[Serpent33]

Anyone knows why? Factory specs shows bore for the Alfa boxers to be tapered. More importantly what are we compromising if it's not tapered. I don't think many have access to machines that can do it.

 

[77SudTi]

I have never come across this phenomenon in my experience with boxer motors. sound's rather odd, particularly as I see no real gain for it being tapered. Can you post some numbers so we can see how tapered the bores are? Is it in the manual under the specs?

 

[Serpent33]

I believe it should be like 0.01 mm. This was highlighted to me by an Alfa service technician. I came across in some factory workshop manual as such too.

 

[BigSwede]

Arn't they all tapered? Tighter at the top to seal better when the pressure is high.

 

[81Sprint]

It's quite possible that they wear into a slight taper, I have never heard that they were tapered out of the factory.

 

[PSk]

I've rebored my old Sud motors and never had any issues ... motors are just motors, they all have pistons, rods, valves and crankshafts ... and yeah a bit of special details but the same concept.
Pete

 

[Alex]

Old artillery guns used to have tapered bores to make the thing go off with a bigger bang (I think the Germans developed it the idea for one of their later tanks, IIRC), but the barrels didn't last very long. First I've heard of this idea applied to a piston barrel, but who knows ....

 

[77SudTi]

I believe it should be like 0.01 mm. This was highlighted to me by an Alfa service technician. I came across in some factory workshop manual as such too.

A taper of 0.01mm in one sweep of a bore is not that greater number and I wouldn't be concerned with it for a rebuild. Many people on here will tell you they have rebuilt their engines (myself included) and never had any issues.
Perhaps the taper arose due to the boring tool expanding from heat as it reached the end of drilling the bore... who knows...if yours is no longer tapered after machining, think of the larger gap as holding more oil for lubrication!

 

[alfavirusnz]

I`ve rebuilt/reconditioned hundreds of boxers and it`s the first I`ve heard of a tapered bore. Don`t worry about it, just treat it as with every other engine and measure/bore to paralell within specs.

Richard J

 

[enri]

another interesting concept from sepent33
i wouldnt worry about it for an everyday car, but if you have to beat someone on the recetrack the .01 taper may become 1/10th second on the track!
sounds like an expensive 1/10th sec