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Help timing my truck

The Quadrajet was original equipment on the Ram 360 in 83. Maybe time to actually check the fuel pressure. If you can run the gauge to some where it can be seen while going down the road. Just don't put it in the passenger compartment.


I question the accuracy of what I've done, but here's where we're at. I ran to Pep Boys, because they had it, and bought a Mr Gasket tee and pressure gauge. I ran fuel line from the tee to the windshield and installed the gauge. I don't know if those 4' of rubber fuel line tee'd off of the actual fuel gives an accurate reading or not. But, at idle, it's showing about 8 psi (way too high). When rev'd, it'll drop to about 7 (still way too high).

Before I install a pressure regulator, do we think this reading is reasonably accurate based on the tool and the way it's run? Also, would having too much pressure cause these issues? (I suppose it would be like having to little air, so I can rationalize how it would cause the engine to stumble.)


Polara, I'm almost at the point where I'm going to swap the carb. I spend about $150, or so, I don't remember exactly, having this carb professionally rebuilt. I hate to just junk it. But, if it'll make it go, I'm open to the idea. I'm just not there yet. I'm trying the cheaper stuff first (which is, cumulatively, costing far more than a carb).
 
That would be accurate way of doing it. But what does the gauge read while driving it and when it stumbles upon itself. For a thermoquad yes the pressure is a tad out the 3-5 range. For the quad you should be ok. We still need to know what happens to fuel pressure on the road and under load. The quad is not that difficult a carb to rebuild and from the vacuum readings you have posted it should not have any vacuum leaks. It could possible have a secondary circuit problem but a simple check for blocked passages with a can of carb cleaner would verify that.
 
I gave up on that carb. I will now join the ranks of the anti-thermojunk crowd.

I picked up a used Elderbrock 1406, bolted it down, truck runs great now.

Still needs fine tuning. I spent all of about 22 seconds timing it by ear (I still can't time the truck with a timing mark). I haven't adjusted a single thing on the carb except to make sure the idle adjustment screws were out 2 full turns. Needs a softer throttle return spring because the gas peddle is super firm. But not bog, not backfire, nothing. I go slow, it runs decent. I put my foot in it, it runs decent.

I bet I could get more performance out of the thermojunk, but, I just need it to work. I am not building a performance machine. It's focus is on hauling stuff and, as time goes on, I'll probably do some fun more rat rod like stuff, cool stake sides for the bed, clean up the interior a bit, basic stuff. The patina will stay. I'll keep factory wheels (although I do have a set of 16s to replace the 16.5s. Maybe replacing some of the lights on the truck just so they're visible. I may also fix windshield wipers and, if I'm feeling really ambitious, fix the washer fluid assembly.

Immediate next step is to fine tune it and enjoy it.

Thank you for all your help. Even though I fixed it the easy way, by replacing the carb, I really learned a lot through this process and I appreciate the help and advice.

Next...
 
The thermoquad is real particular about setup. Getting a step out of order is not good. They got a bad rap on count of bowl and float issues.
Its the only carb I run on the carbed vehicles here.
 
The thermoquad is real particular about setup. Getting a step out of order is not good. They got a bad rap on count of bowl and float issues.
Its the only carb I run on the carbed vehicles here.

I think I got to the point where I intellectually understand that the Thermoquad is a good carb and capable of a pretty good amount of power, but that it takes skill and experience to tune them. I lack both of those things and I really don't have a community of grease monkeys to help me gain that experience, locally, like I did in high school. As such, I went to a carb that's built for idiots like me. Idiots that are fine giving up some power in exchange for a carb that just works right out of the box.

If I were building a performance vehicle, and I wasn't going to invest in fuel injection, I would still consider a Thermoquad because I know what you can get out of them. But, if I were building a performance engine, it would be in a vehicle that I didn't need as a tool to help me with all sorts of projects. So, this method gets the rig on the road and back in action!
 
Well, the problem wasn't the carb and I still think my lack of skills contributed to the problem, but, before I brought the truck into the shop to tune it and make it run right, I decided to run one more test. A compression test.

Most cylinders ran 115psi on my cheap Harbor Freight set. One cylinder ran 110, one ran 120. So, 7 of the cylinders looked great! But then there was #7. Cylinder 7 was running 40psi. I checked twice to confirm that.

So, would low compression in a cylinder allow for a pretty smooth idle but cause the back firing and stumbling I was (am) experiencing?

What are the next steps? Now we're getting into territory I've never been in before. How do I identify bad cam/valve/etc?

There's a good truck in there trying to get out. I need to figure out if I'm the one to find it and I could really use some advice to help me figure it all out.

Thankfully the wife is out for the day so I haven't had to tell her the bad news...that the truck is going to require more time, effort, and money (or some gasoline and match).
 
Couple of tablespoons of oil into the bad cylinder. Pull the coil wire, rotate the engine a few revolutions and test that cylinder again. If the compression comes about to nornal its rings. If not its likely a valve. With the problem with back fire I would lean more to a valve.
 
I would pull the valve cover also and check to see if both rocker arms are moving the same. If rocker movement looks good, take the rocker arms off and if you have the ability to, pump air into the chamber, if air comes out the exhaust, then the exhaust valve is burnt, if it comes out the carb, then the intake valve is bad. There is a hose made just to put air in, but you can use the hose from your compression tester if you remove the schrader valve first.
 
I suppose rotating the engine with the valve cover off would tell if I had a flattened cam lobe?

I think I'm comfortable with the idea of pulling the heads (both) and having them gone through if there's a valve issue. If I need to do that AND pull the cam, I'll look at a used engine. Same for if it's rings. The truck just isn't worth the bother of a full rebuild. Not sure it's worth the bother of pulling the heads, but I was dumb enough to buy this pig, I guess I'm dumb enough to keep working on it.
 
Update. Wet test points to valve train. I'll likely pull the heads and have a decent valve job done along with making sure they're flat and not cracked.

While I'm in there, I'll replace the cast iron intake (mostly so I don't have to lift back into the engine compartment, again), the harmonic balancer, the timing chain and gears, gaskets, and, while I have the room, I'll look at cleaning up the wiring (there's what 6 wires?).

Not excited about doing this, but in the end I 'should' end up with something reliable.
 
Update for those interested. Rebuilt the top end. Engine is running smoothly and quietly. Some issues with how the throttle cable is mounted relative to the Edelbrock carb, but otherwise everything seems solid.

I was looking at this thread again because I'm having some subtly similar issues. (The following is all in neutral in the driveway, I haven't driven the truck yet.) At idle, engine is smooth as silk. If I gradually roll the throttle on, smooth as silk. If I put the hammer, it pops and almost stalls.

Timing is set to 2* BTDC. Looking above, the suggestion is 6*. I'll try that. But, thanks to a new harmonic balancer, I can see the timing marks!!!

The valve guides, seats, springs, and valves themselves were just shot. They're all nice and fresh again so things seem to be better now. Just gotta get it tuned correctly then I can start working on other little projects on the truck...and much bigger house projects that I bought the truck to help with!
 
I put the hammer, it pops and almost stalls.
Great update
What's the compression test now?
You cannot start any diagnostics until you have proved that the engine is mechanically sound. And that starts with the pressure and knowing that the cam is properly timed.

A) Engines will pop when the intake valve is not fully closing. What happens is; as the piston comes up on compression stroke, it forces some of the recently ingested mixture back up into the intake, which is already full of a combustible mixture. When the spark lights off the mixture, the fire goes into the intake, and lights that off as well, which then burns; and the expanding gases go up thru the carb backwards, and with no usable mixture in the plenum, the engine stalls.

B) Engines will also pop from an induction crossfire. This can occur when a spark destined for one cylinder excites a spark in a very nearby wire going to another cylinder, which just happens to be on an intake stroke. Cheap wires have to be well separated to prevent this It is most noticeable when slapping the gaspedal.

C) Engines will crossfire inside the cap, if the rotor phasing is off. The spark always jumps to the tower that presents the least resistance, usually the closest but not always. We can talk more about this later.

D) Engines can pop from a lean misfire. When you nail the pedal, ASSUMING the engine is otherwise mechanically sound; the engine gets a big gulp of air. The engine does not suck this air in; rather the atmosphere is right there on top of the throttle valves, desperately trying to get in there.
1) When you open the valve in a hurry, that inrush of air has no fuel in it. It is the job of the accelerator pump to instantaneously deliver fuel into it. This is your first defense against a stumble,
2) the second defense is; the engine is depending on your transfer slots not having been dried up by a maladjusted idle exposure. more later
3) the third defense is; the metering rods have to pop up and allow the atmospheric pressure above the fuel in the bowls,to push the proper amount of fuel out.
4) the secondary air valve has to be delayed until the primary system is fully functional
5) the ignition timing has to be synchronized to all this activity.
6) if equipped with an auto trans, the convertor has to be properly functioning
7) if equipped with a manual trans, forget slamming the pedal open at 1200 rpm! it will never put up with that, especially with the air-valve set too loosely.

Again I ask; what are the results of a current compression test?

You can find me on FABO as AJ/FormS
 
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Current compression test, taken while hot. All cylinders between 110 and 120. Seems low, but when I took the compression before pulling the heads, the engine was cold. Hoping that explains the lower compression across the board. Happy that the compression numbers are relatively close though.

I also took a little timing out of it and retuned the fuel mixture. Running about 19 in Hg at idle (I need a tach so idle is where it sounds good for now, sadly).

Your talk of metering rods and such has me wondering. I bought the carb used with very little use. It came from an older guy who was looking to improve fuel economy on his old Chevy small block (I think it was 350). He kept sending it back to Edelbrock who would retune it for him and it never gave him the fuel economy he wanted so he pulled it after a few hundred miles and 6 months worth of attempts. He eventually passed away and I bought it from his grandson. Anyway, in those attempts to improve economy, I wonder if I need to undo some of the things Edelbrock did? If those compression numbers make sense and aren't puzzlingly low, I may take it down the street to a shop that has a mechanic dedicated to older carbureted vehicles. He's usually booked a month or so out, but I've heard he's REALLY good at what he does. Might be worth just getting him to tune it if I can get things to a point where it shouldn't take him days to get it right (a few hours would be my goal for him).
 
I need a recap;
From page 1

At TDC, the rotor is pointing to #1 plug wire.

If the timing mark lines up when TDC is found there should be only two reasons for it to not show up with the light. Cam or ignition timing one has to be off. Just because the distributor is orientated with number 1 on the cap would not mean cam timing is correct. That can only be verified by compression at number 1 cylinder when the crank comes up on TDC on number 1 cylinder. The finger over the plug hole or the removal of the right bank valve cover and watch the intake valve close are the only ways to verify that.

I double checked earlier and at TDC, the rotor points pretty close to the #1 plug, within range of being able to to time it. Thus, I bet I just need to do more to set up the distributor.
The pick-up is in between the splines on the reluctor at 0* timing with the rotor point at the #1 plug wire.
While it was running, it was lazy. Moving the distributor in either direction would either make it stumble and stall out or, in the other direction it would kinda buck, then stall out. So, while I could get it running, I couldn’t quite get better...if that makes sense.

From page #2
There doesn't appear to be any slop.
I suspect that your damper has slipped, set the timing by ear until it runs decently, give it more advance in little increments then check the timing. It will be off.
From page #3
I did a once over, or would it be a fifth or sixth over?, looking for vacuum leaks. Found a cracked plug, changed that. I tried plugging all of the vacuum ports and that helped a little. I rehooked them up, one at a time and it seems like the only one that really messed with anything was the vacuum advance.
doesn't totally stall when you hit the gas, but it still stumbles a touch with a hint of a backfire.
I decided to try timing the engine with a vacuum gauge. This, I thought, went well. I discovered the engine ran better, with more vacuum at idle, with the port where I had the PCV valve plug in, plugged. I moved the PCV to share a vacuum port in the manifold itself. With the vacuum advance port plugged, I was able to get about 18 in Hg. With the vacuum advance attached, I managed about 20 in Hg...steady. The idle seems a little high, but I can adjust that down later.

From page 4
I picked up a used Elderbrock 1406, bolted it down, truck runs great now.
Well, the problem wasn't the carb and I still think my lack of skills contributed to the problem, but, before I brought the truck into the shop to tune it and make it run right, I decided to run one more test. A compression test.
Most cylinders ran 115psi on my cheap Harbor Freight set. One cylinder ran 110, one ran 120. So, 7 of the cylinders looked great! But then there was #7. Cylinder 7 was running 40psi. I checked twice to confirm that.
Update for those interested. Rebuilt the top end. Engine is running smoothly and quietly.
At idle, engine is smooth as silk. If I gradually roll the throttle on, smooth as silk. If I put the hammer, it pops and almost stalls.
Timing is set to 2* BTDC. Looking above, the suggestion is 6*. I'll try that. But, thanks to a new harmonic balancer, I can see the timing marks!!!
I also took a little timing out of it and retuned the fuel mixture. Running about 19 in Hg at idle (I need a tach so idle is where it sounds good for now, sadly).
wonder if I need to undo some of the things Edelbrock did?

From the above
it seems to me
that your cam is in wrong.
And to overcome it, you are throwing timing at it, which with a poor reluctor phase, is causing the spark to jump to the wrong tower when you nail the gas.
IMO, you need to prove your cam is in close to where it is supposed to be. This is actually easier than it sounds (see #1 below). Then you gotta phase your rotor (see #2 below), then you gotta put your vacuum hoses ALL back where they belong And make absolutely sure that your Vcan is plumbed to the spark port (see #3 below). Then set your Transfer slot exposure and finally your ignition timing (see #4 below).

Paragraph 66,lol

After that; you will set your idle timing to ZERO at 800 or less rpm; then With the Vcan disconnected, rev the engine up until the timing no longer advances. This could be as high as 4000, usually not more. Write it down. Also write down what the timing is at 3400, and 2800. When yur done, reconnect the Vcan. ( see #4 below)
When you all that done, then we will know what's what. IMO, there are just too many factors pointing to a bad cam-timing.
But before you do anything see #5 below.
 
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#5, pick-up polarity
If the polarity is reversed, you can set your idle timing ok, and it will idle.
But as soon as you rev the engine up, the ECU will start to drop sparks and scatter the timing. If you are watching the mark with the timing lite, they will start flying all over the place. If you see this on your lite, you have the wrong direction of rotation pick-up, in that new D of yours. From the factory, your D should have one orange wire, and NO violet wire. The other wire could be black or maybe gray, I forget. If you have a violet get rid of it or;
or simply cut the connector off, leaving enough wire on both sides, to reverse the connections. Badaboom!
If this fixes your problem then you cab skip numbers 1 and 2 below. But DO do number 3 and 4 below

#1) checking the cam timing.

Set the #1 piston to TDC on the compression stroke. For this test, you can use the mark on your new balancer. Pull the passenger side valve cover off. #6 piston will also be at TDC, but on split overlap. This is the period of cam rotation, where the intake valve and the exhaust valve are both open approximately the same amount. This window is about 10degrees wide, and you want to be close to the middle of it.
Normally I do this with the intake off because I can just put a straight edge across the tops of the lifters. Then I rock the crank backwards or forwards a few degrees until my straight edge touches each lifter in two spots. Then read the balancer degrees. Ideally this will occur at about 4 degrees advanced.
But with the intake on,a short period cam, and hydraulic lifters, it sometimes gets to be a hit/miss affair. I guess you will be watching the tips of the valve stems. We are not looking for absolute accuracy here; I just want to make sure the chain is not retarded a tooth or more. I don't think you can do this alone, because you need to be watching the valve stems moving in opposite directions, trying to get a fix on where split overlap is, then reading the balancer. I think you will need a helper on the crank bolt with a long enough bar, to make the motion smooth. Just do the best you can . At the very top, on a short period cam, there may be little to no motion at all from either valve. If that happens at or near TDC then you are in the window. Good Luck

#2) rotor phasing
Having proved the cam is in right
the rotor phasing should be right.
But you still gotta prove it.
So Put the #1 piston at TDC compression. Then back the crank up to 20* advanced. If your balancer is not marked then, this is about 1/18th of the perimeter around your new damper. This works out to 1.25 inches, close enough.
Next find #1 tower. Take a Sharpie and draw a line on the side if the cap at the center of that tower where it intersects the aluminum body, and continue down the body a short distance. This is where, or very close to where, the rotor must be pointing, when the fire goes out. So pop the cap and look. Not there, hang on. Is the pole piece in the magnetic pick-up aligned with a vane, any vane. It must be within a couple of degrees. If not, then pull the coil wire out of the cap and near ground it, so you can see/hear when it sparks. Now turn the key to run, and pull the vcan until it sparks. Repeat a couple of times because if you move too slow, it may not spark. When you are satisfied, and the Vcan has another inch or so in the pulling direction before it hits something. then secure the D, and turn off the key. Now, where is your rotor? It has to be very near the Sharpie mark! If it is not, then you will have to make it so.
If it is out by a full tower, then you have a choice; either rewire your plugwires, or reindex the magnetic pick-up to the next vane.
Now we gotta figure out what to do about the misalignment. Theoretically you can be out nearly a half a vane. Install the rotor, and crank it over as far as it will go. Does it get closer to the mark?
If it gets to the mark or past it, then leave it alone. So long as it returns to less than halfway towards the previous tower. One quarter would be better.
Now; rotate the crank to TDC, and check your rotor to tower phasing again, the rotor tip HAS to be closer to your index mark, than to the previous tower, and by a good margin, because when you stomp on the pedal, the spark is gonna choose the path of least resistance, which would be the previous cylinder which is now on the exhaust stroke.
But if you need to get the rotor closer , you may be able to use the second alignment slot in the reluctor. Shine a light down in there and look for it.Somebody already mentioned this, but you should see little arrows down there. To use the other slot, just pry the reluctor up (using TWO tools), then transfer the roll-pin key to the other slot and reinstall it, all the way down. Then repeat the spark test. If the rotor is now closer to the index mark, that would be good. If not, then put the reluctor back.
But if you cannot get the rotor into the operating window, something is wrong. You cannot rewire the cap or use a different vane nor reclock the intermediate shaft. None of those will make a difference. So the very first thing you have to do is prove your TDC mark on your balancer is in fact TDC according to the piston. Up to now I have assumed that you already had done this, because it has been mentioned several times, by others. So after you get that done, and if it should be that the mark is in fact correct, then Your D is defective, somebody welded it up wrong. You cannot fix that... but you can work around it.
You got two choices; 1) modify the reluctor location,so the reluctor comes to the tower, or 2) move the alignment slot in the cap, so that the tower comes to the rotor,lol.

#3 hose plumbing.
1) Put the PCV back where it belongs. usually dumping into the primaries very near to the low speed ports.
2), if you have power brakes; then, the FIRST choice for that hose is to go to the backside of the carb. If your carb does not have a port there, THEN, you can use the intake.
3) The Vcan must be plumbed to the spark port. This port is inactive at idle, and it may require more than 1500rpm in neutral to see a signal there. And the signal will be small at first, and grow with rpm; this is normal.
Any other port you might want to use that reads the same or similar as manifold vacuum, is NOT the spark port, and is the wrong port. Use only the spark port.
4) Set your transfer slot exposure to dead square to a little taller than wide. Do this with the curb-idle screw, making sure the fast-idle cam is NOT involved. You will have to remove the carb and flip it over to see the slots. Return the mixture screws to ~2Turns out. Make sure the secondaries are fully closed but not sticking. After this, DO NOT TOUCH the speed screws again. You will set the idle speed with ignition timing and idle air bypass; NOT with the speed screw. It will be reserved for fine-tuning the idle fuel.

#4, ignition timing
If you had to fix the rotor phasing, then you may still be at 20* advanced. leave it there.
Now go find the timing results I asked for, in paragraph 66, and post them up..
First thing is the power timing. The engine must not detonate under power. This breaks engines. To that end, your power-timing must not exceed ~36*, And you may have to decrease it a few degrees to keep detonation at bay. Furthermore you may have to delay that max timing to 3400 to 3800, at full power (later) to keep it at bay. This is your first concern. Do not concern yourself with 6* of idle timing at this time. Your engine will like 20 to 30 degrees of idle timing when you set it by the vacuum gauge method. Do not use that method; it works for idle-timing allrightee, but NOT for anything else.
So what were your timing results? I'll see if we can use that D as is.... or not.

Happy Hotrodding
 
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I’ll give number 5 a shot.

The cam timing I checked the hard way, I had the timing cover off and everything lines up while the pistons are in the position they should be.

You know what I didn’t check with all of the backfiring and such and should have? Bent pushrods. While that wouldn’t prevent a valve from closing, if it was an intake valve, it would prevent the correct amount of air from getting in by not opening enough. Just a thought.

I’m 100% certain the cam timing is set correctly and it’s rare I’m that certain about anything with this truck. But it was a very real concern for me so I made certain while it was all right there in front of me. I figure I’m 50/50 on the distributor so I’ll start there.
 
I’m 100% certain the cam timing is set correctly and it’s rare I’m that certain about anything with this truck. But it was a very real concern for me so I made certain while it was all right there in front of me. I figure I’m 50/50 on the distributor so I’ll start there.

Are you assuming that the cam sprocket was on the key, and the key was in the cam,not sheared, and that the keyway was machined correctly?
That camkey is only there to ballpark the cam timing. Once you have torqued that bolt down, It wouldn't need to be there at all.
But if the bolt is not properly torqued, then is is easily possible for that key to be beat up and this will allow the cam to run retarded. Eventually the key could shear, and the engine stops running.
A retarded cam causes a decrease in low-speed torque, and retarded idle-timing,and a lazy engine. When it gets lazy, the vacuum is reduced, and airspeed thru the carb falls off, leading to hesitations.
So then you check the ignition timing, see that it is retarded, and retime it.
Now not only is the cam-timing wrong to where the piston is, but the new timing is too early and drives the piston back down the hole backwards; so lazy, lazy it is; and timing advance with rpm, lights the fire before the intake valve is closed, and she backfires under load.

I'm not saying this is your problem.
What I am saying is that if it is, you could be spending many many hours chasing your tail around in circles, and throwing parts at it with no results................
What I am also saying is that if your truck showed up at my shop; the first thing I would do is check that pick-up polarity, and if that is ok, then
the second thing I would do is check the cam timing. I get paid by the hour, and people expect results. And in your case, knowing that you have already thrown a D,a carb and a valve job at it, and the very low compression numbers. You could not talk me out of checking the cam timing.
I would send you away first; and I'm not kidding. If I had to, I would offer a free check , with the proviso that if I'm right, then you pay double. Not only do I fix stuff, but I teach lessons. I am not a throw parts at the problem kindo guy, to see what sticks. That is why people used to come several hours one way to whatever shop I was calling home.
And yes, I have told customers to piss-off. With endorsement from my employer. In one hour or less, I can prove the cam timing is close enough to not be the problem.... or it is the problem. Now I can move on.
But if I don't check it, and I spend three hours checking every thing else, and if it should happen that I find nothing; then I have to back to the basics and do the cam-timing check.
If it should then be that is where the problem lies, just try charging the customer for those first three hours.... nevermind the new D I threw at it, or the new fuelpump, the wires and ignition parts, and the different carb. The customers in my neighborhood are mostly farmers, and they ain't stupid. They are gonna hold me accountable.
So i will have to remove all the parts I mistakenly threw at it, costing my boss more time, and now He is not happy. And then all thatcht falls on me. Ain't happening I got no time for that.
I was usually backed up several weeks for work, so if the customer don't play ball, then piss-off. Take yur stuff down the road to that new shop,Slippery John's Place, I hear he's desperate for work,lol.

What I am saying, "charm",
is after the polarity test, just be ready to come back to cam-timing. Your 115psi, after a valve job. is pointing straight to a late-closing intake, or
a high-elevation location.
And I checked; Everett is close to sealevel, ~100 to 400 ft.
 
Bent pushrods. While that wouldn’t prevent a valve from closing, if it was an intake valve, it would prevent the correct amount of air from getting in by not opening enough. Just a thought.
Bent pushroads will cause an awful clatter, and usually fall out sooner or later, the engine runs rough at idle and as the Rs climb gets worse. You did not mention this so I think it's safe to leave it
Just a thought.
 
Thanks "AJ". Finally had time to work on the truck. I'll go through everything I can think of, not necessarily in order.

During the recap you mentioned the balancer and referenced the two reasons it wouldn't line up. You missed the third, that the outer ring slipped. This is what happened and was confirmed in two ways. First, the folks that rebuilt it said so and second because the timing mark magically reappeared when the rebuilt balancer was reinstalled.

Compression. 115 psi +/- 4% on all cylinders. This should indicate that all cam lobes are within spec since all valves are closing similarly. Also consider it's a Harbor Freight gauge and, frankly, +/- 4% is a better margin of error than I would expect. Cam appears solid as do valves, guides, and seats.

Cam timing. #1 cylinder at 0* advance, both lifters are slack and valves appear stationary within a few degrees advanced or retarded. Per advice, no adjustment likely needed.

Ignition. At 20* advanced, the rotor points towards the #1 spark plug tower. The spline points towards the pick up within about 1/32". Per advice, close enough, no adjustment needed.

To find 20* advanced, I set the balancer to the 0* mark and made a single mark next to 10* after. I moved the balancer so that new mark was at 0* and made a double mark at 10* after. I now have marks that tell me to add 10* or 20* to the reading since the factory mark buries itself under the water pump. This also allows me to have an idea if I'm getting anywhere near 36* advance. I'm close, but not so close as to stress me out. I should add a set of 3 marks to tell me to add 30*.

I get backfire through the carb whether timing is set at 2* advance or 20* advance. It happens with or without the vacuum advance line connected. I, logically, get better vacuum at higher advance, but 18 inHg at idle ain't bad. With that, I'm pretty sure I don't have a vacuum leak.

I replaced the coil, something I'd been meaning to do anyway. While messing with it, I also swapped the ballast resistor (new) and the ECU (pretty sure it's used) for one that came with the truck. No change.

I moved (and replaced) the fuel filter from before the pump to after the pump. No change.

I set the idle adjustment screws to 1.5 turns out per the Edelbrock manual. No change.

At some point I'll reroute the fuel from up the front of the block and along the valve cover to along the frame rail and up the firewall. This is more for aesthetics, but if anybody thinks I may be dealing with vapor lock from a 190*F manifold, I'll move it immediately.

I have not yet figured out how to adjust the transfer slot exposure. There's no mention of it in the Edelbrock manual and very few mentions online that I've found. Some mention that it should be adjusted, but none mention how. I have not pulled off the carb to look.

I plan to inspect any filter screens on the carb inlet. I don't believe there's one on the fuel pump.

I still lack a tach so any adjusting having to do with idle is being done by ear. I'm trying to find something digital that I can mount to the fender well or firewall, ideally temporarily for diagnostics only, that's inexpensive and reasonably accurate. I haven't found that yet.

It does feel like I can rev the engine hard at the carb without stumble but if I use my foot on the gas pedal, that's when I get the backfire through the carb. Not sure if my foot hits the gas harder and faster than my hand does or if it's something to do with the linkage.

Plugs look fine, as they should since they're new. Gaps are still correct, whatever Chiltons calls for is where I checked that they were set to. Plug wires are new and I have spark through them.

I may pull the sending unit and inspect the filter sock. Not sure why a clogged sock would flow enough fuel at high RPM but not when I hit the gas real hard. But it's worth a peek since I have relatively easy access.

Did I miss anything? Anything stand out as a concern?

Thanks!
 
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