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felipe heuser
Experienced User
Username: felipe

Post Number: 126
Registered: 07-2017
Posted on Friday, 15 January, 2021 - 07:54:   Edit PostDelete PostView Post/Check IP

Greetings everyone…
Would be very grateful if someone could shed some light regarding a problem on a 1960 S2 engine running a bit rough…
Clearly present whilst idling, yet steadily, however more apparent when accelerating in low speeds and causing some vibration, until reaching higher speeds in fourth gear, then running smooth without judder…
Never coughs or sputters with no reduced engine performance at any time…always starts straight away, even when parked for weeks…oil pressure and temperature are correct and no black smoke…
The irregularity is always present with stop and drive in town…
Many thanks
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David Balfour
Frequent User
Username: sidchrome

Post Number: 213
Registered: 02-2009
Posted on Friday, 15 January, 2021 - 13:52:   Edit PostDelete PostView Post/Check IP

Hi Felipe,

I have had exactly the same problem for the entire time I have had my 1961 SC2. I have had the transmission overhauled, rebuilt the drive shaft (including correctly packing out the detroit coupling and replacing the UJs), new spark plugs, new coil, Pertronix ignition, service kit through the SU's, all new tyres, etc, etc., with no change.

I saw a heritage video and/or read about a vibration issue on a brand new 1957 ish Chrysler running a Detroit coupling with a vibration issue that manifests itself as a shudder that disappears at high speed as does yours, as does mine.

Guess what it turned out to be on the Chrysler?

A faulty crankshaft harmonic vibration damper! It's almost never mentioned on the V8, but I am now wondering if this could be the cause of my issue, as it was on the V8 Chrysler.

If the rubber goes hard, there is no damping effect at all, and resonance is highly speed and load affected. My car has had a full engine overhaul done in the U.S.A. 20 years ago, but I do not know what was done with the damper, as it was well before I had the car. I would guess nothing was done.

It is on my elimination list now - at the top now in fact.

I know it sounds crazy considering all the other possible issues, but for me there is little else to consider. The transmission guy even pulled the transmission out a second time and fully stripped it to find - nothing.

I'd be very curious to know if this has been an issue for others.
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Jeff Martin
Experienced User
Username: jeff_r_1

Post Number: 178
Registered: 07-2018
Posted on Friday, 15 January, 2021 - 15:03:   Edit PostDelete PostView Post/Check IP

Probably not as crazy as you think, problems with the straight sixes and their dampeners can cause this problem as described and are prone to failure due to their complexity and neglect, mostly due to lack of oil changes and short runs.

I wouldn't be surprised if the rubber in the dampener has become hard and stopped doing its job.

Best look after it sooner then later due to the torsional stress on the crank shaft.
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felipe heuser
Experienced User
Username: felipe

Post Number: 127
Registered: 07-2017
Posted on Saturday, 16 January, 2021 - 21:22:   Edit PostDelete PostView Post/Check IP

Hello and very grateful for the information...not familiar with this damper...
Can one troubleshoot the problem before replacing to be sure the issue is with the damper? Haven’t exchanged spark plugs for example…and can replacing be a DIY job?
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Trevor Pickering
Experienced User
Username: commander1

Post Number: 180
Registered: 06-2012
Posted on Saturday, 16 January, 2021 - 23:54:   Edit PostDelete PostView Post/Check IP

Had this problem on my S3 and it turned out to be a bad connection on the solenoid.
May be worth a look!
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David Balfour
Frequent User
Username: sidchrome

Post Number: 214
Registered: 02-2009
Posted on Saturday, 16 January, 2021 - 23:56:   Edit PostDelete PostView Post/Check IP

Hi Trevor, to what solenoid do you refer?
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Trevor Pickering
Experienced User
Username: commander1

Post Number: 181
Registered: 06-2012
Posted on Sunday, 17 January, 2021 - 01:18:   Edit PostDelete PostView Post/Check IP

The strater solenoid
The main power supply for all the electrics on the car is taken from this point and this wire was loose on my car causing an intermittent slight misfire.
I cleaned the connections and tightened everything and that cured my problem.
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NormanGeeson
Unregistered guest
Posted From: 81.99.74.184
Posted on Friday, 15 January, 2021 - 21:04:   Edit PostDelete PostView Post/Check IP

The initial post contained the following comment “Clearly present whilst idling……” At the moment I cannot see how this could be connected with a prop shaft drive line fault.

Unless it is caused by an external engine problem the original comments seem to point to an issue upstream of the initial gearbox reduction gear pack. That is all connections within the engine and gearbox idle train.

Before taking any further action I would check the following:--

Ensure all the engine and gearbox mountings are intact by gently lifting the engine.

Ensure the engine is square in the frame with the drive shaft aligned correctly.

Measure the run out of the flywheel rim by rotating the engine by hand.

Measure the run out of the flywheel rim at two engine speeds, say 750 / 2000 rpm.

Ensure the crankshaft damper is in good condition and secure on the crankshaft.

Take particular care that the exhaust has no blockages and is not in contact with the chassis etc. Note that a number of S2 were fitted with S1 front silencers.

(Message approved by david_gore)
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David Balfour
Frequent User
Username: sidchrome

Post Number: 215
Registered: 02-2009
Posted on Sunday, 17 January, 2021 - 09:17:   Edit PostDelete PostView Post/Check IP

Hi Norman,

The "clearly present whilst idling" may be just a red herring. It is easy to link a rough idle in your mind to a shudder when driving, but I have had both smooth and rough idling, dependent on engine tune, but the shudder did not change, and that the shudder only occurs at specific load, and engine speed, and road speed conditions, which makes it very difficult to rule things in and out. I do also take heed of your comments about all of the items listed, and especially the exhaust. Someone had previously welded the exhaust mounting directly to the chassis near the rear muffler, and I was sure this was going to be the cause, but when fixed there was no obvious change. I don't know about Felipe's S2, but the level of vibration transmitted to the cabin in my SCII at idle is excessive I think, and probably yet another clue. The rear engine / transmission mounts have been off my car many times with the transmission removal, and appear OK, as does the front, but I've never had it off. I wonder how a bad harmonic damper would present itself on the V8. Has anybody had this occur?
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felipe heuser
Experienced User
Username: felipe

Post Number: 128
Registered: 07-2017
Posted on Sunday, 17 January, 2021 - 20:08:   Edit PostDelete PostView Post/Check IP

That would have been my next query regarding rough idling which is present however not excessively, however no vibrations and only when accelerating from stationary through to fourth gear once running 50+ km/h.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 96
Registered: 02-2015
Posted on Monday, 18 January, 2021 - 17:47:   Edit PostDelete PostView Post/Check IP

It might be worthwhile looking at a leak in the inlet manifold gasket. I had a similar problem with my 1978 Corniche DRH32489. See this forum's Silver Shadow Series with the post "Removing the Needle Seat from a Solex 4A1 Carburettor" The post has quite a few entries, so work from the last entry backwards to find the problem which is one of the things I fixed.
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felipe heuser
Experienced User
Username: felipe

Post Number: 129
Registered: 07-2017
Posted on Tuesday, 19 January, 2021 - 00:28:   Edit PostDelete PostView Post/Check IP

Would replacing the harmonic vibration damper require a special tool?
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David Balfour
Frequent User
Username: sidchrome

Post Number: 216
Registered: 02-2009
Posted on Tuesday, 19 January, 2021 - 00:36:   Edit PostDelete PostView Post/Check IP

Hi Felipe,

Yes I think you will need:

https://www.britishtoolworks.com/product-page/crank-hub-socket

It's not a task I have undertaken on the cloud, but imagine that without that tool it would be very difficult.
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felipe heuser
Experienced User
Username: felipe

Post Number: 130
Registered: 07-2017
Posted on Saturday, 23 January, 2021 - 07:16:   Edit PostDelete PostView Post/Check IP

Thanks David...have contacted and seems that's the correct tool...found a used damper from a very respectable source...also read that second smaller metal ring is recommended to exchange however without any references...any ideas?
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Jeff Martin
Experienced User
Username: jeff_r_1

Post Number: 180
Registered: 07-2018
Posted on Saturday, 23 January, 2021 - 08:23:   Edit PostDelete PostView Post/Check IP

Isn't a used damper going to have the same problem, either the rubber being too hard or to soft from age ?
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John Rowney
Experienced User
Username: johnrowney

Post Number: 98
Registered: 02-2015
Posted on Monday, 25 January, 2021 - 16:05:   Edit PostDelete PostView Post/Check IP

Hi Felipe
Have you looked at a leaking inlet manifold yet? Rather than go through my old post, I thought to save effort, I would briefly outline what I did for my 1978 Corniche DRH32489, as originally suggested by Steve Sparks. I had replaced the distributor internals, coil, HT leads, and had the carburettor overhauled - all for zero improvement in the idling. I was rather frustrated at this stage.

I ran the engine until warm and the rough idle was present as normal. I squirted carburettor cleaner around the inlet manifold gasket areas. When the carburettor cleaner got into the areas with the damaged gasket, the engine revs went up and the roughness went away. The reason is that the carburettor cleaner is additional fuel and increases the richness of the mixture, which had been leaned off dramatically by the addditional air sucking in through the damaged gasket.

I cleaned up the areas around the leaking gaskets and filled the gaps with silastic and let it cure overnight. The next day the car ran beautifully, with no leaks in the inlet manifold.
I had the silastic removed and got the gaskets replaced and the car has never been running smoother.

Using the carburettor cleaner on the inlet manifold will tell you instantly if a leaking gasket is the source of the idling roughness.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2415
Registered: 09-2004
Posted on Monday, 25 January, 2021 - 18:48:   Edit PostDelete PostView Post/Check IP

Would it not be worth connecting the car up and check for % Co variation at idle first after checking the dwell scope etc is within limits.
BTW while carrying out spray some wd40 around the manifold when on idle and note any changes to rule out the previous posting possibility!
Cripes keep it simple I have seen many specialist folk make a mountain out of a mole hill costing £sssss without doing the basics first!
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felipe heuser
Experienced User
Username: felipe

Post Number: 131
Registered: 07-2017
Posted on Thursday, 28 January, 2021 - 07:58:   Edit PostDelete PostView Post/Check IP

Many thanks for all recommendations…
After tedious research and correspondences, find the damper is not a common topic or practice with relatively limited knowledge or detailed replacement procedures…(Britishtoolworks is well informed) and it goes without saying can cause crankshaft issues if left unexamined…
I would also query a used damper, but new not available from four suppliers approached…
Haven’t had time to inspect anything so far, however tomorrow finally mechanic is stopping over to test drive and troubleshoot the suggestions offered here…will report back…
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felipe heuser
Experienced User
Username: felipe

Post Number: 132
Registered: 07-2017
Posted on Monday, 01 February, 2021 - 07:40:   Edit PostDelete PostView Post/Check IP

We can now scrap the damper issue…however gained an understanding about something I was totally unaware of…great forum!
Mechanic took car out for a test drive and after checking basics found it was misfiring…checked HT leads and sparkplugs…replaced all plugs and adjusted carburettor…running smoothly!
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Jeff Martin
Experienced User
Username: jeff_r_1

Post Number: 183
Registered: 07-2018
Posted on Monday, 01 February, 2021 - 11:05:   Edit PostDelete PostView Post/Check IP

That's great news !
How old were your leads and were they of the resistor type ?

What was adjusted on the carbs, running rich/lean and/or unbalanced ?
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felipe heuser
Experienced User
Username: felipe

Post Number: 133
Registered: 07-2017
Posted on Tuesday, 02 February, 2021 - 07:47:   Edit PostDelete PostView Post/Check IP

Age unknown of the leads…however look relatively newish and possibly replaced by last owner prior to my purchase in 2017...
they’re the cooper type and all passed the test…
however the one sparkplug was bad…
Sorry, didn’t inquire my (retired R-R) mechanic so can’t respond to the carburettor adjustments…

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