Leyland P76 Owners 2004

Vibration in my P76

Vibration in my P76 - can anyone assist?

From Russell
Date: Tue, 15 Jul 2003 21:38:18
The only story we have about "The Beast" is that we only drove it for a week when a vibration developed in it somewhere and we haven't driven it since that was back in Nov 02, the car can be started then when brought up in its rev range of about 1000rpm this vibration comes in and that's while it's standing still any suggestions?
Than that she's done nothing but sit in silence and I say that because when it's started up it has a nice twin exhaust system with a crisp note and a low rumble on idle.

Comments from Andrew Kloot

Tue, 15 Jul 2003 09:06:05
Call Jilden Reichardt in the SA p76 Owners club on 83708011 or 83392420
It sounds like the auto box has fallen apart to me, I think the g/box was 2 parts dead,2 years ago.
Jilden is the club mechanical guru

Comments from Stuart

The first place to start would be the disy and carby as if it is vibrating while stationary it is out of tune.

Comments from Mike Chadwick

Wed, 16 Jul 2003
Stuart is starting in the right place with the carby and distributor.
Check that the carby isn't worn, or an ignition lead is not leaking its spark, by starting it up and watching for sparks in the dark, at night.
Frankly, I don't think you'll find the solution there. I suspect that there is a leak at the inlet manifold joint(s) to the cylinder heads,
internal, external, or both. If you get a spray bottle with a little bit of water in it, and spray round the joints with the engine running, it will be obvious if it is an external leak, because the water will disappear into the
engine at the point of leak. It may be possible to temporarily remedy an external leak with a little bit of Silastic or some other such sealant, but there maybe an internal leak as well. If you have an internal leak, the only
remedy is to remove the inlet manifold and gasket and to replace the gasket, or to renovate the gasket and refit. Before refitting the manifold and gasket, I suggest you find somebody who is intimately acquainted with the P76 V8 motor, and ask them to do it for you if you don't have the know-how or confidence to do it yourself, preferably somebody in the Club who enjoys doing it and has done it successfully for themselves.

Comments from Matthew Cook

Wed, 16 Jul 2003
Check your engine mounts aren't cracked / disconnected etc.
Check there's not a mixmaster in the glove box

Comments from David Waters

Wednesday, 16 July 2003
The vibration could be lots of things, broken crank to a dry distributor.
Air leaks in the manifold often case misfire at low revs but a blocked jet type thing it one barrel of the carby can do it as you cruise, plus other tune stuff like condensors..
Have a good look at the drive plate; if this cracks or works loose you believe the engines near fell out.

Comments from Barry Sykes

Wed, 16 Jul 2003 18:24:00
I think Stuarts diagnosis is a bit simplistic. If the motor is running sweetly through its range, but still vibrates, then it could be either the engine or gear box mounts.

Comments from Mike

Russell, I have had a similar problem with my P V8.
Started OK, idled nicely, accelerated normally - but running at around 1500 rpm with little
load it was so rough it felt like the engine was about to fall out.
Above 2000 rpm it ran normally, but trying to drive at a steady 60K was a real pain. My first thought was that one or more of the engine mounts was loose or broken, but they were OK. Timing and dwell were reasonable, so it seemed like a classic "flat spot" in the carby. Stripped it,
cleaned it, replaced gaskets and adjusted everything, then tested. Started and idled beautifully, but as rpm was increased towards 1500 it was just as rough as before. To see whether it was rich or lean while running roughly I slowly closed the choke (converted to manual many years ago), but it
made little difference until about 3 quarters closed when it was obviously too rich and nearly stopped. Apparently, the problem was not the carby.
Plugs, leads and dissy cap were reasonably new and looked good, and there was no significant play in the dissy shaft, so I removed the points.
The contact surfaces seemed reasonable (not great) but they were VERY stiff to open and close. Replaced them with a new Bosch set, and the problem went away. Still don't understand why the problem occurred only around 1500 rpm, though. In my experience, problems with points usually affect the total engine performance, but may be isolated to the bottom or top end of the rpm range. I have not seen it affect just a small rpm band in the middle.
That's my story. It may help you.

Comments from Barry

Date: Fri, 18 Jul 2003 13:44:00
I have just read Mike MacKenzie's story.
I don't for one moment dispute any of what he says, because I've been there and done that.
The only bit he didn't cover, and where the fault in his engine could have lain was with the advance and retard mechanism. As we all know, as the motor speeds up, the spark is advanced correspondingly. If this mechanism is sticky or some such, the problem Mike discusses can arise, and a few squirts of some sort of lubrication (eg RP7) usually helps. Indeed, it is quite possible that when Mike replaced his points he squirted that stuff around to enable him to fit them easier, and unwittingly freed up the mechanism in the process. Years ago an auto electrician talked to me about balance bobs being the problem with my timing (it wouldn't advance properly). I've no idea what these are, but I suspect these are what stick, and cause this sort of problem.
I liked the comment about a mixmaster in the glove box!!

Reply from Mike to Barry's comments

Sun, 20 Jul 2003 17:44
On Thu, 17 Jul 2003 22:31:48 -0700, Barry wrote (in part):
I have just read Mike MacKenzie's story.
I don't for one moment dispute any of what he says, because I've been there and done that.
The only bit he didn't cover, and where the fault in his engine could have lain was with the advance and retard mechanism. As we all know, as the motor speeds up, the spark is advanced correspondingly. If this mechanism is sticky or some such, the problem Mike discusses can arise .......
Mike responds
Well, not quite. If the auto advance freezes, or the little springs break or fall off, the timing will either stay retarded or advance too early.
This will have an obvious effect on performance, and may cause overheating, but it should not cause rough running, particularly when lightly
loaded.
In this case acceleration above and below the "rough spot" was normal, and there was certainly no sign of overheating, so I was reasonably sure
That the auto advance was operating normally. Also, this dissy had been professionally checked and graphed about 12,000 miles ago.
However, in this game almost nothing is impossible, and if the points had not fixed the problem I would have had to delve further.
Barry wrote
............ and a few squirts of some sort of lubrication (eg RP7) usually helps. Indeed, it is quite possible that when Mike replaced his points he squirted that stuff around to enable him to fit them easier, and unwittingly freed up the mechanism in the process.
Mike responds
I would not recommend squirting RP7 around the points, because they should be clean and dry. A drop of oil on the pivot and a smear of light
Grease on the cam should suffice. If I need to spray anything around the electrics to displace water without harming their insulating or
conductive properties I use something like CRC2-26 which is designed for that purpose.

Comments from Lisha Kayrooz

Sat, 19 Jul 2003 23:15:16
Here's my story about a nagging mid-range vibration that I eventually got fixed. It might be some help to Russell -- I've heard just about every other part of the engine mentioned!!
My V8 had a noticeable vibration between about 75kph and 90kph. It was also there when I just revved the engine at standstill so that
eliminated tail shaft or something in the drive train. I spent a heap getting all sorts of things checked and nothing made any difference. Finally I remembered that when I had a minor recondition (mainly rings) some time before, the idiot had the camshaft lightly ground but the bigger idiots at the grinding shop gave it a "sports" grind which made it idle lumpy.
Sure enough, I had it replaced with a standard camshaft and no more vibration.

Comments from Adam

Fri, 18 Jul 2003 19:29:48
As people have said, there could be many causes for the vibrations.
Our Targa had this problem after the engine had been bought into use after 14 years of sitting around. The petrol tank had to be replaced because it had stale petrol in it and every 10 klms the fuel filter would clog up with what was very much like black Silastic.
I have lost count of how many carbies I have put on it ( both our other V8's have hollies but this is a club/conssesion car).
Make sure the leads are in good working order and that they ALL work and are on the correct plugs. Make sure there are no sparks from around the plugs, dizzy cap and the top of the coil.
Another problem that we encountered was that we had 2 bent pushrods.
After we replaced one of them (they were both on opposite sides and were close to the shape of a twisted L rather than being straight) it would idle ok but vibrate when hitting certain driving speeds.
Whether the valves had seized or something had lodged in there some how we still do not know.
After all these were rectified, the car ran smoother than any other V8 I have ever seen.

Final comment from Russell

Sat, 19 Jul 2003 19:41
Just letting you know that our P76 has now been fixed, Jilden from the Adelaide club come to our home and found the problem, which was a faulty front uni joint on the tail shaft.

Vibration in the Yobbie

Comments by Yowee

In the last weeks we have had a discussion on vibration.
Well blow me down, my car has suffered the vibrations too, but I would have called it "what in the blazes is that rattling noise coming from under the car".
I have for a long time now had a little tinkling noise which would appear from when the starter motor and ring gear don't pull apart from each other. BUT This noise was very disturbing.
Well Russell I now can understand your reservations.
The sounds were as if I had something rubbing against the tailshaft or loose material rattling inside or against from the exhaust pipe. At one stage I thought it may have been the water pump or the alternator (Bosch 80 amp alternator with the large fan pulley, I should have had the small fan fitted but was able to use a shorten vee belt to get the fan to miss the engine castings) , but this was dismissed due to there being no rubbing and no noises when I revered the motor when parked. I also noted that when I dropped back to neutral when rolling that the noise stop and I could reve the motor freely. I also heard a clunk just as you went into gear.
As the noise got worse, I thought the inside of the auto box was coming apart, like the torque converter fins hitting the inside of the box. (The auto box overhaul last year) I did find that I had lost a lot of oil from the transmission, so refurbishing the oil, it seemed to fix the noise a little. Yesterday afternoon coming home from work I had to stop a number of times because the car was starting to shake and the noises were getting worse.
Last night I was able to pull out the tailshaft and check the universal joints. The back one was in great shape, but when we got to the front yoke and uni joint it seem OK. On closer inspection you could see a tell tale rust stain from the needle bearing housing and the seal was cracked.
Like most P76 owners you have another car in pieces for this very reason, I went down the back yard and found burried under the rubbish another tail shaft coated in rust (over 7 years) but the everything was in good shape. Only worry was it from an auto box
Buffing up the yoke outer areas removing the spiders and dirt etc. I was able to fit the replacement.
A bit of trouble with the rear needle bearings in that when I repack them I used too much grease (trap for young players) and also the needles dropped out of their positions. A little trouble also with the spine not sliding down the inner shaft easly (rusted slightly).
The saying is true, "if you keep something for seven years or more you will use it".
My suggestion is to taken the time to listen to your car. If you can get under the car, check for the rust stain on the inside of the yoke. Physical movement of the tailshaft requires you lifting the rear of the car.
Also check your transmission fluid.
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Dec, 2005
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