I recently had our 4.2 completely overhauled by an experienced Jag machine shop.
Within 100 miles, it has developed a significant valve/camshaft klatter seemingly coming from #6 intake.
After removing the cover and checking all clearances I was surprised to discover:
#6 - .003
#5 - .002
#4 - .004
#3 - .004
#2 - .002
#1 - .003
Any suggestions on what else to look for?
Yep: see if there’s damage to the tappet sleeve: chances are, it popped up… unless it has holddown plates in place.
Those clearances are all too small, too.
Valve clatter is rarely caused by excessive tappet clearance, but FAR more often by loose tappets - Either the tappets and/or guides are worn, allowing the tappets to move back and forth within the guide as the cam lobe passes over it.
That said, your clearances are WAY too tight, and NEED to be widened to the correct spec (0.004-0.006" for early engines, 0.012-0.014" for later engines).
…and note that for the early engines the 0.004" figure is for the intakes, and 0.006" figure is for the exhausts, whereas for the later engines the 0.012"-0.014" is a RANGE for both intake and exhaust. If your 67 has the original camshafts, you should be using the 0.006" value for the exhausts.
Let me ask. What if one sets up the later style camshaft with the earlier closer tolerances??
Dennis 69 OTS
Later camshafts with earlier clearances will be hard to make idle. Way to much overlap. Later camshafts are very sensitive to clearance variances. Why would you want to put difference clearances than the camshaft was designed for anyway?
Before you get too worried, tighten your top timing chain.
It is common for the valves to close up a few thou after a rebuild.
Get whoever did the work to readjust the tappets.
Thanks a lot, guys.
The ID plate shows clearance of .006 exhaust, .004 intake
The head was completely rebuilt with new tappets, guide, valves etc.
I wish taking the car/engine back to the rebuild shop were feasible. This is on me.
Hold downs are on exhaust side only
May I assume that if I remove the cam I will be able to determine if the tappets and/or guides are the cause? (Ray: “…tappets and/or guides are worn,”) (Wiggles: “Yep: see if there’s damage to the tappet sleeve: chances are, it popped up”)
Perhaps the problem here is what degree of noise is acceptable vs indicates a problem.
Some otherwise fine performing engines sound like a bucket of bolts, I know mine has more valve train noise that I would like but all the usual adjustments and checks have had no effect.
You should certainly set the clearances to spec, check the chain tension, examine the tappets, consider hold-downs on the intake side and all the rest - but be prepared for the noise to still be with you.
Mine rattles on start up but quiets as the oil gets flowing…what weight oil are you using?
Good point: the early engines, even when all is set properly, are not silent.
However, to make sure, a recording of what the OP is hearing would be helpful.
Thanks, Wiggles. OP… Is that me? I’m happy to replace the cover and record the noise. What process do I use to attach a video/sound to the post?
On an iPhone—I assume theres a similar process on Androids—you take a voice memo: hold the phone over each valve area, at idle, a few inches above each position, then upload it here.
I know that JL only accepts certain formats.
iPhone- Yes. I do not see a button on the JL page to attach photos or voice recordings. How is that done?
The button is in the bottom right corner of the typing field. If you can’t upload the audio file, take a video, upload it somewhere and post the link.
With a video you can also show what area you are in, just in case that this might help with diagnosis some day.
The exhaust side is where the guides tend to come out; the intake side seems to be far less susceptible. The issue is audible; very loud knocks, far louder than anything else; and you can see where the cam would have contacted the guide. Fitting holddowns on the intake side won’t quiet anything down when nothing’s wrong with the guides.
OP means original poster (?), so that’s you.
Got it. Once I get the cover back on, I’ll give a video a try.
Do a compression test on each cylinder. Maybe a valve was bent during the recent work done.
Something doesn’t make sense. An experienced shop would have set the valves if anything a little wider than spec on a newly rebuilt head, not a couple thou’ tighter.
Me smells a rat afoot.