valves floating?

[daytona kid]

I've got what seems to be a basically stock 1972 440 in my 68 charger with a 727 trans. The 440's history was unknown to me but after compression check, etc, I concluded the motor was good enough for me for now. But, It has a problem and starts missing at about 4300 rpm. I can make it do it in neutral/park while sitting still. It will go dead unless I pump the throttle and then it will recover after about 5 secs. It feels and sounds like some cylinders are not hitting/firing. The motor makes no noise such as valve train rattle, etc. I have a new proform distributor with electronic ignition on it, which I'm not sure to be suspicious of it or not. Somehow I got the idea that it could be floating valves and a bud agreed after I demonstrated it for him. The motor runs like a dream until I shift it myself and let the rpm get to hi, then it is almost like turning off the key except I can hear and feel it not hitting on all 8. I instantly let off the gas. As I coast down I pump the throttle to keep it alive then it recovers and comes back on all 8. Could the valve springs be old and weak and causing the valves to float? Does this seem like valve floating? I'm thinking about buying some new springs just to see if that's it.. Any info appreciated..

 

[turbine68rt]

Carb float settings correct?

 

[440Coronet500]

Sounds fuel/ignition related. 440'

 

[Curiousyellow71]

Check and see if sock filter in the fuel tank on the pickup is plugged. Never had one die from floating the valves...it hits a max rpm like a rev limiter when you float the valves. It sounds like its starving for fuel.

 

[daytona kid]

Check and see if sock filter in the fuel tank on the pickup is plugged. Never had one die from floating the valves...it hits a max rpm like a rev limiter when you float the valves. It sounds like its starving for fuel.

I'm running a fuel cell with big new inline filter. But I agree from what I remember, it shouldn't go dead from valve floating... Here is a pic of something else I am looking at as possible cause of fuel starvation at upper rpms. I have a fuel gauge on the side of the T fitting at the carb dual feed line fork. When I installed the gauge I thought it might be going in too far and blocking flow. It appears to go about 1/3 the way across that inlet hole when threaded all the way in. But I did get a bud to watch the gauge while I revved and stalled it. He said the gauge never moved from where it should be. So that kinda rules that out.

 

[Curiousyellow71]

Its hard to really say what going on with what has been described wo more info. I've seen too hot of spark plugs cause the engine to die at a certain rpm. It literally puts the spark out and dies and you can keep it running pumping the the gas and get it back some, but usually misses.....typically spark issues show up under load mostly from weak spark struggling to ignite. Spark plug wires can look fine and have to much resistance to fire the plugs is another possibility. If your fuel pressure gauge is fine....that may narrow it towards the carb.

 

[Mike67]

I've never heard anything good about Proform distributors, that's where I would start...floating valves would not cause the engine to die...that's a symptom of something else and not a very good one if it's happening at 4300 rpm...

 

[furious70]

Can't be starving for fuel if you can do it in park free revving it imo.
I have a set of heads that behave similar, no other changes but heads the engine didn't do it. It doesn't die, but feels like a JD 2cyl and you have to wait 3sec for it to compose itself.

 

[Cranky]

Had one act similar when some of the lifters started pumping up.....

 

[PRHeads]

floating valves would not cause the engine to die

Hard valve float allows the lifters to pump up and hold the valves open, and the motor dies.

The first time I had this happen wa on a tired old 361 and I thought I blew up the motor.

Wound it up tight and it popped a couple times and shut off like you turned the key off.

Tried restarting....... motor just freewheeled....... no compression.
I was under the hood looking for something amiss...... found nothing.
Tried starting it again ...... it started, but ran poorly for about a minute..... then it was fine.

It took a few minutes for the valve springs to bleed the lifters back down to the correct preload so the motor would run again.

 

[Mike67]

Hard valve float allows the lifters to pump up and hold the valves open, and the motor dies.

The first time I had this happen wa on a tired old 361 and I thought I blew up the motor.

Wound it up tight and it popped a couple times and shut off like you turned the key off.

Tried restarting....... motor just freewheeled....... no compression.
I was under the hood looking for something amiss...... found nothing.
Tried starting it again ...... it started, but ran poorly for about a minute..... then it was fine.

It took a few minutes for the valve springs to bleed the lifters back down to the correct preload so the motor would run again.

Not saying it couldn't happen but doubt it by the OPs description...
No noise from the valve train makes me think something electrical or fuel related.

 

[Cranky]

Not saying it couldn't happen but doubt it by the OPs description...
No noise from the valve train makes me think something electrical or fuel related.

When my lifters pumped up, the car lost some power and ran like crap and don't recall hearing valve train noise......

 

[daytona kid]

Does anyone think it could be the way I have my plug wires twirled around and wadded together? These are comp cam wires with the extra nylon sleeve/cover. Thought I read somewhere that it's good to spiral them around each other like this, can't remember why.. Also I did look at the float levels. The carb is a brawler/holley 750 and has glass windows. The front bowl level is at the top of the window and the rear is nearer to the bottom of the window. Do I need to raise that rear one a little?

 

[MoparLeo]

Sounds like that would be the worse way to route the wires. When they are running parallel to each other the current is flowing in the same direction. This will just make it easier for any ignition leaks to jump to the closet wire and cause misfires. They should be separated . Lifter pump up can be eliminated on an adjustable rocker system. If you have adjustable rockers, they are set too tight, but that is not what you are describing. Sounds ignition related. High rpms demand more voltage to the plugs to fire. Incorrect plug gap can also contribute. You may have several problems. Did this just start to happen out of the blue ?? Or did it start happening after a part change or modification ?

 

[Cranky]

Does anyone think it could be the way I have my plug wires twirled around and wadded together? These are comp cam wires with the extra nylon sleeve/cover. Thought I read somewhere that it's good to spiral them around each other like this, can't remember why.. Also I did look at the float levels. The carb is a brawler/holley 750 and has glass windows. The front bowl level is at the top of the window and the rear is nearer to the bottom of the window. Do I need to raise that rear one a little?

View attachment 980622

Easy way to find out is to separate them.....

 

[Curiousyellow71]

First time I experienced hard valve float I was a passenger in a 69 Ford pickup in the 70s...I was probably 6... barely could see above the dash. Dad was driving and was seriously pissed at a cow...the cows rear was up against the grill of the pickup...with its tail on the hood... and had to be running on its front legs. Whatever that cow did...pissed Dad off cause he was seeing red....he had the 360 wound tight..foot on the floor.....I remember the speedometer at 40.... It was a 4 speed and I think we were in second gear for a 1/8 mile... Dad had it wound up so much the engine finally died and we had to sit there and wait 15 min...did exactly like PRheads described, cranked with no compression then finally ran like crap and slowly smoothed out. I remember Dad say the lifters were pumped up and he floated the valves...pretty vivid memory of that.
The cow got away.
Cow 1. FORD 0. LOL

 

[daytona kid]

Sounds like that would be the worse way to route the wires. When they are running parallel to each other the current is flowing in the same direction. This will just make it easier for any ignition leaks to jump to the closet wire and cause misfires. They should be separated . Lifter pump up can be eliminated on an adjustable rocker system. If you have adjustable rockers, they are set too tight, but that is not what you are describing. Sounds ignition related. High rpms demand more voltage to the plugs to fire. Incorrect plug gap can also contribute. You may have several problems. Did this just start to happen out of the blue ?? Or did it start happening after a part change or modification ?

I'm sure it was doing it when I put the motor in a year ago. I didn't run it hard for a while and didn't notice it. It is a used motor that know one knew the history on. It had good compression so I just cleaned it up, put a new carb on, timing chain and gears, then stuck it in so I could drive the car. I didn't have the money for anything better at the time. I gave $1000 for it and I'm trying to get it running as good as possible without dumping a lot of money in it. I'm saving the big bucks for later on my other 440 block.

 

[MoparLeo]

Starts to cutoff at only 4300 RPM's. That is pretty low. Stock, non-adjustable rockers ? I would first put the stock ignition back on and test it. If you can make it happen while parked hook up a timing light and have someone rev the engine until it "floats" again and keep your eye on the timing light. If it is ignition, the light will stop flashing.

 

[dvw]

Just because you have fuel pressure doesnt mean you have sufficient flow. I think you answered your own question. "Pumping the accelerator keeps it running". In this case it's out of fuel. The only fuel is from pump shot until the bowl refills. " The fuel gauge blocks 1/3 of the line". That's not helping flow. Remove the lines at the carb itself. You haven't mentioned what type of fuel pump. Crank engine or turn the pump on. Measure the amount of fuel pumped in 30 seconds. At 300hp you need about 1/4 - 1/3 of a gallon minimum. You also need a a proper vent in the tank. Dont forget the carb. If there is a screen in the inlet or the float level is very low that will be an issue. To me valvlve float would act as Dwayne has said. Ignition would more than likely misfire.
Doug

 

[PRHeads]

If it’s truly rpm related(doesn’t want to go past a certain rpm under any condition), it’s likely ignition or valvetrain.

If it’s load related, it’s probably fuel.

My test for the fuel would be to run it at wot thru the gears, but shift at an rpm lower than the rpm where you normally see the problem.
If you can start in low, go thru the gears and make it well into high gear at wot without it nosing over....... it’s probably not a fuel supply issue.

Another rpm related test is, go along in low gear at a light throttle setting and crowd the rpm where the problem occurrs.
Lightly crowd the throttle to get to the rpm point where the problem occurs.
If it runs clean right up to just under a certain rpm, and seems to be like there is a rev limiter...... then I’d look more at ignition.
If you’ve ruled everything in the ignition out, then look at the valvetrain.

I can tell you this, on the dyno...... it isn’t that unusual to see a valvetrain issue show up very predictably at the point where things get unhappy.
Just like flipping a switch.