Timed on #1 or #4 cyl?

[keith m 131]

Hi david,

I have opened the throttle at the carb with my hand and both chokes are opening fully (vertical) and I have wedged a piece of wood between the seat and the pedal and again both chokes are open (vertical). So that rules that out.

I find it hard to describe my problem exactly but I will try again, The engine idles ok at 900rpm it revs and sounds ok when standing still and will rev to 6000 rpm in 2nd, 3rd and 4th. From a standing start I can really give it some through the gears and appears to go ok but when I get to 80-85 then the car wont go any faster, when it is flat out I get a loud noise like a heavy drone coming from the engine. This happens if I drive it hard to 80 or just build up 80 slowly. Also when reving the engine hard it doesnt feel smooth.

As I said earlier the engine used to perform very well in my mirafiori. Its the same carb (34ADF) which was just cleaned and put back on. The idle mixture screw is 2 and a bit turns out from seated. As you can see in my previous posts, the carb has all the original spec jets etc. The float is set at 6mm. I fitted a new float jet.

Last week I replaced all the electrical components including the ignition module at the coil.

I thought it might have been fuel starvation due to the mechanical pump so I replaced it with a Facet electrical pump but made no difference.

Cam timing is ok, valve clearances done.

I have been trying to resolve this problem for approx 18 months and I am really getting p---ed off because it took me 9 years on and off to restore the car and after all that hard work I dont get to enjoy the car to its full potential. I rarely drive my cars over 70-80 mph but it is really annoying to know that I cant even if I wanted to.

I will try doing what you recommend regarding setting the timing and see what happens.

If you can think of any other possible causes (although we are running out of options) please let me know.

And theres me thinking that all an engine needs to run is compression, fuel and a spark. Hymmm

Thanks again

Keith
 

[TOAD]

How about doing a plug cut to check under load mixture, or putting it on a Dyno for the same?  could the carb clean have the jets wrong way round?

The vibration is odd though.

[mirafioriman]

I'm with Toad now. Get it on a decent rolling road and see what's actually going on under load. I'm still betting it's something simple.

[keith m 131]

Hi Guys,

The jets are 122 main and 130 secondary, i have checked this.

Vibration is probably a bit strong, from 3000 rpm upwards it just doesnt feel smooth.

Rolling road may be my next option I just wanted to check everything that I possibly can before going on a dyno.

when you say try a plug cut to check underload mixture do you mean drive the car at say 5000 -6000 rpm then put it in neutral and turn off the ignition and pull a plug to see what colour it is?

Something simple, that would be nice I only wish I could find it.

Regards

keith

[Thotos]

when it is flat out I get a loud noise like a heavy drone coming from the engine.

Is that new or has it been reported before? Slight vibration I wouldn't worry about as the 2 litre twin-cams are not the smoothest of engines. I think we are missing a piece of the puzzle here    If the engine can rev to 6000rpm and sustain 6000rpm in 2nd and 3rd  gears then I don't see why it wouldn't do so in 4th gear (maybe not in 5th due to air resistance). 6000rpm in 4th should be over 100mph. If the engine cannot achieve 6000rpm in 4th (but does so in 3rd, 2nd and 1st) then it must be because it cannot overcome wind resistance so it must be down on power. But Keith claims it doesn't seem down on power in lower gears  But it can't be anything else! With the available information, I'd say the engine is down on power enough to make it unable to overcome wind resistance above 80mph but not enough to make the car seem slow in lower gears. So I'll agree with Roger and David and suggest that you get the car on a rolling road and when you see that you're getting 50 or 60bhp at the wheels you can start looking for the reason. Could be something as simple as the exhaust or more serious as engine wear.

[N. Dinis]

what about the gearbox.... vibration, looses power only on higher gears..... the noise... Without wanting to joke, but this looks like a Dr. House case You will get there

[david]

I am now coming back to my original suggestion with regards to the axle ratio but didn't you say this is a 131 unit ?  if so how did you rig it up ? have you got the original 131 set up with four trailing arms and panhard rod ? or have you modified it to use leaf spring as was original on the morris minor ?
I remember reading an article where there was a kit to convert ford escorts to four trailing arms and panhard rod as per 131's and if I recall correctly they said this setup puts 30% more power onto the road compared with a leaf spring setup but I think they were on about pulling from standstill as you get axle tramp with leaf springs.
What is your axle ratio or what 131 was it from ?  I was never keen on mk3 supers 10/35 as I thought they were to high geared and even if it was a 12/43 out of an automatic it would bottom out at 102mph with a 2000 t/c at the front so knowing what ratio it is would help but still doesn't explain 80mph.

[keith m 131]

Hi guys,

Dont get distracted by "vibration" i didnt say that what I said was that at full power there is a drone heard from the engine. The sound actually sums up whats happening and that is the engine struggling to go faster but is being prevented.
The noise has always been there but slipped my mind to mention it. Its not that drastic but there.

The engine will rev to 6000 in 4th but wont go over 80-85.

Theo you mention that it could be a wind resistance issue but as I said in my previous posts, the 131 is shaped like a brick but wind resistance didnt affect that, I could get 110 mph out of that without any problem.

Without regards to the lack of smoothness, well when in the 131 the engine was smooth right up to 110mph.

All the running gear is from the same car 1983 Y reg supermirafiori and as I said it worked perfect before, all I done was check them for leaks etc and drain and replace the oils etc.

The axle is located on new 7 leaf springs with two trailing arms. Adjustable spax dampers. Doesnt axle tramp only affect the car from a hard standing start? I dont get that anyway.

With regards to the gearbox, I have thought that the engine sounds like its over revving for the speed being achieved but it cant remember that being an issue when in the 131, but then again the sound proofing etc was far superior to the moggy.

I have met and spoken to many owners of moggies with 2ltr twinks fitted and none are experiencing the lack of speed problems that I have so the set up works, that may rule out the wind resistance theory.

I will remind you that the engine had a full balance, crank, flywheel, clutch, rods and crank pulley. The gearbox has had all new bearings. Compression is good.

The rolling road will have to wait til after xmas so meantime I was hoping to try and solve it through you guys.

There is a positive in all this and that is I have learned so much on here about the twin cam etc.

Please keep your theories coming, you could be the one to solve this amd make me very very happpy.

regards

keith

[Thotos]

The engine will rev to 6000 in 4th but wont go over 80-85.

  I thought you said before that at 80mph the rev counter is showing 4000rpm! If the engine gets to 6000rpm in 4th but the car is only doing 80mph then it's a gearing issue or the clutch is slipping! 6000rpm in 4th gear with standard 131 gearbox, rear axle and wheel size, the car should be doing over 100mph.

[keith m 131]

Hi Theo,

Before all this started when I was doing 80 the rev counter was reading 4-4500 rpm. If I rev it hard the rpm can be 6000 at 80.

The wheels are not standard but 15" but as I said previously when checked against my sat nav the mph was only showing 4- 5 mph lower, so the wheels size arent affecting it.

I just been speaking to two rolling road garages in Lincs but the dont do cars with carbs, its all fuel injection and mapping work these days. Do you know of any place up this way.

keith

[Thotos]

Before all this started when I was doing 80 the rev counter was reading 4-4500 rpm. If I rev it hard the rpm can be 6000 at 80.

  If at 80mph the rev counter is reading 4000-4500 and then you rev it hard and it goes up to 6000 but the speed stays at 80mph then the clutch is slipping! There's no other possible explanation for this!

[keith m 131]

Theo,

What is your RPM at 8o mph?



Keith

[Thotos]

Theo,

What is your RPM at 8o mph?

Keith

4000rpm in 5th.

[keith m 131]

You may be spot on with clutch slip although its not obvious. Is there a way to check if the clutch is slipping?

I have the cable adjusted so I can engage the gears smoothly,  if I slacken the cable off then it is a little harder to get into first gear and grinds and hard to select reverse gear.


Keith

[Thotos]

If in any gear there's an increase in rpm without a corresponding increase in speed then the clutch is slipping. There could not be any other reason for this in a manual car. So if you are doing 80mph at 4000-4500rpm and you put your foot down and the engine rpm goes up to 6000rpm but you are still doing 80 mph then the clutch is slipping.

The clutch cable should be adjusted to give about 1 inch free play at the actuating arm or pedal. If that means you don't have smooth gear changes then most likely you haven't got enough clutch pedal travel.