218 engine noise at higher rpm's

[48Dodger]

On 8/13/2021 at 11:36 AM, JBNeal said:

Weak valve springs might be causing valves and lifters to bounce around on the cam at high rpm...

 

Valve float or Floating valves.....happens when you "outrun" your valve's spring rate. Usually comes with a few pops or sputters. Any of that?

example: running the 1/4 mile race, you'll hear guys comment when they see fuel burning out the tailpipe "He's shifting to late, his valves are floating" 

meaning he's hitting his rpm ceiling. This can also happen when bubba grabs springs "that'll work" off the back shelf up top where they keep the peanut butter. 

 

48D

[greg g]

Start the truck and run at idle.   Plug the tail pipe with a shop rag and listen carefully at all exhaust system joints.  The thing no one has mentioned is the heat riser.  Is it functional, is it in the summer position, is it free to move about, stuck in one place, are it's pivot bushings in good shape or could the be passing gas so to speak? Could it be the bi metalic spring broken and bouncing around?

 

By the way, run you rpm calculator using tire diameter 27.5 to 29.  16 is the wheel diameter not the road contact measure.

[WPVT]

4 hours ago, greg g said:

Start the truck and run at idle.   Plug the tail pipe with a shop rag and listen carefully at all exhaust system joints.  The thing no one has mentioned is the heat riser.  Is it functional, is it in the summer position, is it free to move about, stuck in one place, are it's pivot bushings in good shape or could the be passing gas so to speak? Could it be the bi metalic spring broken and bouncing around?

 

By the way, run you rpm calculator using tire diameter 27.5 to 29.  16 is the wheel diameter not the road contact measure.

Thanks. The heat riser is perfect and functioning properly.

[WPVT]

9 hours ago, 48Dodger said:

 

Valve float or Floating valves.....happens when you "outrun" your valve's spring rate. Usually comes with a few pops or sputters. Any of that?

example: running the 1/4 mile race, you'll hear guys comment when they see fuel burning out the tailpipe "He's shifting to late, his valves are floating" 

meaning he's hitting his rpm ceiling. This can also happen when bubba grabs springs "that'll work" off the back shelf up top where they keep the peanut butter. 

 

48D

Thanks. At the higher rpm's, it doesn't miss or lose power as it would with valve float. It just starts to sound noisy and "uncomfortable".  Once I rig up an "in cab" tach, I'll be able to say whether this is happening at 2000 or 4000 rpm. I'm not a hot-rodder, so I'm guessing it will be closer to 2000. But better not to be guessing if this is to be a fruitful discussion.  

[WPVT]

As it turns out, the problem, or most of it, was ignition timing. I retarded the spark and it made a significant difference in the engine noise I was hearing. The clattering noise I heard was not what I have normally associated with engine ping, hence my initial reluctance to tamper with the timing. 

In any event, the truck now seems more comfortable at 45-50 mph. 

In terms of timing, I retarded the spark and it ran better. I retarded further still and it was sluggish, so I moved it back a bit. When I was initially timing the engine last year, I did it by ear and idle speed as I had read in another post. Guess that wasn't the best method. 

I'll probably check it with a light, out of curiosity, but considering differences in fuel now as opposed to 50 years ago, I think I'm better off with trial and error rather than sticking to a specification, at least regarding ignition timing.