Alfa Pages

[Porf]

Hi all,

New here, and new to the Alfa engines. I'm currently trying to put an 8v engine into a kit car.

The engine was stripped down by a friend of mine yesterday and he noticed that one cylinder has what looks like a small dull grey worn patch. Apologies for the bad description (I may try and get a photo tonight if it'll help).

The cylinders looked as if they are either coated or lined in some way - can these engines be rebored ?

Thanks

Paul.

[Sprintervention]

Hi,

as far as I am aware the boxer engines can all be rebored, I have one with oversize pistons myself. The blocks do not have liners and are not plated either as far as I know.

Someone will be able to tell you for sure, don't know about the availability of oversize pistons though...

Regards
Chris
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1987 Alfa Sprint Veloce

[knight]

hi paul, got your message, a picture says a thousand words........I reckon it may have locally polished the bore......before you fully strip the lump and pay out major re-bore bills.......I would put it back together, and look at running the engine on a stand for 10 minutes, just to get it up to temperature, and then conduct a compression check of all bores via cranking the engine over with a compression check gauge in the spark plug hole, obviously one cylinder at a time!.......the guys on this forum will be able to advise what pressures are acceptable or not........if it has good compression, I'd leave it alone and carry on with the installation!

[bobbber]

Good compression is when the cylinders are similar pressure.

Bob
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Fiat Bravo 165 Sport

[paulhide]

Surely not if all cylinders were about 40 psi
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Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188

[bobbber]

Good point

Seriously though - you shouldn't be removing the sparkplugs with a hot engine.

Bob
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Fiat Bravo 165 Sport

[Sprintervention]

If you have a very minor amount of polishing in the bores I would put the engine back together after a very light hone of the bores just to deglaze them.

Don't go mad and remove too much material, just enough to remove the carbon at the the top of the cylinders and the shine from the rest. Rings could be replaced in the pistons just to be sure of a decent seal.

Good luck.
Chris
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1987 Alfa Sprint Veloce

[knight]

Paul - I have just had a chat to a few engine builders at work , and it sounds like the engine has glazed the bores......but a picture will still be nice to see......if this is the case, you need a "glaze breaker" tool from the following link

http://www.machinemart.co.uk/search.asp?q=glaze+breaker

I reckon it will cost about £30 sent to your door........what you need to do is rotate the crank, so the piston is at bottom dead centre.......then run the drill not too fast, and run the glaze breaker up and down the bore, doing your best impression of an automated honong machine!.......just enough to remove the glazing, ans re-create the honing pattern......

once finished do your best to clean the bore of all the honing swarf and particles, a can brake cleaner will be ideal (light solvent).......you may as well do all bores to ensure consistency.........the beuty of this method is its cheap and cheerfull and wont require a full engine strip. I'm told its not a bodge and is a widley used method.

[Porf]

Cheers for all the comments so far.

I'll be back over the garage where the engine is tomorrow (Wednesday) night and will grab a few photos to see if they help clarify things.

Knight : Machine Mart are about a 5 minute walk from work if I need to go there, I try and avoid it most of the time though as it gets a bit "Oooh look at that" and the bill soon adds up!!

Cheers

Paul.

[Ben_nz]

[knight]

Paul – I have asked the question on another forum and got some answers regarding whats acceptable for a compression check.

For an engine with a compression ration around 10:1 or below, anything below 100Psi is generally accepted as having a problem with either worn bores/rings, a broken ring, or broken valve. Ideally you should be seeing something around 130Psi……this falls in line with my 1.5 alfa-sud motor, I had it compression checked by an AA man when I broke down once and it measured 125Psi

For a more highly strung motor with more than 10:1 compression ratio, you should be seeing around 150Psi.

The mechanics at work tell me that a compression check will soon tell you if there are any problems. Heres the tool you need:-

http://www.britishminiclub.co.uk/tools/Sealey_CT951_Compression_Tester.html

you want a screw-in type of compression checker……avoid the cheap crappy push-on checkers as they easily give bum readings


And heres an interesting article about compression testing – quite interesting

http://www.pumaracing.co.uk/comp.htm

[Guest]

OK - here's a couple of pics (click the thumbnails for full size versions) that show the issue that made us initially suspect the bores may coated and that it may have been partially worn away. From the previous replies it seems the bores aren't coated or lined.

The dull and rough area can be seen in one bore, it's tricky to tell if it's worn away or on top, but it looks more like wear.



Any comments welcome !!

Cheers for the help.

Paul.

[knight]

Paul - I'm thinking its one of two things........1) excessive localized bore glazing - but I doubt it as that area at the top of the stroke does not see the greatest piston side loads under the compression stroke..........2) or more likley, where the engine has been stored, some moisture/water/condensation/coolant has got in the bore and rusted/corroded that little area, but when the engine has been turned over, it scrapes away the orange rust colour, and leaves the witness mark you have there........it dosent look anything major to me.......your bores certainly look quite shiny and glazed........so while you have the heads off, I'd get hold of a glaze breaker, and give em all a whirl for a new lease of life and good compression.

[hugh jinjin]

have seen this many times on various engines. Knight is correct with suggestion 2 ie corrosion. if there is no "step" round the effected area just glaze bust the bores and you should be ok.