Rover V8 & Brake servo - Help!

[tommobot]

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

[tommobot]

The vacuum was open when it was running properly so it was definitely drawing air through this valve.

Possibly stupid question but what do you mean by make sure its closed?

[tommobot]

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 things can only run better for the O/Per when he corrects this along with the carb fueling

I presumed somebody had done something like that. I am unfortunately a total 'n00b' to carbs.

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?

[tommobot]

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!

[tommobot]

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.

Edited by tommobot on Monday 29th June 13:47

[tommobot]

I was using automatic transmission oil, but on further reading it would appear there are many other options available.

Would something like 20w50 oil be better?

[tommobot]

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

Edited by Tony427 on Tuesday 30th June 13:48

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.

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

Edited by PeterBurgess on Tuesday 30th June 13:37

Jets 80-85? Eh?

I will load them up with some proper oil and take some photos of the needles... See whats what

[tommobot]

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?