Noisy injectors after 3 hour drive

[Sept]

This is a car we've owned for 6 months and this was the first long drive taken with it, 180 miles one way starting from the Blue Ridge Mountains of NC back to Raleigh, N.C.  I'd driven the car to the mountains about 10 days earlier, elevation 3600-4000 ft.  The car is a '71 280 SL showing 58,000 miles  ( +/- ) which according to the previous owner who had it 17 years is close to accurate. He had purchased it from the mechanic who worked on it for the previous owner ( daughter of the original buyer ). 

Questions:

1 - Upon arriving at the destination on the drive back I heard an erratic tapping noise from the engine, the engine was running smoothly but the noise seemed to be coming from the injectors, a "clicking" sound that wasn't a pattern but erratic.   I first thought it was coming from the front of the engine but as best I could determine from "listening" it seemed to be coming more from the mid to rear length of the engine.
I turned the engine off, unloaded and about an hour later, started it to take it to the storage where we keep it.  No noise.  Any thoughts appreciated.

2 - My wife who was driving behind the car noted some white exhaust from the car when it was decelerating.  Might this be related to the injector noise, although I would have thought this would be darker exhaust gas if it was related to fuel.

3 - This being the longest drive I've taken with the car, I noted the automatic transmission face plate in the drivers compartment was extremely warm after about 40-45 minutes driving, normal?  Transmission fluid checks ok.

4 - Downshifting coming to stop signs at the end of the journey seemed a bit rougher/ louder. No transmission noises or shifting problems were noted in the drive, just the downshifting "bump" as your approach a stop. Normal for this transmission?

1971 280 SL
 

[Cees Klumper]

Sept, some ideas to your questions,

1- the noise could be the 'towers' that the valve cover attaches to. sometimes they get twisted and start touching the camshaft. Remove valve cover to see if that could be your problem, if so, just straigthen them by bending back in opposite direction of how they were 'twisted'. I have not heard of an intermittent noise like this before that I can recall.

2- not sure but whit-ish smoke could indicate a fuel mixture problem. Check the CO level, or have it checked

3- this is normal, nothing to worry about (mine does the same, it gets very hot at times)

4- rough downshift can be many things and it's a common issue that can and should be fixed. Many, many posts on this in the forums and jnfo in the technical manual. Probably nothing serious but can tale some time to track down.

Good luck, I'm sure real mechanics can contribute more meaningfully, but this is what I know at least.

[DaveB]

The oil feed line might be worth checking in relation to the tapping noise. It is attached to the towers and delivers oil to the cam and rockers, from the front to the back. If it's partially blocked the rear lobes and rockers might not get enough oil and could get noisy when hot.
The smoke might indicate oil being pulled through or past the valve guides.

[Sept]

Thanks..

[DaveB]

I could easily be wrong on both counts. The reason I'm concerned about the oil feed is that my car did exactly the same thing, started ticking from the rear after warmup, and I could see the rear lobes looked a little more scored than the front. It also smoked badly despite consistent 160 psi compression. That was back when it was running. I've never had it registered or on the road and I didn't resolve either problem (valve clearances were all correct).

[garymand]

Cees is right on,  you might double check the smoke on deaccel.  Typically if you are doing 3500 rpm on the free way and take you r food off to exit, the manifold valuum goes up and can such oil past the valuve guid seals into the intake and exhaust.  When you accelerate again the accumalated oil is puffed out the back.  I think a light amount would be whitish on a hot exhaust.  I've seen it with my old 250 motor with the top down, in the rear view mirror.  Not too much to worry about and takes a lot to fix, because you get into refurbishing the whole head.

I've never head a noisy FIP or injectors, so can't advise.

"Downshifting coming to stop signs at the end of the journey seemed a bit rougher/ louder. No transmission noises or shifting problems were noted in the drive, just the downshifting "bump" as your approach a stop. Normal for this transmission?"  I really don't know what you mean.  Is it all gears, what is rougher, when is the bump, what do you mean by a bump?