the tank to return excess fuel. I, too, thought there should be and thought that the regulator would maintain the set pressure. Of course, it could be set too high. The setup was on the car when I bought it.
 

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Discussion Starter #12
Looks like two cylinders aren't running.
Yes, the plugs that I took out and replaced with these were about the same condition. Some were fouled and others looked practically new. Should I start by replacing the plug wires and cap/rotor? I checked all of the wires for spark to the ends with the plugs out and the wires attached and all 8 had good spark, so I don't know what is going on. If there is spark at the plugs in all the cylinders, then they should all be firing.

Also, there is no vacuum advance on the distributor and this car will be pretty much 100% street driven. Should I replace the distributor with one that provides for vacuum advance? I am thinking I probably should.
 

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Discussion Starter #13
Does the above situation seem odd to anyone else. I am not familiar the Aeromotive regulator, but it is my understanding the the gauge port in the regulator is for pressure regulated/controlled fuel.
I would think it shouldn't matter whether the engine was running or not. The regulator should have kept the fuel pressure to the carb at 6 psi (if adjusted to 6 psi max pressure) no matter how long the pump was running... even with the engine off.
  • Does your fuel pressure regulator have a bypass valve/line to direct a portion of the pressurized fuel back to the gas tank?
This is my regulator setup. It was on the car when I bought it. I don't think there is anything running back to the tank and I also thought the pressure would be held at whatever it was set at. I guess it could be set too high.
 

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Also, there is no vacuum advance on the distributor and this car will be pretty much 100% street driven. Should I replace the distributor with one that provides for vacuum advance? I am thinking I probably should.
YES!

your car will run pig rich at idle and part throttle (read like 90% of your "street" use) otherwise...sound like something you are dealing with now?

You really want around 20-22 degrees of timing at idle with VA hooked up. Generally initial of 8-10 degrees and the VA providing 10-12 degrees =20-22

You very likely will also need to limit the VA the new dizzy brings in but at minimum initially get a VA dizzy

The limit thing is another topic but Crane makes the limiting plate which can be purchased alone for around $9 or the kit which comes with a adjustable VA can and limiting plate

If your current dizzy can accept a VA than all you would need is the Crane kit for around $30
 

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Yes, the plugs that I took out and replaced with these were about the same condition. Some were fouled and others looked practically new. Should I start by replacing the plug wires and cap/rotor? I checked all of the wires for spark to the ends with the plugs out and the wires attached and all 8 had good spark, so I don't know what is going on. If there is spark at the plugs in all the cylinders, then they should all be firing.

Also, there is no vacuum advance on the distributor and this car will be pretty much 100% street driven. Should I replace the distributor with one that provides for vacuum advance? I am thinking I probably should.
YES
 

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Discussion Starter #18
So, in studying the pics of the plugs, I may have stumbled across the answer to my problem. The plugs that look brand new still may be firing but, if there is no fuel getting into those cylinders (as in, intake valves not opening), they will not fire.

If there was fuel getting into those cylinders, the plugs would have some residue of it on them. The fact that these plugs have no residue of any kind on them tells me that there has not been any fuel in those cylinders.

Next question, what could cause it? I am hoping it could be something as simple as adjusting the valves, but I guess it could also be something like a worn out or broken camshaft.

Thoughts?
 

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Discussion Starter #19
YES!

your car will run pig rich at idle and part throttle (read like 90% of your "street" use) otherwise...sound like something you are dealing with now?

You really want around 20-22 degrees of timing at idle with VA hooked up. Generally initial of 8-10 degrees and the VA providing 10-12 degrees =20-22

You very likely will also need to limit the VA the new dizzy brings in but at minimum initially get a VA dizzy

The limit thing is another topic but Crane makes the limiting plate which can be purchased alone for around $9 or the kit which comes with a adjustable VA can and limiting plate

If your current dizzy can accept a VA than all you would need is the Crane kit for around $30
Yep, sounds like what I am dealing with but please see my update to the post that I just added.

Also, it currently has a MSD 85551 distributor, so I don't believe it will accept VA.

Thanks for the response.
 

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If that's a dead head regulator setup it will creep higher than the setting if the engine isn't running. You need to replace those fuel lines. I saw cracks in the picture.

Capture.JPG
 
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