1289 or 1397?

potentz

potentz

Active member
Fellow Frogger
Joined
Jul 6, 2011
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335
Location
adelaide australia
hi guys, just looking for advice. if you had the choice on which engine to moderately work for an r8 for road use. which one will be sweeter? the 1251 with 1289 pistons and sleeves or the 1397 virage motor,??:confused:

cheers brian

just finished r8 prject,running a stock 1108 cc and now looking to "warm" it up a bit
 

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Last edited:
Hi Brian

I'd go for the 1289.
Lighter crank spins up better and IMO a sweeter engine.
1397 crank is heavier with bigger journals and not so revvy.
..unless of course you modify with more bore and lightened flywheel etc...

Cheers Steve
 
Hi Brian


Depends on what you mean by "sweeter". IN the AF world the 1108 always seems to get the "sweet" tag in comaprsion to the other motors in the family.

A fresh 1108 using a 10s motor and extractors is perky and economical. I drive an R10 with such a motor. Some of the specifications I've read has the 1108 "s" motor with a higher output than the 1300 that went into the R10.

A standard 1289 (from an R12 with the Weber and not the Solex) is a free reving motor has just a bit more zip than the 1108. The 1397 has a little more torque but seems less buzzy. Some engine parts for the 1.4 are hard to find, like the timing chain tensionr and the rear main seal.

You will probably need to change the gearbox input shaft to match the 1.4 motor, but that's not the issue. If you use the 1.4 motor you might find the gearing a bit on the short when cruising at highway speeds. However, I find the 1.4 with the sidedraft Weber pulls well from low revs. (Well, thats in the hour before dusk for 4 days in Autum and 2 in Spring when it seems to be on song...)

Another issue that is hard to get around is that the dizzies are getting old and probably need a careful rebuild as new ones can't be got. This has a HUGE impact on the perkiness (notice I don't use the word "power") of any of the motors.

People like to bolt sidedraft Webers onto the motors, find a cam and fabricate an exhaust for them and they seem to go pretty well but they can get a tad stroppy if they're not driven regularly (that's been my experience with a 1.4 in an R8 given such treatment). I've owned a couple of Lynx crossover manifolds (on R8 s) and both developed cracks during their lives and sealing was always an issue. There's an unresolved AF debate re intake manifolds and sidedrafts for these engines.

Gekoeng likes a downdraft Weber from an R16 on such motors and the more I think about it the more it appeals. Simple to mount fits existing manifolds with not much tinkering.

What motor you pick will pretty much depends on what you intend to do with your "road car". If you want a pretty-looking daily driver that gets better than 30mpg and turns heads, you've already got that.

A weekend tourer, well you're on the money there too.

But if you want a weapon to go out hunting Commadores and Falcons on dark wet nights forget about the donk, see a doctor now. You'll wind up doing doing it sooner or later...

All the best

P
 
thanks steve and exfrogger, what you both say is what i was leaning towards.what i already have handy in a donor car is a 1251 mated to an r10 box. the gearbox in my r8 is also r10 type 330.i have already purchased a 1289 piston and liner kit.
i have the down draught weber and 4-2-1 extractors on the 1251 motor.(842-01)
im thinking;

port and polish head

lighten flywheel

mild cam grind

custom exhaust

what do you reckon guys (keep in mind i have not done this before )

would the 1289 be better than the 1108 if they both got the same treatment?

cheers brian
 
potentz said:
thanks steve and exfrogger, what you both say is what i was leaning towards.what i already have handy in a donor car is a 1251 mated to an r10 box. the gearbox in my r8 is also r10 type 330.i have already purchased a 1289 piston and liner kit.
i
would the 1289 be better than the 1108 if they both got the same treatment?

cheers brian
Click to expand...

Yes the 1289 will always be better. Easier to get higher compression ratio with the 1289, and will have more torque. In standard form the 1.4 is less revvy than the others, and if fitting the 1.4 liners to an 1108 or 1289 block you will need to machine it to accept the bigger liners. The rear main seal is the same as a 15/16/17 and is not hard to get.

The 1.4 flywheel is already much lighter and takes a bigger clutch. Most fit a 1.4 clutch to a machined down 1289 flywheel when modifying the engine. Best and cheapest mod to a 1289 is to take away all of the huge ring of material around the outside of the flywheel.

A reasonable cam, 1289cc, stay with a downdraft Weber (16TS), 10 to 1 comp, porting and some better pipes will get you somewhere around 90 flywheel Hp, which is a lot better than the 50 you possibly have now.
 
1108 to 1289

I was running a 1108 with twin downdraft weber 32 and upgraded to a 1289 with same carb and no extractors and the difference was significant. I improved my hill climb times at Mt Tarrengower by 13secs. The difference was noticeable and was a cheap upgrade (cost of recently rec'd engine $250)
I was planning an extractor upgrade with lynx manifold and single weber 40 sidedraft which would have improved times by least another 5 secs!
The 1289 reved well and readily available via R12's etc and hooks up to 330 gbox easily.
Unfortunately the R8 is now with it's "maker".
 
potentz said:
hi guys, just looking for advice. if you had the choice on which engine to moderately work for an r8 for road use. which one will be sweeter? the 1251 with 1289 pistons and sleeves or the 1397 virage motor,??:confused:

cheers brian

just finished r8 prject,running a stock 1108 cc and now looking to "warm" it up a bit
Click to expand...

potentz said:
thanks steve and exfrogger, what you both say is what i was leaning towards.what i already have handy in a donor car is a 1251 mated to an r10 box. the gearbox in my r8 is also r10 type 330.i have already purchased a 1289 piston and liner kit.
i have the down draught weber and 4-2-1 extractors on the 1251 motor.(842-01)
im thinking;

port and polish head

lighten flywheel

mild cam grind

custom exhaust

what do you reckon guys (keep in mind i have not done this before )

would the 1289 be better than the 1108 if they both got the same treatment?

cheers brian
Click to expand...



At first you say 1251 or 1397, then ask 1289 or 1108. The advice I received from those in the industry is that a 1251 will never be a 1289, and a actual 1289 is way better than a 1397.

I have a 1108 gathering dust, a 1251 in my current floride and a 1397 in my rusty floride and out of the three if I were to put the time, money and effort I'd do the 1397, but if I had a 1289 I think I'd take the advice and do it.

Whats wrong with blowing away someone off a set of lights from 1st to 3rd, all the fun is getting from 0 to 80 and then sitting on the speed limit and then they finally pass you, doing it again at the next set is even better.:2cents:
 
If you can get your hands on a R5 alpine head or a R8G head the 72mm stroke can be converted to the following with some machining and bigger sleeves.
76mm x 72mm = 1306cc
78mm x 72mm = 1376cc
80mm x 72mm = 1447cc

Using side draftt webers on these with a 270 cam could really pull well as it's a nice revving motor. The 1397cc engine is a nice replacement if you have a well pampered head although not as high revving as the 72mm stroke. I wanted to do a 1480 from the 1397 engine to bring me close to the magical 160hp but compression would have been too high for pump fuel so I opted for a turbo as solution. Engine would go in over the next week and plumbing for the turbo can then be done.

I used a 1289cc motor with well done head and a rather wildish cam that gave me more power than a standard G and RPM used was 6500 to 7000. although compression was less you could not feel it. I didn't use the twin webers on it only a 36/38mm down draft weber.

With these engines there are som many options that it becomes an adventure to do something else from standard.
 
I would still like to know what you want to do with the car. Is it to be your DD or will it be for weekends and drive days. Normal or club rego?
 
the car will be a weekender mainly,but not strictly as i believe a car has to be used regulary. i guess i would like to add reasonable power to make acceleration respectable and increase torque for hills. 90hp to 100 hp would be very nice
i appreciate all the input from you guys and look forward to deciding on a spec and to get it going. it would be nice to surprise a few doubters at the lights. vroom

cheers brian.
 
potentz said:
. it would be nice to surprise a few doubters at the lights. vroom

cheers brian.
Click to expand...

My Floride is powered by the 1397, I still have the skinny wheels and get a kick out of other drivers pulling over besides me at the lights so as not to get stuck behind a slower car.....I can give most of them a shock for the first 100 metres......:wink2:
 
I like Alan Moore's mods he mentioned above but instead of doing it to a 1289, do it to the 1397. With those humble mods the difference in being a revvy motor will be negligible and I think the additional cc's will push the horse power up a little more. If you use the head out of a R9 or R11 the effects will be even greater because of the improved port design on those heads.
If you are willing to buy a set of Mazda pistons (I have the part no.) it will cost you only the machining of the small ends and a rebore to 78mm and then you have 1480cc with a standard 1397 head gasket. Then you have the same revvy motor with even more horses. You can keep the downdraught but just jet it accordingly. All above won't bust the bank either.
If you then decide to go fullhouse the bottom end will be there already and it will only mean head work.
Regards
Frans
 
1480cc

Frans can you tell me if you can get low compression pistons to suit the 1480 conversion as i'd like to supercharge one but don't like the idea of decompression plates.
Cheers Peter.
 
Peter,
No, unfortunately I have never done forced ind on the non crossflows.

I would think of doing an eccentric bush in the small end to lower the piston deck and then machining a fraction off the top of the piston. You might just get in spec with that. The Mazda pistons have a slight dome in them, about 1mm and that can be shaved off safely.
Frans
 
My 5 cents Worth !!!

PotentZ,
We are all talking hypothetical theory here, so lets see where it leads.

Mr. P, from Geraldton, has me right, as the weekend before, we lent into the back of a very nice R10, with twin 45s, and it was running terrible (French accent). Because sides have to be run very regular, and set (mainly float levels) very regular, to run nice. So for good street I recommend a Weber down draft.

Now comes, how much work do you want to do for your project? A good basic 1300 or 1400 (Virage), with a mild cam, some home done gentle head work. A good exhaust manifold. Is going to work very well. 1300 I would use a 32 Weber, a 1400 I would use a 36 Weber. Not sure of inlet manifolds sold in Australia with the 1300, but in Africa we had a Weber unit on the last 3 years. But then you could always use a R9/11 with an adapter plate to turn it sideways, as they flow more air, and match ports. This would be a very good car, and a lot of fun.

If you want to hunt Falcons and Commadores, you will need a 16TS type motor and big box, and big cheque book. Anything more than above you have got to go big box, as a well modified 1400, unblown, will destroy a 330 box eventually. The Weakest Link.

Enjoy yourself !!!!
 
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