What's up with it?

mordzy said:

Funny.

It's tdc highest point of piston? Or just before? Yes passed emissions so can't be too far out like you say

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Yes highest point. I said to turn to a bit before - say 12deg - then insert probe in pot, as the piston comes up you'll see your probe top out for a couple of degrees before descending

Ok thanks. You know these restrictor plates. Is it possible to see them through the throat of the carb with the butterfly open and piston up? Presuming they are these ones with a tongue in the middle.

Yes highest point of piston, so go JUST past it to confirm [by seeing probe drop} that you've found it, [then you can back up] my fear is that the advance mechanism in your dizzy is either knackered or wrong. You've got "bob" weights in there that give a certain amount of advance under load - it can run smooth as a Swiss watch on the drive then bog down as soon as you try to boot it. Most basic test is to suck on the vacuum pipe with distributer cap off - you should see movement below the rotor arm, again lots available online, as usual, good luck. ps. I was hoping some of the more knowledgeable commentators would advise on best carbs/cams etc. Maybe start a new thread?

mordzy said:

Ok thanks. You know these restrictor plates. Is it possible to see them through the throat of the carb with the butterfly open and piston up? Presuming they are these ones with a tongue in the middle.

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yes if you remove enough to lift pistons and needles up 4 holes not one big one

Bloody freezing and snowing this morning so only managed to check for restrictor and have a look at the dizzy/throttle before my fingers packed up.

Apart from the obvious scoring on the base of the piston I can't see any restriction behind the butterfly. Looks like a clear run into the manifold...



So I guess it's not that.

I checked the throttle cable will fully open the butterfly's when peddle depressed and it does. I popped the dizzy cap off and had a look. Only thing that looks odd to me is the excessive ware on two of the contacts. I'm not sure if this is normal but the rest are no way as bad







I sucked on the advance pipe and could see something moving inside the dizzy. I did notice the dizzy arm has about 10mm free play/movement left and right... Is that normal?

I guess my next step is tdc which I'll attempt after a coffee and my hands move again.

Rotor arm looks a bit past it, if you choose to replace it, get a genuine Lucas one and the same for the cap, more expensive but well worth it. I've said it before and will say it again, do not put pattern ignition parts on, I know they are cheap but you'll find they won't last.

When you check vac advance, suck on the pipe then put your tongue on the end, your tongue should stick to the pipe (if you see what I mean) if it doesn't then either the vac advance unit is shot or the pipe has a hole/split in it.

I'm not much of a carb guy but it might also be worth checking to see if the pistons rise when you open the throttle (engine running of course!) If you're not getting smooth movement of the pistons and needles then you're going to struggle to make good power - saw something similar on a RRC a couple of years ago, different carbs but after a bit of investigation found the diaphragm in one carb was split so needle wasn't rising and carb not working properly, certainly worth checking.

As has been suggested a compression test would be worth doing as well as setting up the ignition timing (and dwell if it has points). Have just been doing similar on my '91 but it is efi, found duff vac advance unit and failing ignition amplifier. Replaced vac advance unit, ignition amplifier, dizzy cap and rotor arm - all fixed and running much better.

Nearly forgot, movement on rotor arm is normal, should rock when light pressure applied back and fore, you should also hear the mechanical advance mechanism moving when you do this, sounds like a dull clunking/clicking sort of noise, this means the mechanical advance hasn't seized up, the rotor arm should spring back to position against spring pressure.

Agree with all the above............................. well done on your persistence, was hoping it'd be something blindingly simple [like throttle cable or restrictors] carbs next then

I seem to have made a little progress. I took the no1 plug out to find TDC with a probe down the hole. Supprisingly it was bang on the mark. Not sure what to make of the plug? They all look like this



Not sure if the gap is too big....

I wasn't happy with the vacuum advance pipe manifold side. It was on its spigot but I could pull it off easy. Figured air could be rushing past. I just stuck a temp tie wrap on as I didn't have a small jubilee. Started her up and let it warm up and drove up and down street. Seemed to want to go more. I got a 0-30 0-60 app. And timed myself. 0-30 in 2.44 seconds doesn't sound too bad . Never hit 60 Ran out of road

Running a bit rich. Also check heat rating of plug. Check all for damage, clean and gap to 0.8mm

cooltide said:

Running a bit rich. Also check heat rating of plug. Check all for damage, clean and gap to 0.8mm

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It's Deffo wider than .8 . I have an after market thermostat that had two spade connectors. One to tell fans to come on at low temp and the other at a higher temp. The needle on the temp gauge never gets higher than 3/8 for way up. Should it be running hotter?

It could be rich because I've mostly got the choke on...

It'll struggle worn past 1mm gap.
Thermostat got a temp rating stamped on? 80 odd deg
You could remove and check its operation in a bowl of hot water.
Short journeys or not happy running without choke?

Plug should be Ngk bp5es or equivalent in a low comp iirc rather than sixes

Inch is better than a mile in the right direction - plus excellent news that there's no oily plugs - vacuum pipe replace and check for other vacuum leaks around intake manifold - then it's carbs. Double check vacuum connections to servo - which gearbox have you got? Old 4 speeds have a vacuum operated difflock so plenty of leak possibilities!

It's an after market thermostat... I seem to recall 60 odd and 80 odd on the manual but I'll check. The rad fan is also after market. It had two fans like you'd see on a competition Landy when they put the rad in the back.

I'll take all the plugs out, clean and set the gap through the week and report back if that has any improvements. I'd like to do things a step at a time so I can see what makes a difference.

The gearbox is 5 speed and the reverse is next to 1st.

Mordzy, I have the same set up as you and I’ve also spent quite a lot of time trying to solve the same problems – low compression V8 running on SU carbs (so no restrictor plates) with LT85 gearbox (so no vacuum difflock to worry about) and running fairly well but felt severely low on power.

I've spent quite a lot of time (and money) trying to fix the problem with some success so happy to go through what I've done, what made a difference and what didn't. But I have a couple of questions:

What age is your vehicle?
What is the engine number on the block?
Had the engine been rebuilt when you got it or was it just a straight out of the original vehicle?
Are you also running LPG?
Looking at the photo of the engine earlier on I couldn't see the coil - has it been moved?

Pete-B said:

Mordzy, I have the same set up as you and I’ve also spent quite a lot of time trying to solve the same problems – low compression V8 running on SU carbs (so no restrictor plates) with LT85 gearbox (so no vacuum difflock to worry about) and running fairly well but felt severely low on power.

I've spent quite a lot of time (and money) trying to fix the problem with some success so happy to go through what I've done, what made a difference and what didn't. But I have a couple of questions:

What age is your vehicle?
What is the engine number on the block?
Had the engine been rebuilt when you got it or was it just a straight out of the original vehicle?
Are you also running LPG?
Looking at the photo of the engine earlier on I couldn't see the coil - has it been moved?

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Thanks Pete.

Its a 1989 model. Though i believe most of the bits have come from a donor V8 stuff has come from a RRC.. its been a TD in its history but i do not know the full history.
Engine number is earlier in the thread -
CR8 13.1
S24G00181b
Not on LPG
Coil/Balast? is mounted to the wheel arch. i can take a pic.

I here what your saying on power. its torque under load i think. like going up a hill is hard work. on flat it seems ok.

Looks like your engine is a bit of mash-up of parts like mine. My engine block is also a 24G suffix B engine (which originally is a 90/110 detoxed engine). But the rest of mine is from a non-detoxed engine so it has less emission control stuff on it. Yours certainly has the RRC air filter as the standard Defender one for a 1989 vehicle has more pipework. If anything your's look more efficient in terms of airflow but may require different needles in the carbs to benefit from it.

It looks like your coil might be mounted quite low do so could be close to the exhaust and getting very hot which won't help. They should be mounted high up on the wing next to the windscreen washer bottle.

What's to the right of the radiator? It looks like it's part of an LPG system which is why I asked.

In tuning an engine the carbs are the last thing to look at. Everything else needs to be right first. I'd recommend a service as a starting points. The spark plugs should be a pale beige colour and yours certainly look black. Plug gap is 0.8mm. A new distributor cap would also be worthwhile and leads as well if your's look old. Go for OEM quality if you can.

While the spark plugs are out, have a look into the cylinder bores to see if there is much carbon build up and whether it is worth taking off the cylinder heads for a deck. Mine was quite bad.

The timing can be set quite a lot more advanced than the 'correct setting' and that does seem to help. Des Hamill’s book of V8 tuning suggests over 12 degrees static advance but I found that a bit much. Easy enough to try different values to see what works for your engine. Check that the timing advances when you rev the engine to make sure the mechanical advance is working. I had to replace my distributor because one of the advance springs had failed and it was generally worn so, even when idling, the timing was moving all over the place. It’s also worth checking that all the cylinders are firing as the engine will still run smoothly on 7 or possibly even 6 cylinders.

Check all the vacuum pipes from the carbs and manifold have a good seal. This includes the pipe to the brake servo and the servo itself (if the brakes work well then these should be OK).

Check the fuel pressure if you can. Low pressure could be down to a worn fuel pump or fuel pipe blockage. The higher ethanol content in petrol nowadays can cause the rubber in old fuel pipes to breakdown which can then block the pipe restricting the amount of fuel getting to the carbs. I definitely had this problem so replaced most of mine but need to replace the remainder. I also put in a new fuel pump because the pressure seemed low at less than 2 psi. That didn’t seem to make any noticeable difference though.

Also check the compression. Mine were all fairly close to 150 psi which I think is a bit low but they’re all within 5% of each other which is good.

The camshaft will start wearing out at 50,000 miles and likely to be knackered by 80,000 miles. If you take off the rocker covers you can just about see down to the cam with and with a torch you may be able to see whether the lobes look worn or not. But even if it looks OK, it is still likely to be worn at high mileage. You can run the engine with the rocker covers off to make sure all the valves train is operating. When I did this I noticed that one of the inlet valves was barely moving and that was down to a completely worn out tappet. If the inside of the rockers covers and the valve gear are covered in black sludge then that would suggest that the engine is very worn and hasn’t been looked after. The RPI website has some good pictures showing what it should be like.

Finally make sure all the crankcase breather pipes and oil traps are clear. The carbs will have been set up originally with some air coming in via this route so if there’s a blockage then it might have a small impact.

When I had fixed all the problems identified from my checks the engine felt as though it had slightly more power but wasn’t as smooth. So my final step was to rebuild the carbs with the proper SU kit and then set them up in accordance with the official Land Rover manual. After this it finally ran smoothly. I’m not sure whether the carbs needed rebuilding but as I was taking them apart anyway to set them up I thought I might as well do the full job.

I now get 17 mpg on a long run, even when towing, and it runs more smoothly and feels more lively. There is still more work to do but it is a lot better.

If you decide to replace parts then I can tell you what I did in terms of the camshaft and cylinder heads.

Agree with the above except "the carbs are the last thing to look at" since you can only make small changes and adjustments if you're on the wrong carbs, or they're knackered then you'll never know if you're getting anywhere, at the very least a strip down and inspection.
When you say it's "spot on" do you mean TDC lines up exactly with the pointer? Did you mark number one lead position and see if rotor was pointing dead at it? I agree with Pete-B - they like to run advanced, get your timing light out, clean up your timing marks and maybe tipex TDC. Set it advanced [mine is off the scale] then leaving the dizzy SLIGHTLY loose go for a run - make adjustments as feel right, as always, good luck

You are assuming mordzy knows what pinking sounds like, could cause damage if he doesnt . if he gets it as far advanced as possible now, it still may pink under heavy load and high summer temps, or if he changes thermostat

I have faith in Mordzy!