I don't normally rev my 2F this high, but lately whenever I get it over 3500 rpm it starts breaking up. I've never taken it above 4200. Below that everything is great. But knowing it isn't right is bothering me.Its a desmogged 2f with a recent weber, downey header, and a mallory full centrifugal advance points distributor. The cap and rotor are good, points are gapped to .019 its got new ngk plugs. I haven't put new wires on it yet, but they seem fine. I have been wondering about the distributor, although it seems fine, and there isn't any play in the shaft, it doesn't seem like anybody uses these. Is there a reason? It was on the truck when I bought it. It looks like man-a-fre still sells them. Would I get better performance from a non-usa distributor?

High RPM stumble is usually an ignition problem. Typically bad points, bad points gap, points bouncing, bad coil, bad condensor, plug gap, etc. The gap needs to be on the low side of the range for the coil to saturate.

Why do you want to rev it that high? Trying to throw a rod? :D

When I had my '79 with 2F it had a stumble or cut out at higher RPM (under load). Turned out to be the fuel pump...Just a thought.

High RPM stumble is usually an ignition problem. Typically bad points, bad points gap, points bouncing, bad coil, bad condensor, plug gap, etc. The gap needs to be on the low side of the range for the coil to saturate.

Why do you want to rev it that high? Trying to throw a rod? :D

Maybe I am trying to throw a rod. That would give me a good excuse to swap in the tbi 350 sitting in the corner of my shop. Actually I very rarely drive it that hard, except when trying to keep up with my buddies 72 bronco with a slightly modified 302. My poor 2f doesn't stand a chance. On the pavement anyway. I've got a new set of points and a condensor in the truck, as well as another coil. Maybe i'll try that and checking the plug gap this weekend. Anyone have any input on the mallory? Are these things crapco or just something that isn't too popular.

I'm thinking spark scatter too. It should show up on a scope, if you can get your truck plugged in on one.

Also need to check where your advance curve maxes out. If the curve is maxed at 2400, then your obviously falling further behind as you continue increasing rpm.

how about float level, and or fuel filter clogging?

Fuel starvation is more directly load related (like trying to maintain 60 MPH up hill) than RPM (like revving it up in first gear) and usually results in bucking and spitting.

Mallory makes a good distributor, but I don't know that it is correct for your engine. Points are old school and electronics really shine at high RPM. Still though, there is no reason that a good points set up can't do 4,500 RPM all day (just not in F/2F).

Ken-

If it's a Mallory dual point full centrifugal you may be running out of advance. I ran one years ago and if I recall, most of the advance comes on early and thats all you get. But it was great in the low end, and that's all that matters.

Oh yeah, the only way to set the dual points is with a dwell meter, only reason I have one in the tool box today.

Valve float with some tired ass valve springs. Land cruisers have the softest seat pressures I have seen. I redid a head on a cruiser with a high end stumble and it was bad valve springs that let the intake valve float way too much...

I drove the cruiser to work today, and the problem seems to have dissapeared. Ran it up to 4000 in 2cnd coming out of a toll booth. Very , very odd. It's reassuring to hear some positive comments on this distributor. I don't think it's a dual point. It only has one set of points. Of course there are two contact surfaces. Does that make it a dual point? I do have an old school dwell meter that belonged to my grandfather. But he's not around anymore to show me how to use it. Any tips?

Hook it up to power and the distributor side of the coil. set it for six cylinders, start the engine, read the gauge.

This is the dist. that I run (for the past ten years) in my 2F and it works great. I run a 38/38 weber, RV grind cam, MAF header, Holley Fuel pump, etc... I get high RPM stumble but only near 6K RPM. Don't see that kind of RPM very often, and the rods are still inside the engine. I would suspect valve float (pretty sure that is my rev limiter) or fuel or weak coil. The wires could also be leaking a bit of voltage. New plug wires are pretty cheap.
Spray them down with some water at night and see if you can see any stray voltage.
Or run your tounge down them in the day light :)

Good Luck

I've been running a mallory unilite optical pickup dist paired with a jacobs coil in my trail rig for about 10 years, no prob...I'd rahter have 78-on stock stuff though...

I don't normally rev my 2F this high, but lately whenever I get it over 3500 rpm it starts breaking up. I've never taken it above 4200. Below that everything is great. But knowing it isn't right is bothering me.Its a desmogged 2f with a recent weber, downey header, and a mallory full centrifugal advance points distributor. The cap and rotor are good, points are gapped to .019 its got new ngk plugs. I haven't put new wires on it yet, but they seem fine. I have been wondering about the distributor, although it seems fine, and there isn't any play in the shaft, it doesn't seem like anybody uses these. Is there a reason? It was on the truck when I bought it. It looks like man-a-fre still sells them. Would I get better performance from a non-usa distributor?


good god! :eek: 4,200? :eek: damn! 3,500 is pretty much red line for a stocker . I would take that 3,500 RPM stumble and call it my rev limiter :D. winding that por thing like that, ya better start looking for a V8 :p

I get high RPM stumble but only near 6K RPM.
:eek: :eek:
Damn Don 4200's got nuttin' on this OMG, what's that sound like? :confused:

Kent

6 grand!!!!! 4" stroke at 6 grand!!!!!

c-mon :confused:

6 grand!!!!! 4" stroke at 6 grand!!!!!

c-mon :confused:

Only happened a couple of times...

Pretty much sounds like a wide open free flowing engine with the valves floating. All four of my tires spinning pulling another stuck Cruzer out of deep mud. We are talking about a VERY short (2 sec maybe) amount of time.
It's amazing what an engine will rev to if it doesn't have to move it's own vehicles weight. I would never think the thing would do this... But, I saw the tach a couple of times...
Hard accel and a 4 grand shift is really no big deal on a NON-STOCK engine.
Bad idea to hold it there... And, if the engine blew... I'd just tell myself that that sucked and was pretty stupid of me.

Bad idea to hold it there... And, if the engine blew... I'd just tell myself that that sucked and was pretty stupid of me.
You're foresight is exceeded only by your humility :laughing: :laughing:

Walt

Only happened a couple of times...

Pretty much sounds like a wide open free flowing engine with the valves floating. All four of my tires spinning pulling another stuck Cruzer out of deep mud. We are talking about a VERY short (2 sec maybe) amount of time.
It's amazing what an engine will rev to if it doesn't have to move it's own vehicles weight. I would never think the thing would do this... But, I saw the tach a couple of times...
Hard accel and a 4 grand shift is really no big deal on a NON-STOCK engine.
Bad idea to hold it there... And, if the engine blew... I'd just tell myself that that sucked and was pretty stupid of me.


WOW! :D

the very first Cruiser I picked up had #5 conecting rod laying in the glove box :eek:

so from day one I have been paranoid winding up an over square motor :D

here is a neat little tid bit for ya :D a 2003 mazda 3 has a rev limiter that kills the throttle at around 8g's :D (rent a car) :D

needless to say I opted for the insurance:D