Valve Float or Points Gap

[69L48Z27]

I’m sorting out an engine that I put together over the winter. Everything is broke in and I’m starting to beat on it. At 5k RPM I feel like it’s floating the valves but I’m not sure that’s the case. It’s a Hughes cam and 1.6 rocker setup from ??? (Gold) can’t think of the name. And we tested all valves at time of rebuild and they were in spec with cam card.

What do points do if they aren’t opened up far enough at higher RPM. It’s not breaking up or anything, smooth on the pull but just feel like valve float. This engine build should pull hard to 6K.

 

[Nate S]

What cam and what springs? 1.6 rockers require more spring than 1.5. Gotta size the springs by what the valves see, not by what the cam says.

 

[69L48Z27]

Hughes told me to follow the cam card for either ratio. Thats what we did.

I was interested to here what happens to points ignition at high RPM.

 

[Jerry Hall]

More spring.

 

[1967coronet]

On the points..... Cheap points will have a weak spring and will bounce off the lobes at higher rpm.



I copied this next part and it may help you understand the dwell,
you need 28 to 32 dwell, lets call it 30.


[The dwell is adjusted by setting the points gap to a specified distance at maximum opening. A narrower gap gives more dwell and a wider gap gives less. Taking it to extremes, excessive dwell means that the points close too soon after opening, cutting off the magnetic field collapse before it delivers all its energy. Too little dwell gives the magnetic flux insufficient time to build up to the maximum

produces misfiring at normal operating speeds. The dwell, as well as spark plug gap, do have an effect on ignition timing. The later the points open, the later the spark comes and retards the timing. The earlier the points open the sooner the spark comes and advances the timing. That is why timing is the last thing to be set in a tune-up.]
produces misfiring at normal operating speeds. The dwell, as well as spark plug gap, do have an effect on ignition timing. The later the points open, the later the spark comes and retards the timing. The earlier the points open the sooner the spark comes and advances the timing. That is why timing is the last thing to be set in a tune-up.

 

[Nate S]

Not much happens to points. Even regular single points are “good” meaning not floating, past 6000. Done this many times. Wouldn’t recommend it much.

 

[eldubb440]

timing?

 

[dadsbee]

I put a $32 complete distributor from Parts Monkey on my 383HP as a quick "get'r done" during restoration, so I could take the time later to rebuild my OE dizzy. Running on the points the cheap thing came with and I was shifting 5500 on Wednesday without issue. Don't think it's your points...

 

[turbine68rt]

Agree with Jerry....check what spring tension you have currently. If you have a digital fish scale that may help. You may need something closer to 30 oz if you're going that high in rpm. Only drawback, more rubbing block wear.

 

[69L48Z27]

Timing is 36 total, all in. Engine pulls good until I hit this ‘float’.

Just curious if points float felt like valve float. What I have feels like valve float. I know points are good to where I’m trying to go. @1967coronet mentioned cheap points. They’re Standard Ignition but I would call them cheap.

 

[RJRENTON]

Curiosity question...
Single or dual point distributor? Turbine68rt is correct measure the tension of tge breajer point spring. This is the purpose of the dual point distributor.....longer dwell time for greater time to build the coil charge and higher voltage. I can buzz my RS23V0A GTX with the recurved Prestolite dual point distributor to 6000 RPM WITHOUT misfire (or valve float). Plus you can hear valve float....it sort of sounds like detonation....
If you are experiencing valve float.....be careful or you may "grenade" the engine.....when the valves can't close because of insufficient spring pressure, you run a very good possibly of hitting a piston....ecpecially the exhaust valve because its opening while the piston is rising and there is any rod "stretch" st high RPM, collision is a real possibility. Just my opinion of course.
BOB RENTON

 

[Jerry Hall]

Valve float is a loss of power and power doesn't return until the valves stabilize. Points so called floating results in engine missing and breaking up at high rpms. My stock 67 383 in 1967 straight off the showroom floor would float the valves at 5200 rpm and drop back to 5000 rpms. It would do this as long as you could hold your foot on the floor. I couldn't have possibly blown that engine in stock configuration.

 

[69L48Z27]

Single point distributor.

Hmmm. Don’t hear anything that reminds me of detonation.

 

[69L48Z27]

Valve float is a loss of power and power doesn't return until the valves stabilize. Points so called floating results in engine missing and breaking up at high rpms. My stock 67 383 in 1967 straight off the showroom floor would float the valves at 5200 rpm and drop back to 5000 rpms. It would do this as long as you could hold your foot on the floor. I couldn't have possibly blown that engine in stock configuration.

Thx Jerry. That what I was looking for, seat of the pants. It’s definitely not breaking up or missing. I’ll call Hughes in the AM and get a new set of springs. I just can’t believe these float at only 5k RPM since they matched the spec. When I click 2nd and 3rd it starts pulling again.

 

[mopar 3 B]

Coil break down could also cause the same results. If it can not fill the bill of high speed and load conditions power goes all to crap.

 

[R413]

Try a different points distributor or electronic dist, then a different coil just to test the parts and see if it’s still acting up.

 

[66Satellite47]

My single point 383 would "nose over" before it started missing (@ 5000 ish). The HP Accel points moved it up slightly. But in hindsight could also be valve springs (stock 2bbl cam & springs). An electronic conversion cures the ignition issue.

 

[beanhead]

Hydraulic lifters?

 

[69L48Z27]

Hydraulic lifters?

Yes sir.

 

[1967coronet]

I would try a different dizzy and coil like R413 posted.
If the springs are matched to the cam , you checked push rod length , and have a little preload on the lifters.

whoa... did you check the install spring height and check for coil bind.
At upper rpm coil bind may be shutting things down ?