Here is the symptom:

When I reach highway speed (aka wot) the engine starts stumbling and choking as though it isn't getting enough gas. If I back off the throttle, it comes right back to life. Sure seems like fuel delivery to me.

So I first assumed that it was a clogged fuel filter and replaced that. It didn't change anything.

Next, I assumed that given the circumstances, it seemed likethe fuel line might have a hole in it, and when it reaches wot, it was sucking enough air in to make the engine stumble.

So I replaced all the fuel line. While I was at it, I replaced the sending unit, and the whole damn gas tank.

Symptom didn't go away.

I was starting to get mystified at this point. For good measure, I replaced the fuel pump too.

So my entire fuel delivery system is brand new all the way up to the carb. I've checked the vacuum lines. They look alright to me.

WTF did I miss? What could be causing this behavior? If it's the carb itself, what should I be looking for in it?

What carb?
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And how long has it been since the carb rebuild?

What carb?

It's a stock IH Holley 2210.

And how long has it been since the carb rebuild?

About 2.5 years. The power valve is shot, but the power valve has been shot since about 5 minutes after the carb was rebuilt due to the fact that my worn cam loves to backfire through the carb.

Adriana yelled at me for asking if we could bring the dog today, she's still embarrassed that he was a pain in the ass knocking kids over the last time we were at your place.

Adriana yelled at me for asking if we could bring the dog today, she's still embarrassed that he was a pain in the ass knocking kids over the last time we were at your place.
:laughing: :laughing: I forgot all about that!! Maybe you better keep him at home to avoid another verbal assault.:laughing:

About 2.5 years. The power valve is shot, but the power valve has been shot since about 5 minutes after the carb was rebuilt due to the fact that my worn cam loves to backfire through the carb.
So your power valve is shot, you have a worn cam and your worried about breaking up? To solve your breaking up problem I think a new set of plugs and checking the ignition system would help.

So your power valve is shot, you have a worn cam and your worried about breaking up?

As a matter of fact I am. Previously, I could drive my rig. Now it's essentially undrivable, because getting out of Phoenix requires highway driving.

Refer to my vendor-issues thread to see where my "worn cam" replacement status is.

To solve your breaking up problem I think a new set of plugs and checking the ignition system would help.

Plugs are about 4 months old. As for the rest of the ignition system, could you elaborate on what you think might be causing this symptom there?

It's not RPM dependant, it's when I've got the hammer down, or am working the engine climbing a hill. It will cut out, just as if there is no gas... I back off the throttle and the engine takes a second... seems to "catch up" and is fine. (as long as I slow down.) I can sit in the driveway and rev it up till it's ready to blow and it doesn't miss a beat, because it isn't under load.

Did you check to see if your air bleeds are clear in the carb. I used to have that same problem with my old carb. It would act up like that on a trail and I would just take carb cleaner with the straw and blow it back thru the air bleeds. :) Hope this is some help for you.

Float level, ignition (timing dwell plugs cap rotor wires) check fuel pressure/swap pumps.

Thats starters :flipoff2:

Sounds to me like it's your cam (you said it's 'worn' afterall). Tinkering with the ignition, timing, carb, etc. is pointless if your cam is sick. BTDT... You do realize that your cam will not stay at the same 'level' of wear once a lobe is gettin' flat. Once the surface hardness on the lobe and lifter is shot the softer meat underneath will RAPIDLY die.

BTW- 2210s don't have a diaphragm type power valve that can be 'blown out' by a backfire like a 2300/4150. It has a piston type power valve that wears out. Sometimes the welch plug above the power valve piston in the carb top leaks too. Also, the carb top WILL WARP and cause a vacuum leak that screws up the power valve if the air filter nut is tightened too much. Also BTDT...

My 76 304A ran fine in the driveway. But under load it would pop and bang and stumble. When yours does this, pull over and remove the air filter cover. I'll bet the underside of the cover and the inside of the filter element will be wet with gas. Mine sure was...

It turned out that the #7 exhuast lobe was COMPLETELY flat. The rocker would just barely move when the engine was cranked. The underside of the lifter was dished like a :beer: bottle. Every other lobe/ lifter, and every cam bearing and journal were fine. Wierd...

I swapped in a 'cam kit' from northern auto parts. It was about $175.00 at the time (now they're a shade over $200.00 IIRC) and came with a stock cam, lifters, and timing set. If you talk to them on the phone they can also sell you the rubber FelPro valve cover gasket set and the Felpro timing cover gasket set (oil pan gasket segment, water tube o-rings, timing cover gasket, and fuel pump gasket) and some assembly lube. They stock a LOT of IH application stuff that they just don't list in the catalog. They are VERY helpful and willing to make special shipping arrangements for you IME(fast and cheap).

You can do the shadetree cam swap with the engine in the Scout (like I did). You don't even have to pull the intake manifold. Just get an 'expanding fingers' type lifter tool to snake the lifters through the pushrod holes in the heads. If you drop one (I dropped two...) don't panic, as the lifter will just roll around in the valley. You can reach through the other pushrod holes to push the errant lifter into a possition where it can be retrieved.

Good luck with it. The cam swap is not that big a deal. The biggest PITA for me was removing the metal grill structure, fan shroud, and radiator goodies for access to the timing cover. Lot's of rusty bolts! BTW, watch out as that water pump housing is HEAVY and will smoke your back. Holding it up while reaching through the grill opening is MUCH different than putting a water pump on a stand mounted engine...

I hope you can keep your Scout running, and can get the 'vendor' issue resolved without any more cost or hassle.

:beer:

As a matter of fact I am. Previously, I could drive my rig. Now it's essentially undrivable, because getting out of Phoenix requires highway driving.

Refer to my vendor-issues thread to see where my "worn cam" replacement status is.

Plugs are about 4 months old. As for the rest of the ignition system, could you elaborate on what you think might be causing this symptom there?

It's not RPM dependant, it's when I've got the hammer down, or am working the engine climbing a hill. It will cut out, just as if there is no gas... I back off the throttle and the engine takes a second... seems to "catch up" and is fine. (as long as I slow down.) I can sit in the driveway and rev it up till it's ready to blow and it doesn't miss a beat, because it isn't under load.Yes I read the vendor issue, tough spot to be in and it's sounds like your daily driver...

What is it? 345? I don't really know what you drive?

I said breaking up because a lot of times if you get a good mixture or lean a weak spark will break up or die. 4 months on a set of plugs, stock motor should be fine. But I have run race motors that need a set of plugs every 4 runs...

If you have points? set to 30 degrees dwell. Points can change fast, that's why everyone runs electronic.

A 2210 holley sucks! I know some will defend them... look at the accelerator pump linkage and see that there is no play in it, adjust it. If your not getting a full squirt of fuel from the accelerator pump that will also cause your problem. Or if the accelerator pump is worn.

I am not the expert for sure, (Jeff is :D ) but you can easily disconnect the vacuum line from the EGR, plug the line with a golf tee and try it. I was going round and round with mine a while back and it turned out the EGR was over acting. Two things were clues, did not happen when cold, below 160 and only when I mashed on the pedal. The EGR is temp controlled so it does not come on until temp is reached. It was a pain to figure out, since at the time it was over 100 degrees everyday. So it took a while before I caught on to the temp clue. By then I had allready tested everything else on my other Scout :shaking:

What about installing an inline fuel pump? Possibly the lobe for the fuel pump arm is flat and not allowing full fuel pressure. When you come up here to pick up your parts or go to the police line up, bring cash. I got a running 304 & 345 with your name on it. :smokin:

Check your timing. If the distributor isn'nt/wasn't tight its possible its crept forward making the engine over advance at rpms above 2500. Check timing at 2500-3000 rpm to see what your overall advance is. If its over 35-40 degrees then back off timing and go for a drive.
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