Rover V8 & Brake servo - Help!
Discussion
After a bit of advice as i am left completely stumpted by this..
Brought a hybrid landy with a missmatch of parts and struggling to get it going properly. Main issue revolves around brakes and the lack of servo assistance. As you can see on photos below a servo is already present and i believe a vacuum port for the servo is also located on the top of the engine.
However, when I brought the car this wasnt connected / no servo assitance and the car ran well, idle'd perfectly and stopped with a bit of an effort but obviously no servo working is MOT fail.
So without the servo hose attached car runs perfectly, idles anywhere between approx 300 and 1000rpm (adjusting idle speed) and sounds perfect, no smoke etc..
With servo attached car fails to idle... I can adjust the idle so that it idles about 1000rpm again, however when i rev it the revs refuse to return to idle and it sits at about 2000/2500rpm approx. Also it doesn't sound quite right and theres bit of black smoke out the back.
Please see photos below, any advice / input welcome
Brought a hybrid landy with a missmatch of parts and struggling to get it going properly. Main issue revolves around brakes and the lack of servo assistance. As you can see on photos below a servo is already present and i believe a vacuum port for the servo is also located on the top of the engine.
However, when I brought the car this wasnt connected / no servo assitance and the car ran well, idle'd perfectly and stopped with a bit of an effort but obviously no servo working is MOT fail.
So without the servo hose attached car runs perfectly, idles anywhere between approx 300 and 1000rpm (adjusting idle speed) and sounds perfect, no smoke etc..
With servo attached car fails to idle... I can adjust the idle so that it idles about 1000rpm again, however when i rev it the revs refuse to return to idle and it sits at about 2000/2500rpm approx. Also it doesn't sound quite right and theres bit of black smoke out the back.
Please see photos below, any advice / input welcome
You say there is a vacuum port but don't say if that was open or closed when the engine was running well.
If it was open then the engine was getting some of its air through that and the carbs had been tuned to compensate. now you have closed it off the engine is running very rich.
Steve
If it was open then the engine was getting some of its air through that and the carbs had been tuned to compensate. now you have closed it off the engine is running very rich.
Steve
Remove the servo adaptor from the intake manifold and clean it. Make sure it's closed and that you can only breath through it one way. If it's faulty it could be causing all sorts of problems.
Connect the servo pipe and then readjust the idle settings etc. The engine may have been drawing in air via the open servo valve.
Connect the servo pipe and then readjust the idle settings etc. The engine may have been drawing in air via the open servo valve.
Lol. This funny 
Some twonk has adjusted the carbs to compensate for the vacuum stub being open all the time and drawing in air. Hardly surprising it goes off scale rich when you plug a servo pipe onto that. It's probably supplying most of the air needed at idle.
Stick the servo pipe back on. Adjust the idle mixture nuts under the carbs until the mixture is correct again. Fastest possible idle speed then weaken off a tad should be close.
Some twonk has adjusted the carbs to compensate for the vacuum stub being open all the time and drawing in air. Hardly surprising it goes off scale rich when you plug a servo pipe onto that. It's probably supplying most of the air needed at idle.
Stick the servo pipe back on. Adjust the idle mixture nuts under the carbs until the mixture is correct again. Fastest possible idle speed then weaken off a tad should be close.
Pumaracing said:
Lol. This funny
Some twonk has adjusted the carbs to compensate for the vacuum stub being open all the time and drawing in air. Hardly surprising it goes off scale rich when you plug a servo pipe onto that. It's probably supplying most of the air needed at idle.
Stick the servo pipe back on. Adjust the idle mixture nuts under the carbs until the mixture is correct again. Fastest possible idle speed then weaken off a tad should be close.
This ^ also worth noting where that servo port is situated right next to no 8 runner this must run strange on idle with one pot noticeably leaner than the rest while open like that Some twonk has adjusted the carbs to compensate for the vacuum stub being open all the time and drawing in air. Hardly surprising it goes off scale rich when you plug a servo pipe onto that. It's probably supplying most of the air needed at idle.
Stick the servo pipe back on. Adjust the idle mixture nuts under the carbs until the mixture is correct again. Fastest possible idle speed then weaken off a tad should be close.
things can only run better for the O/Per when he corrects this along with the carb fueling 
Sardonicus said:
Pumaracing said:
Lol. This funny
Some twonk has adjusted the carbs to compensate for the vacuum stub being open all the time and drawing in air. Hardly surprising it goes off scale rich when you plug a servo pipe onto that. It's probably supplying most of the air needed at idle.
Stick the servo pipe back on. Adjust the idle mixture nuts under the carbs until the mixture is correct again. Fastest possible idle speed then weaken off a tad should be close.
This ^ also worth noting where that servo port is situated right next to no 8 runner this must run strange on idle with one pot noticeably leaner than the rest while open like that Some twonk has adjusted the carbs to compensate for the vacuum stub being open all the time and drawing in air. Hardly surprising it goes off scale rich when you plug a servo pipe onto that. It's probably supplying most of the air needed at idle.
Stick the servo pipe back on. Adjust the idle mixture nuts under the carbs until the mixture is correct again. Fastest possible idle speed then weaken off a tad should be close.
things can only run better for the O/Per when he corrects this along with the carb fueling When I adjust each carb separately how do I know when I'm getting it correctly.
I've found the guide below which pointed me in the direction of the idle speed adjustment, but I'm slightly confused to go any further as it all looks rather complex!
http://britishclassicmotors.com/media/b542a3b3e31a...
It refers to 'piston lifting pins'? What / Where are these?
Surely the servo port is limited by where the vacuum ports are? - Theres one at the front which has a blanking plug over, but surely then the same issue would be repeated, just on a different cylinder or am I missing something?
The lifting pins are at the rear of the carbs on the outside underneath the flange.
Basically they are used to alter the air flow a bit without opening the throttle, then depending on the response of the engine - revs up/down - you can do some fine adjustments.
You can use a flow meter to set the carb balance or a piece of piping to listen to the hiss. Get it set the same both sides and they should be balanced.
I use my noise meter with a big foam ball on it - just get the dB level the same both sides.
I had trouble with mine for a while not running on the one cylinder - it turned out to be a broken 'thing' that was bolted into the lower face of the booster, when i plugged the hole the engine ran fine.
No idea what the 'thing' was though, I assume some sort of relief valve perhaps.
Basically they are used to alter the air flow a bit without opening the throttle, then depending on the response of the engine - revs up/down - you can do some fine adjustments.
You can use a flow meter to set the carb balance or a piece of piping to listen to the hiss. Get it set the same both sides and they should be balanced.
I use my noise meter with a big foam ball on it - just get the dB level the same both sides.
I had trouble with mine for a while not running on the one cylinder - it turned out to be a broken 'thing' that was bolted into the lower face of the booster, when i plugged the hole the engine ran fine.
No idea what the 'thing' was though, I assume some sort of relief valve perhaps.
tommobot said:
......Surely the servo port is limited by where the vacuum ports are? - Theres one at the front which has a blanking plug over, but surely then the same issue would be repeated, just on a different cylinder or am I missing something?
The situation you had was the port open allowing air directly into the manifold. As it was positioned at the end of the manifold almost all of that fresh (un-fueled) air was going into one cylinder which could have made it very lean with the risk of melting the piston.Once it is connected to the servo the problem goes away because there is very little flow and then only when actually braking.
Steve
Thanks for the help guys.. Got brave today and following some YouTube vids took the tops off the carbs, cleaned the up etc and reset the jets ( I think that's what there called).. Anyways all adjusted and I think it's running a tad lean on 1 carb but if I adjusted any more it goes rich very quickly.
Unfortunately I broke one off the ball end bolts when tightening the bolt so haven't run it with both carbs linked... But think it's pretty much there. Sounds good, no smoke and servo working properly!
Unfortunately I broke one off the ball end bolts when tightening the bolt so haven't run it with both carbs linked... But think it's pretty much there. Sounds good, no smoke and servo working properly!
So got out in it for a quick test over the weekend.
Still idles and brakes with servo working properly.
However at low revs when pulling away / there is very little power, I'd guess between 1000-2500rpm, however after that it kicks in and charges off down the road.
If I pull the choke out at lower revs it runs fine again at low revs.
Any ideas? I guess I should richen up the mixture on the carbs a bit?
Should probably add that was driving perfectly a few months ago - I.e last time it was in regular use.
Still idles and brakes with servo working properly.
However at low revs when pulling away / there is very little power, I'd guess between 1000-2500rpm, however after that it kicks in and charges off down the road.
If I pull the choke out at lower revs it runs fine again at low revs.
Any ideas? I guess I should richen up the mixture on the carbs a bit?
Should probably add that was driving perfectly a few months ago - I.e last time it was in regular use.
Edited by tommobot on Monday 29th June 13:47
If it is doing it just on acceleration then my question would be what oil are you using in the carb dash pots.
You may be unaware of the function they perform.
When you progressively increase speed the slider lifts with vacuum allowing more air into the engine and at the same time removing a tapered needle from the main jet allowing more fuel.
When you accelerate harder you need a richer mixture so the dash pot acts as a damper preventing the slider from lifting. The engine is still trying to pull in more air but the slider is preventing it which causes a bigger venturi effect which draws more fuel than normal from the main jet.
If there is not enough oil or it is too thin this acceleration enrichment will not take place.
Steve
You may be unaware of the function they perform.
When you progressively increase speed the slider lifts with vacuum allowing more air into the engine and at the same time removing a tapered needle from the main jet allowing more fuel.
When you accelerate harder you need a richer mixture so the dash pot acts as a damper preventing the slider from lifting. The engine is still trying to pull in more air but the slider is preventing it which causes a bigger venturi effect which draws more fuel than normal from the main jet.
If there is not enough oil or it is too thin this acceleration enrichment will not take place.
Steve
You haven't mentioned what the carb needles are to complement the K&N (free flow) filters. If they look not very tapered they may be too weak, BBC needles are usually a good starting point.
Often folk set 'em really rich at idle with std needles so they drive 'near enough' when cruising and accelerating.
Rule of thumb for the SD1 carbs, jets 80-85 thou down from bridge as a starting point.
Peter
Often folk set 'em really rich at idle with std needles so they drive 'near enough' when cruising and accelerating.
Rule of thumb for the SD1 carbs, jets 80-85 thou down from bridge as a starting point.
Peter
Edited by PeterBurgess on Tuesday 30th June 13:37
So, with servo disconnected the car ran well, connect up servo and it all goes to pot with carburation all over the place.
Have you checked that you haven't got a split diaphragm in the servo which is leaking air into the manifold and leaning the mixture out.
If you start the engine with the servo connected , listen carefully close to the servo and if you hear some hissing the servo diaphragm is your problem.
HTH,
Cheers
Tony
Have you checked that you haven't got a split diaphragm in the servo which is leaking air into the manifold and leaning the mixture out.
If you start the engine with the servo connected , listen carefully close to the servo and if you hear some hissing the servo diaphragm is your problem.
HTH,
Cheers
Tony
Edited by Tony427 on Tuesday 30th June 13:48
Tony427 said:
So, with servo disconnected the car ran well, connect up servo and it all goes to pot with carburation all over the place.
Have you checked that you haven't got a split diaphragm in the servo which is leaking air into the manifold and leaning the mixture out.
If you start the engine with the servo connected , listen carefully close to the servo and if you hear some hissing the servo diaphragm is your problem.
HTH,
Cheers
Tony
Well yes, but it was appear that a previous owner had tuned the carbs to run without the servo, i.e taking alot of air in through open vacuum in engine as suggested towards top of thread.Have you checked that you haven't got a split diaphragm in the servo which is leaking air into the manifold and leaning the mixture out.
If you start the engine with the servo connected , listen carefully close to the servo and if you hear some hissing the servo diaphragm is your problem.
HTH,
Cheers
Tony
Edited by Tony427 on Tuesday 30th June 13:48
The servo is brand new, and haven't heard any noise around that area.
Staionariliy it runs well, as good as it ever has. Just appears to be not so good on the move.
One thing I did notice was that when I was setting the carbs was that when they were separated the 1 side did not rev particually cleanly and was very 'fluttery / hesitant' as such. However it must be said that once it got warmer this went away but I guess this is how it was when driving it. To be fair it was only a few short drive round the block (less than 0.5 mile and wasn't particually warm) so the issue might go away once fully warm. Its got an MOT on Friday which is a good 6 or 7 miles away so that should give it a good run
PeterBurgess said:
You haven't mentioned what the carb needles are to complement the K&N (free flow) filters. If they look not very tapered they may be too weak, BBC needles are usually a good starting point.
Often folk set 'em really rich at idle with std needles so they drive 'near enough' when cruising and accelerating.
Rule of thumb for the SD1 carbs, jets 80-85 thou down from bridge as a starting point.
Peter
Jets 80-85? Eh?Often folk set 'em really rich at idle with std needles so they drive 'near enough' when cruising and accelerating.
Rule of thumb for the SD1 carbs, jets 80-85 thou down from bridge as a starting point.
Peter
Edited by PeterBurgess on Tuesday 30th June 13:37
I will load them up with some proper oil and take some photos of the needles... See whats what
Hiya
I should have explained myself better. From the flat ally part (bridge) of the carb adjacent to the brass jet to the central part of the jet where the needle slides in 80-85 thousandths of an inch.
The standard needles may be BAK, stamped on the needle, you may have to remove the needle from the piston to see the lettering.
Peter
I should have explained myself better. From the flat ally part (bridge) of the carb adjacent to the brass jet to the central part of the jet where the needle slides in 80-85 thousandths of an inch.
The standard needles may be BAK, stamped on the needle, you may have to remove the needle from the piston to see the lettering.
Peter
Couldn't see any lettering on the needle, do I need to fully take them out of what the recessed into.
I loaded the floats up with 15w 50, couldn't find 20w 50.
Seems to have worked, dramatically improved performance, no hesitation at all.
However, I took it for its MOT, passed beautifully but when I left the MOT the hesitation has reappeared. The chap did take it on a road test for about 5mins so he may have ragged it.
Anyway, I was going to check / top up the floats, how full should they be with oil ideally?
I loaded the floats up with 15w 50, couldn't find 20w 50.
Seems to have worked, dramatically improved performance, no hesitation at all.
However, I took it for its MOT, passed beautifully but when I left the MOT the hesitation has reappeared. The chap did take it on a road test for about 5mins so he may have ragged it.
Anyway, I was going to check / top up the floats, how full should they be with oil ideally?
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