Unexpected Overbore
Discussion
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?
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?
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)
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)
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. 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)
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.
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