How do you solve a problem like Giulietta? - Alfa Romeo Bulletin Board & Forums
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post #1 of 30 (permalink) Old 10-25-2018, 02:50 PM Thread Starter
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How do you solve a problem like Giulietta?

I've been so preoccupied with rebuilding my Giulia Sprint GT Veloce and trying to get my 1900C SS project back on track that I've had no time to drive or participate in this corner of the forum...until now.

So last Spring I was driving our Giulietta (750F) when the water pump and fan blade failed. That led to rebuilding the pump and installing a later style fan blade, which led to us discovering that a couple of the valves were burned, which led to a rebuilt head with later cams (to improve drivability) which led to my current conundrum.

The builder of the head is not only a friend, but a trusted member of the North American Alfa Romeo community, and one who is very knowledgeable about 750/101/105/115 models. I don't believe the head is the cause for the symptom I'm about to describe.

If I didn't know any better I might think it was a rod knock, but I'm almost positive it's not a rod knock (I'll support this statement in a minute). There is a knocking noise coming from somewhere under the hood that occurs only between 3000 and 4000 RPM. I've drained the oil and there is no indication of any metal or shiny particulate in the oil which you'd expect if a conrod bearing had failed. The compression is healthy across all 4 cylinders so it's not a piston and valve kissing. I've removed the exhaust system so it's not a baffle. The engine is relatively low mileage (less than 20K miles) and was built by reputable people prior to my acquisition of the car. I cannot find anything attached to the engine that is loose which would cause this rattle, and it's not the timing chain or the tensioner. The carbs were gone through just recently and I don't hear any noise coming from the exhaust manifold. It does not have any cracks in it.

The only thing I haven't checked is the gearbox to see if something came loose inside the bell housing.

Who wants to weigh in on potential sources for the noise?

-tj in the Cruz Mtns


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post #2 of 30 (permalink) Old 10-25-2018, 06:08 PM
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Seems to me you have lost faith in your stream of local "experts' who have done the previous work. .. I can't believe Sahines can't figure it out. If you don't know him, I can't imagine, then you should. An old fashioned stethoscope or a big screw driver to the ear will set the record straight on what is going on.
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post #3 of 30 (permalink) Old 10-25-2018, 06:19 PM Thread Starter
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Quote:
Originally Posted by divotandtralee View Post
Seems to me you have lost faith in your stream of local "experts' who have done the previous work. .. I can't believe Sahines can't figure it out. If you don't know him, I can't imagine, then you should. An old fashioned stethoscope or a big screw driver to the ear will set the record straight on what is going on.
I'm not sure how you come to the conclusion that I've lost faith in the locals, but I'd prefer to figure it out myself. I've built numerous engines, including Alfa engines. Tom is actually a good friend and has had heard the noise. Short of me taking it to him on a trailer there's not much he can do, and again, I'd like to figure it out myself. We've done the stethoscope thing....it's unclear as to exactly where the noise is coming from, and I'd just like some thoughts before I remove and disassemble the engine.

-tj in the Cruz Mans


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post #4 of 30 (permalink) Old 10-25-2018, 06:32 PM
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I gave you my two cents.. It sounded like you had run out of options locally. I'm sure you have done the right thing. It just seemed from your post that you were at the end of your line on local help. Like desperately frustrated. We've all been there. It's always good to retrace your steps and try to find out when the noise started and what you did just before that maintenance wise. if Tom hasn't figured it out from his distance maybe someone else can from here...The only thing I can think of is a stuck valve or broken or bound up valve spring . You did say the cams were changed... Could it be related? Skipped a few links on the timing chain? .. easy to do.I'm leaning in that direction.

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post #5 of 30 (permalink) Old 10-25-2018, 06:54 PM
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Piston slap?

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post #6 of 30 (permalink) Old 10-25-2018, 08:06 PM
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A couple of thoughts—

Try pulling the plug leads in order and rev it up. If the knock goes away or reduces at least you’ve found the cylinder. No change means no need to sweat the bottom end.

If it’s a 750 motor and you have big cams installed I think the “lifter” bores have to be clearanced for the cam lobes. Maybe the cams are walking and striking the bores? Just a SWAG but easy to check out.

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post #7 of 30 (permalink) Old 10-25-2018, 08:40 PM Thread Starter
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I'm not at the end of my line, it's just that I like to do my own work when possible. I'm frustrated but not deeply so. Deeply frustrated was the 5 year restoration of my Giulia coinciding with being screwed out of $40K by a supposed master fabricator on my 1900 project. Deeply frustrated was having a tire detonate and damage the front fender and paint on my newly finished Giulia. This is just confounding.

The thing about it being a stuck valve or spring is that one, it only occurs at certain RPM, and you'd think that if it was one of those, it would occur at all speeds. Of course it is hard to imagine that this is not related to the rebuilt head and camshafts, but if it was the timing chain I would think it would not run (I also checked it numerous times). Tom is the one that built the head, by the way.

My main reason for the post is that I have covered all the things that seem obvious, and while the only way to know for sure is to take the engine apart, I was soliciting the collective wisdom for something that I hadn't thought of already.

-tj in the Cruz Mtns


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Originally Posted by divotandtralee View Post
I gave you my two cents.. It sounded like you had run out of options locally. I'm sure you have done the right thing. It just seemed from your post that you were at the end of your line on local help. Like desperately frustrated. We've all been there. It's always good to retrace your steps and try to find out when the noise started and what you did just before that maintenance wise. if Tom hasn't figured it out from his distance maybe someone else can from here...The only thing I can think of is a stuck valve or broken or bound up valve spring . You did say the cams were changed... Could it be related? Skipped a few links on the timing chain? .. easy to do.I'm leaning in that direction.


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57 1900C SS (10321) Carrozerria Touring (in process)
59 Giulietta Spider Veloce (05431)
66 Giulia Sprint GT Veloce (242922) Reborn
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post #8 of 30 (permalink) Old 10-26-2018, 05:48 AM
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I salute you on your willingness to share your mechanical issues. That's how we all learn. Lucky for us, there is Google...

I did a search on ---"Engine knocking when accelerating" and "Engine knock in mid-range RPM dual overhead cam"

There are some very nice video/youtubes that demonstrate what could be happening.. from external rattles to spun bearings and detonation in one cylinder... I know the engines aren't Alfa but all engines perform with the same principles when you boil it down . Hope this helps you and keep us informed. We feel the pain.

One last question, how long was the engine laid up between when it ran good to knocking? .. Did you reprime the oil circuits by spinning the motor on only the starter without the spark plugs in to get oil pressure before you put the plugs back in and ignited the engine?

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post #9 of 30 (permalink) Old 10-26-2018, 06:11 AM
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TJ this is just a stab in the dark but what is the generator condition? like bearings ok there, V belt all ok there? New water pump bearings good?
Tim
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post #10 of 30 (permalink) Old 10-26-2018, 06:15 AM
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Cam caps tight all round?
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post #11 of 30 (permalink) Old 10-26-2018, 09:09 AM
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Hi all,
It is always difficult to join an item like this as all what might be adviced or suggested has perhaps already been tried out. Ok so be it, In my case be sure I only hope it can be of any help.
Did the sound started just after the rebuilding of the head or were you able to drive the car a periode of time without that sound?
Have there been mounted any higher compression pistons or was the head perhaps shaved extensively?
I had this once with the engine of my 1300cc 101 giulietta TI wherein I had mounted higher compression pistons from a 105 1300 junior gt. ( this way the compression would change from 8.5 to 9 if I remember well)
I thought, in all my naivety,that those slightly higher pistons couldn’t do any harm. I tested the engine by turning the crankshaft by hand and it felt perfect and when I first started the finished engine it iddled so nice and I remember that I loved that first sound. But once the engine reached a certain higher rev, I don’t remember anymore how high, I had the same problems as yours.
I found out what was the sound by looking into the spark plug hole with a torch where I could see the traces on the new pistons where they had touched the head ( edge of the dome).
The cure was to get the pistons out again and I had to get them shaved at the outside edge.
Now the engine works perfect for years already and gives me all the pleasure I need, the little devil !
This is one possibility that you could check easily.

If this all is not the case, my first search would be to determine whether the sound comes from the outside or the inside of the engine.
Outside of the engine:
That the sound is there at a specific rev could point to a certain frequency for loose parts, badly fastened parts or parts that touch one to another only at a certain frequency. ( f. i. striking of the oil filter, dinamo, starter , air filter housing or inlet manifold etc. against the chassis ?)
What about the parts related to the belt: dinamo, waterpump? You could check the running of the engine without any tension on the belt for the elimination of those parts?
Inside noise:
In most of the cases the sound of an inside failure can be recognised as being more agressive, sharp,dangerous, raw, metal to metal…

Of course I don’t know what you have checked with the stethoscope but if I may say, I’m sure that a good ( extensive) stethoscopic researche will give the most chance to locate ,the easy way, any trouble or at least will eliminate some parts of being the trouble maker if on their location the sound seems softer or sharper.
Finally and in most of the cases , it gives a definitive idea whether the problem is at the top or at the bottom , at the back or at the front of the engine, at the first or at the fourth cilinder, at the inlet or the exhaust side. I think it is important to know in which area the sound is the sharpest. It is always easier to dismantle only a head than dismantling a complete engine .
You can also use the stethoscope at every part and accessoire of the engine to eliminate all of these parts. Even the gearbox if you want.
I definitaly would prefer using the stethoscope, or a big screw driver as correctly mentioned by someone else before , for another hour or even more if needed than having to take the engine out of the car.
Other thoughts:
Does the oil pressure change on the gauge when the sound occurs?
Is there any play on the crank pulley turning it forwards and backwards by hand?
If the sound is stronger at the bottom, I would suspect the bearings on the crankshaft. Sometimes they just start to fail without any loss of material but with some play at certain revs.
If I remember good, you can take away the oil pan to check the crank and rod bearings and their caps (+ bolts) on any play. I have to admit that I would choose this as my last possibility to find the source of the sound before taking the engine out of the car as it is not the most pleasant job but again better that than having to take out the complete engine and finding out later that it wasn’t a crank problem at all.
Finally I would always have some ‘second opinions’ before starting dismantling the engine just like writing an important letter and having it checked on errors by another person.
This all is only to tell you how I would approach this problem.
I hope this can help a little.
Rgds
Thierry
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post #12 of 30 (permalink) Old 10-26-2018, 10:57 AM Thread Starter
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Thanks for your continued contributions.

The car has never been in a state of long term storage and even after a month or two of not being driven she always takes a bit of cranking before she'll start. Personally I've never been a believer in the idea that an engine's crank journals run dry after long term storage. Regardless, again, if I had a big end that had failed because of oil starvation I'd expect to see evidence of the oil, which is pristine.

TJ

Quote:
Originally Posted by divotandtralee View Post
I salute you on your willingness to share your mechanical issues. That's how we all learn. Lucky for us, there is Google...

I did a search on ---"Engine knocking when accelerating" and "Engine knock in mid-range RPM dual overhead cam"

There are some very nice video/youtubes that demonstrate what could be happening.. from external rattles to spun bearings and detonation in one cylinder... I know the engines aren't Alfa but all engines perform with the same principles when you boil it down . Hope this helps you and keep us informed. We feel the pain.

One last question, how long was the engine laid up between when it ran good to knocking? .. Did you reprime the oil circuits by spinning the motor on only the starter without the spark plugs in to get oil pressure before you put the plugs back in and ignited the engine?


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57 1900C SS (10321) Carrozerria Touring (in process)
59 Giulietta Spider Veloce (05431)
66 Giulia Sprint GT Veloce (242922) Reborn
95 Ducati 916
92 Ducati 900SS
91 Ducati 851
66 Ducati Mach 1 Replica
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post #13 of 30 (permalink) Old 10-26-2018, 11:01 AM Thread Starter
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Tim,

I'll respond to both posts here. I'd love it if the cam caps are the problem....I thought I'd checked them, would have thought I'd notice if any were loose, but I'm going to check them this afternoon.

As for the water pump, generator and belt, all good ideas. Again, I think I've checked them but removing the belt and running her without the water pump and generator is a great idea and I'll do that.

I'd love it if one of these simple items was the problem but again I'd think it would be quite obvious listening to the engine. I've laid hands and stethoscope all over it and haven't found any obvious source of the sound. That's what's so confounding....it's really hard to isolate where it's coming from. I may just end up having to remove the head...which is a bummer as we just installed it.

-TJ
Quote:
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Cam caps tight all round?


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57 1900C SS (10321) Carrozerria Touring (in process)
59 Giulietta Spider Veloce (05431)
66 Giulia Sprint GT Veloce (242922) Reborn
95 Ducati 916
92 Ducati 900SS
91 Ducati 851
66 Ducati Mach 1 Replica

Last edited by alfa_corsa; 10-26-2018 at 04:48 PM.
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post #14 of 30 (permalink) Old 10-26-2018, 12:32 PM
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TJ sometimes you are lucky with things, I replaced a water pump on my '60 Spider due to a high pitch squeal that sounded exactly like a failing water pump bearing - no change to the noise.... turned out to be a dry cam in the distributor and the composite material of the points running dry on the dizzy cam gave out exactly the same noise.... a drop of oil from the dipstick on my finger wiped lightly over the dizzy cam has kept things happy for 12 years now.

I should have removed the belt and isolated the water pump and the generator before 'diagnosing' the wrong part.

Keep at it, you will eventually find the source of your noise

Aye
Greig

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post #15 of 30 (permalink) Old 10-26-2018, 04:50 PM Thread Starter
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Well it's not the water pump, generator, or cam bearing caps.

At this point all I can think to do is try to remove the oil pan to check the main bearing caps and con-rods to see if I can see one loose. Removing the pan and checking the bottom end seems a better start than removing the head.

I've heard that it's very hard to get the oil pan off with the engine in place. Anyone done this?

-tj in the Cruz Mtns


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57 1900C SS (10321) Carrozerria Touring (in process)
59 Giulietta Spider Veloce (05431)
66 Giulia Sprint GT Veloce (242922) Reborn
95 Ducati 916
92 Ducati 900SS
91 Ducati 851
66 Ducati Mach 1 Replica
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