My rebuilt 292 just doen't seem to run as good as I think it should; I have been adjusting the valves over and over again trying to get them right, and they just seem to start making noise again, like they are loosening themselves up. The engine runs pretty good, but has some hesitation at light throttle. After working on them again on saturday, I thought I had it perfect (albeit still a little noisy), no hesitation, ran smooth-for about 5 miles, then It started with the hesiation again.
New short block with new cam and lifters, new carb, heads rebuilt, ORIGINAL rocker assemblies (w/ 122K miles on them). I get the engine nice and warm, and them set the valves with a feeler gauge at .018". Timing is dead on at 6 degrees.
How did the rocker's valve ends look before installation? Pitted, or have they been recently machined to a smooth radius? If they are pitted it can be hard to get a good valve adjustment.
Did the new cam and lifters receive proper breakin, 2000 rpm for 20 minutes, upon initial startup?
A log book comes in handy if you have to frequently adjust lash. Keep track of the valve/rocker location and how much excess lash each valve had and the date. Then you can pick out the recurring problems easily. This assumes that only a few and not all are needing adjustment. The threads of the self locking adjusters could be getting worn and work out. Snug down all the rocker shaft stand bolts in case they are getting loose.
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1946 1/2 ton with Y-block
1964 F-250, 292 4 speeed
1990 Ranger 4WD
1954 Model 600 tractor
Thanks. The rocker ends looked good, and the valve stems were worked over when I had the heads rebuilt. I followed the proper procedure on the cam break-in. A couple of the adjusters were kind of loose compared to the others; I was thinking of using some medium loctite on those and see how that works.
A few new self-locking adjusters would not be a bad investment. They have been known to be "not very self-locking" from the factory. Does the hesitation come with the return of the valve train noise?
You said the valve stems were 'worked over' when the head was done. Does that mean that the tips were cleaned up of mushrooming? Is the valve stem installed height within tolerance. That can affect the geometry of the rocker tip as it comes down and presses on the valve. Too low, and you get more wiping motion on the tip than normal. Not that this has anything to do with the topic at hand...
tom
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It's not how hard you work, it's how much you get done. Simplificate and add lightness
Not sure about what they did to the valve stems, I just know that the did a complete valve job and I'm pretty sure they took a little off the end just to square it up.
The hesitation seems to be directly correllated to the valve adjustment. Before I rebuit this motor, it did the same thing. The only thing that is not new/rebuilt on the entire motor is the rocker assemblies and the distributor - EVERYTHING else is new or re-built. I think I'll try to get some new adjusters and see what happens.
Ahah as the saying goes. My sister had a '57 that hesitated on initial acceleration. We fiddled an finally figured that the vacuum advance was working too well. The springs inside the vacuum advance, on the vacuum side of the diaphragm, were too weak. We put some washers to shim the springs a bit and make them a bit stronger, and the hesitation ceased. Of course that was back when gas was 33.9 for regular.
In hindsight, it would have been more professional (ha) to get the springs in the centrifugal advance re-curved, or replaced and the same with the original inside the vacuum advance. I expect that suppressing the vacuum may have affected gas mileage, as the advance would have been retarded. [late or non-existant]
tom
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It's not how hard you work, it's how much you get done. Simplificate and add lightness
That's interesting, because one of the first things I did when I bought the truck was install a brand new vacuum advance, along with the usual tune up parts.
Well I am talking back when I was in HS, over 40 years ago. The '57 was white over inca gold 2 door hardtop. Was a whole $275 over on the west side of Indpls. Ford-O-Matic was actually a 3 speed when you took off in L, it was the true 1st gear. D took off in 2nd gear. It would backfire through the carb, and stutter a little. You were never sure if it would stall when you went to pull out. I am pretty sure we checked the accelerator pump, as that can cause the same thing. Finally went to the dist advance modification. Who knows where the distributor came from on a 5-6 year old car back in those days...
tom
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It's not how hard you work, it's how much you get done. Simplificate and add lightness
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