Unexpected Overbore

[Ali B]

Whilst dismantling and cleaning the 2.8i in my S1.5 I discovered these marks on my piston crowns.

J 0.5 -> H

So I dug out my vernier gauge and measured the bore, 93.6mm
Mr Haynes says 93.55mm is a 0.5mm overbore.

Bonus!

Sadly the stroke is standard, so 2822cc

Has to be worth a couple of horses, anyone know how many?

[Ali B]

phillpot said:

Only about 1.25 I'm afraid, about one old nag and a Shetland pony

Every little helps! It's 1.25bhp I'll be seeing for the first time, when the engine is rebuilt.
Looking forward to a cam with 12 rather than 11 lobes

[Ali B]

greymrj said:

You will be pleased to hear that the 0.5mm overbore is apparently considered to be the 'optimum' size for this engine. As researched for me by a very well respected engine re-manufacturer, who then overbored my 'new' engine to that size. However I am not expecting a noticeable performance increase!
Putting a new or reprofiled cam in should however make a very noticeable difference. These cams are not the best and they can suffer some serious wear which significantly reduces both valve lift and dwell angle, having a significant effect on breathing. 2 lobes on my old engine had gone through the case hardening and I was having to keep adjusting clearances. He reckoned I would be more than 20bhp down on that alone.
(Incidentally, if you go for a good second hand cam, the earlier ones have a smaller journal size)

Found an NOS standard cam on eBay, the company assures me it is the later type.
I considered a fast road cam, but researching on PH and wider internet, I could find no reports from anyone who had put one in a 2.8.
If only you were a little further on in the task! I have found your posts on your engine very useful.
I decided not to risk driveability in traffic, I want to use the beast as my daily chariot as I used to before it broke.