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post #16 of 30 (permalink) Old 10-26-2018, 07:42 PM
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Giulietta pans come off in situ far easier then 105 oil pans, but yours is still a Veloce which means that complicated little gooseneck seal. Take off in 1 piece, put back as 2 piece so you can confirm that the gooseneck is actually sealing

Re-reading your post - when you rebuilt the head was it shaved at all ?? If so it sounds like you might have a light piston-to-head touch, especially if you are running a 1400 kit.

If this is indeed the case, then the head will need to come off and the pistons out to shave them down - rather shave the readily available pistons than the scarce heads

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post #17 of 30 (permalink) Old 10-26-2018, 08:04 PM
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I'd give a push on each tappet to make sure a valve spring wasn't broken before removing any more parts-be careful of collisions with pistons and other valves. The pan IIRC can be easily removed, esp with power tools.
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post #18 of 30 (permalink) Old 10-26-2018, 09:27 PM
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Hi TJ,

from my own experiences, but not universal :

- if you have a broken valve spring, the engine starts very hard and can not operate normally. so you know right away that you need to remove the head.

- if the noise cannot be defined precisely, it is probably a damaged crankshaft bearing. it is possible that the oil is still clean or without visible evidence. If you check all the upper engine, you have to investigate now in the lower engine.

I had this problem on a 1750, the grinding of the crankshaft, made by a specialized workshop, had not been correct.
I had confidence in the workshop, I rebuilt the engine 3 times. the first and second time, crankshaft gone to this workshop because I thought I made a mistake. The third time I changed the workshop, and they found that the grinding of crankshaft was not perfectly made...

Hope you will find the solution in short time.

Chris, in love with Alfa from...'68, but it wasn't always reciprocal !
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post #19 of 30 (permalink) Old 10-27-2018, 12:25 AM
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Hi tj

I have been following this interesting thread, and unfortunately have no great wisdom to offer you.

Since all of the posters have suggested the most obvious paths to pursue; returning to your first post, it does seem this problem arose after work on the head, prior to that the bottom end was fine.

Thus, I feel next step should be head removal and examination rather than sump! this is purely my observation from afar....

Good luck.

Richard
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post #20 of 30 (permalink) Old 10-27-2018, 04:24 PM Thread Starter
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Richard,

Agreed 100%.

-tj
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Originally Posted by richards View Post
Hi tj

I have been following this interesting thread, and unfortunately have no great wisdom to offer you.

Since all of the posters have suggested the most obvious paths to pursue; returning to your first post, it does seem this problem arose after work on the head, prior to that the bottom end was fine.

Thus, I feel next step should be head removal and examination rather than sump! this is purely my observation from afar....

Good luck.

Richard


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57 1900C SS (10321) Carrozerria Touring (in process)
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post #21 of 30 (permalink) Old 10-27-2018, 04:58 PM Thread Starter
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Thanks Greig,

I appreciate the information.

The head was skimmed minimally but it's an old head that has been skimmed before. We did install a thicker head gasket hoping to compensate, but you never know.

-tj

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Originally Posted by AlfistiSA View Post
Giulietta pans come off in situ far easier then 105 oil pans, but yours is still a Veloce which means that complicated little gooseneck seal. Take off in 1 piece, put back as 2 piece so you can confirm that the gooseneck is actually sealing

Re-reading your post - when you rebuilt the head was it shaved at all ?? If so it sounds like you might have a light piston-to-head touch, especially if you are running a 1400 kit.

If this is indeed the case, then the head will need to come off and the pistons out to shave them down - rather shave the readily available pistons than the scarce heads

Ciao
Greig


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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 #22 of 30 (permalink) Old 10-27-2018, 09:32 PM
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Quote:
Originally Posted by alfa_corsa View Post
Thanks Greig,

I appreciate the information.

The head was skimmed minimally but it's an old head that has been skimmed before. We did install a thicker head gasket hoping to compensate, but you never know.

-tj
Bingo..... a Dollar to a dime this is your problem, as soon as you start to rev the engine and the rods stretch infinitesimally you start to tap the pistons to the underside of the head. Usually its the one edge of the piston just above the rings that makes contact & leaves a very light shiny crescent mark at the point of contact - if you have access to a boroscope you should see this mark on one side of the piston next to the liner - usually the point of contact with a very shaved head.... no prizes for how I know this !!

Don't be tempted to file away under the head even though this is the simplest and easiest solution, rather remove the pistons and rods and have the pistons slightly relieved where they are touching - reason for this is that pistons are readily available, good heads are not and 750 heads even less so.

Pulling the head isn't difficult.... especially if it's been off recently

Ciao
Greig

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post #23 of 30 (permalink) Old 10-27-2018, 09:58 PM
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I would take off the oil pan and check the connecting rod bearings. I would not run the engine until it was inspected because a friend destroyed his engine due to a bad rod bearing. I had worn out pistons in my Sprint Veloce and you could hear a bell like sound when the engine was started. The motor burned lots of oil. The engine had 100K miles and drove many AROSC time trials before rebuilding the engine.
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post #24 of 30 (permalink) Old 10-28-2018, 05:59 AM
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Greig, my thinks is a stethoscope on top of the head would have pinpointed it if that was the case. Only at the RPM range of the knock. FWIW as you know the SS and SZ had a shaved engine block from the factory. The pistons on these engines had a radius around the perimeter of the pistons to relieve this contact. Tom O'Brien a racer of the time diagrams the radius in an interesting article in Sports Car graphic June 1961 issue. I also have seen valve pockets relieved on pistons to prevent the edge of the valves from skimming the sharp edge of the pocket which usually goes unnoticed when turning over a motor by hand on the bench. After that the skim is done by the action of the motor during break-in with no harm to the valves if you are lucky, remarkably. I've seen tear down engines that were perfct but showed witness marks on the valve pockets that would have not otherwise been detected. It is why SS/SZ factory pistons have a scalloped valve pocket. I always radiused any pistons as a safety just because it was the thing to do regardless of the thickness of the head.

You are very correct to note this stuff won't show up on hand-turning an engine on the bench but when things start heating up all bets are off.
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post #25 of 30 (permalink) Old 10-28-2018, 07:00 AM
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I test fit the head in place on the motor without a head gasket installed.
Bolt down the head just enough to hold it securely.
Hand rotate the bottom end around to see if anything touches.
If not, you are assured that you have the thickness of the head gasket as clearance for temp change.
If it touches anywhere without the head gasket in place, that should be clearanced on the Pistons like Greig says.
DB
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post #26 of 30 (permalink) Old 10-28-2018, 08:38 AM
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me too..almost .. but I used an old crushed gasket.. i don't know if this is likely but it did come to mind that if there was some contact o the piston, I would think that at least initially , the brunt of the force could telegraph down to the rod bearings which are the softest material in the chain. Just thinkin'

Last edited by divotandtralee; 10-28-2018 at 08:48 AM.
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post #27 of 30 (permalink) Old 10-28-2018, 09:49 AM
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This may sound daft but I had a similar problem with a 2000 engine and we found that the plug electrode on one cylinder was coming into contact with the piston and making a clicking noise. Replaced the plugs with B7ES and the problem went away. Cheap solution!

Stuart
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post #28 of 30 (permalink) Old 10-28-2018, 02:18 PM
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post #29 of 30 (permalink) Old 11-01-2018, 10:00 AM Thread Starter
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Yesterday I removed the cylinder head. The first thing I noticed was that when I turned it upside down and set it on my workbench was that one of the two airbox support rods was loose at the top (where it connects to the airbox). I thought to myself, "was that the source of the noise?" before turning my attention to the valves and pistons.

A couple of the pistons show the slightest (and I mean extremely minimal) contact from the intake valve in their valve reliefs. Obviously this is not right and needs to be rectified. It's also not surprising on a head which has been cut .040" from the factory and then skimmed who knows how many times since 1959. Today there aren't many options for 750F engines past a complete rebuild with a 1400 kit and later cams, which I would happily consider were I not in the process of completing my Giulia GT Veloce build and trying to finish the body on the Super Sprint.

IMG_0287 by tjveloce, on Flickr

That said, after sleeping on it I have come to the conclusion that the sign of valve kissing piston could not possibly be the source of the noise I heard. I tested each combustion chamber for leakage and none of the valves are bent. After sleeping on it I believe that the source of the noise was the loose airbox support rod, which I was not able to discover with the engine in place. There's just no way that such a pronounced noise would have resulted in the very light contact mark, and lack of bent or damaged valves. The valves themselves show virtually no sign of contact.

None of this means that the pistons don't need to be relieved a bit, and as crude as it is it's my only real option for now. Perhaps some day I'll build another engine for her, but for now, given the small amount of use she gets, I'll get out the Dremel, clearance the piston a little and reassemble.

Thanks for all your advice and input. I'll let you know how it goes once she's back together, this time with a properly tightened airbox support rod.

Ciao!

-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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post #30 of 30 (permalink) Old 11-01-2018, 10:41 AM
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Why to parts of the valve cutouts look like they were done by somebodies unsteady hand?

This is an area where accuracy is required ...
Pete

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156 Series 1 v6 ... and remember it's all just opinions
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