Rodeo Recommissioning

[edwin]

Hi. I used a system from Frosts, called POR something. It comprises a cleaner, a stabiliser and a coating. I have used it twice and been very pleased with the result. Only problem was getting the tank back on.

 

[malcolm]

I needed a new fuel sender. The old one could be opened up for servicing but one of the tiny wires was stray and I couldn't figure out where it went or how to put it back there. So thought if I'm going to wait 2 weeks for the sender to get through customs I might as well go for a new tank as well.

I had a list of stuff that needed to be ordered. For the R5 chrome trim clips and the bushes that stop the gearstick from rattling and some exhaust mounts..

 

[malcolm]

The fuel tank took 3 weeks to arrive. A week in customs then a week and a half trying to get the reference number I needed to pay the customs charge. Still, it's here now and fitted with the tank guard in case I go off-roading.

This one was from Der Franzose but I suspect all the suppliers sell the same one. It's the smaller earlier tank and quite a good reproduction apart from the untidy bends in the filler pipe. It looks bare metal in the photos but is painted silver. It needed the edges bending upwards to clear the suspension bolts but otherwise fitted well. The fuel gauge works now!

Everything that broke over the last 200 miles is fixed now so hopefully the Rodeo is ready for summer (should we get one this year).

 

[malcolm]

The Rodeo is great in the hot weather - lots of ventilation and a roof for shade. Unfortunately it overheats driving at a constant 80km/h. Yesterday the red cooling light came on but everything was fine. Today it was 28C and some water came out of the expansion bottle. Radiator is full but the expansion bottle is empty.

The old radiator looks OK and is hot to the touch but I'm going to guess a new radiator might be a good idea. Anyone know of a UK source for a 1971 850 radiator?

 

[Homegrown]

Maybe I miss understand what you’re writing!
Radiator should be full and all system bleed and “half full” expansion bottle as a starting point.
If everything above is as it should then it can be problem with the water pump like the engine I fixed some year back ( pump impeller spins on the pump axle).
Radiator can need a flush inside, sometimes the bars get clogged inside the radiator.

 

[malcolm]

The expansion bottle was half full this morning and it was only that quantity of coolant that was lost. The system is bled.

I turned the interior heater and fan on after the coolant light came on. That should have added some extra cooling and there was plenty of very hot air coming out of the vents. It'll be radiator, water pump, or clogged up engine. Water pump is probably worth a try - I can have one at the weekend where a radiator will take 3 weeks to get through customs.

 

[Homegrown]

I guessed it was like that ( have read your threads before I became member) but I wanted to make shore the basics was right. Radiator flush and check water pump is made quickly once you get started.
Can also be an idea to check that engine fan sucks through radiator (and not blowing) due to Billancourt and ventoux versions rotate opposite each other (could explain overheating problems at speed).
Hope it's an easy quick and cheap fix. Best regards from Sweden

 

[malcolm]

I've been thinking a lot about the overheating. I've been having trouble setting the ignition timing so it works in all conditions. When I set it by the book it is way off and I think It's because the distributor advance no longer works as designed.

I've been advancing the ignition a little bit every few days to try to find a good timing setting. When it overheated I think it was too advanced as the power was less than an earlier setting. I advanced it to make it more driveable on part throttle but that made the car down on power on higher throttle openings, and more wasted heat combined with 28C weather would have made it more prone to overheating. A 50 year old cooling system probably doesn't help either but I think the cooling problem is only marginal for UK weather.

So to try to fix a cooling problem I've ordered a 123 tune distributor at vast expense (123TUNE-4-R-V-RENAULT-OLD). I can program it so I get the advance curve where it works and also know how many degrees advance I have at 'speed' when I can't really hear the engine. Then I can get the driveability nice by adding a vacuum advance curve. The Rodeo was becoming better to drive and this should make it easy and hopefully help me optimise the power which is important when you are running a 747cc engine in a car with really bad aerodynamics.

 

[angel]

Do you have the fan cowl fitted? I don't see it anywhere on your pictures and it's a must.
Also, try to find and fit the later plastic 6-blade fan - this was the hot mod (well...cool anyway!) for the small engine R4s to cope with our hot weather.

 

[malcolm]

I didn't realise there was supposed to be a fan cowl. Mine is missing. There is a photo in the manual so I can make one unless anyone has a spare.

 

[Piet]

There are two types, earlier sheetmetal and later moulded plastic but they are both interchangeable. Likewise for the fan there is the much more desirable later nylon one or the earlier sheetmetal 6 blade version. On Ebay there are a couple of US sellers of Wheelhorse 250 ride-on tractor parts (Belgian brand of ride-on tractors that used 800 series ventoux engines rebranded as Continental) , my recollection is one of them, Matt Verdill, was selling spare 6 bladed sheetmetal fans andhe posts overseas. Just don't get a dinged up one. Good luck!

 

[angel]

Cowl is plastic, too, and a bit tricky to fabricate, I think. I have both the cowl and the plastic fan if you can't source them locally.

 

[malcolm]

The 123 distributor is in. The distributor cap is a bit bigger than the original and the leads are tight against the dynamo. Looks like a 90 degree cap would work better.

I've only done a rough tune so far and haven't connected vacuum advance, but already it is so much better than the original distributor. I couldn't find a good timing setting for the original distributor.



But I'll need to do a bit of work on the cooling first. Radiator is the first suspect as it didn't feel all that hot.

 

[malcolm]

I've been out tuning this afternoon and have come to the conclusion that the 747cc (680) engine isn't all that sensitive to timing. There will be a timing setting at each rpm that gives maximum torque. On a modern or tuned engine you'll get into a position where you get into detonation (knock) before you achieve maximum torque. The 747cc engine is so under-tuned that detonation is not a problem. Also the torque from a 747cc engine is hardly noticeable which makes it difficult to optimise the settings. Ignition timing can be way off and it'll still work fine.

So far I've reduced max advance to 34 degrees from TDC and have increased the steepness of the curve. Haven't finished fiddling and still need to try max speed on a longer trip and see what effect the advance and retard buttons have. I'll post a curve later in case someone needs it in the future.

The timing with my original distributor was way off and it did need reconditioning or replacing. The 123 tune distributor is overkill. Any replacement distributor that even half worked would have been completely fine.

The blasted thing even runs fine with no vacuum advance. But here's my win - I dialled in 8 degrees vacuum advance below -0.4 bar and it does make driving in town nicer.

I can see why Gordini had the impulse to tune these engines. I'm feeling the same way especially as I haven't got past 90kmh in the Rodeo yet.

 

[malcolm]

I went out onto a dual carrageway to tune the high rpm and it turns out the Rodeo is sensitive to timing after all. If you get to the sweet spot of precisely 28 degrees at 4000rpm (90km/h) it'll start accelerating again. My new speed record is 95km/h and it'll sit at 90km/h on full load! That's 10km/h faster than the old record so the 123 distributor was worth it after all.

The rest of the curve is by feel on full throttle and it seems to work well. The car is much faster to accelerate than before. The vacuum is just added in to make it a bit happier on very low throttle openings around town and doesn't do anything above 30 percent throttle. So here's an advance curve for a 747cc Billancourt engine with a 123-tune distributor for the French to find on the internet. 0 degrees is top dead center. Won't work for everyone as the ideal advance depends on fuel mixture, but it would be a starting point.

 

[Homegrown]

I had everything optimized when i rebuilt my 845cc in the GreenOne. I can recommend all modifications I did (only cost labor and some consumables) except I think a 32mm carb is more then sufficient. 130km/h and no issues with engine temp.
Maybe a mapable 123 would be a stepp in right direction so I can get part throttle advance when cruising.

 

[malcolm]

I had everything optimized when i rebuilt my 845cc in the GreenOne. I can recommend all modifications I did (only cost labor and some consumables) except I think a 32mm carb is more then sufficient. 130km/h and no issues with engine temp.
Maybe a mapable 123 would be a stepp in right direction so I can get part throttle advance when cruising.

Sounds like yours is working well already. My distributor wasn't working very well at all. You probably wouldn't get much vacuum advance on cruising on an 850 engine as cruising will have quite a big throttle opening. I think that's a trick for larger engines.

I wonder how much speed I would get out of an 850 engine. The Rodeo is supposed to have an 850 but probably the aerodynamics of the Rodeo would still be a problem.

 

[malcolm]

My longest trip so far - 110km in 30C temperature to pick up a pallet truck and it went very well. I think the Rodeo is becoming reliable now.

I was keeping it to 80km/h and the temperature gauge was sitting at 100C all the way but no water came out this time. I ordered the new radiator a couple of weeks ago.

Wondering how practical the Rodeo can be. I want to collect some 3.6m lengths of wood. The van can do it but I would need to MOT and tax it. I've got an idea to collect the wood in the Rodeo.

 

[malcolm]

My radiator arrived. It is made from aluminium and slightly wider than the original radiator and is the same one you can buy direct from China (offer them £200) . The extra width is on the right side where there is plenty of space so is good to have. It seems quite well made but there was a lot of work involved to fit it.

I don't think an aluminium radiator is necessary for cooling but the copper/steel ones were out of stock and I didn't want one with the plastic top. I think my original radiator was bad. The water coming out of the old radiator after I removed it was rusty brown and not bright green like the rest of the cooling system so I think it has some blockages inside.



The radiator mounting and gear lever mounting studs were 10mm round bar. I threaded them with M10 threads. They are too close together so the gear lever bracket had to be bent as well as the holes drilling out. The stay mounting on the side was at the wrong height so I had to shorten the radiator stay



But it looks nice and shiny. The radiator cap is the sprung type which I think will work, but it means you can't suspend an expansion bottle above the engine to bleed the cooling system which is annoying. The original cap doesn't fit so I've ordered a blanking cap so things work as designed and I can keep this one in case the expansion bottle cap ever stops working.

I haven't tested it yet. If this doesn't fix the cooling I'll know the problem is the water pump.

 

[malcolm]

I went out for a drive this morning. Seems to sit at 80C and the maximum temperature at full load was 85C. Before it would overheat at full load.

Had to modify the gear lever bracket again as the mounting studs were too far to one side causing the end of the gearlever to slip off the lever on the gearbox tearing the nice new rubber bush that I fitted last month.