I finally got my truck running again yesterday...
Put a shiny new Edelbrock 1411 on there in place of the leaky old Holley(caused a nice 'lil engine fire, was parked 2 months as a result.)Ever since I've had it, it hasn't run quite right at idle, and, it's always had a bad off idle stumble. When this showed up with the new carb, and, I actually had time to do some investigating, I started pulling plug wires, 1, 4, 6, 3 and 7 don't make any difference in it's running at idle, and, it is definatley missing, it shakes the truck all over the place. However, once I get it rolling on the road, it seems fine, it seems to sound like it's running right, however, after driving a K-Car for the last 2 months, I can't really tell if it actually has power, or it just seems like it... Also, my factory tach is reading low, although sometimes it seems to be right, but, it has been reading as low as 1250 at 50 mph...
Any ideas?
Plugs, wires, dizzy cap and rotor are new, and, I have a new pickup for the distributor I have yet to install. There is no unwarranted noise from the valvetrain, I'd pull the rocker covers and investigate, however, I do not have a garage, and, it's freakin cold out there(-6 F right now)
Evan MacDonald
86 F250 HD XLT Lariat Explorer 4x4 ex. Extended Cab: 460 with factory 2.25" catless duals to the muffler(still running the stocker aaargh)
/T19(syncroed granny low)/BW 1345/3.55 geared Full Floater 10.25 and Dana 50 TTB/ 265/75R16 Hankook FR04's on 16x8 Whitespokes(street tires... Need mudders)
78 F150, 351M/C6, eventually to be repowered with a 400

 

Assuming that your idle mixture is set right, you probably have a ignition problem. Usually a pickup coil will work, or not. You may want to check out your ignition module, and just double check your firing order.

Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear

 

Ignition module is known good, firing order is correct(checked it twice...) Idle mixture is set acording to the manual for the carb.
Perhaps this would be better posted in another forum...
Evan
86 F250 HD XLT Lariat Explorer 4x4 ex. Extended Cab: 460 with factory 2.25" catless duals to the muffler(still running the stocker aaargh)
/T19(syncroed granny low)/BW 1345/3.55 geared Full Floater 10.25 and Dana 50 TTB/ 265/75R16 Hankook FR04's on 16x8 Whitespokes(street tires... Need mudders)
78 F150, 351M/C6, eventually to be repowered with a 400

 

I'm betting it's something with the carb, in particular, the transition circuit. Try checking the gap between the butterfly valve and the throttle bore with a feeler gage. Do this on both the primaries and secondaries. Check with edelbrock on the findings. In anycase, you should have no more than .040 gap. Of course, there should be some opening as well. I am assuming you set the idle mixture properly on both the primary and secondary (if present). You have done too much work on the ignition for me to think there is a problem there.

 

Evan, you need to cover the basic elements of what it takes to make an engine run. 1. Compression, which you verified with a compression guage. 2. Spark, which you verified by replacing all the wearing parts, and using a known good module, also by double checking the firing order, and hopefully timing as well. 3.Fuel, which we know the supply is good as it will drive, but is the idle mixture correct? Is it set by ear? maybe it is turned in too lean? You may have a metering problem on one barrel.

You must also be sure that your engine has developed no vacuum leaks, either by the gaskets, vacuum lines, power brake booster. It may be possible that your EGR valve is either leaking, or stuck open, have you taken it off and cleaned and checked it?

I know that it is a frustrating thing to have happen, but you need to be patient and logical. Your previous post only gave us a few peices of information, and we can't see or touch you rig through our screens. This is the best forum for your problem, if you want it fixed fast, take it to a good shop. If you want to fix it then you need to work with us.
Good luck Evan

Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear

 

The problem is definatley not carb related, it ran the same with both Holley carbs I had on it. I bought the truck in August as a roll-over, and, it had sat for a while with no carb on it.
The engine has 10,000 miles since a $3000 rebuild, I know nothing more than that because it has had 3 owners previous to me since it was rolled.
The idle mixture is set per Edelbrock's instructions(find highest idle with one IMS, then reset the idle speed screw to your base idle speed, repeat for the other, re-set the idle to base, trim mixture for highest idle, and then so it drops 20 RPM, then re-set to base idle speed)
Timing is set to 10 degrees BTDC, and, the distributor is hooked to manifold vacuum(it runs even worse hooked to ported)
I have checked and found no vacuum leaks, brake booster was replaced by the P/O(the one that rolled it) a little over a year ago, EGR valve is new(I have some recipts for work done to the truck), but, does not have a vacuum line hooked to it, and, the EGR port in the intake manifold is plugged off.
I am suspicious of perhaps a stuck valve because it sat with no carb, but, I have no valvetrain noise to make note of, there is a little bit of noise at idle when it's cold, but, it sounds like might be one lifter, and goes away shortly after startup.
Another thing that comes to mind are flat cam lobes, but, with that mileage, it shouldn't be.
I can't really tell if it runs right at criuse or not, this is only the second V8 I've had, and the other one I had stayed in my F100 for 3 days before I put the I-6 back in... I'm far from familiar with the sound of a properly running V8, but, when it comes to an I-6, I know them inside out and backwards...
Taking it to a "good" shop is out of the question here, there ain't one, and, I don't think they'd want to work on it anyway once they saw the big 'ol bead of weld that holds the frame together....
This one really has me baffled
Evan
86 F250 HD XLT Lariat Explorer 4x4 ex. Extended Cab: 460 with factory 2.25" catless duals to the muffler(still running the stocker aaargh)
/T19(syncroed granny low)/BW 1345/3.55 geared Full Floater 10.25 and Dana 50 TTB/ 265/75R16 Hankook FR04's on 16x8 Whitespokes(street tires... Need mudders)
78 F150, 351M/C6, eventually to be repowered with a 400

 

I went back and read all your posts very carefully. This time it sunk in about the tach not being right. Since the tach is connected into the coil and distributor circuit, I would focus on those. Verify that the coil and ignition advance mechanisms work properly. Verify the bushings in the distributor are not loose. Also, make sure all grounds are well connected, strange things can happen when grounds are not connected well.
In order for 5 cylinders not to be getting spark, the distributor/coil has to be involved. Wouldn't you say?

 

Bad vacuum leak? New manifold installations are famous for that.

 

I'm getting good healthy spark when I pull those plug wires off, and, the coil is a new one I yanked off of my 300. As for the tach problem, it an be disregarded, I hooked up an aftermarket one, and, it reads just fine. All grounds are definatley good, I went through everything when I swapped cabs and shortened the frame.
As for a vacuum leak at the manifold, that's one of the few things I haven't checked, but, with all the times the rear float in one of those Holleys stuck and poured gas on the intake, I never noticed anything being sucked in at the manifold to head joints.
It supposeldy ran great before it was rolled, and, the only thing that happened to it before I got it was that someone yanked the carb off of it, and, I have not had anything off of it other than the carb. I'm really leaning towards a valvetrain problem.
I have yet to hook a vacuum guage to it, as mine went missing, and I haven't had time to get another yet. I really don't think it's ignition or fuel, as it starts really good, it just runs like crap.
Also, I have beeen noticing when I shut it off, I can smell oil, not burning, it just smells like oil. I haven't pulled the PVC valve out, but, I'm willing to bet it has more than a bit of blow-by from non-operational valves.
Evan
86 F250 HD XLT Lariat Explorer 4x4 ex. Extended Cab: 460 with factory 2.25" catless duals to the muffler(still running the stocker aaargh)
/T19(syncroed granny low)/BW 1345/3.55 geared Full Floater 10.25 and Dana 50 TTB/ 265/75R16 Hankook FR04's on 16x8 Whitespokes(street tires... Need mudders)
78 F150, 351M/C6, eventually to be repowered with a 400

 

 

I thought you said there was no vacuum leaks? That will cause idle problems. Spray some WD40 around the intake gaskets while engine is running, see if rpms change.

Is there water in the gas? Is the gas good? Is it even gas?

I can't wait to see how this one turns out.