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Ticking or knocking at 1500-2000 rpm

R

Rh242603

New member
Got a 1992 chapparel with a VP AQ271C I have had for about 2 months. I am trying to get an idea of what the ticking/knocking noise is at around 1500 rpms. Motor starts and makes no noise while in neutral. Once in gear and accelerating, it will start ticking or knocking. I have no significant bouncing of oil pressure. Oil pressure will stay in the 50 range. Don't seem to have any issues with the engine other than a simple hard start every once in awhile due to me needing to dial in the carb a little better. What I have done so far

rebuilt the Holley 2 barrel carb
changed oil with mobile 1 and k&n filter
changed fuel/water seperater
changed all plugs

I really don't think it's rod knock as I figured it would be evident at all RPMs

Im going to pull the valve covers this weekend and see if I can determine anything. Will try and do a compression test as well.

maybe exhaust manifold leak causing a knocking noise?

I will post a video once I get one but any ideas where to start?
 
Stable or high oil pressure is generally a good sign and hopefully not an indication of lower end mechanical issues - that's the good news. The noise you're hearing could be coming from a variety of places but most notably the mechanical rockers is a prime suspect here and fairly easy to identify if so. Remove the valve cover(s) and observe the stud threads across the tops of all the rockers, generally they should have an equal number of threads exposed on the retaining stud bolts. Im not familiar with your engine specifically but generally speaking you should see the same 5 to 7 threads exposed at the top per rocker bolt. If any are obviously loose and have a low count of threads exposed , you may just have loose rockers. Now with the engine off and valve cover off , gently see if you can wiggle the rockers by hand. Some will feel very tight some will feel somewhat loose ( depends on where the engine crank and camshaft is sitting at that moment ) but if you find one or several of them loose enough they clatter by hand AND have a low number of threads exposed that may be the culprit and can be tightened down by the manufacturer's recommended method. This can vary greatly so be sure to follow the path the manufacturer recommends. One caveat is the bolt itself may have come loose from the head but kept 5 to 7 thread exposed a the top, this is rare but using a level across the tops of all the rocker bolts can reveal a bolt unseating from the head. I bought a used boat and the engine wouldn't rev past 2200 rpm without sounding like it was going to throw a rod when in fact it was just loose rockers on top which caused valves not to open adequately and made horrific rapping noises. There's probably more to suggest here but I'll wait to see if you indeed found this as a possible source of the noises. I was able to tighten the loose ones down a few turns and it helped a great deal but found I didn't tighten quite enuf and had to do it again but better to take it in carefully than over crank em down as you could do major damage if not careful. Today mine's quiet as a mouse in terms of the previous rapping sounds once heard. Youtube has several videos that demonstrate how to tighten noisy rocker arms so you may want to check that as a resource but again look it up based on the engine type. Question - what engine do you have ??
 
"Once in gear and accelerating, it will start ticking or knocking." ( Timing advance off or not working , bad fuel - possibly combination )

"Im going to pull the valve covers this weekend and see if I can determine anything. " - check rockers for being tightened to spec based on manufacturer's recommendations . Engine off - Visually check by looking for loose rockers with obviously less threads exposed to match on rockers that seem looser than others. Tightening usually involves rotating engine by hand to specific top dead center and tightening rocker retaining nuts in a specific sequence and rotating engine one turn and doing the others. That's a VERY short summary of the process... make certain you follow the engine manufacturer's recommendations on HOW to do this properly. I had a similar noise where the engine ran well but once above 1500 or so it would rattle as if it were shaking apart and it was just loose valve rockers. Also had loose rear engine mounts which created abnormal vibration under load and some racket. Post the video !
 
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