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  1. #1
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    Default R8G Engines

    In a previous thread in archives, http://www.aussiefrogs.com/forum/arc...p/t-89720.html scotty dread commented:

    "The 8G on the other hand, has its spark plug in a small chamber above the combustion chamber which feeds into a pair of flame ports which connect to the combustion chamber - this gives two flame fronts in the main combustion chamber (essentially twin spark with one spark plug). It had a beautiful set of intake manifolds / throttle assembly with 2 x double barrel side draught webers (or solex) and a proper air cleaner, as well as a lovely exhaust manifold.

    The 8G motor really is a work of art, there is reason for the stigma."

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    And geokoeng commented that:

    "Being nostalgic is not being the best, the R8G was not a good motor, it worked well enough for its time. Head did not like modified cams, and cracked a lot between valves and the fire holes, and out of the combustion chamber from the exhaust valve to the steam hole on the inside of the head, normally 2 and 3. I have also seen them form cracks from the water gallery in to the rocker area, white oil."

    I am thinking of changing the standard R8 motor in my A110 to an R8G and in view of the above was wondering if that would be a good move? Are the issues serious enough or frequent enough to avoid the R8G motor although I understand the head can be repaired?

    Cheers

    bazzamac

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    I think the two comments quoted above refer to different aspects. One is praising the design the other is deploring the engineering. I think both can be true.

    But if you want more power why not go the 807 route? 120HP without any effort out of a run-of-the-mill R17G engine with no stress (and perhaps a lot less money - I take it you checked what an R8G engine goes for these days). Plus endless relatively straightforward mods possible after that if more power is desired. The swap is more involved, but the reliability gains are worth it in my opinion.
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    Go you good thing 807!! Our Rally 12 at 9.4:1 compression gets 110hp at the wheels on the dyno at 5000 RPM. Hard to find 807's and local piston/liner kits though.

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    Thanks for the comments to date. I appreciate that I can get more power with alternative engines like the 807 but what I want is an idea whether the R8G is one to be avoided or what causes the problems with the motor. Are the problems due to overstressing the motor or do they occur with just normal running? The R8G appeals to me because that was what the 1300S was built with in France. With higher powered motors I would need to consider upstream changes like installing the radiator up front and I was hoping to avoid that although I do understand that improves cooling and weight distribution.

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    Default R8G motor

    Quote Originally Posted by schlitzaugen View Post
    I think the two comments quoted above refer to different aspects. One is praising the design the other is deploring the engineering. I think both can be true.
    Hi
    A good summary I think. From my memory a 8G motor did not have a long trouble free life if it was driven hard. The heads were troublesome. And who owned one and did not drive it hard. It was a factory hot up of a budget economical family motor, so it could be used as a flagship competion model. Mass production and normal use was not really considered necessary.

    The bottom end was no problem but the head was a work of art as a design for power, but had "issues". There were a lot of clever ideas squeezed in. The original engine was only 1108cc which makes it very dimensionally small and there was not too much room on the block for some other things. But it was a pretty motor and looked the "goods" also. "Out there" for the 60s.

    As suggested a larger capacity motor will get the power easier and much cheaper. Depends on how deep your pockets are and what you want to end up with

    Jaahn
    Last edited by jaahn; 14th March 2013 at 08:04 PM. Reason: spelling !!

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    I'm obviously biased, but an 8G 1300 motor is my fave motor. So far my 1300 has completed circa 17,000 miles as a fully rebuilt motor. It has done a couple of track days, and plenty of open road work, but whilst it has been used, I can't say it has been used in anger. Whether the head had been replaced in the past up to its completed 90,000 miles is unknown, but when rebuilt there were no cracks in the flame ports, and there were no problems when it was checked over and tested. Also, my 8G motor is the only one I've seen or worked on, so obviously my knowledge is limited.

    Also note that there were a couple of different heads, the 1100 heads were a different casting than the 1300, and from various readings, the 1100G motor was peakier than the 1300G with less longevity. And Renault issued a service instruction NT 285 in June 1965 for the R1134 noting that small cracks were of no concern, with the castings being changed post the service instruction. However as indicated above, the cracks can enlarge causing problems. New reproduction replacement heads are available at a price.

    Rather than incurring the cost though, how about using a 5 Alpine motor? A later motor without the unique 8G flameports, with decent parts availability, and replica 8G rocker covers available as well as twin Weber manifolds. I guess it depends on the budget and purpose you are going to use the vehicle for. But I'd guess the 5 Alpine base could be built to produce a similar power output to the 8G motor, which would be qite reliable. However if it is a genuine 1300S body, a genuine 8G motor would be the go. Also, don't forget the 353 five speed 'box, IMO the 8G motor would take on a completely different character with the four speed (or wide ratio 5 speed). The 353 close ratio really suits the characteristics of the 8G motor, and would be wasted behind a four speed.
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    Very useful comments, Simon. The engine will be mated to a 5 speed box with 385 internals. Apart from occasional track days with club members, the car will not be used in hard competition. It will be used on club drive days and to travel to car shows here in Canberra as well as interstate to Sydney and Melbourne and perhaps further afield such as Tassie. So I am after a reasonably fast car which is reliable and fun to drive. The R8G motor or as you say the R5 Alpine motor would be ideal for what I want provided the former has no reliability issues if looked after properly. The later is in the offering but is in pieces and would need rebuilding whereas the R8G motor is a going concern and can be test driven before buying. A step up to a larger motor could be an option at a later stage if I want to do the downstream modifications like moving the radiator upfront and putting in a big brake package with, incidently, a much better hand brake than is currently on the car.

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    Quote Originally Posted by Simon View Post
    <snip>
    Rather than incurring the cost though, how about using a 5 Alpine motor? A later motor without the unique 8G flameports, with decent parts availability, and replica 8G rocker covers available as well as twin Weber manifolds. I guess it depends on the budget and purpose you are going to use the vehicle for. But I'd guess the 5 Alpine base could be built to produce a similar power output to the 8G motor, which would be qite reliable. However if it is a genuine 1300S body, a genuine 8G motor would be the go. Also, don't forget the 353 five speed 'box, IMO the 8G motor would take on a completely different character with the four speed (or wide ratio 5 speed). The 353 close ratio really suits the characteristics of the 8G motor, and would be wasted behind a four speed.
    I've fitted an internally standard R5 A/G motor to my 4CV. Externally, it now has an electric water pump, pointless ignition, a ceramic coated stainless steel 4:2:1 exhaust system with a straight through muffler & twin 40 DCOEs feeding from a cold air box through a k&n panel filter. I'm not sure what the original motor's condition was (except that I had to do a crank grind & big ends) but the dyno guy who set my motor up got 50kw at the wheels from the standard one and 65kw at the wheels after the above listed changes. I'm using a late 330 four speed box (with my finger crossed) & the 5 motor is torquey enough not to be upset by the gap between 2 & 3.

    The 4CV weighs about the same as the A110. It goes rather briskly. My impression is that it is a bit quicker than Simon's 1.3 R8G (which I've driven briefly but not briskly). In my view, it was a nice conversion & has the minor merit over the alloy R16 motor of having the same weight but a lower CG. (Contemporary tests of Alpines suggested that the 1300 cars were sweeter handling than the 16O0 ones.) I wouldn't have any hesitations really - the only hassle is missing engine block mounts & there are easy solutions to that.

    If you come to Tassie then please give me a PM contact!

    A pic. is attached

    cheers! Peter
    Attached Thumbnails Attached Thumbnails R8G Engines-750-001-engine.jpg  

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    One useful addition (that would have to be mandatory with an Alpine, if only for looks!) for track days would be a baffled alloy sump. The standard flat bottom steel sump can lead to oil surge, limiting corner speeds.

    My car has been used for similar criteria for your requirements, the odd track day, a few interstate road trips and lots of Sunday Runs, reliably. I reckon it is a nice open-road car for today's speed limited world, the low overall gearing (with stock 4.125 diff in a 353 'box) gives good pick up and performance for overtaking. So I'm guessing an 8G motor in a flyweight Alpine body would perform even better. If going for the 8G motor, my preference would be for a 1300 (Type 812) rather than 1100 (Type 804). Simply because it is newer, and benefited from the various upgrades over time, (the 1100G block is different to a 1300G block, so you can't just slot in a set of 1300 liners into an 1100 block). And as with any motor, condition and history is the key. An unknown motor is probably closer to an overhaul, than one with a known history of being rebuilt in the past. So do the usual due diligence things on the running motor, compression test, even one of those epidiascope things down the plughole may give a very limited idea of the condition of the flame ports.

    Sounds like you have a choice though, which may be hard to make. I'm happy to be corrected by those who likely know better, but given the wider ratios of the 385 internals, and that the stock 5A motor produces similar maximum torque to the 8G motor at 4000 instead of 5000 rpm, the 5A motor may be easier to live with, as well as being more modern and amenable to squeezing extra power out of it.

    As for the handbrake, that sounds like it may need a little work first, as they can be made to work fairly well.
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    Quote Originally Posted by superfred View Post
    Go you good thing 807!! Hard to find 807's and local piston/liner kits though.
    Now you want them! Threw away at least 4-5 807s over the years

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    Quote Originally Posted by driven View Post
    Now you want them! Threw away at least 4-5 807s over the years
    That is why you keep things. They go from common, through old to desirable. You have to recognise the "old" period, when no-one wants them, as 10-15 years later they become "desirable".

    Patience.....

    In parallel, of course, the number of people who understand "desirable" for any item actually diminishes with time, which partly balances out the unfortunate premature "throw away" actions.
    JohnW

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    [QUOTE=Simon;1147448]One useful addition (that would have to be mandatory with an Alpine, if only for looks!) for track days would be a baffled alloy sump. The standard flat bottom steel sump can lead to oil surge, limiting corner speeds.
    <snip>
    QUOTE]

    forgot to add that we did baffle the steel sump mildly - just an arched dwarf wall around the oil pick up to limit flow away from it on hard right handers - seems to work ok but not as pretty as the alloy ones.

    incidentally, I stuffed up my before and after dyno scenario. the exhaust and pump were already done for the "before" - the extra changes were just inlet manihold, webers and cold air box and k&n

    cheers! peter

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    Thanks for the additional comments Simon. The motor is type 812 and comes with a baffled alloy sump. Test drove the motor and it is all good. Would be interested in how you make the handbrake work better. I have tried by inserting spacers on the cable at the mechanism end and adjusting the brakes so they just grab the disks. Enough to get me thru rego but hardly more than justing holding the car still - certainly could not operate as an emergency brake if the main brakes failed. One option I have seen is to make them hydraulic but not sure what is involved apart from having a separate master cylinder? What calipers etc would be used?

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    Quote Originally Posted by bazzamac View Post
    Thanks for the additional comments Simon. The motor is type 812 and comes with a baffled alloy sump. Test drove the motor and it is all good. Would be interested in how you make the handbrake work better. I have tried by inserting spacers on the cable at the mechanism end and adjusting the brakes so they just grab the disks. Enough to get me thru rego but hardly more than justing holding the car still - certainly could not operate as an emergency brake if the main brakes failed. One option I have seen is to make them hydraulic but not sure what is involved apart from having a separate master cylinder? What calipers etc would be used?
    Hi Bazzamac

    I don't think that hydraulic hand brakes are legal (meet the ADR's). The rally boys fit them for a very efficient way of locking the back wheels for hand brake turns.

    Disc brake hand brakes are renowned for being ineffective.
    Regards Col

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    Quote Originally Posted by COL View Post
    Hi Bazzamac

    I don't think that hydraulic hand brakes are legal (meet the ADR's). The rally boys fit them for a very efficient way of locking the back wheels for hand brake turns.

    Disc brake hand brakes are renowned for being ineffective.
    Hi,
    Been a while but I cannot recall the disc handbrake being ineffective. I do recall having to "setup" some ineffective disc brake handbrakes, on various makes, in the past to get them to work OK. People did say that they "never worked well". Just clean, lube and correctly adjust the mechanism and cables and they work OK. They worked when they left the factory.
    Jaahn

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    Quote Originally Posted by jaahn View Post
    Hi,
    Been a while but I cannot recall the disc handbrake being ineffective. I do recall having to "setup" some ineffective disc brake handbrakes, on various makes, in the past to get them to work OK. People did say that they "never worked well". Just clean, lube and correctly adjust the mechanism and cables and they work OK. They worked when they left the factory.
    Jaahn
    Compared to a drum hand brake they are ineffective, thats why some mamufactures of disc brakes incorporated a small drum brake of the hand brake function.
    Regards Col

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    Quote Originally Posted by bazzamac View Post
    Would be interested in how you make the handbrake work better. I have tried by inserting spacers on the cable at the mechanism end and adjusting the brakes so they just grab the disks. Enough to get me thru rego but hardly more than justing holding the car still - certainly could not operate as an emergency brake if the main brakes failed. One option I have seen is to make them hydraulic but not sure what is involved apart from having a separate master cylinder? What calipers etc would be used?
    What condition/type is the cable? If it has to be packed with washers, the cable may be an incorrect type, or is stretched. I've no idea with Alpines, but the R8/10 has a couple of different types of cables, as well as a couple of different types of operating levers. A stretched cable with mis-matched and/or worn components could lead to odd leverage points giving the impression of an ineffective handbrake. At least with mine, the 8 handbrake is more effective and nicer to use than any Renault 12 drum brake handbrake I've had.

    Also if the portion of the lever bearing on the rear of the pad had been worn, again it will be difficult to get the required leverage.

    The usual adjustment procedure for me is to release the handbrake, loosen off the large thin brass nut, then tighten the hollow adjusting screw until the pads are just lightly gripping the disc. Once this is done on both sides, loosen each adjuster screw by 1/2 a turn, press the brake pedal to centralise everything, then check the adjustment again, before tightening the large brass nut (whilst holding the adjusting nut so it doesn't turn), after that, the handbrake usually works quite well.
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    I will also agree that the R8/10 rear disc handbrake is fine. While it is not really suitable to induce handbrake slides at motorkhanas, it holds the car quite fine on hills. I have the std R8 setup on the 4CV and have not seen any need to upgrade it. My adjustment procedure is the same as Simon.

    With the R8G engines it does seem that cracks across the flame ports are almost standard, but don't seem to cause any problems. I would probably go the 5A, for the same reasons as others. Cheaper,newer, much more parts available, and most likely more power. The R8G motor would add more value to your car, but then like me, you hardly ever sell the interesting ones.
    Last edited by alan moore; 25th March 2013 at 02:12 PM.
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    Quote Originally Posted by alan moore View Post
    <snip>
    like me, you hardly ever sell the interesting ones.
    hmm! come to think of it, I've not yet sold a car of mine.

    I did give my Midget to my first wife upon split-up; & gave two Renault Virage wagons to my mechanic (when the first died of old age & intense usage & the second had its engine die) - he R18 engine/transaxled the second one & still uses it 8 years later; & I did sell my second wife's pre-existing Nissan Stanza (shudder) to be replaced by the first R12 mentioned above but it wasn't mine in the relevant sense. I've also had two 4CVs get killed (one by me & one by a dill-brained mate). But _sell_ one of mine? No. At least not while I can drive them.

    I can't imagine selling the 4CV ('68 purchased), R8 ('66 purchased by my mother & '96 inherited by me) Moke ('79 purchased) or Djet ('12 purchased).

    cheers! Peter

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