Renault R8 project
Alez - 27/3/21 at 02:04 PM
Hi, all.
I'm having thoughts of replacing the power train on a Renault R8. Originally this car has a small engine longitudinally mounted at the rear.
I'd like a modern engine, mid mounted longitudinally, and small. The Subaru 4 pot boxer seems the way to go, do you agree?
I see that this engine has been configured like that before, is that normally mated to a particular transaxle all the time? I mean a default choice
like the G50 is used all the time for a small block Chevy, or the Renault UN1 goes well with the Rover V8, etc.
On the other hand, I'm attracted to the idea of keeping the French theme and mount something from Renault, but I don't really know what I
could use. I've seen a neat build using an R5 Copa Alpine engine at the rear, but I don't fancy going rear engined as this car's
handling suffers from too light a front. I wonder if I could use the same engine and transmission, mid mounted by using the transmission upside down
or something else?
R5 engined build:
https://es.wallapop.com/item/renault-r8-1970-571051891
Cheers,
Alex
Alez - 27/3/21 at 02:07 PM
Looks like the R5 engined car advert has expired... I wonder if it will appear again in a few days, shame I didn't download the engine bay
pictures :-(
Theshed - 28/3/21 at 12:22 PM
I like the R8. Personally I would be trying to upgrade it to Gordini spec and leave the engine where it is. But if you want to play and stick an
engine in the middle why not use the R21 transaxle? You have lots of choices from there on renault engines fro a 4 pot turbo to the v6 as in the
alpine. The transaxle can be used in either orientation. Loads are used in GT40 replicas etc.
Alez - 28/3/21 at 04:02 PM
The Gordini route is very attractive but expensive. The R21 gearbox looks great. The reason why I had the Subaru engine in mind is its size. I'd
like the engine to sit towards the rear in an effort to keep the car looks. Z-Cars are stuffing those engines in small cars and they can even retain
the rear seats in some cases. I wonder if I could do something like that with a Renault power train.
Alez - 28/3/21 at 04:19 PM
I've just read a little about the Renault R21. I'm sure you all know this but I didn't. If I understand correctly, these used UN1
transaxles with differing legths depending on torque capability. These were mated to an engine at the front, which could be longitudinal or transverse
depending on model. It looks like I could take a complete power train pretty much as is and stick it at the rear. If I go for a smaller one (short
transaxle and transverse engine) I may be able to keep much of it inside the engine bay. I think retaining a Renault theme for the power train would
be nice in this case.
Theshed - 28/3/21 at 09:38 PM
I really like the UN1 transaxles. They have a weak point at the 2 piece input shaft but nothing that will be of consequence in a r8.
I had a mate with an R25 turbo in about 1980 something - he loved it. The same gearbox is found in the early Lotus esprit....so fancy a V8 turbo....
Alez - 30/3/21 at 04:31 PM
quote:
Originally posted by Theshed
I had a mate with an R25 turbo in about 1980 something - he loved it. The same gearbox is found in the early Lotus esprit....so fancy a V8 turbo....
These days I like it when things are the right size. I owned a Fury 4.0 V8 and that didn't work that well TBH 
Alez - 1/4/21 at 03:20 PM
I wonder why they made the alpine A110 rear engined... the R8 and Simca 1000 had to have rear seats but not the Alpine. I wonder if it's because
the short wheelbase makes the mid engine less desirable.
sebastiaan - 1/4/21 at 04:15 PM
Beetle box + adapter plate to pretty much anything you could think of?
Alez - 1/4/21 at 04:21 PM
quote:
Originally posted by sebastiaan
Beetle box + adapter plate to pretty much anything you could think of?
Rear engined, though. But yes, always an option.
sebastiaan - 2/4/21 at 07:16 AM
Ah, I missed the mid-engined bit. In that case, the obvious(ly not French...) option'd be a VAG/Audi transaxle, or in keeping with the french
theme maybe the R21 or R16 options. But in terms of parts for those there's not much out there I guess?
Alez - 10/4/21 at 11:29 AM
What VAG/Audi transaxle would suit? I owned an Ultima with an Audi 4.2 V8 engine (from an S4 I think) mated to a transaxle from a VW Passat 2.5 TDI
IIRC. That worked extraordinary well but I don't want something even remotely as big for the R8. I'd like it light and nimble in the
original R8 spirit.
As for the Renault options, spares are not a problem as many Renault models are manufactured and sold here in Spain. The R8 was manufactured for the
Spanish market by company Fasa under license, not even by Renault themselves.
The R16 was never sold here, however, so that's not a convenient route. Also if I understand correctly, the R16 has its engine sitting behind the
transmission, so you'd have to reverse the whole arrangement somehow (the usual trick of running the transmission upside down I guess), right?
The R21 has its engine in front of the transmission, correct? Transverse in some cases, longitudinal in others. That car was sold here in big numbers,
so that's a great option. Not sure what engine options were available, though.
Thanks 
Alez - 2/6/21 at 07:19 AM
Well...
Mr Whippy - 2/6/21 at 09:51 AM
quote:
Originally posted by sebastiaan
Ah, I missed the mid-engined bit. In that case, the obvious(ly not French...) option'd be a VAG/Audi transaxle, or in keeping with the french
theme maybe the R21 or R16 options. But in terms of parts for those there's not much out there I guess?
Beetle gearboxs can be used mid engine as well as rear engined. To do this only requires the diff to be flipped round internally which is very easy
and their used that way in many porshe replicas.
ReMan - 2/6/21 at 12:24 PM
Love it!
I also have a soft sport for the older renaults.
Late 80's I set out to own all the numbered models, but got stuck at 12 and had four of them. :-0
Regret letting an R17 go, but didnt have anyof the rear engined ones
Alez - 2/6/21 at 04:22 PM
quote:
Originally posted by Mr Whippy
Beetle gearboxs can be used mid engine as well as rear engined. To do this only requires the diff to be flipped round internally which is very easy
and their used that way in many porshe replicas.
Hey, now I wonder if the R8 original transaxle would allow that too... I could then keep the original power train in its entirety. Now that'd be
cool. In fact, I'm really happy about the power train currently in the car, it runs really sweet.
quote:
Originally posted by ReMan
Love it!
I also have a soft sport for the older renaults.
Late 80's I set out to own all the numbered models, but got stuck at 12 and had four of them. :-0
Regret letting an R17 go, but didnt have anyof the rear engined ones
Ha ha ha, that's quite remarkable! I like the R8, R10 and, in a similar enough theme, the Simca 1000 and the Hillman Imp.
Mr Whippy - 2/6/21 at 04:52 PM
quote:
Originally posted by Alez
quote:
Originally posted by Mr Whippy
Beetle gearboxs can be used mid engine as well as rear engined. To do this only requires the diff to be flipped round internally which is very easy
and their used that way in many porshe replicas.
Hey, now I wonder if the R8 original transaxle would allow that too... I could then keep the original power train in its entirety. Now that'd be
cool. In fact, I'm really happy about the power train currently in the car, it runs really sweet.
quote:
Originally posted by ReMan
Yeah at first glance it looks like it would be possible with that gearbox. Will have to split the case but easy enough then flip the diff and reshim.
Alez - 2/6/21 at 05:06 PM
quote:
Originally posted by Mr Whippy
Yeah at first glance it looks like it would be possible with that gearbox. Will have to split the case but easy enough then flip the diff and reshim.
That's good to know, thanks!