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Discussion Starter · #1 ·
Hi,
I have just put new Pistons and liners in my 67 Giulia. It's a 1600 veloce..

Now the motor starts and runs really smooth and ticks over nicely..

Here is the BUT, it has what sounds like a cam knock that is quite loud and get louder as you rev it..

I have checked the cam tolerances they are all a little tight but not a lot.

The Pistons I installed could be installed anyway round I am sure for the 1.6.. Can anyone confirm I have not done something stupid! Compression is very good now at 110 on all.. See picture of the new installed Pistons and liners...

I have cranked up the exhaust manifold nuts in case but it's not that I am sure..

Q how does a knackered bottoms end sound?
Could I have stuffed a main bearing or big end when the engine would only run on 2 or 3 cylinder prior to the rebuild? Didn't run it far only a few meters..

Any ideas would be appreciated.

Thanks,

Jon.
 

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Did you check piston/valve clearance, particularly if the new pistons are not stock?
 

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Q how does a knackered bottoms end sound?
Could I have stuffed a main bearing or big end when the engine would only run on 2 or 3 cylinder prior to the rebuild? Didn't run it far only a few meters..

How does a bad main-bearing (big end) sound? They'll make a steady, solid, ugly, very depressing KA-KNOCK, KA-KNOCK, KA-KNOCK at idle. If you have a bad rod bearing it will make a lighter, more rapid noise that follows the rpm rise when you accelerate the engine. Both are bad news.

In all likelihood, if you just replaced the piston/liners and left the crank in place on an otherwise good engine, then you may very well have a rod-knock.

The first thing to do is check the top-end to make sure everything is as it should be. In particular check to see if the cam timing is correct and that the cams rotate freely in their bores. Then remove the cam caps and see if you can see evidence of scoring.

My long-distance guess is that you have a bottom-end problem and that, of course, requires you to remove the bottom pan and check each main and rod bearing cap.

Good luck and keep us posted.
 

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Discussion Starter · #4 ·
Hi,

The pistons are from Classic Alfa in the UK.. i assume they would just drop in as required?

They were not original parts but the pattern parts that they highly commend..(as fitted in two of there own cars)

Q: How would i check the piston to Valve clearance?

thanks,

Jon.
 

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Piston to valve clearance. Do a search for P to V or look in the RJ Suggestions thread. Essentially, you stick a zip tie of appropriate thickness down the plug hole and position it so it will be between a valve and the piston. Then rotate the engine through by hand and ensure there is no interference. Then repeat for the other valve using a tie of the appropriate thickness. Sorry for the lack of details but can't do my own search right now and don't want to provide incorrect numbers.
 

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Hi Jon

You don't say if you skimmed the head while you had it off. If you did, did you remember to chamfer the edge of the combustion chambers ...?

I made that mistake once many years ago and the sound of the piston tapping the edge of the combustion chamber made a sound very similar to the one that you describe.

Good luck and keep us posted.

Mike
 

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The pistons usually have an arrow stamped or engraved on the crown showing the correct orientation. Arrow points to exhaust side, also the rods have a slight offset, these must be assembled correctly. Good luck.
 

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If the valve cutouts are different sizes on the pistons, larger ones go on the intake side. With many current pistons, you have to dummy it up and check for interference. I had new 1300 pistons from Centerline on which the valve cutouts were smaller than the stock valves; there was no way it would work without checking and machining.
Andrew
 

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Discussion Starter · #9 ·
Hi all, after a lot of digging around I have found the culprit.. I think !

The Head was the original 67 Head, I had it skimmed during re-work of the block.
I think the valves are stretched or someone fitted new Valve guides & seats at some point not correctly.

When I began to check all gaps again the intake was way too tight on all cylinders 0.2-0.3 mm (0.47 is normal i am told) one follower #4 had a wear mark and the cam also was worn on the edges, Exhaust is also too tight on all.

I bought a new cam (standard) and new followers but there is no chance the cam will fit there is zero clearance on any cam lobe and all my shims are already small 1.3mm or Less (some must be worn as 1.3 is the minimum)...

I juggled the shims I have fitted around with the old cam and new follower on #4 and did get it running a lot nicer no "clap, clap, clap" as it revved now it sounds like a car with bad cam shaft clearances.. which is what it is..

So I have decided to strip the head off and replace it with a good 1965 1.6 head I have.

thanks for all your help.

Will let you know next week when i get the new head on if its a success..

cheers,
Jon.
 

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I thinck that your valve seats are deeper than it should be with no valve clearance has result, you need to change them or like you said, use another good head. I just did a 1,6 head and I had to change all 8 seats & valves for the same reason stated above.

Your clearances where to tight and the valve touched the piston slightly
 

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Discussion Starter · #11 ·
Hi

I thinck that your valve seats are deeper than it should be with no valve clearance has result, you need to change them or like you said, use another good head. I just did a 1,6 head and I had to change all 8 seats & valves for the same reason stated above.

Your clearances where to tight and the valve touched the piston slightly
Hi Quadrifolio, I agree this was the diagnosis i had come too.. i think skimming the head compounded the issue ( maybe it was a skim on a skim I can't be sure now).

Ill refurb the old head and see what it looks like.. but fit the 65 head for now.

I bought the car unseen and I never really heard it running correctly so it was a can of worms i think...

thanks :)
 
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