DDK - Die Deutschen Klassiker

Hello,
I am having my 73 911E engine rebuilt and thought some DDk help could be useful.

As a quick background, my main reasons for the rebuild were cylinder leaking between 18-40%, a few engine leaks on the crankcase and recently loss of power once the car had warmed up.

One of the cylinders has some light scoring but the others look ok. There has been some work done on these in the past since they now measure to first oversize. I’m not sure why there was such cylinder leakage but planning ahead I see a few options and would appreciate your thoughts and experiences on these:

1) a new set of Mahle pistons and cylinders. Back to factory spec. A set of these are quite expensive. Retro line do a cheaper set but no idea if these are good.
2) rebore the cylinders by 1mm and fit JE forged pistons 9.5 CR. I am hoping the rebore will help address the leakage.
3) replace the single damaged cylinder and using existing set up although I am not sure if oversized piston rings are still available and the cylinder leakage may still be an issue since we haven’t done anything to address this other than fit new rings.

While parts are expensive so is labour and I don’t want to have to go through the process again.

Thanks
Gitesh

Hi Gitesh

I have a set of used Biral 2.4 cylinders 84ZD3 all matched height 5 which ‘might’ have been slightly oversized (can’t measure just at the moment) because the box they are in has a label with 84.99 marked on it. However, they would need to be measured to be sure. I believe they came from a 2.4E. I do not have pistons or rings.

Regards
Mike

I have six original biral cylinders taken from a 1970 2.2E. Others may be able to confirm but I believe they're the same. I would probably have preferred selling the whole set of pistons and cylinders together, although at least two of the pistons are likely no good.

Personally, the road i chose to go down was to buy the new forged JE pistons and AA cylinders. you can get them directly from AA in USA for a few £hundred less than sold in the UK, even after allowing for duties, and they arrive within days. Go that route and you can stretch the bore out to 86mm giving you a 2.5l engine and increase compression at the same time, making a slightly more aggressive modern cam with overlap driveable at lower revs.

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Just following up on my previous reply... bear in mind if you were to change cams it occurred to me you might run into problems tuning your MFI. Others would know from actual experience, which I do not.

The extra bore on the other hand, that should be a straight scale up of fuel demands at any given rpm so I'd imagine it could be accommodated with a mixture adjustment.

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Hi Rob and Mike,

Thank you for your replies and for your offers. I will PM you if we need a set but I think I only need one.

Like everything, the cost of rebuilding and parts is higher than it was so I need to be careful but I also want to make sure I get a reliable engine since I don’t want to have to go through this again.

Thanks
Gitesh

If you decide to replace individual cylinders they will need to be the same height group as the existing ones.

Hi Angus,

Thanks for the heads up.

Kind regards
Gitesh