Loose Metal Knocking/Banging Sound during Rough Idle

[Michael Oritt]

Roscoe--

Correct on both accounts. When I fished the first pieces out of the oil I had drained in a routine change I was perplexed as the stuff seemed like hard plastic and I could not think of anyplace where plastic was used inside the engine. Upon dropping the sump I bigger pieces some of which resembled segments of a belt and things began to add up.

I took the opportunity to replace the timing chain as well and since there is no adjustment or tensioner for it getting the camshaft gear back into place was no mean feat.

[RAC68]

Hi All,

Using Bob's suggestion and obtained a Harbor Freight Stethiscope, an Healey friend and I continued the pursuit yesterday with only frustration to show for the effort. Setting the idle speed low enough to create engine vibration, we listened to the sounds from the pan and front engine cover and, although not completely rulling the banging from either, could hear the sounds more clearly from outside then in. Friday, I will be driving to another Healey friend's garage to put my car on his lift for a more agressve look. Since the banging noise predated the installation of a version of John effective good fan shroud, I don't think it will be necessary to remove it or the half belly pan installed to better direct engine compartment cooling air.

Hopefully I will find this elusive sound maker during Fridays pursuit and I will keep all informed.
Thank you for all the suggestions,
Ray(64BJ8P1)

[Michael Oritt]

I should have mentioned in my earlier post that I wrapped up the job by installing an item I purchased from BCS (Nock): a stiffener ring that goes under the perimeter bolts of the front cover. Whether due to it or a new gasket or whatever, at the end of the job I not only got rid of the noise but also a persistent oil drip from the front cover that had defied previous attempts to eliminate with sealant, a new gasket and elbow grease. The stiffener ring did not cost too much and can be added to any engine without the need to do much more than remove the fan belt.

[Bob_Spidell]

You are not mistaken. The 6-cyl cars have an oil pressure-activated tensioner, which I hear can disassemble itself, which certainly could cause these symptoms (though I'd expect the noise to get more emphatic with increasing RPMs). DWM sells an upgraded tensioner, which I wish I'd installed in my recent overhaul, but I wasn't aware of the potential problem at the time.

Edit: Ironically, perhaps, this potential problem hasn't been completely solved even today. The 'Modular' V8 in some Fords is known for breaking tensioners--they're hydraulically-actived as well but made of plastic--in their DOHC configurations.

[Bob_Spidell]

I should have mentioned in my earlier post that I wrapped up the job by installing an item I purchased from BCS (Nock): a stiffener ring that goes under the perimeter bolts of the front cover. Whether due to it or a new gasket or whatever, at the end of the job I not only got rid of the noise but also a persistent oil drip from the front cover that had defied previous attempts to eliminate with sealant, a new gasket and elbow grease. The stiffener ring did not cost too much and can be added to any engine without the need to do much more than remove the fan belt.

I've heard of 'stiffener rings' before, but not in that particular application

Edit: Michael, did you also get Nock's modified timing cover, with a modern front crankshaft seal?

[Michael Oritt]

Bob--

No I did not and though at the time I know I had a (good) reason, i am kinda sorry I did not. However the ring did eliminate the persistent oil drip

[RAC68]

Hi All,

A few of my local Healey friends got together and, using a friends lift for better under engine compartment access, more carefully pursued the identification of the source of my irregular metalic banging sound during a rough idle. Thankfully, the sound did not come from within the engine pan or behind the engine front cover but from an exhaust down pipe hitting the frame. This condition was the result of the flattening of the top rubber portion of the engine mount bringing the exhaust down pipe closer to the frame and allowed the pipe to strike the frame when the engine experienced rough idling. Keep in mind that the engine motor mount on the driver's side is hidden by the intake/exhaust manifolds along with the carburetors and can't be as easily seen as on the passenger's side. It appears that both PDPLOT and Captain Randy presented the correct diagnosis (and I really am happy with it rather then something in the pan or under the engine's front cover).

Although I expect replacement would satisfy this issue, it may be quite difficult to replace this part of the engine mount and I was wondering how best to resolve this issue. One suggestion provided was to create a 1/4" spacer to be inserted under the top rubber to make up the lost height although I would rather replace the top rubber completely if is possible without removing the engine.

I would appreciate any suggestions,
Ray(64BJ8P1)

[steveg]

...Or a spacer under the motor mount itself:

screenshot.1933.jpg

I used similar in order to raise the engine 1/4" on the left side for the rear carb on the DMD manifold to clear the steering column. (Carbs are horizontal). Longer bolts were needed. You may need to adjust the throttle linkage slightly, though that won't be a factor if you're merely raising the engine back to its normal height.

BTW, aluminum works OK for these. I've had mine in for several years and out with no observable distortion.

This should hold you until you can remove the carbs/manifolds for a proper overhaul of the motor mount.

[Lin]

I apologize for jumping in on this. I probably should have started a new thread.
Congrats Ray on locating your noise!

Are motor mounts now available that are quality products and the correct size for proper fit? If so, from where?

When I was doing my major restoration about eleven years ago (whew, cannot believe it was sooo long ago) there was a problem with the mounts. In fact, I recall ordering a pair but eventually gave up on using them because I just couldn’t get the engine in place with them. I resorted to using my originals and I know they are tired. I expect that there are a lot of restored Healeys out there that still have their original mounts.

I would be interested in people’s experience.

Lin

[Bob_Spidell]

The last couple sets of mounts I've bought have been, essentially, crap. The bottom mounts' rubber will peel away from the brackets in a short period of time. There is a spec for the gap between the top of the bottom mounts and the bottom of the top mounts--15 thou IIRC--and the mounts I bought had about 3/8". I shimmed the top mounts using fender washers with a slot cut in them to clear the stud.

You can replace the mounts w/o pulling the engine; obviously, you have to raise the engine to do so, but it can be done. Be sure to disconnect the throttle linkage lest you bend it, and don't forget the gearbox/OD tie rod. Unbolt the bottom mounts, tie rod and throttle and lift carefully under the pan; use a piece of 1x12" wood or similar on the jack, or you'll leave an impression in your pan (ask me how I know). The hardest part is getting the mount brackets to line back up, but it can be done.

[steveg]

Just started a new thread for the motor mounts.

[RAC68]

Hi All,

Steve, I made the shims you drew to raise the motor mount and compensate for what looked like a compressed top rubber buffer. I cut an access panel into the wheel well (that can be reinstalled with 5 screws after) but have not yet been able to install the shims due to very tight bolts combined with restrictive access.

I initially thought the noise was coming from an exhaust down pipe hitting the frame but now I am wondering. before trying to loosen the left motor mount, I jammed a few aluminum shims between the down pipe and frame to better secure any movement. However, again at idle, the banging was easily heard and no movement was observed by the downpipe.

Leaving the downpipe shims in place, and taking a short drive, I purposefully drove on rough road and NO banging sound could be heard. Arriving at home, I idled the Healey for a short period and the banging could again be easily heard.

Now I am more perplexed. The sound can be heard when at a rough (low rpm) idle but not at higher engine idle speeds and not when driving on rough roads. The sound doesn't appear to be coming from within the engine but no loose components have yet been found around the engine compartment.

The shims are not yet installed at the base of the engine mount due the difficulties mentioned above and I am beginning to think this is going to be my winter project and will require the removal of carbs, intake and exhaust manifolds and downpipes will be required.

Any thoughts would be appreciated,
Ray(64BJ8P1)

[steveg]

Ray,
If you're going to all the trouble this winter, might as well replace the top motor mount rubber.

My car occasionally makes a similar sound at idle when cold. I'm sure it's my downpipes hitting the outrigger cutout at the front of the muffler. I don't worry about it because it never happens when the car's warmed up.