Technical Camshaft Bearing - Repair?

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Technical Camshaft Bearing - Repair?

SPA

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Hi all
I've dismantled my 650 engine for the first time - and I'm on a steep learning curve!
I've yet to look at the head properly but it mostly looks in pretty good condition - except for a heavily scored camshaft bearing surface in the block, and corresponding (but not so severe) scoring on the camshaft. This is at the oil pump end. My question is whether this is worth fixing, and if so how do I go about it? I've seen repair bearings online - and I'm assuming the block needs machining and the bearing insert fitted? Anyone got experience of this?

The repair bearings I have seen are only drilled once for oil. How does this work when the block has two holes diametrically opposite?

Finally (for now!) - I've seen 'new' blocks online for 350 Euros. Any feedback on their quality? By the time I've paid for machining & fitting of the camshaft bearing, removal of a broken stud, fitting of a couple of helicoils - I wonder if I may as well get a replacement block instead? Originality is not a concern here.

TIA
 
I have a couple of good used 650 crankcases here. Could post a good one to you for £60 all in. I also have a brand new late 650 crankcase, the type that does not have a distributor, that I could do a good price on :)
 
I have one of the 'repair' camshaft bearings in my spares, purely as a 'hope I never need it' move. Unless you are determined to retain the number of your original engine, I think that David's offer of a good 2nd-hand 650 crankcase is the most economical way of attending to the problems you have with your current crankcase.
Instead of using 'heli-coils' may I suggest that you use "Self-tapping steel inserts" to rectify damaged threads. These are obtainable from "MEMFAST" and/or "The Steel Insert Company". The products are practically identical from either of the companies and are almost identical to the inserts that Abarth used to use. They are very easy to insert, you just have to make up a small 'insert' tool, instructions for which are supplied with the parts.
Before you re-fit the timing-cover, don't forget to pack the oil-pump with Vaseline (petroleum jelly--NOT grease). It give the pump something to suck on upon initial engine start.
 
the hobbler

Appreciate the advice! Interesting re the self-tapping thread inserts - tbh I have never come across these. What are the advantages over a helicoil type - greater tolerance over the hole drilled?

Ta
 
Personally I think that the "self-tapping-steel-inserts" are easier to insert than 'helicoils', and you don't need a special tool--just a deep socket, the appropriate sized cap-head (allen key) bolt, a plain washer and a nut to match the bolt. You also need a steady (possible 2nd pair) pair of hands so that you drill the required fitting hole 'square'. The inserts are threaded on both the inside and outside---the inner thread being the size of the bolt that you require to fit and the outer thread being the 'fitting' thread. For the insert for a 8mm bolt/stud, in aluminium, you would drill a 11mm hole for the fitment of the insert. Look on the 'MEMFAST' site and you will see what I am talking about. These inserts are almost identical to inserts recommended by Abarth for the threaded holes in the head where the exhaust 'elbows' are fitted. When I was at Radbourne Racing we fitted these inserts even on brand new heads---saved a heck a lot of problems later in the car's life.
 
Anyone know what the clearance should be for the larger camshaft journal? I’m having a repair bush fitted in crankcase and can’t find out the size the bush should be bored out to....
 
Would it help you if I was to measure my 'repair' journal?
 
Anyone know what the clearance should be for the larger camshaft journal? I’m having a repair bush fitted in crankcase and can’t find out the size the bush should be bored out to....

Assuming that you're having an engineering shop bore out the block, they would use the actual bush you have and will know from tables and/or experience excactly what diameter to machine to.

If it's the diameter within the bush once fitted to the block that you're looking for, there is guidance by looking at the specifications for a new engine. It probably makes sense to fit a new camshaft if you're fitting a new bush?
 
Hi - the hobbler
Thanks for the offer but I do have a repair bush.

Thanks
 
Hi Peter
Yes - I agree and I have the new camshaft (freshly arrived in 3 days from Italy..!). Any idea where I would find engine specifications? I've had a good search but not finding the required info yet.!
Cheers
 
What info are you after? If it is camshaft details, they are as follows:-- The diameter of the timing-gear end journal on the camshaft is between 42.975mm and 43mm. The bearing internal diameter is between 43.025mm and 43.064mm ---the clearance is between 0.025mm and 0.089mm. These measurements are for the 500---I am not aware that the measurements were changed for the 126 engine.
 
Hi Peter
Yes - I agree and I have the new camshaft (freshly arrived in 3 days from Italy..!). Any idea where I would find engine specifications? I've had a good search but not finding the required info yet.!
Cheers


I don't know anything about what dimensions to bore the block for the correct interference fit for the bush. But the internal diameter of the camshaft bore at the timing gear end when new should be 43.030 to 43.045 mm. The running clearance with the camshaft is .015 to .055mm; I'm assuming the camshaft journal will measure up somewhere around 43.00mm? (Data from Haynes Manual for the Fiat 126).
 
I don't know anything about what dimensions to bore the block for the correct interference fit for the bush. But the internal diameter of the camshaft bore at the timing gear end when new should be 43.030 to 43.045 mm. The running clearance with the camshaft is .015 to .055mm; I'm assuming the camshaft journal will measure up somewhere around 43.00mm? (Data from Haynes Manual for the Fiat 126).
Hi Peter
I am not very observant, I too have the Haynes manual!
I had a look at mine; interesting that the journal size in the crankcase for the 652cc is listed as 42.975-43.000mm (43.020-43.045mm for the 600cc). I wonder why it’s different to the no’s from yours? Unless I missing something else..
The clearance does match mine at 0.015-0.055mm. So that’s the important measurement that the machining co can work from once they have the camshaft in front of them.
 
I have both a '595 only' Haynes book and a '595+652' Haynes book. Both of the books have the same measurements for the '595':--43.020/43.045mm for the timing-gear end journal of the camshaft, but the 652 engine journal size is 42.95/43.00mm . The flywheel-end journal for the '595' is again the same in both books at 22.015/22.036 whilst for the '652'engine the flywheel-end journal on the cam-shaft is 21.979/22.00mm. This apparent slight difference in journal size is interesting---has anybody seen a camshaft specifically for the '595' OR '652' engines?---All the cam-shafts that I have seen for sale are for 'any and all' 126 engines!
 
Hi Peter
I am not very observant, I too have the Haynes manual!
I had a look at mine; interesting that the journal size in the crankcase for the 652cc is listed as 42.975-43.000mm (43.020-43.045mm for the 600cc). I wonder why it’s different to the no’s from yours? Unless I missing something else..
The clearance does match mine at 0.015-0.055mm. So that’s the important measurement that the machining co can work from once they have the camshaft in front of them.

The clearance is the important measurement and as with all engine machining work, you're wise to work from actual component dimensions. There is a slight typo, making it 0.01mm out for which I am full of remorse :D; your "43.020mm" is correct. The measurements I quoted are listed in the main part of the manual for the 594cc and the different ones you have found are in the Supplement for the 652 engines.

I've previously asked for comment from knowledgeable Forum contributors about the range of standard camshafts that were obviously fitted from new. I'm surprised that there seems to be a "one camshaft fits all" policy from all suppliers. You only need to look at the specs. in the manuals to see there were regular changes in valve timing and with such significant difference it wouldn't be surprising if journal sizes changed.

I've noticed that in a similar way, many of the torque settings change as you move to the +499cc engines and that doesn't always correspond to different components being used. It's a bit confusing when you're making fine measurements and careful calibrations so as to produce an accurate result. :bang:
 
The clearance is the important measurement and as with all engine machining work, you're wise to work from actual component dimensions. There is a slight typo, making it 0.01mm out for which I am full of remorse :D; your "43.020mm" is correct. The measurements I quoted are listed in the main part of the manual for the 594cc and the different ones you have found are in the Supplement for the 652 engines.

I've previously asked for comment from knowledgeable Forum contributors about the range of standard camshafts that were obviously fitted from new. I'm surprised that there seems to be a "one camshaft fits all" policy from all suppliers. You only need to look at the specs. in the manuals to see there were regular changes in valve timing and with such significant difference it wouldn't be surprising if journal sizes changed.

I've noticed that in a similar way, many of the torque settings change as you move to the +499cc engines and that doesn't always correspond to different components being used. It's a bit confusing when you're making fine measurements and careful calibrations so as to produce an accurate result. :bang:
That last emoji definitely applies!
So I have the same 594 / 652 manual as you then. No mention of clearance in the 652 section but I’m assuming it’s the same as for the 594...
 
I concur---the '652' supplement in the 'Both engines' Haynes manual gives no clearances fir the '652' cam---one can onlyassume that the clearance distances must be the relative same. However, it still doesn't explain how, with the differing figure available "one cam can fit all"https:
 
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