HELP CCKW Engine knocking

[deadline]

4 Bbls are overrated. Most of the time the engine is never going to suck enough CFM through it to get best power. I'd rather go with the dual or triple single Bbls carbs for power. More even distribution. Can be a bit of a chore to sync them up, but one you do it and know what to listen for its pretty easy. I had a 72 MG Midget and learned to sync them up in an hour or so. Now if I could only keep the brakes working, and electrical and .....

Edited November 30, 2011 by deadline

[deadline]

Well I have been also going thorough the bits and bobs of the inlet manifold, checking hydrovac non return valve which was ok. However the steel pipe connecting the rocker cover to the inlet manifold via a non return valve was a different story !!!!!!!!!

 

[ATTACH=CONFIG]53943[/ATTACH]

This is the valve removed from the inlet connection and the steel tube to the rocker cover.

 

[ATTACH=CONFIG]53944[/ATTACH]

This is how it splits in half.

 

[ATTACH=CONFIG]53945[/ATTACH]

This is what is inside it........

 

[ATTACH=CONFIG]53946[/ATTACH]

Here is the main valve part and return spring. There is a small hole in the centre of this valve and can sometimes get gummed up with oil deposits. ( in TM for regular cleaning )

 

[ATTACH=CONFIG]53947[/ATTACH]

Here is a view of the back of the valve and spring.

 

[ATTACH=CONFIG]53948[/ATTACH]

Here is the inside view of one half of the valve housing, (this is the half which screws into the inlet manifold connection) where the valve and spring in the pic above go in spring first.

 

[ATTACH=CONFIG]53949[/ATTACH]

Last of all the other side of the valve housing.

 

 

That is not the hydrovac Vacuum check valve, at least is not the factory check valve.

 

That is the crankcase ventilation metering valve. The intake always has a vacuum pulling blow by out of the engine. Its a two stage orifice that is spring loaded to the ventilation system does not screw up the carb.

 

 

 

You have part 'AJ'

 

The hydrovac vacuum check valve is part 'AF'

 

Definitely clean it, and there is a test for the spring tension.. its in the TM IIRC.

 

As for the hydrovac check valve they are available and can be repaired.

[R Cubed]

I can see I am going to have to come up there and sort that Mans Truck out in a minute!!

 

 

 

You just stay down there I am getting it sorted now and I dont want to add your electrical problems to it as well.

[R Cubed]

That is not the hydrovac Vacuum check valve, at least is not the factory check valve.

 

That is the crankcase ventilation metering valve. The intake always has a vacuum pulling blow by out of the engine. Its a two stage orifice that is spring loaded to the ventilation system does not screw up the carb.

 

[ATTACH=CONFIG]53955[/ATTACH]

 

You have part 'AJ'

 

The hydrovac vacuum check valve is part 'AF'

 

Definitely clean it, and there is a test for the spring tension.. its in the TM IIRC.

 

As for the hydrovac check valve they are available and can be repaired.

 

 

If you see my post with the pics today you will see that I have explained that the hydrovac non return valve is fine its the valve for the crankcase breather from the top of the rocker cover to the inlet manifold which I am talking about.

Edited December 2, 2011 by R Cubed
Making the post more clear

[deadline]

It may be a translation thing: 'non return valve' is a check valve, right?

 

The crankcase ventilation valve is NOT a check valve. Its always got a suction on the crankcase via the intake manifold. Its a two stage metering device to pull moisture/blow-by gasses into the intake manifold to be burned.

 

If it gets clogged with carbon it will not make any noise. Symptoms of a clogged PCV valve are poor idle and blowing oil out the crankcase air filter, dipstick on oil fill tube (the engine becomes pressurized by blow by gasses and shoots oil out of any convenient vent).

 

 

 

Edited December 1, 2011 by deadline

[Vulture]

Removed by Vulture

Edited December 1, 2011 by Vulture
duplicate posting

[Vulture]

 

So no body found the deliberate mistake in the pics then !!!!!!!!!!!!!!!!

As the Noob to GMCs round here, I'll put my hand up and say I can't see the deliberate mistake.... Looks just like the drawing....I think... (scratch head)

[Adrian Barrell]

So no body found the deliberate mistake in the pics then !!!!!!!!!!!!!!!!

 

Your valve is shown in the wrong orientation.

[deadline]

Since the valve always has an open metering orifice there really isn't a way you can install it and have it stop flow. The valve is designed so that there is ALWAYS a vacuum pulling moisture out of the engine.

 

Only way you can seal it up it with carbon or dirt... and that's why the TM says clean it.

 

And even if the valve does clog, its not going make an engine knock.

[Richard Farrant]

And even if the valve does clog, its not going make an engine knock.

 

That is true, but having followed this thread from the begining and offered my thoughts at times, I would say that, to the inexperienced, a blow from one exhaust port due to a badly fitting manifold, can sound a little like a knock, and recollection of Rcubed saying he removed HT leads one by one, and a particular cylinder was noted, this could have been the problem all along. Somehow, I think the inlet manifold could well have been sealing, although it does not look good once removed, if it had been drawing large amounts of air there would have been difficulties starting, etc.

[N.O.S.]

...this could have been the problem all along....

 

If so then the way to look at the episode once sorted is this: having treated her to a new set of rings/shells etc you'll have a 'freshened up' engine which you can be confident will last well. If you'd just sorted the manifold, sure the rest would still be running but not as good as it will be now. Trust me :cool2:

 

Mind you my problem wasn't blowing manifold joints - not saying any more as I have the remnants of my reputation to consider :whistle:

Edited December 1, 2011 by N.O.S.

[deadline]

Yes, his post about the sad state of the the intake and exhaust manifolds (even a broken stud IIRC) would make some noise. But not a knocking sound.

 

The hard part of help with advice on the net is one's person knock is another persons ping.

 

I would say that most people never do a proper rebuild or overhaul of their motor unless it is acting up.

 

Even the form 461 'Preventative Maintenance Service and Technical Inspection Worksheet for wheeled and half-track vehicles':

 

6000 and 1000 mile inspection:

 

Item 9: Engine (idle)(acceleration)(power)(noise)(governed speed)

Item 21: Compression Test (record)

[Degsy]

Since the valve always has an open metering orifice there really isn't a way you can install it and have it stop flow. The valve is designed so that there is ALWAYS a vacuum pulling moisture out of the engine.

 

Only way you can seal it up it with carbon or dirt... and that's why the TM says clean it.

 

And even if the valve does clog, its not going make an engine knock.

 

I agree up to a point but the idea of the valve is that if fitted the correct way there will always be a small orifice but if there is a sudden increase in gas pressure or a gob of oil gets through the spring will compress allowing the valve to open to a larger orifice.

Richard (Cube) is not suggesting that the knock is caused by the valve, merely posting it as useful info for jimmy owners. It is something I have posted about in the past but Richard's pics make it much clearer.

As regards the knock, I have experienced similar problems with the manifold and the noise it made could have been described as a knock.

[deadline]

What confuses me (and again, it may be more of a translation issue than anything else) is that the mention was made that the pics showed something backwards. I believe that the metering valve really has no 'right way'. And no matter the orientation it will not cause a knock.

 

I know a common issue in jeeps for the 'idle stumble' lots of times is related to lose manifold/piping.

 

Many people have given many good things to check... and from the description of the state of the intake/exhaust manifold it may be that the block is simply broke (that's a technical term). Could be a worn crank/cam journal, worn wrist pin, worn bearings, worn valves or springs etc etc etc.

 

Basically its time to take out the engine and start mic'ing the parts.

[R Cubed]

If you see my post with the pics today you will see that I have explained that the hydrovac non return valve is fine its the non return valve for the crankcase breather from the top of the rocker cover to the inlet manifold which has the problem......... So no body found the deliberate mistake in the pics then !!!!!!!!!!!!!!!!

 

 

Ok to clear up the confusion, Deadline you are right about the valve this is the one I am referring to.

 

 

The "deliberate mistake" I was lead to believe there should have been a steel ball in there to act as a valve but investigating it more I now see that it IS a restriction and NOT a non return valve, as Deadline points out with his pic of the TM page. It can pass air either way but in its installed position there is a vacuum caused in the rocker cover due to this connection to the inlet manifold and with the oil filler air filter this allows air in to the crankcase and flows up through the cylinder head into the rocker cover and then in to the inlet manifold taking with it blow by gasses and oil mist in the process.

 

So there is no deliberate mistake everything is as it should be.

 

There is a right and wrong way for it to fit ( the threads are also different ) the inner valve and spring must face towards the inlet manifold for it to work correctly.

[R Cubed]

It may be a translation thing: 'non return valve' is a check valve, right?

 

Yes your translation is quite right.

 

 

 

The crankcase ventilation valve is NOT a check valve. Its always got a suction on the crankcase via the intake manifold. Its a two stage metering device to pull moisture/blow-by gasses into the intake manifold to be burned.

 

If it gets clogged with carbon it will not make any noise. Symptoms of a clogged PCV valve are poor idle and blowing oil out the crankcase air filter, dipstick on oil fill tube (the engine becomes pressurized by blow by gasses and shoots oil out of any convenient vent).

 

[ATTACH=CONFIG]53979[/ATTACH]

[ATTACH=CONFIG]53980[/ATTACH]

[R Cubed]

As the Noob to GMCs round here, I'll put my hand up and say I can't see the deliberate mistake.... Looks just like the drawing....I think... (scratch head)

 

You are sooooo right there is NO mistake looks like I am the nooob :blush: 15 years of having the truck and I am still learning.

[R Cubed]

That is true, but having followed this thread from the beginning and offered my thoughts at times

 

All very much appreciated, thanks.

 

I would say that, to the inexperienced, a blow from one exhaust port due to a badly fitting manifold, can sound a little like a knock

 

Well, I am not all that inexperienced with engines, however the sound it was making in my opinion did sound like a "banging futt sound" you could say it was a knock which is what I thought, suspect this is because the size of the cylinders and the resultant combustion volume made a larger sound than I am usually use to with playing about with Rover 3.5 Ltr V8's and 2 Ltr 4 pots. In hindsight though having stripped the engine and not found anything except worn piston rings and pitted big end bearing shells the search continued, to the point I am at now !!!

 

 

and recollection of R cubed saying he removed HT leads one by one, and a particular cylinder was noted, this could have been the problem all along.

 

Yes reckon you are right.:blush:

 

Somehow, I think the inlet manifold could well have been sealing, although it does not look good once removed, if it had been drawing large amounts of air there would have been difficulties starting, etc.

 

I think the gaskets on the inlet were fine until I disturbed them all when I cleaned the loose bits off the exhaust ports, this then lead to the inlet not pulling up tight to get the exhaust manifold to seal ( sort of ) at that time did not want to get into the situation of replacing both the manifolds, but there you go maybe I should have changed them years ago !!!!

You live and learn......

 

Since putting the engine back together the first time the knocking was as bad, coupled with the massive lack in power, due to the two end inlet ports leaking lots, I now know they were leaking lots as when I wiped grease round them when the engine was ticking over you could see the grease being pulled in through the gasket joints, this would account for the loss of power as these two end inlet ports each serve 2 cylinders so 4 cylinders were running very weak :shocked:

 

 

Note Richard, please do not think this is a moan at you I am just trying to tell everyone my errors in diagnosis of the fault was and how you can get side tracked into thinking it is something more serious than it actually is..

[R Cubed]

If so then the way to look at the episode once sorted is this: having treated her to a new set of rings/shells etc you'll have a 'freshened up' engine which you can be confident will last well. If you'd just sorted the manifold, sure the rest would still be running but not as good as it will be now. Trust me :cool2:

 

Mind you my problem wasn't blowing manifold joints - not saying any more as I have the remnants of my reputation to consider :whistle:

 

You are sooo right, maybe a blessing in disguise. The piston ring issue was well worth doing as in the stripping down several of the pistons just slid down the cylinders of their own accord :shocked: and after checking the ring gaps of the old rings found them to be over 50 thou gap so needed doing.

[Richard Farrant]

Note Richard, please do not think this is a moan at you I am just trying to tell everyone my errors in diagnosis of the fault was and how you can get side tracked into thinking it is something more serious than it actually is..

 

Hi R,

Not a problem, I am glad you have answered my post that way. As for the possibility of the exhaust blow being mistaken for a knock, without going back to the beginning, I seem to think there could have been questions regarding ignition timing, if it had been a touch retarded, that will give you a very harsh exhaust note so could be interpreted as a knock.

 

One thing I was not sure about was when you found the rings were worn so badly, did you use a Mercer guage to check the bore wear? Could not remember reading about it, as with very worn rings, I would expect bore had suffered as well.

 

regards, Richard

[David Robertson]

Hi R Cubed,

 

Have you sourced replacement manifolds yet ?

Just a thought as i came across an ad' for some this evening.

 

David.

[marmon]

Hi, is this fixed now or would you possibly be interested in selling it as is?

 

Cheers,

Quentin

[Gordon_M]

Am I the only one thinking all those compression figures seem very low?

 

 

Maybe - I was thinking they were nice and high and relatively consistent :cool2:

 

Bottom line here is that although most of your engine is fine, you seem to have worn though either the big or little end bearings on cylinder 4.

 

If you run the engine - it will only inflict more damage. At the minute you MIGHT get away with dropping the sump, pulling number 4 big end, checking the crank journal, and fitting a new pair of shells.

 

If you run it any more you will damage the crank journal and then your are in a whole world of pain. In your situation I'd drop the sump and check all the big ends before I did anything else.

 

Don't think you can reply on your oil pressure gauge. The oil flow down the crank is restricted to the point that you only see it on the oil gauge if a main bearing gives way.

[R Cubed]

Hi, is this fixed now or would you possibly be interested in selling it as is?

 

Cheers,

Quentin

 

Not quite fixed, soom will be ( with fingers crossed )

 

Selling what !!!!!!! If you mean my truck no way

 

If you think a silly thing like a knock will cause me to sell my truck not know way not ever ever ever ever

[R Cubed]

Maybe - I was thinking they were nice and high and relatively consistent :cool2:

 

Bottom line here is that although most of your engine is fine, you seem to have worn though either the big or little end bearings on cylinder 4.

 

If you run the engine - it will only inflict more damage. At the minute you MIGHT get away with dropping the sump, pulling number 4 big end, checking the crank journal, and fitting a new pair of shells.

 

If you run it any more you will damage the crank journal and then your are in a whole world of pain. In your situation I'd drop the sump and check all the big ends before I did anything else.

 

Don't think you can reply on your oil pressure gauge. The oil flow down the crank is restricted to the point that you only see it on the oil gauge if a main bearing gives way.

 

To clear up some points, it turned out that the low compression readings for cylinder No3 and No4 were down to two exhaust valves which were slightly bent on their heads so leaking through the valve seats, this has been sorted out now new valves and re seated.

 

Big ends shells were pitted the journels on the crank have been checked and are smooth and circular so I have replaced the big end shells with new ones oil pressure still good. I am aware of the difference of flow and pressure and all the oil ways in the crankshaft are clear also main bearings are ok too.

 

It was the exhaust ports on the head to manifold joint which was the cause of the knock( exhaust blow ) due to distortion and not being able to mover the bolts on the joint between the exhaust and inlet manifolds which prevented the exhaust maifold pulling up tight. Now this has been proved a new manifold is being made as a temp measure.