V8 newbie

[66landyv8]

Evening All,

I am very much a novice with engines but am after some advice. I have recently put my V8 powered series Land Rover back on the road after a restoration. The engine is out of a late 80's V8 defender and I believe it is a standard 3.5 with SU carbs. It has K&N filters and little in the way of silencing in the exhaust system. The oil pressure sits around 20 - 25 psi.

My problem is it sounds sweet without any load but when out on the road is hesitant and never really revs high. I have the carbs balanced and the mixture is as per factory settings (I don't have anything to fine tune mixture but pulling out the choke doesn't seem to improve things). I originally set the timing to 8 deg BTDC but the running was horrific so I have road tested and advanced (if that's the correct phrase - made it more degrees before TDC) and there is a huge improvement but it still doesn't pick up like it should. Having said this every now and again it seems spot on but this only lasts for a minute or two.

The other thing I should mention is that it always starts straight away but is flat as a pancake for the first 30 seconds and is totally unresponsive to throttle.

Can anyone give me any pointers as to where to look next please??

Thanks in advance.

Ed.

[DaveEFI]

I'd first check the carb pistons are moving feely and not sticking. With the engine stopped, remove the filters and lift by hand. They should lift smoothly to fully open and drop to closed with a slight clunk. Both should be the same.
Not running properly on the maker's static timing setting could be due to many problems. Hopefully not the common RV8 one of badly worn camshaft.

Just a couple of things to check first.

[66landyv8]

Thanks Dave I will have a look at the Pistons. I guess it is a case of this could be loads of things but I was wondering (/ hoping!) could it be a distributor issue (I have checked that it does advance when rev'ed but I don't know if it is by the correct amount) or could it be to do with the hydraulic lifters? (Again I don't fully understand how these work but the fact that every now and again it seems to really go....)

I should add that the timing quoted is off the timing marks on the pulley so again being an optimist I was hoping the timing marks were simply out...

I am slowly coming around to the reality that this may be a lot more work than the few tuning tweaks I had hoped!

Cheers

Ed.

[ChrisJC]

I would also check that the fuel pump is running properly and that the float chambers are full of fuel. You might find one carb is 'dry' so the engine is running but only on 4 cylinders.

Chris.

[66landyv8]

Thanks Chris. I am running an electric SU pump but to be honest the fuel filter never appears to carry much fuel so I did wonder if that could be a problem. I have previously disconnected the fuel at the carbs and it pumps like mad into a jar. I did look at the float heights when I first had the landy but the engine was sat in my garage for 2+ years so I guess a re-check would not go a miss. I see you have a series 2 with a 4.6 - must be fun! Ed.

[Ian Anderson]

Old / stale fuel?

Amazing how quickly the unleaded stuff seems to go off!

Ian

[unstable load]

Thanks Chris. I am running an electric SU pump but to be honest the fuel filter never appears to carry much fuel so I did wonder if that could be a problem.

The filter not being full is not an issue. When your pump starts on a dry fuel line and filter, it will fill the filter to the highest point before it exits the outlet. If you want to see a full filter, you need to have it mounted vertically, but it's not essential.

I have previously disconnected the fuel at the carbs and it pumps like mad into a jar.

This is more important, it means the fuel is being delivered to the carbs, so the issue isn't the pump or a blocked line.

Check the needle and seats on both carbs, some of the kits with the needle having a rubber tip can stick in the seat bore and mess up the level. Set the float heights to spec, too.
Also check the jets for fouling of the choke mechanism. If you pull the choke out with the engine running and nothing happens, then it is possibly either already running on a stuck choke or very rich.
Do a physical check of the choke activation mechanism and whether the jets drop and rise when you move the choke knob. They can be sticky and that causes all sorts of swearing to issue forth.....

Then, move to the jets' position relative to the carb body and needles. The jets need to be specifically set relative to the internal body of the carb and the needles have to be set according to the dashpot piston. There are different types of needles and they have different fixing specifications. Check that the pistons don't stick in the dashpots. Even a tiny tight spot will cause problems.

Once you are happy that is all good, then go back to basic settings again. Do you know how to do the dashpot pin test for the idle mixture?

I'd also look at the ignition again, specifically the vacuum advance mechanism. I'd also look at the advance weights for worn/sticky bits in the pins and springs etc. Is the baseplate in the dizzy free to rotate and if you suck on the vacuum pipe, does it move forward and return to the original position?
If you are on points, is the dwell set correctly and is the condenser good?

Is the cam timing OK? You don't say if you had the front cover off, so it may be worth establishing that, too. Like DaveEFI says, it could also be a worn cam. The Rover engine can run deceptively smoothly on an almost totally worn cam, up to a point...

Happy rummaging, I hope you get sorted out and back on the road soon.

[66landyv8]

Much appreciated John plenty for me to go at! I will let you know how I get on...

[66landyv8]

Had a play around this afternoon. Lifting the piston in one carb caused the engine to cut out (too lean?) whilst the other piston could go all the way up and not affect the engine speed one bit! I disconnected the linkage are either carb can Rev the engine. I then looked at the choke mechanism and found their to be not much left of the o ring in the problem carb so I'm thinking maybe this one carb is getting fed fuel by the failed o ring and this is why it doesn't care that I lift the piston?? I'm going to put a new o ring in and try again... Float levels etc seem fine. Ed.

[DaveEFI]

If you can lift a piston and it makes no difference, that carb is doing nothing at all.

With the engine running shine a torch on the needle of the carb that is OK. Can you see fuel being drawn up past the jet? If so, do the same with the other one. I suspect none is. A seal failure etc round the jet can cause a lack of differential pressure, so no fuel flows

[66landyv8]

I disconnected the throttle linkage (between the two carbs) and the dodgy carb revs the engine on its own? I assume the fault may just be at low revs... The carb is off the manifold at the moment so I think I will replace all seals and o rings. Cheers Ed.

[unstable load]

Ed, go the the Burlen website, they will have all you need to rebuild those carbs to serviceable spec.
Do both, is my advice.

[DaveEFI]

I disconnected the throttle linkage (between the two carbs) and the dodgy carb revs the engine on its own? I assume the fault may just be at low revs... The carb is off the manifold at the moment so I think I will replace all seals and o rings. Cheers Ed.

Could be one carb is closed at idle - hence lifting the piston not making a difference. Balancing them to an equal flow at idle is part of the tuning procedure. But as was said stripping then down and giving them a good clean and replacing all the seals is not a bad idea with any older carbs.

[66landyv8]

Having stripped and added new o rings etc to the problem carb I put it back on today to find no change! However, as I was fiddling around I started the engine without the breathers and it sounded the best it ever has! Long story short is I must have cocked up the breathers on the problem carb (I had both connected to the rocker cover and having done a bit of Google research it seems one is an overflow not a breather???) I need to look into this further but having gone for a quick spin she is running like a V8 should and I have a large smile which I'm struggling to get rid of right now!!

Thanks all for your help!

Ed.

[DaveEFI]

If you'd connected a carb overflow to the vacuum side of the engine, you'd get little or no fuel flow.