Some Pistons for a Pistonhead...

[Basti450s]

Hey guys,

I've been off for a while now, since the Cerb was stuck on its Jack stands since 2010. It is now in the process of being rebuild, which did require some money saving beforehand. However, now the engine has been taken out and is in pieces - it looks as if it already benefited from a rebuild "less than 5k miles ago". If I can figure a way to post pics, I'll add them lateron. I basically have 2/3 questions. Number 1 - if you have a new set of liners (4.2), but your pistons are crap, is it possible to buy a set of 4.5 pistons to use them and keep the liners? Since the difference is only 288ccm divided by 8 means its just 36ccm each. If I do the math correctly - that's just 4mm "overbore-diameter" (2mm each side looks "possible"). 4.7 pistons would require a lot more money and new liners, though. Number 2 - is there anybody out there who has a new or at least very good set of 4.5 pistons that he/she would consider parting with? Has anbody taken the route towards a new ECU with knock-sensors? I know there has been discussions 10 years ago..... but would be nice to bring it back ro life, as there must be newer and better options nowadays?

all the best, Sebastian

[FarmyardPants]

You can't put 4.5 pistons in 4.2 liners, they won't fit.
Are you building the engine yourself?

[Basti450s]

I started to rebuild the car myself, but came to a point where I had to admit it has to be a body off and now everything is "apart" the had a closer look at the engine and noticed, that the pistons are worn. you can move them about a milimeter ...

[Basti450s]

I thought the 4.2 has 88mm of bore and the 4.5 91mm - the liners are 2.8mm so if you hone them 1.3 would be left?

[Tanguero]

I have a set of 4.2 pistons...

[ukkid35]

Would you be using 4.5 pistons with a 4.2 crank?

[Tanguero]

AFAIK large journal 4.2 and 4.5 cranks are the same. The only difference is the early 4.2 "small journal" ones.

[Basti450s]

So how could one know, if it is a small or big journal crank and moreover - will it make any differnce concerning the use of pistons?

[ukkid35]

With some help you could probably get a fair indication from the engine number, no guarantee though!

[Basti450s]

So how could one know, if it is a small or big journal crank and moreover - will it make any differnce concerning the use of pistons?

[Basti450s]

´Thx - don't know why that's been posted twice - btw: merry Christmas everybody

[Tanguero]

Basti450s said:

So how could one know, if it is a small or big journal crank and moreover - will it make any differnce concerning the use of pistons?

Measuring the crank is the only way to be sure. There is no precise change over engine number, though the earlier it is the more likely to be small journal it is and vice versa.

It doesn't make any difference to the pistons. I think that it is only the engine journals that are smaller, but if you can give me the dimensions of the big end of the con rods that you are planning to use I can check.

[gruffalo]

I have a set of 4.5 Pistons and bottom end if it helps.

[Chuggaboom]

gruffalo said:

I have a set of 4.5 Pistons and bottom end if it helps.

YHM